Publications by authors named "Adi Radian"

12 Publications

  • Page 1 of 1

Systematic evaluation of activated carbon-FeO composites for removing and degrading emerging organic pollutants.

Environ Res 2021 07 5;198:111187. Epub 2021 May 5.

Civil and Environmental Engineering Faculty, Technion, Haifa, 32000, Israel. Electronic address:

In this study, a comparative activity assessment of several activated carbon (AC) and AC-FeO composites was performed to evaluate their efficiency and versatility as Fenton-like catalysts. Although many studies have demonstrated the advantages of AC-based materials as Fenton-like catalysts, most have been developed using only one oxidant and/or one pollutant. Here, untreated (AC) and acid-treated AC (AC) iron-oxide composites were synthesized, characterized, and compared in terms of activity to bare AC using several oxidants and pollutants, the activation efficiency of hydrogen peroxide (HO) and ammonium persulfate ((NH)SO), and the subsequent oxidation extent and kinetics of bisphenol-A, atrazine, and carbamazepine by the AC-based materials were studied in depth. The persulfate-based systems showed considerably higher pollutant removal in the presence of the catalysts, despite lower persulfate decomposition rates: atrazine and carbamazepine were partially degraded, mainly through a radical-dependent pathway; the highest removal of atrazine was achieved with the AC-iron composite, whereas carbamazepine was best removed by the AC-iron composite. In contrast, bisphenol A was completely mineralized, probably via a non-radical pathway, in the presence of all AC-based composites, even at very low persulfate concentrations. Furthermore, bisphenol A removal remained high for several consecutive cycles, with the most efficient removal and stability observed in the presence of AC. These findings reveal the high complexity of AC-based systems, with multiple binding sites and degradation pathways unique to each combination of pollutants, catalysts, and oxidants. In general, the composition of the waste stream governs the applicability of these materials. Thus, the structure-function correlations and degradation mechanisms revealed here are crucial for improving sorbent-catalyst design and accelerating the implementation of low-cost remediation and in situ regeneration technologies.
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http://dx.doi.org/10.1016/j.envres.2021.111187DOI Listing
July 2021

Solid peroxides in Fenton-like reactions at near neutral pHs: Superior performance of MgO on the accelerated reduction of ferric species.

Chemosphere 2021 May 16;270:128639. Epub 2020 Oct 16.

School of Environmental Science and Engineering, Key Laboratory of Thin Film and Microfabrication Technology (Ministry of Education), Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240, China. Electronic address:

Fenton-like reactions at near neutral pHs are limited by the slow reduction of ferric species. Enhancing generation of from solid peroxides is a promising strategy to accelerate the rate-limiting step. Herein, the HO release and Fenton-like reactions of four solid peroxides, MgO, CaO, ZnO and urea hydrogen peroxide (UHP), were investigated. Results indicated that UHP can release HO instantly and show a similar behavior as HO in the Fenton-like reactions. MgO released HO quickly in phosphate buffered solutions, which was comparable to CaO but faster than ZnO. Metal peroxides induced higher initial phenol degradation rates than UHP and HO when the same theoretic HO dosages and Fe(III)-EDTA were used. MgO displayed a superior performance for phenol degradation at pH 5, resulting in more than 93% phenol reduction at 1.5 h. According to kinetic analyses, the generation rate of in the MgO system was 18 and 3.4 times higher than those in ZnO and CaO systems, respectively. The addition of MgO significantly promoted HO based Fenton-like reactions by increasing production of , and the mixture of MgO and HO had an improved utilization efficiency of active oxygen than the MgO system. The findings suggested the critical roles of metal peroxides in favoring Fenton-like reactions and inspired strategies to simultaneously accelerate Fenton-like reactions and improve utilization efficiency of active oxygen.
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http://dx.doi.org/10.1016/j.chemosphere.2020.128639DOI Listing
May 2021

Iron-Montmorillonite-Cyclodextrin Composites as Recyclable Sorbent Catalysts for the Adsorption and Surface Oxidation of Organic Pollutants.

ACS Appl Mater Interfaces 2020 Nov 10;12(47):52873-52887. Epub 2020 Nov 10.

Faculty of Civil and Environmental Engineering, Technion-Israel Institute of Technology, Technion City, Haifa 32000, Israel.

Iron-clay-cyclodextrin composites were designed as sorbent catalysts to adsorb and oxidize pollutants from water. The clay-iron backbone served as a mechanical support and as a heterogeneous Fenton catalyst, and the cyclodextrin monomers or polymers cross-linked with polyfluorinated aromatic molecules were used to accommodate adsorption of the pollutants. The composite based on iron-clay-cyclodextrin-polymers (Fe-MMT-βCD-DFB) exhibited superior adsorption and degradation of the model pollutants, bisphenol A (BPA), carbamazepine (CBZ), and perfluorooctanoic acid (PFOA), compared to the monomer-based composite and the native iron clay. The variety of adsorption sites, such as the polyfluorinated aromatic cross-linker, cyclodextrin toroid, and iron-clay surface, resulted in high adsorption affinity toward all pollutants; BPA was primarily adsorbed to the cyclodextrin functional groups, CBZ showed high affinity toward the Fe-MMT surface and the Fe-MMT-βCD-DFB composite, whereas PFOA was adsorbed mainly to the βCD-DFB polymer. Degradation, using HO, was highly efficient, reaching over 90% degradation in 1 h for BPA and CBZ and ∼80% for PFOA. The composite also showed excellent degradation efficiency in a multicomponent system with all three model pollutants. Furthermore, the composite's activity remained steady for five consecutive cycles of adsorption and degradation. The ability to remediate a broad range of pollutants, and the high overall removal exhibited by this novel material, demonstrates the potential for future application in water remediation technologies.
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http://dx.doi.org/10.1021/acsami.0c17510DOI Listing
November 2020

The effect of gallic acid interactions with iron-coated clay on surface redox reactivity.

Water Res 2020 Oct 16;184:116190. Epub 2020 Jul 16.

Civil and Environmental Engineering Faculty, Technion, Haifa, 32000, Israel. Electronic address:

Adsorption and redox reactions between organic matter and natural reactive surfaces have a significant impact on pollutant sequestration and transformation, and on the effectivity of water and soil remediation practices. Herein, the interactions between an organic phenolic acid, gallic acid (GA), and clay coated with iron oxides (FeOx-MMT), were explored. Adsorption and desorption experiments revealed that GA has a higher affinity for FeOx-MMT than for native clay. The adsorption to FeOx-MMT was irreversible and only slightly affected by salinity, suggesting strong inner-sphere complexation. The GA-FeOx-MMT complex was characterized using cyclic-voltammetry, UV-Vis spectroscopy, FTIR, and XPS measurements. The results showed oxidation and transformation of GA on the surface and a considerable reduction of the surface iron. The resulting GA-FeOx-MMT complex had increased catalytic properties, enhancing hydrogen peroxide decomposition, and creating significantly more radicals than FeOx-MMT and raw clay. This led to the destruction of GA on the surface of the clay-iron complex, resulting in loss of activity over time. Our findings suggest a correlation between overall GA adsorption, consequent iron reduction and oxidant decomposition. This means that in systems where such constituents are present, these types of interactions need to be taken into consideration in terms of predicting the fate of pollutants in the environment, and for properly evaluating soil and water chemical treatment processes.
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http://dx.doi.org/10.1016/j.watres.2020.116190DOI Listing
October 2020

Spectral induced polarization of clay-oxide hybrid particles.

J Colloid Interface Sci 2020 Oct 20;577:173-180. Epub 2020 May 20.

Civil and Environmental Engineering Faculty, Technion, Haifa, Israel. Electronic address:

The properties of clays and oxides govern many environmental processes, consequently, ongoing effort is invested in developing non-destructive, in-situ analytical tools that reflect these properties. Herein, the physicochemical properties of montmorillonite (MMT) and iron-oxide coated montmorillonite (FeOx-MMT) were characterized using common analytical techniques, and the results were compared to spectral induced polarization (SIP) measurements. FeOx-MMT particles showed a lower CEC, higher pH dependency of the surface charge, and lower suspension stability. Also, the size of the primary particles increased following iron-oxide deposition. SIP measurements over a range of salinities showed that the effective polarization length of the clays was in the order of several microns, suggesting the measurements of aggregates (not primary particles). Moreover, FeOx-MMT particles were more compact than MMT, and their size decreased with increasing salinity due to compaction of the EDL and arrangement of primary particles in the aggregate. The SIP-response to pH changes agreed with zeta potential measurements; at low pH values, MMT exhibited higher polarization due to the higher CEC. However, at a high pH, the differences diminish due to deprotonation of the Fe-OH surface groups. These findings suggest that SIP is a sensitive method that can detect changes in the surface chemistry of soil particles.
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http://dx.doi.org/10.1016/j.jcis.2020.05.029DOI Listing
October 2020

Curli production enhances clay-E. coli aggregation and sedimentation.

Colloids Surf B Biointerfaces 2019 Oct 20;182:110361. Epub 2019 Jul 20.

Faculty of Civil and Environmental Engineering, Technion - Israel Institute of Technology, Technion City, Haifa 32000, Israel. Electronic address:

Curli are amyloid fibrils that polymerize extracellularly from curlin, a protein that is secreted by many enteric bacteria and is important for biofilm formation. Presented here is a systematic study of the effects of curli on bacteria-clay interactions. The aggregation trends of curli-producing and curli-deficient bacteria with clay minerals were followed using gradient-sedimentation experiments, Lumisizer measurements, bright-field and electron microscopy. The results revealed that curli-producing bacteria auto-aggregated into high-density flocs (1.23 g/cm), ranging in size from 10 to 50 μm, that settle spontaneously. In contrast, curli-deficient bacteria remained relatively stable in solution as individual cells (1-2 μm, 1.18 g/cm), even at high ionic strength (350 mM). The stability of clay suspensions mixed with curli-deficient bacteria depended on clay type and ionic strength, the general trends being consistent with the classic DLVO theory. However, suspensions of curli-producing bacteria mixed with clays were highly unstable regardless of clay type and solution chemistry, suggesting extensive interactions between the clays and the bacteria-curli aggregates. SEM measurements revealed interesting differences in morphologies of the aggregates; montmorillonite particles coated the bacterial auto-aggregates whereas the kaolinite platelets were embedded within the larger curli-bacteria aggregates. These new observations regarding the densities, aggregation trends, and morphologies of bacteria-curli and bacteria-curli-clay complexes make it clear that production of surface appendages, such as curli, need to be considered when addressing the fate, activity and transport of bacteria - particularly in aquatic environments.
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http://dx.doi.org/10.1016/j.colsurfb.2019.110361DOI Listing
October 2019

Enhanced biodegradation of atrazine by bacteria encapsulated in organically modified silica gels.

J Colloid Interface Sci 2018 Jan 11;510:57-68. Epub 2017 Sep 11.

Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN 55455, USA; BioTechnology Institute, University of Minnesota, St Paul, MN 55108, USA. Electronic address:

Biodegradation by cells encapsulated in silica gel is an economical and environmentally friendly method for the removal of toxic chemicals from the environment. In this work, recombinant E. coli expressing atrazine chlorohydrolase (AtzA) were encapsulated in organically modified silica (ORMOSIL) gels composed of TEOS, silica nanoparticles (SNPs), and either phenyltriethoxysilane (PTES) or methyltriethoxysilane (MTES). ORMOSIL gels adsorbed much higher amounts of atrazine than the hydrophilic TEOS gels. The highest amount of atrazine adsorbed by ORMOSIL gels was 48.91×10μmol/mlgel, compared to 8.71×10μmol/mlgel by the hydrophilic TEOS gels. Atrazine biodegradation rates were also higher in ORMOSIL gels than the TEOS gels, mainly due to co-localization of the hydrophobic substrate at high concentrations in close proximity of the encapsulated bacteria. A direct correlation between atrazine adsorption and biodegradation was observed unless biodegradation decreased due to severe phase separation. The optimized PTES and MTES gels had atrazine biodegradation rates of 0.041±0.003 and 0.047±0.004μmol/mlgel, respectively. These rates were approximately 80% higher than that measured in the TEOS gel. This study showed for the first time that optimized hydrophobic gel material design can be used to enhance both removal and biodegradation of hydrophobic chemicals.
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http://dx.doi.org/10.1016/j.jcis.2017.09.044DOI Listing
January 2018

Silica Gel for Enhanced Activity and Hypochlorite Protection of Cyanuric Acid Hydrolase in Recombinant Escherichia coli.

mBio 2015 Nov 3;6(6):e01477-15. Epub 2015 Nov 3.

BioTechnology Institute, University of Minnesota, St. Paul, Minnesota, USA Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, Minnesota, USA

Unlabelled: Chlorinated isocyanuric acids are widely used water disinfectants that generate hypochlorite, but with repeated application, they build up cyanuric acid (CYA) that must be removed to maintain disinfection. 3-Aminopropyltriethoxysilane (APTES)-treated Escherichia coli cells expressing cyanuric acid hydrolase (CAH) from Moorella thermoacetica exhibited significantly high CYA degradation rates and provided protection against enzyme inactivation by hypochlorite (chlorine). APTES coating or encapsulation of cells had two benefits: (i) overcoming diffusion limitations imposed by the cell wall and (ii) protecting against hypochlorite inactivation of CAH activity. Cells encapsulated in APTES gels degraded CYA three times faster than nonfunctionalized tetraethoxysilane (TEOS) gels, and cells coated with APTES degraded CYA at a rate of 29 µmol/min per mg of CAH protein, similar to the rate with purified enzyme. UV spectroscopy, fluorescence spectroscopy, and scanning electron microscopy showed that the higher rates were due to APTES increasing membrane permeability and enhancing cyanuric acid diffusion into the cytoplasm to reach the CAH enzyme. Purified CAH enzyme was shown to be rapidly inactivated by hypochlorite. APTES aggregates surrounding cells protected via the amine groups reacting with hypochlorite as shown by pH changes, zeta potential measurements, and infrared spectroscopy. APTES-encapsulated E. coli cells expressing CAH degraded cyanuric acid at high rates in the presence of 1 to 10 ppm hypochlorite, showing effectiveness under swimming pool conditions. In contrast, CAH activity in TEOS gels or free cells was completely inactivated by hypochlorite. These studies show that commercially available silica materials can selectively enhance, protect, and immobilize whole-cell biocatalysts for specialized applications.

Importance: Hypochlorite is used in vast quantities for water disinfection, killing bacteria on surfaces, and washing and whitening. In pools, spas, and other waters, hypochlorite is frequently delivered as chlorinated isocyanuric acids that release hypochlorite and cyanuric acid. Over time, cyanuric acid accumulates and impairs disinfection and must be removed. The microbial enzyme cyanuric acid hydrolase can potentially remove cyanuric acid to restore disinfection and protect swimmers. Whole bacterial cells expressing cyanuric acid hydrolase were encapsulated in an inert silica matrix containing an amine group. The amine group serves to permeabilize the cell membrane and accelerate cyanuric acid degradation, and it also reacts with hypochlorite to protect against inactivation of cyanuric acid hydrolase. Methods for promoting whole-cell biocatalysis are important in biotechnology, and the present work illustrates approaches to enhance rates and protect against an inhibitory substance.
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http://dx.doi.org/10.1128/mBio.01477-15DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4631802PMC
November 2015

Effect of humic acid on pyrene removal from water by polycation-clay mineral composites and activated carbon.

Environ Sci Technol 2012 Jun 16;46(11):6228-35. Epub 2012 May 16.

The Robert H. Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.

Pyrene removal by polycation-montmorillonite (MMT) composites and granulated activated carbon (GAC) in the presence of humic acid (HA) was examined. Pyrene, HA, and sorbent interactions were characterized by FTIR, fluorescence and zeta measurements, adsorption, and column filtration experiments. Pyrene binding coefficients to the macromolecules were in the order of PVPcoS (poly-4-vinylpiridine-co-styrene) > HA > PDADMAC (poly diallyl-dimethyl-ammonium-chloride), correlating to pyrene-macromolecules compatibility. Electrostatic interactions explained the high adsorption of HA to both composites (∼100%), whereas HA adsorption by GAC was low. Pyrene removal by the composites, unlike GAC, was enhanced in the presence of HA; removal by PDADMAC-MMT increased from ∼50 (k(d) = 2.2 × 10(3) kg/L) to ∼70% (k(d) = 2.4 × 10(3) kg/L) in the presence of HA. This improvement was attributed to the adsorption of pyrene-HA complexes. PVPcoS-MMT was most efficient in removing pyrene (k(d) = 1.1 × 10(4) kg/L, >95% removal) which was explained in terms of specific π donor-π acceptor interactions. Pyrene uptake by column filters of GAC reached ∼50% and decreased to ∼30% in the presence of HA. Pyrene removal by the PVPcoS-MMT filter was significantly higher (100-85% removal), exhibiting only a small decrease in the presence of HA. The utilization of HA as an enhancing agent in pollutant removal is novel and of major importance in water treatment.
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http://dx.doi.org/10.1021/es300964dDOI Listing
June 2012

Applying zeta potential measurements to characterize the adsorption on montmorillonite of organic cations as monomers, micelles, or polymers.

J Colloid Interface Sci 2010 Dec 10;352(1):171-7. Epub 2010 Aug 10.

The Robert H. Smith Faculty of Agriculture, Food, and Environment, The Hebrew University of Jerusalem, Rehovot 76100, Israel.

A systematic study was carried out to characterize the adsorption of organic cations as monomers, micelles, or polymers on montmorillonite by monitoring zeta potential (ξ) as a function of cation loading on the clay. In general, the clay's ξ became less negative as cation loading increased. A fairly good linear correlation between adsorption of organic cations on the clay, up to the cation exchange capacity (CEC) of the clay, and ξ potential of the composites was fitted. However, when the adsorption of the larger cation exceeded the CEC, a nonlinear increase in ξ was measured. The degree of this increase corresponds to the cation size and affinity to the clay (in the order surfactant
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http://dx.doi.org/10.1016/j.jcis.2010.08.010DOI Listing
December 2010

Atrazine removal from water by polycation-clay composites: effect of dissolved organic matter and comparison to activated carbon.

Water Res 2009 Feb 8;43(3):677-83. Epub 2008 Nov 8.

Department of Soil and Water Sciences, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Rehovot 76100, Israel.

Atrazine removal from water by two polycations pre-adsorbed on montmorillonite was studied. Batch experiments demonstrated that the most suitable composite poly (4-vinylpyridine-co-styrene)-montmorillonite (PVP-co-S90%-mont.) removed 90-99% of atrazine (0.5-28 ppm) within 20-40 min at 0.367% w/w. Calculations employing Langmuir's equation could simulate and predict the kinetics and final extents of atrazine adsorption. Column filter experiments (columns 20x1.6 cm) which included 2g of the PVP-co-S90%-mont. composite mixed with excess sand removed 93-96% of atrazine (800 ppb) for the first 800 pore volumes, whereas the same amount of granular activated carbon (GAC) removed 83-75%. In the presence of dissolved organic matter (DOM; 3.7 ppm) the efficiency of the GAC filter to remove atrazine decreased significantly (68-52% removal), whereas the corresponding efficiency of the PVP-co-S90%-mont. filter was only slightly influenced by DOM. At lower atrazine concentration (7 ppb) the PVP-co-S90%-mont. filter reduced even after 3000 pore volumes the emerging atrazine concentration below 3 ppb (USEPA standard). In the case of the GAC filter the emerging atrazine concentration was between 2.4 and 5.3 microg/L even for the first 100 pore volumes. Thus, the PVP-co-S90%-mont. composite is a new efficient material for the removal of atrazine from water.
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http://dx.doi.org/10.1016/j.watres.2008.10.050DOI Listing
February 2009

Characterizing and designing polycation-clay nanocomposites as a basis for imazapyr controlled release formulations.

Environ Sci Technol 2008 Mar;42(5):1511-6

Seagram Center for Soil and Water Sciences, Faculty of Agricultural, Food and Environmental Quality Sciences, Hebrew University of Jerusalem, Rehovot 76100, Israel.

A novel controlled release formulation (CRF) of the herbicide imazapyr (IMP) was designed to reduce its leaching,which causes soil and water contamination. The anionic herbicide IMP was bound to polydiallyldimethylammonium-chloride (PDADMAC)-montmorillonite composites. PDADMAC adsorption reached a high loading of polymer, which resulted in charge reversal of the clay and promoted IMP binding. The composites were characterized by Fourier transform infrared, zeta potential, and X-ray diffraction measurements, indicating electrostatic interactions of the polycation with the surface, polycation intercalation in the clay and suggesting a configuration as loops and tails on the surface at high loadings. IMP binding to the composites is affected by polycation loading and flocculation. Upon adding high concentrations of IMP to a composite of 0.16 g/g, we obtained high herbicide loadings (66% active ingredient). IMP release from the CRFs applied on a thin layer of soil was substantially slower than its release from the commercial formulation (Arsenal). Accordingly, soil column bioassays indicated reduced herbicide leaching (nearly 2-fold) upon applying the CRFs while maintaining good herbicidal activity. The new PDADMAC-clay formulations are promising from the environmental and weed control management points of view.
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http://dx.doi.org/10.1021/es7023753DOI Listing
March 2008