Publications by authors named "Yu-Min Tzou"

27 Publications

  • Page 1 of 1

Unravelling the mechanism of amitriptyline removal from water by natural montmorillonite through batch adsorption, molecular simulation and adsorbent characterization studies.

J Colloid Interface Sci 2021 Sep 26;598:379-387. Epub 2021 Apr 26.

Environmental Contaminants Group, Future Industries Institute, University of South Australia, Mawson Lakes, SA 5095, Australia.

Amitriptyline (AMI) is one of the most common tricyclic antidepressant personal care medications. Due to its environmental persistence and bioaccumulation, release of AMI into the environment via wastewater streams in elevated levels could lead to significant ecological and human health impacts. In this study, the adsorption of AMI by montmorillonite (SWy-2), a naturally abundant smectite clay with sodium ions as the main interlayer cations, was investigated. Maximum AMI adsorption (276 mg/g) occurred at pH 7-8. After adsorption, examination of the adsorbent's X-ray diffraction pattern indicated that interlayer expansion had occurred, where chemical stoichiometry confirmed cation exchange as the principal adsorption mechanism. AMI adsorption reached equilibrium within 4 h, with kinetic data best fitting the pseudo-second order kinetic model (R = 0.98). AMI adsorption was unaffected by solution pH in the range 2-11, where adsorption was endothermic, and molecular simulations substantiated by Fourier transform infrared spectroscopy and thermogravimetric investigations indicated that the orientation of AMI molecules in the interlayer was via an amine group and a benzene ring. Overall this research shows that SWy-2 has significant potential as a low cost, effective, and geologically derived natural material for AMI removal in wastewater systems.
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http://dx.doi.org/10.1016/j.jcis.2021.04.033DOI Listing
September 2021

Organic fragments newly released from heat-treated peat soils create synergies with dissolved organic carbon to enhance Cr(VI) removal.

Ecotoxicol Environ Saf 2020 Sep 13;201:110800. Epub 2020 Jun 13.

Department of Soil and Environmental Sciences, National Chung Hsing University, 145 Xingda Rd., Taichung, 40227, Taiwan; Innovation and Development Center of Sustainable Agriculture, National Chung Hsing University, 145 Xingda Rd., Taichung, 40227, Taiwan. Electronic address:

Surface fires occur naturally or anthropogenically and can raise the temperature at the soil surface up to 600 °C. The heat derived from the surface fire can be subsequently transferred into CO-enriched subsoils. As a result, the chemical compositions of soil organic matter (SOM) may be altered in fire-impacted anaerobic environments, indirectly influencing the redox transformations of pollutants, such as Cr(VI). In this study, a peat soil was heated up to 600 °C with limited air flow to simulate the effects of heat on the SOM during surface fire events. Then, Cr(VI) removal, including reduction and sorption, by the heat-treated peat soils was determined in relation to changes in the soil organic components. The results showed that the amount of O-containing functional groups, -CH/-CH units of aliphatic groups, and dissolved organic carbon (DOC) in the SOM gradually decreased with an increase in the heating temperature. The removal of 0.1932 mM Cr(VI) did not exhibit a consistent decline along with the changes in these soil components. The heating temperatures of 200 and 250 °C were the thresholds that led to the decomposition of temperature-sensitive soil organic components such as lignin and other labile SOM. Such newly released organic fragments synergized lignin-like substances and carboxyl groups, resulting in up to 99% removal of the initially added Cr(VI). As the heating temperatures were increased from 300 to 600 °C, Cr(VI) reduction decreased from 66% to 20%. The black carbon-like materials and/or aromatic-containing moieties were the major components responsible for Cr(VI) reduction in 600°C-treated peat soils.
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http://dx.doi.org/10.1016/j.ecoenv.2020.110800DOI Listing
September 2020

Redox reactions between chromium(VI) and hydroquinone: Alternative pathways for polymerization of organic molecules.

Environ Pollut 2020 Jun 23;261:114024. Epub 2020 Jan 23.

Department of Soil and Environmental Sciences, National Chung Hsing University, 145 Xingda Rd., Taichung, 40227, Taiwan; Innovation and Development Center of Sustainable Agriculture, National Chung Hsing University, 145 Xingda Rd., Taichung, 40227, Taiwan. Electronic address:

Chromium (VI) reduction by organic compounds is one of the major pathways to alleviate the toxicity and mobility of Cr(VI) in the environment. However, oxidative products of organic molecules receive less scientific concerns. In this study, hydroquinone (HQ) was used as a representative organic compound to determine the redox reactions with Cr(VI) and the concomitant oxidative products. Spectroscopic analyses showed that Cr(III) hydroxides dominated the precipitates produced during redox reactions of Cr(VI) and HQ. For the separated filtrates, the acidification induced the oxidative polymerization of organic molecules, accompanied with the complexation with Cr(III). The aromatic domains dominated the chemical structures of the black and fluffy organic polymers, which was different to the natural humic acids due to the shortage of aliphatic chains. Results of linear combination fitting (LCF) for Cr K-edge X-ray absorption near edge structure (XANES) spectra demonstrated that up to 90.4% of Cr inventory in precipitates derived after the acidification of filtrates was Cr(III) complexed with humic-like polymers, suggesting that Cr(III) possibly acted as a linkage among organic molecules during the polymerization processes of HQ. This study demonstrated that Cr(VI) may lead to the polymerization of organic molecules in an acidic solution, and thus, it could raise scientific awareness that the oxidative decomposition of organic molecules may not be the only pathway while interacting with the strong oxidant of Cr(VI).
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http://dx.doi.org/10.1016/j.envpol.2020.114024DOI Listing
June 2020

Removal and simultaneous reduction of Cr(VI) by organo-Fe(III) composites produced during coprecipitation and coagulation processes.

J Hazard Mater 2019 08 27;376:12-20. Epub 2019 Apr 27.

Department of Soil and Environmental Sciences, National Chung Hsing University, 145 Xingda Rd. Taichung 40227, Taiwan; Innovation and Development Center of Sustainable Agriculture, National Chung-Hsing University, 145 Xingda Rd. Taichung 40227, Taiwan. Electronic address:

Composites formed during the coprecipitation and/or coagulation of ubiquitous dissolved organic matter (DOM) and Fe in natural and waste water systems might be potential scavengers for Cr(VI) in terms of sorption and reduction. Our objective here was to determine sorption and simultaneous reduction of Cr(VI) on organo-Fe(III) composites (OFC) in relation coprecipitated pH and C/(C + Fe) ratios. Results showed the greatest Cr sorption of 51.8 mg g on the OFC sample that was precipitated at pH 3 and contained the C/(C + Fe) molar ratio of 0.71. Wherein the Cr(VI) removal subsequent to the coprecipitation was dominated by the sorption on Fe hydroxides. Although amounts of total sorbed Cr decreased with increasing C/(C + Fe) molar ratio, the reverse trend on Cr(VI) reducibility compensated the Cr(VI) removal capability of OFC samples. With C/(C + Fe) molar ratios ≥ 0.89, the increasing amounts of coprecipitated organic matter that homogeneously distributed with Fe domains on OFC surfaces could trigger a significantly pronounced Cr reduction. Collectively, our results suggested an alternative method for Cr(VI) remediation by manipulating C/Fe ratios in suspensions. After the sorption of most Cr(VI) on Fe hydroxides, increasing C/Fe ratio in systems could further improve the Cr(VI) removal efficiency by the reduction of remaining Cr(VI) to Cr(III).
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http://dx.doi.org/10.1016/j.jhazmat.2019.04.055DOI Listing
August 2019

Use 3-D tomography to reveal structural modification of bentonite-enriched clay by nonionic surfactants: Application of organo-clay composites to detoxify aflatoxin B1 in chickens.

J Hazard Mater 2019 08 29;375:312-319. Epub 2019 Apr 29.

Department of Soil and Environmental Sciences, National Chung Hsing University, Taichung 40227, Taiwan; Innovation and Development Center of Sustainable Agriculture, National Chung-Hsing University, Taichung 40227, Taiwan. Electronic address:

Although nonionic surfactants are relatively eco-friendly compared with cationic and anionic surfactants, few studies have investigated their application in modified clay. Herein we prepared organo-clay composites (OCCs) by mixing bentonite-enriched clay (BEC) with nonionic surfactants (Brij 30 and Igepal CO-890) and determined if these modifications would enable chickens to detoxify aflatoxin B1 (AFB1). For the first time, in situ three-dimensional (3-D) microstructures of modified BEC was characterized in suspension using transmission X-ray microscopy. Although X-ray diffraction patterns indicated the expansion in the spacing between planes of atoms (basal spacing) of surfactant-modified BEC, 3-D images indicated shrinkage in its microscale porous framework with increasing surfactant additions from 1 to 30 wt%. Such declining trends in porous dimensions caused by the dehydration in interlayer galleries of clays positively correlated with sorption amounts of AFB1 on OCCs. After chickens had consumed amended feeds for 11 weeks, AFB1 concentrations in liver, kidney, and plasma were significantly lower than in the control treatment. Thus, we suggest using BEC with 1 wt% surfactant addition, an amendment to chicken feeds, to detoxify AFB1. Modifying BEC with nonionic surfactants show the promise in mitigating AFB1 accumulation in chickens, which should improve food safety and reduce environmental contamination.
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http://dx.doi.org/10.1016/j.jhazmat.2019.04.084DOI Listing
August 2019

Adsorption mechanisms of chromate and phosphate on hydrotalcite: A combination of macroscopic and spectroscopic studies.

Environ Pollut 2019 Apr 8;247:180-187. Epub 2019 Jan 8.

Department of Soil and Environmental Sciences, National Chung-Hsing University, 145 Xingda Rd., Taichung 402, Taiwan; Innovation and Development Center of Sustainable Agriculture, National Chung-Hsing University, 145 Xingda Rd., Taichung 402, Taiwan. Electronic address:

Hydrotalcite (HT) is a layered double hydroxide (LDH), which is considered as a potential adsorbent to remove anion contaminants. In this study, adsorption of chromate (CrO) and phosphate (PO) on HT was conducted at various pH and temperatures. Related adsorption mechanisms were determined via the isotherm, kinetic, and competitive adsorption studies as well as the Cr K-edge X-ray absorption fine-structure (XAFS) spectroscopy. The maximum adsorption capacities for CrO and PO on HT were 0.16 and 0.23 mmol g. Regarding adsorption kinetics, CrO and PO adsorption on HT could be well described by the second order model, and the rate coefficient of CrO and PO on HT decreased significantly with the increasing pH from 5 to 9. The adsorption kinetics for CrO and PO were divided into fast and slow stages with the boundary at 15 min. This biphasic adsorption behavior might be partially attributed to multiple reactive pathways including anion exchange and surface complexation. Fitting results of Cr K-edge EXAFS analysis showed a direct bonding between CrO and Al on HT surfaces. Such a surface complexation appeared to be the rate-limiting step for CrO adsorption on HT. By contrast, the diffusion through the hydrated interlayer space of HT was the major rate-limiting step for PO. This study determined the adsorption behaviors of CrO and PO on HT, including the initial transfer process and the subsequent adsorption mechanisms. Such information could improve the strategy to use HT as the potential adsorbent for the remediation of anionic pollutants.
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http://dx.doi.org/10.1016/j.envpol.2019.01.012DOI Listing
April 2019

Phosphate Removal in Relation to Structural Development of Humic Acid-Iron Coprecipitates.

Sci Rep 2018 07 9;8(1):10363. Epub 2018 Jul 9.

Department of Soil and Environmental Sciences, National Chung Hsing University, 145 Xingda Rd., Taichung, 40227, Taiwan.

Precipitation of Fe-hydroxide (FH) critically influences the sequestration of PO and organic matter (OM). While coatings of pre-sorbed OM block FH surfaces and decrease the PO adsorption capacity, little is known about how OM/Fe coprecipitation influences the PO adsorption. We aimed to determine the PO adsorption behaviors on humic acid (HA)-Fe coprecipitates in relation to surface and structural characteristics as affected by HA types and C/(C + Fe) ratios using the Fe and P X-ray absorption spectroscopy. With increasing C/(C + Fe) ratios, the indiscernible changes in the proportion of near-surface C for coprecipitates containing HA enriched in polar functional groups implied a relatively homogeneous distribution between C and Fe domains. Wherein PO adsorbed on FH dominated the P inventory on coprecipitates, yielding PO sorption properties nearly equivalent to that of pure FH. Structural disruptions of FH caused by highly associations with polar functional groups of HA enhanced the C solubilisation. While polar functional groups were limited, coprecipitates consisted of core FH with surface outgrowth of HA. Although surface-attached HA that was vulnerable to solubilisation provided alternatively sites for PO via ternary complex formation with Fe bridges, it also blocked FH surfaces, leading to a decrease in PO adsorption.
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http://dx.doi.org/10.1038/s41598-018-28568-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6037709PMC
July 2018

Adsorption of tetracycline on Fe (hydr)oxides: effects of pH and metal cation (Cu, Zn and Al) addition in various molar ratios.

R Soc Open Sci 2018 Mar 28;5(3):171941. Epub 2018 Mar 28.

Division of Environmental Studies, Graduate School of Frontier Sciences, University of Tokyo, 332 Building of Environmental Studies, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8563, Japan.

Iron (Fe) (hydr)oxides control the mobility and bioavailability of tetracycline (TC) in waters and soils. Adsorption of TC on Fe (hydr)oxides is greatly affected by polyvalent metals; however, impacts of molar metal/TC ratios on TC adsorptive behaviours on Fe (hydr)oxides remain unclear. Results showed that maximum TC adsorption on ferrihydrite and goethite occurred at pH 5-6. Such TC adsorption was generally promoted by the addition of Cu, Zn and Al. The greatest increase in TC adsorption was found in the system with molar Cu/TC ratio of 3 due to the formation of Fe hydr(oxide)-Cu-TC ternary complexes. Functional groups on TC that were responsible for the complexation with Cushifted from phenolic diketone groups at Cu/TC molar ratio < 1 to amide groups at Cu/TC molar ratio ≥ 1. For the addition of Al, the complexation only took place with phenolic diketone groups, resulting in the enhanced TC adsorption at a molar Al/TC ratio of 1. However, TC adsorption decreased for Al/TC molar ratio > 1 as excess Al led to the competitive adsorption with Al/TC complexes. For the Zn addition, no significant correlation was found between TC adsorption capacity and molar Zn/TC ratios.
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http://dx.doi.org/10.1098/rsos.171941DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5882719PMC
March 2018

Capacity and recycling of polyoxometalate applied in As(III) oxidation by Fe(II)-Amended zero-valent aluminum.

Chemosphere 2018 Jun 12;200:1-7. Epub 2018 Feb 12.

Division of Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, 332 Building of Environmental Studies, 5-1-5 Kashiwanoha, Kashiwa City, Chiba 277-8563, Japan.

Arsenic remediation is often initiated by oxidizing As(III) to As(V) to alleviate its toxicity and mobility. Due to the easy availability, zero-valent Al (ZVAl) like Al can was considered as potential alternatives to facilitate As(III) oxidation. This study determined the capability and recycling of polyoxometalate (POM) to catalyze As(III) oxidation in Fe(II)-amended ZVAl systems. POM acquired electrons from ZVAl more effectively at pH 1 than at pH 2. While 76% of the reduced POM [POM(e)] reacted with O to generate HO at pH 1, only 60% of POM(e) was used to produce HO at pH 2. The remaining POM(e) was oxidized by the generated HO. Such additional consumption of POM(e) and HO led to the incomplete As(III) oxidation in the system without residual ZVAl and emphasized the need for a continuous electron supply from ZVAl to compensate the depletion of POM(e). After the hydrolyzation at pH 6.0, the XANES data evidenced that not only As(V) but WO released from the POM retained on surfaces of Al/Fe hydroxides. The competition for sorption sites on Al/Fe hydroxides between As(V) and WO led to the incomplete As removal. Despite the loss of WO, the POM re-polymerized at pH 1 still showed the comparable capability to catalyze As(III) oxidation with original POM. This study revealed electron transfer pathways from ZVAl to As(III) as catalyzed by POM and evidenced the effective POM recycling after As removal, which lowers the cost of POM application and turns the ZVAl/Fe(II)/POM/O system into a practical strategy for As remediation.
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http://dx.doi.org/10.1016/j.chemosphere.2018.02.071DOI Listing
June 2018

Stabilization of Natural Organic Matter by Short-Range-Order Iron Hydroxides.

Environ Sci Technol 2016 12 16;50(23):12612-12620. Epub 2016 Nov 16.

Division of Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo , 332 Building of Environmental Studies, 5-1-5 Kashiwanoha, Kashiwa City, Chiba 277-8563, Japan.

Dissolved organic matter (DOM) is capable of modifying the surfaces of soil minerals (e.g., Fe hydroxides) or even forming stable co-precipitates with Fe(III) in a neutral environment. The DOM/Fe co-precipitation may alter biogeochemical carbon cycling in soils if the relatively mobile DOM is sorbed by soil minerals against leaching, runoff, and biodegradation. In this study, we aimed to determine the structural development of DOM/Fe co-precipitates in relation to changes in pH and C/(C + Fe) ratios using XRD, XPS, Fe K-edge XAS, FTIR, and C-NEXAFS techniques. The results showed that in the system with bulk C/(C + Fe) molar ratios ≤0.65, the ferrihydrite-like Fe domains were precipitated as the core and covered by the C shells. When the C/(C + Fe) molar ratio ranged between 0.71 and 0.89, the emerging Fe-C bonding suggested a more substantial association between Fe domains including edge- and corner-sharing FeO octahedra and DOM. With C/(C + Fe) bulk molar ratios ≥0.92, only corner-sharing FeO octahedra along with Fe-C bonding were found. The homogeneously distributed C and Fe domains caused the enhancement of Fe and C solubilization from co-precipitates. The C/(C + Fe) ratios dominated structural compositions and stabilities of C/Fe co-precipitates and may directly affect the Fe and C cycles in soils.
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http://dx.doi.org/10.1021/acs.est.6b02793DOI Listing
December 2016

Accumulation of heavy metals and trace elements in fluvial sediments received effluents from traditional and semiconductor industries.

Sci Rep 2016 Sep 29;6:34250. Epub 2016 Sep 29.

Department of Soil and Environmental Sciences, National Chung-Hsing University, 145 Xingda Rd., Taichung 402, Taiwan (R.O.C.).

Metal accumulation in sediments threatens adjacent ecosystems due to the potential of metal mobilization and the subsequent uptake into food webs. Here, contents of heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) and trace elements (Ga, In, Mo, and Se) were determined for river waters and bed sediments that received sewage discharged from traditional and semiconductor industries. We used principal component analysis (PCA) to determine the metal distribution in relation to environmental factors such as pH, EC, and organic matter (OM) contents in the river basin. While water PCA categorized discharged metals into three groups that implied potential origins of contamination, sediment PCA only indicated a correlation between metal accumulation and OM contents. Such discrepancy in metal distribution between river water and bed sediment highlighted the significance of physical-chemical properties of sediment, especially OM, in metal retention. Moreover, we used Se XANES as an example to test the species transformation during metal transportation from effluent outlets to bed sediments and found a portion of Se inventory shifted from less soluble elemental Se to the high soluble and toxic selenite and selenate. The consideration of environmental factors is required to develop pollution managements and assess environmental risks for bed sediments.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5041097PMC
http://dx.doi.org/10.1038/srep34250DOI Listing
September 2016

MS title: Catalytic oxidation and removal of arsenite in the presence of Fe ions and zero-valent Al metals.

J Hazard Mater 2016 Nov 24;317:237-245. Epub 2016 May 24.

Department of Soil and Environmental Sciences, National Chung Hsing University, Taichung, Taiwan. Electronic address:

Arsenic immobilization in acid mine drainage (AMD) is required prior to its discharge to safeguard aquatic organisms. Zero-valent aluminum (ZVAl) such as aluminum beverage cans (AlBC) was used to induce the oxidation of As(III) to As(V) and enhance the subsequent As removal from an artificially prepared AMD. While indiscernible As(III) oxidation was found in aerated ZVAl systems, the addition of 0.10-0.55mM Fe(II) or Fe(III) into the AMD significantly promoted the As(V) production. Reactions between Fe(II) and H2O2, which was produced through an oxidative reaction of ZVAl with dissolved oxygen, generated OH radicals. Such OH radicals subsequently induced the As(III) oxidation. Over the course of the Fenton like reaction, ZVAl not only directly generated the H2O2, but indirectly enhanced the OH radical production by replenishing Fe(II). Arsenite oxidation in the aerated ZVAl/Fe and AlBC/Fe systems followed zero- and first-order kinetics. Differences in the kinetic reactions of ZVAl and AlBC with respect to As(III) oxidation were attributed to higher productive efficiency of the oxidant in the AlBC systems. After the completion of As(III) oxidation, As(V) could be removed simultaneously with Al(III) and Fe(III) by increasing solution's pH to 6 to produce Al/Fe hydroxides as As(V) scavengers or to form Al/Fe/As co-precipitates.
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http://dx.doi.org/10.1016/j.jhazmat.2016.05.071DOI Listing
November 2016

Molecular Structures of Al/Si and Fe/Si Coprecipitates and the Implication for Selenite Removal.

Sci Rep 2016 Apr 20;6:24716. Epub 2016 Apr 20.

Division of Environmental Studies, Graduate School of Frontier Sciences, The University of Tokyo, 332 Building of Environmental Studies, 5-1-5 Kashiwanoha, Kashiwa City, Chiba 277-8563, Japan.

Aluminum and iron oxides have been often used in the coagulation processes during water purification due to their unique surface properties toward anions. In the presence of silica, the coprecipitation of Al/Si or Fe/Si might decrease the efficiency of wastewater purification and reuse. In this study, surface properties and molecular structures of Al/Si and Fe/Si coprecipitates were characterized using spectroscopic techniques. Also, the selenite removal efficiency of Al/Si and Fe/Si coprecipitates in relation to their surface and structural properties was investigated. While dissolved silicate increased with increasing pH from Fe/Si coprecipitates, less than 7% of silicate was discernible from Al/Si samples over the range from acidic to alkaline conditions. Our spectroscopic results showed that the associations between Al and Si were relatively stronger than that between Fe and Si in coprecipitates. In Al/Si coprecipitates, core-shell structures were developed with AlO6/AlO4 domains as the shells and Si frameworks polymerized from the SiO2 as the cores. However, Si framework remained relatively unchanged upon coprecipitation with Fe hydroxides in Fe/Si samples. The Si core with Al shell structure of Al/Si coprecipitates shielded the negative charges from SiO2 and thereby resulted in a higher adsorption capacity of selenite than Fe/Si coprecipitates.
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http://dx.doi.org/10.1038/srep24716DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4837376PMC
April 2016

Comparison of the spectroscopic speciation and chemical fractionation of chromium in contaminated paddy soils.

J Hazard Mater 2015 Oct 24;296:230-238. Epub 2015 Mar 24.

Department of Soil and Environmental Sciences, National Chung Hsing University, 250 Kuo Kuang Rd., Taichung 40227, Taiwan, ROC. Electronic address:

Sequential extraction has been widely used to classify metal species in soils and sediments; however, the lack of selectivity in extraction reagents may lead to the misinterpretation of metal speciation. In this study, we used X-ray absorption near edge structure (XANES) spectroscopy to classify Cr species based on its molecular form. These results complement the conventional Cr fractionation derived from the Tessier extraction method. The linear combination fitting (LCF) for the Cr-XANES spectra indicated that the Cr species in the soils could generally be described as Cr(III) sorbed on ferrihydrite (Cr-FH), Cr(III) complexed with humic acid (Cr-HA), and precipitated Cr. While the sum of the adsorbed Cr(III) and Cr(III)/Fe coprecipitates showed a nearly 1:1 relationship with reducible Cr, the total of Cr precipitates and organic Cr also followed the same trend with oxidizable Cr. This result indicated that there might be a underestimation in the reducible fraction as pure Cr(III) precipitates associated with surfaces of Fe minerals would not be extracted in the reducible process. Instead, such pure Cr(III) precipitates were dissolved during the oxidizable process, resulting in a overestimation in the fractionation of organic-related Cr.
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http://dx.doi.org/10.1016/j.jhazmat.2015.03.044DOI Listing
October 2015

Degradation of antibiotic amoxicillin using 1 x 1 molecular sieve-structured manganese oxide.

Environ Technol 2013 Jul-Aug;34(13-16):2443-51

Department of Soil & Environmental Sciences, National Chung Hsing University, Taichung, Republic of China.

The kinetics and mechanism ofamoxicillin (AMO) degradation using a 1 x 1 molecular sieve-structured manganese oxide (MnO2) was studied. The presence of the buffer solution (i.e., NaHCO3, NaH2PO4 and KH2PO4) diminished AMO binding to MnO2, thus reducing AMO degradation in the pretest; therefore, all other experiments in this study were conducted without the addition of a buffer. Third-order rate constants, second-order on AMO and first-order on MnO2 increased with elevating pH level (2.81-7.23) from 0.54 to 9.17 M(-2) s(-1), and it decreased to 4.27 M(-2) s(-1) at pH 8.53 beyond the pk(a2) of AMO (7.3). The dissolution of the MnO2 suspension with and without AMO exhibited a similar trend; that is, Mn2+ concentration increased with decreasing pH. However, the dissolution of MnO2 with AMO was greater than that without AMO, except for the reaction occurring at pH 8.53, partially indicating that MnO2 acts as an oxidant in AMO degradation. The preliminary chromatogram data display different products with varying pH reaction s, implying that AMO elimination using this 1 x 1 molecular sieve-structured MnO2 is by adsorption as well as oxidative degradation. A complementary experiment indicates that the amount of oxidatively degraded AMO increases substantially from 65.5% at 4 h to 95% at 48 h, whereas the AMO adsorbed onto MnO2 decreases slightly from 4.5% at4 h to 2.4% at 48 h. The oxidative degradation accounted for more AMO removal than adsorption over the whole reaction course, indicating that the oxidative reaction of AMO on MnO2 dominated the AMO removal.
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http://dx.doi.org/10.1080/09593330.2013.772658DOI Listing
January 2014

Catalytic and atmospheric effects on microwave pyrolysis of corn stover.

Bioresour Technol 2013 Mar 4;131:274-80. Epub 2013 Jan 4.

Graduate Institute of Environmental Engineering, National Taiwan University, 71 Chou-Shan Rd., Taipei 106, Taiwan, ROC.

Corn stover, which is one of the most abundant agricultural residues around the world, could be converted into valuable biofuels and bio based products by means of microwave pyrolysis. After the reaction at the microwave power level of 500W for the processing time of 30min, the reaction performance under N2 atmosphere was generally better than under CO2 atmosphere. This may be due to the better heat absorbability of CO2 molecules to reduce the heat for stover pyrolysis. Most of the metal-oxide catalysts effectively increased the maximum temperature and mass reduction ratio but lowered the calorific values of solid residues. The gas most produced was CO under N2 atmosphere but CO2 under CO2 atmosphere. Catalyst addition lowered the formation of PAHs and thus made liquid products less toxic. More liquid products and less gas products were generated when using the catalysts possibly due to the existence of the Fischer-Tropsch synthesis.
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http://dx.doi.org/10.1016/j.biortech.2012.12.177DOI Listing
March 2013

Removal of hexavalent Cr by coconut coir and derived chars--the effect of surface functionality.

Bioresour Technol 2012 Jan 10;104:165-72. Epub 2011 Nov 10.

Department of Soil and Environmental Sciences, National Chung Hsing University, Taichung 40227, Taiwan, ROC.

The Cr(VI) removal by coconut coir (CC) and chars obtained at various pyrolysis temperatures were evaluated. Increasing the pyrolysis temperature resulted in an increased surface area of the chars, while the corresponding content of oxygen-containing functional groups of the chars decreased. The Cr(VI) removal by CC and CC-derived chars was primarily attributed to the reduction of Cr(VI) to Cr(III) by the materials and the extent and rate of the Cr(VI) reduction were determined by the oxygen-containing functional groups in the materials. The contribution of pure Cr(VI) adsorption to the overall Cr(VI) removal became relatively significant for the chars obtained at higher temperatures. Accordingly, to develop a cost-effective method for removing Cr(VI) from water, the original CC is more advantageous than the carbonaceous counterparts because no pyrolysis is required for the application and CC has a higher content of functional groups for reducing Cr(VI) to less toxic Cr(III).
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http://dx.doi.org/10.1016/j.biortech.2011.10.096DOI Listing
January 2012

Biosorption of Cr(VI) by coconut coir: spectroscopic investigation on the reaction mechanism of Cr(VI) with lignocellulosic material.

J Hazard Mater 2010 Jul 26;179(1-3):160-5. Epub 2010 Feb 26.

Department of Soil and Environmental Sciences, National Chung Hsing University, 250 Kuo Kuang Road, Taichung 40227, Taiwan.

In this study, the removal mechanism of Cr(VI) from water by coconut coir (CC) was investigated using X-ray photoelectron spectroscopy (XPS), Cr K-edge X-ray absorption near edge structure (XANES) and FTIR spectroscopy. The results showed that, upon reaction with CC at pH 3, Cr(VI) was reduced to Cr(III), which was either bound to CC or released back into solution. As revealed by the FTIR spectra of CC before and after reacting with Cr(VI), the phenolic methoxyl and hydroxyl groups of lignin in CC are the dominant drivers of Cr(VI) reduction, giving rise to carbonyl and carboxyl groups on CC. These functional groups can subsequently provide binding sites for Cr(III) resulting from Cr(VI) reduction. In conjunction with forming complexes with carbonyl and carboxyl groups, the formation of Cr(III) hydroxide precipitate could also readily occur as revealed by the linear combination fitting of the Cr K-edge XANES spectrum using a set of reference compounds. The phenolic groups in lignin are responsible for initiating Cr(VI) reduction, so lignocellulosic materials containing a higher amount of phenolic groups are expected to be more effective scavengers for removal of Cr(VI) from the environment.
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http://dx.doi.org/10.1016/j.jhazmat.2010.02.073DOI Listing
July 2010

Enhanced chlorophenol sorption of soils by rice-straw-ash amendment.

J Hazard Mater 2010 May 28;177(1-3):692-6. Epub 2009 Dec 28.

Agricultural Research Institute, Wufeng, Taichung 41301, Taiwan.

Rice-straw burning is a common post-harvest practice on rice paddy land, which results in the accumulation of rice-straw ash (RSA) in paddy soil. Because the occurrence of RSA in soil may affect the fate and transport of contaminants, this study investigated the sorption of 3-chlorophenol (3-CP) on RSA and RSA amended soils to evaluate the sorptive properties of RSA in soils. The results showed that the sorption of 3-CP to RSA proceeds through a surface reaction rather than through partitioning and that the neutral form of 3-CP is preferentially sorbed to the surface when compared to the deprotonated anionic form of 3-CP. The addition of RSA to the soils enhanced the overall 3-CP sorption, indicating that RSA amendment may be applied to retard the movement of 3-CP in contaminated soils. As the RSA content in the soils was increased from 0% to 2%, the Langmuir sorption maximum of the soils increased from 18-80 to 256-274 mg kg(-1). Thus, RSA contributed more to the total sorption of the soils than other major components in the soils. Nonetheless, the 3-CP sorption of the soils containing RSA was less than the combination of pure RSA and the soils, thereby indicating that the 3-CP sorption of RSA was suppressed. This may be attributed to the competition of organic matter or other soil components for the surface binding sites of RSA.
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http://dx.doi.org/10.1016/j.jhazmat.2009.12.086DOI Listing
May 2010

Removal of hexavalent chromium from acidic aqueous solutions using rice straw-derived carbon.

J Hazard Mater 2009 Nov 27;171(1-3):1066-70. Epub 2009 Jun 27.

Department of Soil and Environmental Sciences, National Chung Hsing University, Taichung 40227, Taiwan.

This study evaluates the removal of Cr(VI) from water by carbon derived from the burning of rice straw. Rice straw was burned in the air to obtain rice carbon (RC), and then the removal of Cr(VI) by RC was investigated under various pHs and ionic strengths. After the experiments, the oxidation state of Cr bound to RC was analyzed using X-ray photoelectron spectroscopy, which revealed that Cr bound to RC was predominately in the trivalent form. The results showed that upon reacting with RC, Cr(VI) was reduced to Cr(III), which was either adsorbed on RC or released back into solution. The extent and rate of Cr(VI) removal increased with decreasing solution pH because the Cr(VI) adsorption and the subsequent reduction of adsorbed Cr(VI) to Cr(III) both occur preferentially at low pH. The minimal effect of ionic strength on the rates of Cr(VI) removal and Cr(III) adsorption indicated specific interactions between Cr(VI)/Cr(III) and their surface binding sites on RC. These results suggest that rice straw-based carbon may be effectively used at low pH as a substitute for activated carbon for the treatment of Cr(VI) contaminated water.
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http://dx.doi.org/10.1016/j.jhazmat.2009.06.112DOI Listing
November 2009

A mechanism study of light-induced Cr(VI) reduction in an acidic solution.

J Hazard Mater 2009 May 9;164(1):223-8. Epub 2008 Aug 9.

Department of Soil & Environmental Sciences, National Chung Hsing University, 250 Kuo-Kuang Road, Taichung 40227, Taiwan, ROC.

The mechanisms of photo-catalytic reduction of Cr(VI) were investigated in acidic solutions with and without Fe(III). In a system without Fe(III), no Cr(VI) reduction was observed in dark conditions; conversely, under light conditions, the reduction reaction rate increased to 0.011 and 0.020microM min(-1) at pH 2 and pH 1, respectively, indicating the occurrence of Cr(VI) photo-reduction. The Cr(VI) photo-reduction reaction was induced by the photolysis of water molecules, leading to O(2) production. Upon the addition of Fe(III), the photo-reduction rate of Cr(VI) was significantly enhanced due to the formation of Fe(II), which is the photolytic product of FeCl(2)(+) and the electron donor for Cr(VI) reduction. However, with the same concentration of FeCl complexes, a strong inhibition of Cr(VI) reduction at pH 2 was observed, compared with pH 1. A possible explanation is that FeOH(2+) becomes predominant with increasing pH and that its photolytic product, the OH free radical, is an oxidant for Fe(II) and Cr(III) and can compromise Cr(VI) reduction. The kinetic result of each photo-reduction reaction pathway shows zero-order kinetics, suggesting that the photolysis reaction of H(2)O or FeCl(2+) is the rate-determining step in each pathway. The results also show the potential of developing a homogeneous photo-catalytic method to treat Cr(VI)-containing water.
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http://dx.doi.org/10.1016/j.jhazmat.2008.07.145DOI Listing
May 2009

Influence of inorganic anion on Cr(VI) photo-reduction in the presence of ferric ion.

J Hazard Mater 2008 Aug 23;156(1-3):374-80. Epub 2007 Dec 23.

Department of Soil & Environmental Sciences, National Chung Hsing University, Taichung, Taiwan, ROC.

Photo-reduction of Cr(VI) in a solution with single or multi-inorganic anions was evaluated. The results show that 38.5 microM Cr(VI) is photo-reduced in the presence of NO(3)(-) at pH 1. The photolysis of NO(3)(-), producing NO(2)(-) or H(2)O(2), may contribute to Cr(VI) reduction. The addition of 0.001-0.1 M chlorite to NO(3)(-) enhanced Cr(VI) photo-reduction when 35.8 microM Fe(III) was present. This enhancement was the combinative result of photolysis of NO(3)(-) and Fe-Cl complexes, leading to the formation of NO(2)(-) and Fe(II), respectively, for Cr(VI) reduction. On the contrary, a significant decrease in Cr(VI) photo-reduction was observed with the addition of PO(4)(3-) and SO(4)(2-). This decrease was due to their strong competition with Fe(III) from Cl(-), resulting in a marked decrease in the concentrations of Fe-Cl complexes. The results suggest that a direct irradiation of acidic wastewaters containing Cl(-), NO(3)(-), and Fe(III) is a feasible strategy for eliminating Cr(VI).
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http://dx.doi.org/10.1016/j.jhazmat.2007.12.028DOI Listing
August 2008

Photocatalytic reduction of Cr(VI) in the presence of NO3- and Cl- electrolytes as influenced by Fe(III).

Environ Sci Technol 2007 Nov;41(22):7907-14

Department of Soil & Environmental Sciences, National Chung Hsing University, Taichung, Taiwan 40227.

Photoreduction of Cr(VI) involving Fe is strongly affected by the presence of organic or inorganic compounds in an acidic environment. In this study, we have found a new pathway of Cr(VI) photoreduction in the presence of Fe-(III) that is influenced by two inorganic electrolytes (i.e., NO3- and Cl-) and the pH. In NO3- and Cl- systems without Fe(III), Cr(VI) photoreduction could occur and was independent of the Cr(VI) concentration. The zero-order rate constant of the photoreduction reaction increased when the solution pH was decreased from 2 to 1; the reaction rate was higher in the NO3- system than in the Cl- system. The higher reaction rate in the NO3- system was attributed to the photolysis of NO3-, which resulted in the formation of NO2- for reduction of Cr(VI). Conversely, the effect of Fe-(III) addition on the increase in Cr(VI) photoreduction rate in the Cl- system was more significant than that in the NO3- system. The addition of Fe(III) to the Cl- system caused the formation of [Fe(OH2)5Cl]2+, the photolysis of which subsequently resulted in the formation of Fe(II) for reduction of the Cr(VI). This study suggests that the photolysis of NO3- and Fe-Cl complex may contribute significantly to Cr(VI) reduction in surface water that receives electroplating wastewater containing high levels of NO3-, Cl-, and Fe-(III). Therefore, under the acidic conditions that are favorable for Fe-Cl complex formation or in the presence of NO3-, the effects of inorganic components on Cr(VI) photoreduction cannot be ignored for the precise evaluation of the transformation of Cr in the environment.
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http://dx.doi.org/10.1021/es0718164DOI Listing
November 2007

Influences of preparative methods of humic acids on the sorption of 2,4,6-trichlorophenol.

Chemosphere 2008 Jan 4;70(7):1218-27. Epub 2007 Oct 4.

Department of Soil and Environmental Sciences, National Chung Hsing University, Taichung 40227, Taiwan.

Humic acids (HAs) are a major component of soil organic matter which strongly affects the sorption behavior of organic contaminants in soils. To assess the sorption-desorption characteristics of organic compounds on HAs, the organic adsorbent is usually isolated using an acid-base extraction method followed by air-drying or freeze-drying. In this study, a peat soil from the Yangming mountain area of Taiwan was sampled and repeatedly extracted followed by either air-drying or a non-drying treatment (denoted DHAs and NDHAs, respectively). The sorption of 2,4,6-TCP on HAs was evaluated using the batch method. Kinetic sorption results indicated that DHAs exhibited a two-step first-order sorption behavior, involving a rapid sorption followed by a slow sorption. The slow sorption may be attributed to the diffusion of 2,4,6-TCP through the condensed aromatic domains of HAs. On the contrary, the sorption of 2,4,6-TCP on NDHAs was extremely rapid, and the sorption data did not fit existing kinetic models. Each HA sample exhibited a nonlinear sorption isotherm. Sorption nonlinearity (represented by Freundlich N values) and K(oc) had a positive relationship with aliphaticity for DHAs; however, nonlinearity and K(oc) correlated positively with aromaticity when NDHAs adsorbents were used. We conclude that the air-drying technique may artificially create a more condensed area, which strongly affects the sorption characteristics of HAs. Thus, an incorrect evaluation of the sorption capacity and its relationship with the chemical composition of HAs would arise following use of the air-drying method.
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http://dx.doi.org/10.1016/j.chemosphere.2007.08.052DOI Listing
January 2008

Removal of 2,4,6-trichlorophenol from a solution by humic acids repeatedly extracted from a peat soil.

J Hazard Mater 2008 Apr 20;152(2):812-9. Epub 2007 Jul 20.

Department of Soil & Environmental Sciences, National Chung Hsing University, Taichung 40227, Taiwan.

Humic acid (HA) is one of the major components of soil organic matter. It strongly affects the sorption behavior of organic and inorganic contaminants in soils. To obtain a better understanding of the interactions of contaminants with HA, a repeated extraction technique has been applied to a peat soil to obtain HA fractions with varying aliphaticity and aromaticity, which were subsequently correlated to the sorption properties of 2,4,6-trichlorophenol (TCP). HA fractions were extracted repeatedly using an alkaline solution and each HA fraction was separated into two portions with an air-drying or re-suspending (denoted as RSHAs) process. Solid-state (13)C NMR and elemental analysis demonstrated that the aromaticity and polarity of HAs decreased with extractions. Kinetic results indicated that air-dried HAs exhibited two-step first order sorption behavior with a rapid stage followed by a slower stage. The slower sorption is attributed to the diffusion of 2,4,6-TCP in the condensed aromatic domains of HAs. Conversely, sorption of 2,4,6-TCP on RSHAs was extremely rapid and could not be fitted with any kinetic model. For air-dried HAs the sorption capacity (K(oc)) was weakly correlated with the chemical compositions of HAs. However, a positive trend between K(oc) and aromaticity was observed for RSHAs. Compared with the results of air-dried HAs with their counterparts of RSHAs, it is therefore concluded that air-drying may alter the structure of HAs through artificially creating a more condensed domain in HAs. The structural alternation may result in an incorrect interpretation of the relationship between sorption capacity and chemical composition of HAs and a misjudgment of the transport behavior of 2,4,6-TCP in soils and sediments.
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http://dx.doi.org/10.1016/j.jhazmat.2007.07.047DOI Listing
April 2008

Removal of 3-chlorophenol from water using rice-straw-based carbon.

J Hazard Mater 2007 Aug 12;147(1-2):313-8. Epub 2007 Jan 12.

Department of Soil and Environmental Sciences and Center of Nanoscience and Nanotechnology, National Chung Hsing University, Taichung 40227, Taiwan.

The removal of 3-chlorophenol (CP) from water by carbon derived from burning of rice straw was evaluated in this study. Rice straw was burned at 300 degrees C in the air to obtain rice carbon (RC). Scanning electron micrographs showed a highly porous structure of RC. NMR and FTIR spectroscopy suggested an enhanced aromaticity of RC and the presence of oxygen-containing functional groups. Adsorption of CP by RC was characterized by L-shaped nonlinear isotherms, suggesting surface adsorption rather than partitioning. The adsorption occurred most strongly when CP existed as a neutral species. The adsorption decreased with increasing pH due to increased deprotonation of surface functional groups of RC and dissociation of CP. The adsorption capacity determined by data-fitting to the Langmuir model was 14.2, 12.9, 11.4 and 4.9 mg g(-1) at pH 4, 6, 8 and 10, respectively. These results suggest that rice-straw-based carbon may be effectively used as a low-cost substitute for activated carbon for removal of chlorophenols from water.
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http://dx.doi.org/10.1016/j.jhazmat.2007.01.031DOI Listing
August 2007

Phosphate removal from water using lithium intercalated gibbsite.

J Hazard Mater 2007 Aug 4;147(1-2):205-12. Epub 2007 Jan 4.

Department of Soil and Environmental Sciences, National Chung Hsing University, Taichung, Taiwan.

In this study, lithium intercalated gibbsite (LIG) was investigated for its effectiveness at removing phosphate from water and the mechanisms involved. LIG was prepared through intercalating LiCl into gibbsite giving a structure of [LiAl2(OH)6]+ layers with interlayer Cl- and water. The results of batch adsorption experiments showed that the adsorption isotherms at various pHs exhibited an L-shape and could be fitted well using the Langmuir model. The Langmuir adsorption maximum was determined to be 3.0 mmol g(-1) at pH 4.5 and decreased with increasing pH. The adsorption of phosphate was mainly through the displacement of the interlayer Cl- ions in LIG. In conjunction with the anion exchange reaction, the formation of surface complexes or precipitates could also readily occur at lower pH. The adsorption decreased with increasing pH due to decreased H(2)PO(4)(-)/HPO4(2-) molar ratio in solution and positive charges on the edge faces of LIG. Anion exchange is a fast reaction and can be completed within minutes; on the contrary, surface complexation is a slow process and requires days to reach equilibrium. At lower pH, the amount of adsorbed phosphate decreased significantly as the ionic strength was increased from 0.01 to 0.1M. The adsorption at higher pH showed high selectivity toward divalent HPO4(2-) ions with an increase in ionic strength having no considerable effect on the phosphate adsorption. These results suggest that LIG may be an effective scavenger for removal of phosphate from water.
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http://dx.doi.org/10.1016/j.jhazmat.2006.12.067DOI Listing
August 2007