Publications by authors named "Eunsung Kan"

26 Publications

  • Page 1 of 1

Removal of Fluoride from Water Using a Calcium-Modified Dairy Manure-Derived Biochar.

J Environ Eng (New York) 2020 Dec;146(12):1-10

Dept. of Civil and Environmental Engineering, Southern Methodist Univ., Dallas, TX 75275.

This study investigated the removal of fluoride from water using a calcium-modified dairy manure-derived biochar (Ca-DM500). The Ca-DM500 showed a 3.82 - 8.86 times higher removal of fluoride from water than the original (uncoated) manure-derived biochar (DM500). This is primarily attributed to strong precipitation/complexation between fluoride and calcium. The Freundlich and Redlich-Peterson sorption isotherm models better described the experimental data than the Langmuir model. Additionally, the removal kinetics were well described by the intraparticle diffusion model. The Ca-DM500 showed high reactivity per unit surface area [0.0001, 0.03, 0.16 mg F per m for Douglas fir-derived biochar (DF-BC), DM500. and Ca-DM500, respectively] for retention of fluoride reflecting the importance of surface complexation. The copresence of anions reduced removal by Ca-DM500 in the order . The sorption behavior of fluoride in a continuous fixed-bed column was consistent with the Thomas model. Column studies demonstrated that the Ca-DM500 shows a strong affinity for fluoride, a low release potential, and a stable (unreduced) removal capacity through regeneration and reuse cycles.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1061/(asce)ee.1943-7870.0001812DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7970507PMC
December 2020

Adsorption and regeneration on iron-activated biochar for removal of microcystin-LR.

Chemosphere 2021 Jun 13;273:129649. Epub 2021 Jan 13.

Department of Biological and Agricultural Engineering & Texas A&M AgriLife Research Center, Texas A&M University, TX, 77843, USA; Department of Wildlife, Sustainability, and Ecosystem Sciences, Tarleton State University, TX, 76401, USA. Electronic address:

Novel iron activated biochars (FA-BCs) were prepared via simultaneous pyrolysis and activation of FeCl-pretreated bermudagrass (BG) for removing microcystin-LR (MC-LR) in aqueous solution. Compared to the raw BC (without activation), the surface area and adsorption capacity of FA-BC at iron impregnation ratio of 2 (2 g FeCl/g BG) were enhanced from 86 m/g and 0.76 mg/g to 835 m/g and 9.00 mg/g. Moreover, FA-BC possessed various iron oxides at its surface which provided the catalytic capacity for regeneration of MC-LR spent FA-BC and magnetic separation after the MC-LR adsorption. Possible mechanisms for the MC-LR adsorption onto FA-BC would include electrostatic attraction, π-π, hydrogen bond, and hydrophobic interactions. The detailed adsorption studies indicated mainly chemisorption and intra-particle diffusion limitation would participate in the adsorption process. The thermal regeneration at 300 °C kept high regeneration efficiency (99-100%) for the MC-LR spent FA-BC during four cycles of adsorption-regeneration. In addition, the high regeneration efficiency (close to 100%) was also achieved by persulfate oxidation-driven regeneration. FA-BC also exhibited high adsorption capacity for the MC-LR from the real lake water to meet the MC-LR concentration below 1 μg/L as a safe guideline suggested by WHO.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.chemosphere.2021.129649DOI Listing
June 2021

Iron-activated bermudagrass-derived biochar for adsorption of aqueous sulfamethoxazole: Effects of iron impregnation ratio on biochar properties, adsorption, and regeneration.

Sci Total Environ 2021 Jan 13;750:141691. Epub 2020 Aug 13.

Department of Biological and Agricultural Engineering & Texas A&M AgriLife Research Center(,) Texas A&M University, TX 77843, USA; Department of Wildlife, Sustainability, and Ecosystem Sciences, Tarleton State University, TX 76401, USA. Electronic address:

This work focused on the impacts of FeCl impregnation ratio on the properties of FeCl-activated bermudagrass (BG)-derived biochars (IA-BCs), adsorption of sulfamethoxazole (SMX) onto IA-BCs and regeneration of SMX-spent IA-BC. Compared with the control BC (85.82 m/g), IA-BCs made via pyrolysis with FeCl to BG mass ratio between 1 and 3 (1-3 g FeCl/g BG) resulted in significantly enhancing surface area (1014-1035 m/g), hydrophobicity, Fe content in IA-BCs (3.87-7.27%), and graphitized carbon. The properties of IA-BCs supported magnetic separation and higher adsorption (32-265 mg SMX/g BC) than the control BC (6-14 mg SMX/g BC) at various pH. Adsorption experiments indicated various adsorption mechanisms between SMX and IA-BCs via π-π EDA, hydrophobic interactions, and hydrogen bond with intraparticle diffusion limitation. The adsorption was also found to be spontaneous and exothermic. The IA-BC made at FeCl to BG mass ratio of 2 (IA-BC) showed the maximum adsorption capacity for SMX (253 mg SMX/g BC) calculated from Langmuir isotherm model. Additionally, both NaOH desorption and thermal oxidation showed effective regeneration of SMX-saturated IA-BC over multiple cycles. After three cycles of adsorption-regeneration, 64% and 62% of regeneration efficiencies were still achieved under thermal treatment at 300 °C and desorption with 0.1 M NaOH solution, respectively, indicating a cost-efficient adsorbent for the elimination of SMX in water.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2020.141691DOI Listing
January 2021

Facile and Economical Functionalized Hay Biochar with Dairy Effluent for Adsorption of Tetracycline.

ACS Omega 2020 Jul 30;5(27):16521-16529. Epub 2020 Jun 30.

Department of Biological and Agricultural Engineering & Texas A&M AgriLife Research Center, Texas A&M University, 1229 North US Highway 281, Stephenville, Texas 76401, United States.

The present study reports a novel hay biochar functionalized with dairy effluent for enhanced tetracycline (TC) adsorption in the aqueous phase for the first time. The enrichment of hay (i.e., alfalfa) with dairy effluent led to significant accumulation of cationic metals during biochar production. The dairy effluent-functionalized alfalfa biochar (DEAF-BC) possessed strong crystallization (i.e., CaCO), functional groups (i.e., CO, C-O stretching), and high surface area (334 m/g) related to TC adsorption. Therefore, DEAF-BC showed higher TC adsorption capacity (835.7 mg/g) than that of the alfalfa biochar (94.5 mg/g). The adsorption isotherm and kinetic results for the DEAF-BC were correlated with the Freundlich, pseudo-second-order, and intraparticle diffusion models for TC. For the TC adsorption onto DEAF-BC, the thermodynamic analysis implied a spontaneous and endothermic process. Possible mechanisms would include metal complexation, hydrogen bonding, van der Waals forces, and π-π interaction.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsomega.0c01099DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7364554PMC
July 2020

Chemical Activation of Forage Grass-Derived Biochar for Treatment of Aqueous Antibiotic Sulfamethoxazole.

ACS Omega 2020 Jun 3;5(23):13793-13801. Epub 2020 Jun 3.

Department of Biological and Agricultural Engineering & Texas A&M AgriLife Research Center, Texas A&M University, College Station, Texas 76401, United States.

Chemically activated forage Bermudagrass-derived biochar (A-BC) was produced, characterized, and utilized for adsorption of sulfamethoxazole (SMX) in water for the first time. After NaOH activation, A-BC showed a higher surface area (1991.59 m/g) and maximum adsorption capacity for SMX (425 mg SMX/g BC) than those of various biochars and commercial activated carbons. The detailed analysis for adsorption of SMX onto A-BC indicated the efficient sorption of SMX through π-π EDA and hydrophobic and hydrogen bond interactions. Additionally, the adsorption of SMX on A-BC was limited by pore and liquid film diffusions. The SMX adsorption on A-BC was found to be endothermic and spontaneous from thermodynamic studies. Furthermore, the highly efficient regeneration of SMX-saturated A-BC over multiple cycles was achieved by NaOH-driven desorption, indicating that the adsorption of SMX onto A-BC would have high potential for cost-effective solution for elimination of SMX from water.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acsomega.0c00983DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7301585PMC
June 2020

Adsorption behavior of tetracycline onto Spirulina sp. (microalgae)-derived biochars produced at different temperatures.

Sci Total Environ 2020 Mar 26;710:136282. Epub 2019 Dec 26.

Department of Biological Engineering, Konkuk University, Seoul 05029, Republic of Korea. Electronic address:

We evaluated the production of Spirulina sp. (microalgae)-derived biochars (SPAL-BCs) at different pyrolysis temperatures for the removal of an emerging water contaminant, tetracycline (TC). Physicochemical properties of SPAL-BCs were characterized and related with their capacity to adsorb TC. Increasing pyrolysis temperatures led to higher aromaticity, higher hydrophobicity, and higher specific surface area. In particular, SPAL-BC750 possessed the highest hydrophobicity, various strong crystallizations (i.e., calcite, hydroxyapatite, and rhenanite) and functional groups (i.e., CH, CN, CO, and CO), which may be associated with high TC adsorption. SPAL-BC750 also presented the highest TC adsorption capacity (132.8 mg TC/g biochar) via batch experimentation because of hydrophobic, π-π interactions, functional groups, and metal complexation. The best fitting isotherm and kinetic models of TC adsorption by SPAL-BC750 were the Langmuir and pseudo-first order models, respectively. SPAL-BCs obtained as a by-product of pyrolysis may be an economical and potentially valuable adsorbent for aqueous antibiotic removal.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.scitotenv.2019.136282DOI Listing
March 2020

Engineered biochar from agricultural waste for removal of tetracycline in water.

Bioresour Technol 2019 Jul 27;284:437-447. Epub 2019 Mar 27.

Department of Biological and Agricultural Engineering, Texas A&M AgriLife Research Center, Texas A&M University, 1229 North US Highway 281, Stephenville, TX 76401, USA; Department of Wildlife, Sustainability, and Ecosystem Sciences, Tarleton State University, 1333 W. Washington, Stephenville, TX 76401, USA. Electronic address:

For the first time the present study investigated the production, characterization and application of engineered biochar derived from alfalfa hays for removal of tetracycline (TC) in water. The NaOH activation of alfalfa-derived raw biochar (BC) made significant increase in surface area (796.50 m/g) and pore volume (0.087 cm/g). The NaOH-activated BC (BC) showed much higher adsorption capacity for TC (Q = 302.37 mg/g) than BC, but comparable to the commercial activated carbon (Calgon F400). The detailed analyses of the kinetic and isotherm studies suggested the strong chemisorptive interactions between TC and BC via multiple mechanisms. In addition, intraparticle diffusion was considered as the major limitation for the adsorption of TC onto BC. Furthermore, the fixed bed experiments revealed that BC could be a promising adsorbent for treating large volume of TC-contaminated water in columns.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.biortech.2019.03.131DOI Listing
July 2019

A novel hay-derived biochar for removal of tetracyclines in water.

Bioresour Technol 2019 Feb 23;274:162-172. Epub 2018 Nov 23.

Department of Agricultural and Biological Engineering & Texas A&M AgriLife Research Center at Stephenville, Texas A&M University, USA; Department of Wildlife, Sustainability, and Ecosystem Sciences, Tarleton State University, USA. Electronic address:

The biochars derived from alfalfa (AF) and bermudagrass (BG), the abundant grass hays to cows, were prepared, characterized and used for removal of tetracycline (TC) in water. The alfalfa-derived biochar (AF-BC) has exhibited outstanding TC adsorption capacity (372 mg/g), which was about 8-fold higher than that of bermudagrass-derived biochar (BG-BC). In addition, the TC adsorption capacity of AF-BC was comparable with those of the commercial activated carbons under the same conditions. The surface structure, chemistry and high ash contents of AF-BC suggested the hydrogen bonding, electrostatic interactions and surface complexation between AF-BC and TC. Furthermore, hydroxyapatite (HAP; Ca(PO)OH) and calcite (CaCO) on the surface of AF-BC may also contribute to adsorption of TC via surface complexation, hydrogen bonding and electrostatic interactions. The alkaline desorption-driven regeneration of TC-spent AF-BC led to effective adsorption-desorption for multiple cycles, which indicated AF-BC could be a cost-effective adsorbent for TC in water and wastewater.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.biortech.2018.11.081DOI Listing
February 2019

Effects of pyrolysis temperature on the physicochemical properties of alfalfa-derived biochar for the adsorption of bisphenol A and sulfamethoxazole in water.

Chemosphere 2019 Mar 24;218:741-748. Epub 2018 Nov 24.

Department of Agricultural and Biological Engineering & Texas A&M AgriLife Research Center at Stephenville, Texas A&M University, USA; Department of Wildlife, Sustainability, and Ecosystem Sciences, Tarleton State University, USA. Electronic address:

The present study reports alfalfa (one of most abundant hays in U.S)-derived biochar for effective removal of emerging contaminants in water for the first time. The physicochemical properties of alfalfa-derived biochar (AF-BC) made at various pyrolysis temperatures were investigated, and correlated with the adsorption of bisphenol A (BPA) and sulfamethoxazole (SMX) in water. The increase in pyrolysis temperatures from 350 °C to 650 °C for the pyrolysis of AF led to a drastic increase in surface area and carbonization with the loss of functional groups. The AF-derived biochar made at 650 °C showed much higher adsorption capacities for BPA and SMX than those made at 350-550 °C, mainly owing to the hydrophobic and π-π interactions supported by its high surface area and degree of carbonization. The adsorption isotherms fitted the Freundlich for BPA and Temkin models for SMX well, respectively. The adsorption capacities of AF 650 for BPA and SMX were higher than those of other biochars but lower than those of commercial activated carbon. The pH-dependent desorption for AF 650 showed high efficiency for SMX, but low efficiency for BPA indicating needs for alternative regeneration methods for BPA.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.chemosphere.2018.11.151DOI Listing
March 2019

Additional reduction of antibiotic resistance genes and human bacterial pathogens via thermophilic aerobic digestion of anaerobically digested sludge.

Bioresour Technol 2019 Feb 9;273:259-268. Epub 2018 Nov 9.

School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712, Republic of Korea. Electronic address:

Thermophilic aerobic digestion (TAD) was applied to further reduce ARGs and heavy metal resistance genes (HMRGs) as well as class 1 integrons (intI1) in sludge from anaerobic digestion (AnD). Unlike after AnD, there was no enrichment of ARGs, HMRGs and intI1 after TAD. Residual gene fractions of intI1 and total ARGs (sum of targeted ARGs) were 0.03 and 0.08, respectively. Two kinetic models (Collins-Selleck and first-order) described the decay patterns of targeted genes, revealing rapid removal of intI1 during TAD. After TAD, the relative abundance of human bacterial pathogens (HBPs) and the numbers of HBPs species decreased to approximately 68% and 64% compared to anaerobically digested sludge, respectively. Thus, TAD, subsequent to AnD, may possess high potential for reducing biological risks resulting from ARGs, HMRGs, intI1 and HBPs in sewage sludge.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.biortech.2018.11.027DOI Listing
February 2019

Response of antibiotic and heavy metal resistance genes to two different temperature sequences in anaerobic digestion of waste activated sludge.

Bioresour Technol 2018 Nov 11;267:303-310. Epub 2018 Jul 11.

School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology, Buk-gu, Gwangju 500-712, Republic of Korea. Electronic address:

Response of antibiotic resistance genes (ARGs) and heavy metal resistance genes (HMRGs) to two different temperature sequences (i.e., mesophilic-thermophilic and thermophilic-mesophilic) were investigated. Higher removal of total ARGs (twenty-one targeted subtypes) and HMRGs (three targeted subtypes) was achieved by the mesophilic-thermophilic sequence than by the thermophilic-mesophilic sequence. The sequence of mesophilic-thermophilic showed the highest removal of total ARGs, but the sequence of thermophilic-mesophilic proved more suitable for removal of class 1 integrons (intI1). Correlation analysis indicated that intI1 correlated significantly with tetG, tetQ, tetX, sul2, aac(6')-lb-cr, bla, ermB and floR. High-throughput sequencing revealed that the mesophilic-thermophilic sequence TPAD removed more human bacterial pathogens (HBPs) than did the thermophilic-mesophilic sequence. Also, significantly positive correlation was observed between ARGs and HBPs. For instance, Mycoplasma pneumonia showed significantly positive correlation with several ARGs including tetE, tetQ, tetX, tetZ, sul1, sul2, aac(6')-lb-cr and floR.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.biortech.2018.07.051DOI Listing
November 2018

Biotechnological potential of microbial consortia and future perspectives.

Crit Rev Biotechnol 2018 Dec 15;38(8):1209-1229. Epub 2018 May 15.

a Department of Biological Engineering, College of Engineering , Konkuk University , Seoul , South Korea.

Design of a microbial consortium is a newly emerging field that enables researchers to extend the frontiers of biotechnology from a pure culture to mixed cultures. A microbial consortium enables microbes to use a broad range of carbon sources. It provides microbes with robustness in response to environmental stress factors. Microbes in a consortium can perform complex functions that are impossible for a single organism. With advancement of technology, it is now possible to understand microbial interaction mechanism and construct consortia. Microbial consortia can be classified in terms of their construction, modes of interaction, and functions. Here we discuss different trends in the study of microbial functions and interactions, including single-cell genomics (SCG), microfluidics, fluorescent imaging, and membrane separation. Community profile studies using polymerase chain-reaction denaturing gradient gel electrophoresis (PCR-DGGE), amplified ribosomal DNA restriction analysis (ARDRA), and terminal restriction fragment-length polymorphism (T-RFLP) are also reviewed. We also provide a few examples of their possible applications in areas of biopolymers, bioenergy, biochemicals, and bioremediation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/07388551.2018.1471445DOI Listing
December 2018

Adsorption isotherm, kinetic modeling and mechanism of tetracycline on Pinus taeda-derived activated biochar.

Bioresour Technol 2018 Jul 6;259:24-31. Epub 2018 Mar 6.

Texas A&M AgriLife Research Center, 1229 North US Highway 281, Stephenville, TX 76401, USA; Office of Sponsored Projects, Tarleton State University, 1333 W. Washington, Stephenville, TX 76401, USA. Electronic address:

The objective of this study was to evaluate the adsorption of tetracycline (TC) on the Pinus taeda-derived activated biochar (BC). After NaOH activation, the well-developed porous surface structure was observed with a significantly increase in surface area (959.9 m/g). The kinetic and isotherm studies indicated that hydrogen bonding and π-π interaction on the heterogeneous surface would be the possible mechanisms, while intra-particle diffusion was considered as the major limitation for the adsorption of TC on the activated BC. The maximum adsorption capacity of the activated BC (274.8 mg TC/g BC) was higher than those of various activated BCs from the previous studies while it was similar to those of commercial activated carbons. It indicated that the activated BC had the high potential for TC removal in water.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.biortech.2018.03.013DOI Listing
July 2018

Effects of dairy manure-derived biochar on psychrophilic, mesophilic and thermophilic anaerobic digestions of dairy manure.

Bioresour Technol 2018 Feb 27;250:927-931. Epub 2017 Nov 27.

Texas A&M AgriLife Research Center, 1229 North US Highway 281, Stephenville, TX 76401, USA; Office of Sponsored Projects, Tarleton State University, 1333 W. Washington, Stephenville, TX 76401, USA. Electronic address:

Effects of dairy manure-derived biochar (M-BC) on methane production in anaerobic digestion (AD) of dry dairy manure were investigated with three different concentrations of biochar (0, 1 and 10 g/L) and temperatures (psychrophilic, 20 °C; mesophilic, 35 °C; thermophilic, 55 °C). Compared with the AD without any biochar, the cumulative methane and yield in the AD with 10 g/L biochar were increased to 27.65% and 26.47% in psychrophilic, 32.21% and 24.90% in mesophilic and 35.71% and 24.69% in thermophilic digestions. The addition of M-BC shortened the lag phases of AD at all temperatures in the study while it lowered the concentration of total VFAs and propionic acid. It was suggested that the high nutrients and alkalinity potential of M-BC (i.e. 9.1% Ca, 3.6% Mg, 1.3% N, 0.14% P) would play significant roles in enhancing methane production and shortening lag phases from the AD of dairy manure.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.biortech.2017.11.074DOI Listing
February 2018

Alginate/bacterial cellulose nanocomposite beads prepared using Gluconacetobacter xylinus and their application in lipase immobilization.

Carbohydr Polym 2017 Feb 26;157:137-145. Epub 2016 Sep 26.

Department of Microbial Engineering, Konkuk University, Seoul 143-701, South Korea. Electronic address:

Alginate/bacterial cellulose nanocomposite beads, with well-controlled size and regular spherical shapes, were prepared in a simple manner by entrapping Gluconacetobacter xylinus in barium alginate hydrogel beads, followed by cultivation of the entrapped cells in culture media with a low sodium ion concentration. The entire surface of the alginate hydrogel beads containing the cells was covered with cellulose fibers (∼30nm) after 36h of cultivation. The cellulose crystallinity index of the alginate/bacterial cellulose beads was 0.7, which was slightly lower than that of bacterial cellulose prepared by cultivating dispersed cells. The water vapor sorption capacity of the alginate/bacterial cellulose beads increased significantly from 0.07 to 38.00 (g/g dry bead) as cultivation time increased. These results clearly indicate that alginate/bacterial cellulose beads have a much higher surface area, crystallinity, and water-holding capacity than alginate beads. The immobilization of lipase on the surface of the nanocomposite beads was also investigated as a potential application of this system. The activity and specific activity of lipase immobilized on alginate/bacterial cellulose beads were 2.6- and 3.8-fold higher, respectively, than that of lipase immobilized on cellulose beads. The alginate/bacterial cellulose nanocomposite beads prepared in this study have several potential applications in the biocatalytic, biomedical, and pharmaceutical fields because of their biocompatibility, biodegradability, high crystallinity, and large surface area.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.carbpol.2016.09.074DOI Listing
February 2017

Heterogeneous photocatalytic degradation of sulfamethoxazole in water using a biochar-supported TiO2 photocatalyst.

J Environ Manage 2016 Sep 20;180:94-101. Epub 2016 May 20.

Department of Molecular Bioscience and Bioengineering, University of Hawaii at Manoa, Honolulu, HI 96822, USA. Electronic address:

The present study reports an effective heterogeneous photocatalytic degradation of sulfamethoxazole (SMX) in water using a biochar-supported TiO2 (biochar/TiO2). The biochar was used as a low cost and effective support for TiO2 to lower the recombination rate of electrons and electron holes during photocatalysis, allow efficient attachment of TiO2, increase adsorption capacity and help easy separation of the photocatalyst after use. The biochar/TiO2 showed much higher adsorption of SMX than the commercial TiO2 powder due to the hydrophobic interaction between the biochar and SMX. Particularly this study focused on the effects of water quality and operating conditions on the photocatalytic oxidation of SMX. The addition of low concentration of bicarbonate made drastic enhancement in SMX removal and mineralization while the final effluent showed high biotoxicity. On the contrary, the presence of nitrate exhibited slight enhancement in SMX removal efficiency. The photocatalyst loading and UV irradiation time also played their important roles in enhancement of SMX removal and mineralization. In overall the photocatalytic oxidation of SMX using the biochar/TiO2 at the selected catalyst loading and irradiation time (5 g biochar-supported TiO2 L(-1), 6 h) resulted in the high removal and mineralization of SMX and negligible toxicity.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jenvman.2016.05.016DOI Listing
September 2016

Carbon dioxide capture using Escherichia coli expressing carbonic anhydrase in a foam bioreactor.

Environ Technol 2016 Dec 12;37(24):3186-92. Epub 2016 May 12.

a Department of Molecular Bioscience and Bioengineering , University of Hawaii at Manoa , Honolulu , HI , USA.

The present study reports CO2 capture and conversion to bicarbonate using Escherichia coli expressing carbonic anhydrase (CA) on its cell surface in a novel foam bioreactor. The very large gas-liquid interfacial area in the foam bioreactor promoted rapid CO2 absorption while the CO2 in the aqueous phase was subsequently converted to bicarbonate ions by the CA. CO2 gas removal in air was investigated at various conditions such as gas velocity, cell density and CO2 inlet concentration. Regimes for kinetic and mass transfer limitations were defined. Very high removal rates of CO2 were observed: 9570 g CO2 m(-3) bioreactor h(-1) and a CO2 removal efficiency of 93% at 4% inlet CO2 when the gas retention time was 24 s, and cell concentration was 4 gdw L(-1). These performances are superior to earlier reports of experimental bioreactors using CA for CO2 capture. Overall, this bioreactor system has significant potential as an alternative CO2 capture technology.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/09593330.2016.1181110DOI Listing
December 2016

Effects of novel auto-inducible medium on growth, activity and CO₂ capture capacity of Escherichia coli expressing carbonic anhydrase.

J Microbiol Methods 2015 Oct 8;117:139-43. Epub 2015 Aug 8.

Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, Honolulu, HI 96822, USA. Electronic address:

A glucose-based auto-inducible medium (glucose-AIM) has been developed to enhance both growth and expression of lac operon-linked carbonic anhydrase (CA) expression in a recombinant strain of Escherichia coli. When the E. coli expressing CA was grown on various media, the glucose-based auto-inducible medium (glucose AIM) resulted in a CA activity of 1022 mU OD(600 nm)(-1) mL(-1) at 24 h and a specific growth rate of 0.082 h(-1). The CA activity was four to fourteen times higher than those by LB-IPTG. The E. coli expressing CA grown on the glucose-AIM showed highest activity at pH8.5 while it kept high stability up to 40°C and an inlet CO2 concentration of 6%. These findings indicate that the glucose-AIM would be a cost-effective medium to support high cell growth, CA activity and stability for effective CO2 capture.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.mimet.2015.07.024DOI Listing
October 2015

Fenton-driven chemical regeneration of MTBE-spent granular activated carbon--a pilot study.

J Hazard Mater 2012 Feb 29;205-206:55-62. Epub 2011 Dec 29.

U.S. Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, Robert S. Kerr Environmental Research Center, P.O. Box 1198, Ada, OK 74820, USA.

Three columns containing granular activated carbon (GAC) were placed on-line at a ground water pump and treat facility, saturated with methyl tert-butyl ether (MTBE), and regenerated with hydrogen peroxide (H2O2) under different chemical, physical, and operational conditions for 3 adsorption/oxidation cycles. Supplemental iron was immobilized in the GAC (≈6 g/kg) through the amendment of a ferrous iron solution. GAC regeneration occurred under ambient thermal conditions (21-27 °C), or enhanced thermal conditions (50 °C). Semi-continuous H2O2 loading resulted in saw tooth-like H2O2 concentrations, whereas continuous H2O2 loading resulted in sustained H2O2 levels and was more time efficient. Significant removal of MTBE was measured in all three columns using $(USD) 0.6 H2O2/lb GAC. Elevated temperature played a significant role in oxidative treatment, given the lower MTBE removal at ambient temperature (62-80%) relative to MTBE removal measured under thermally enhanced (78-95%), and thermally enhanced, acid pre-treated (92-97%) conditions. Greater MTBE removal was attributed to increased intraparticle MTBE desorption and diffusion and higher aqueous MTBE concentrations. No loss in the MTBE sorption capacity of the GAC was measured, and the reaction byproducts, tert-butyl alcohol and acetone were also degraded.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jhazmat.2011.12.003DOI Listing
February 2012

Persulfate oxidation of MTBE- and chloroform-spent granular activated carbon.

J Hazard Mater 2011 Sep 1;192(3):1484-90. Epub 2011 Jul 1.

US Environmental Protection Agency, Office of Research and Development, National Risk Management Research Laboratory, Robert S. Kerr Environmental Research Center, PO Box 1198, Ada, OK 74820, United States.

Activated persulfate (Na(2)S(2)O(8)) regeneration of methyl tert-butyl ether (MTBE) and chloroform-spent GAC was evaluated in this study. Thermal-activation of persulfate was effective and resulted in greater MTBE removal than either alkaline-activation or H(2)O(2)-persulfate binary mixtures. H(2)O(2) may serve multiple roles in oxidation mechanisms including Fenton-driven oxidation, and indirect activation of persulfate through thermal or ferrous iron activation mechanisms. More frequent, lower volume applications of persulfate solution (i.e., the persulfate loading rate), higher solid/solution ratio (g GAC mL(-1) solution), and higher persulfate concentration (mass loading) resulted in greater MTBE oxidation and removal. Chloroform oxidation was more effective in URV GAC compared to F400 GAC. This study provides baseline conditions that can be used to optimize pilot-scale persulfate-driven regeneration of contaminant-spent GAC.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.jhazmat.2011.06.070DOI Listing
September 2011

Effects of temperature and acidic pre-treatment on Fenton-driven oxidation of MTBE-spent granular activated carbon.

Environ Sci Technol 2009 Mar;43(5):1493-9

National Research Council, Robert S. Kerr Environmental Research Center, P.O. Box 1198, Ada, Oklahoma 74820, USA.

The effects of temperature and acidic pretreatment on Fenton-driven chemical oxidation of methyl tert-butyl ether (MTBE)-spentgranular activated carbon (GAC) were investigated. Limiting factors in MTBE removal in GAC include the heterogeneous distribution of amended Fe, and slow intraparticle diffusivetransport of MTBE and hydrogen peroxide (H2O2) into the "reactive zone". Acid pretreatment of GAC before Fe amendment altered the surface chemistry of the GAC, lowered the pH point of zero charge, and resulted in greater penetration and more uniform distribution of Fe in GAC. This led to a condition where Fe, MTBE, and H2O2 coexisted over a larger volume of the GAC contributing to greater MTBE oxidation and removal. H2O2 reaction and MTBE removal in GAC increased withtemperature. Modeling H2O2 transport and reaction in GAC indicated that H2O2 penetration was inversely proportional with temperature and tortuosity, and occurred over a larger fraction of the total volume of small GAC particles (0.3 mm diameter) relative to large particles (1.2 mm diameter). Acidic pretreatment of GAC, Fe-amendment, elevated reaction temperature, and use of small GAC particles are operational parameters that improve Fenton-driven oxidation of MTBE in GAC.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/es802360fDOI Listing
March 2009

Modeling of a foamed emulsion bioreactor: II. model parametric sensitivity.

Biotechnol Bioeng 2009 Feb;102(3):708-13

Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521, USA.

The sensitivity of a conceptual model of a foam emulsion bioreactor (FEBR) used for the control of toluene vapors in air was examined. Model parametric sensitivity studies showed which parameters affect the removal of toluene (as model pollutant) in the FEBR the most significantly, and enabled definition of the limits of the process. Detailed examination of the results indicated that the process is highly complex and that both mass transfer and kinetic limitations can coexist in the bioreactor system. These results will help with the optimization of the design and operation of FEBRs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/bit.22122DOI Listing
February 2009

Modeling of a foamed emulsion bioreactor: I. Model development and experimental validation.

Biotechnol Bioeng 2008 Apr;99(5):1096-106

Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521, USA.

Recently, a new type of bioreactor for air pollution control referred to as the foamed emulsion bioreactor (FEBR) has been developed. The process relies on the emulsion of an organic phase with a suspension of an actively growing culture of pollutant-degrading microorganisms, made into a foam with the air undergoing treatment. In the current paper, a diffusion and reaction model of the FEBR is presented and discussed. The model considers the fate of the volatile pollutant in the emulsion that constitutes the liquid films of the FEBR. Oxygen limitation as well as substrate inhibition were included in the biokinetic relationships. The removal of toluene vapors served for the validation of the model. All the model parameters were determined by independent experiments or taken from the literature. The model predictions were found to be in good agreement with the experimental data and the model provided useful insights on the phenomena occurring in the FEBR. Model parametric sensitivity studies and further discussion of the factors that limit the performance of the FEBR are presented in Part 2 of this paper.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/bit.21666DOI Listing
April 2008

Cometabolic degradation of TCE vapors in a foamed emulsion bioreactor.

Environ Sci Technol 2006 Feb;40(3):1022-8

Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521, USA.

Effective cometabolic biodegradation of trichloroethylene (TCE) vapors in a novel gas-phase bioreactor called the foamed emulsion bioreactor (FEBR) was demonstrated. Toluene vapors were used as the primary growth substrate for Burkholderia cepacia G4 which cometabolically biodegraded TCE. Batch operation of the reactor with respect to the liquid feed showed a drastic decrease of TCE and toluene removal over time, consistent with a loss of metabolic activity caused by the exposure to TCE metabolites. Sustained TCE removal could be achieved when continuous feeding of mineral medium was implemented, which supported cell growth and compensated for the deactivation of cells. The FEBR exhibited its highest TCE removal efficiencies (82-96%) and elimination capacities (up to 28 gTCE m(-3) h(-1)) when TCE and toluene vapors were fed sequentially to circumvent the competitive inhibition by toluene. The TCE elimination capacity was 2-1000 times higher than reported in other gas-phase biotreatment reports. During the experiments, 85-101% of the degraded TCE chlorine was recovered as chloride. Overall, the results suggestthatthe FEBR can be a very effective system to treat TCE vapors cometabolically.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/es0510055DOI Listing
February 2006

Continuous operation of foamed emulsion bioreactors treating toluene vapors.

Biotechnol Bioeng 2005 Nov;92(3):364-71

Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521, USA.

Continuous operation of a new bioreactor for air pollution control called the foamed emulsion bioreactor (FEBR) has been investigated. The effect of several liquid feeding strategies was explored. The FEBR exhibited high and steady toluene removal performance (removal efficiency of 89%-94%, elimination capacity of 214-226 g/m3h at toluene inlet concentration of 1 g/m3) for up to 360 h, when 20% of the culture was replaced every 24 h by a nutrient solution containing 4 g/L of potassium nitrate as a nitrogen source. This feeding mode supported a high cell activity measured as INT reduction potential and active cell growth without being subject to nitrogen limitation. In comparison, operating the FEBR with the liquid in a closed loop (i.e., batch) resulted in a significant decrease of both the removal efficiency of toluene and INT reduction activity. Operation with feeding active cells resulted in stable and effective treatment, but would require a significant effort for mass culture preparation. Therefore, the continuous process with periodically feeding nutrients was found to be the most practical and effective operating mode. It also allows for stable operation, as was shown during removal of low concentration of toluene or after pollutant starvation. Throughout the study, INT reduction measurements provided insight into the process. INT reduction activity data proved that under normal operating conditions, the FEBR performance was limited by both the kinetics and by mass transfer. Overall, the results illustrate that engineered gas-phase bioreactors can potentially be more effective than conventional biofilters and biotrickling filters for the treatment of air pollutants such as toluene.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/bit.20619DOI Listing
November 2005

Development of foamed emulsion bioreactor for air pollution control.

Biotechnol Bioeng 2003 Oct;84(2):240-4

Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521, USA.

A new type of bioreactor for air pollution control has been developed. The new process relies on an organic-phase emulsion and actively growing pollutant-degrading microorganisms, made into a foam with the air being treated. This new reactor is referred to as a foamed emulsion bioreactor (FEBR). As there is no packing in the reactor, the FEBR is not subject to clogging. Mathematical modeling of the process and proof of concept using a laboratory prototype revealed that the foamed emulsion bioreactor greatly surpasses the performance of existing gas-phase bioreactors. Experimental results showed a toluene elimination capacity as high as 285 g(toluene) m(-3) (reactor) h(-1) with a removal efficiency of 95% at a gas residence time of 15 s and a toluene inlet concentration of 1-1.3 g x m(-3). Oxygen limited the reactor performance at toluene concentration above about 0.7-1.0 g x m(-3); consequently, performance was significantly improved when pure oxygen was added to the contaminated air. The elimination capacity increased from 204 to 408 g x m(-3) h(-1) with >77% toluene removal at toluene inlet concentrations of 2-2.2 g x m(-3). Overall, the results show that the performance of the FEBR far exceeds that of currently used bioreactors for air pollution control.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/bit.10767DOI Listing
October 2003