Treatment of arsenic contaminated water in a batch reactor by using Ralstonia eutropha MTCC 2487 and granular activated carbon

Metabolic coupling of arsenic, carbon, nitrogen, and sulfur in high arsenic geothermal groundwater: Evidence from molecular mechanisms to community ecology

Groundwater arsenic (As) poses a global environmental problem and is regulated by complex biogeochemical processes. However, the As biogeochemistry and its metabolic coupling with carbon (C), nitrogen (N), and sulfur (S) in high As geothermal groundwater remain unclear. Here, we reported significant shifts in the geothermal groundwater microbiome and its functional ecological clusters along the flow path with increased As levels and dynamic As-C-N-S biogeochemical cycle from the Guide Basin, China. Strong associations among As(III), NH4+, HCO3-, and corresponding functional microbial taxa suggest that microbe-mediated As transformation, ammonification, and organic carbon biodegradation potentially contributed to the As mobilization in the discharge area. And As oxidizers (coupling with denitrification or carbon fixation) and S oxidizers were closely linked to the transformation of As(III) to immobile As(V) in the recharge area. Our study provides a comprehensive insight into the complex microbial As-C-N-S coupling network and its potential role in groundwater As mobilization under hydrological disturbances.

Effects of dissolved organic matter derived from cow manure on heavy metal(loid)s and bacterial community dynamics in mercury-thallium mining waste slag

Organic amendments in aided phytostabilization of waste slag containing high levels of heavy metal (loid)s (HMs) are an important way to control the release of HMs in situ. However, the effects of dissolved organic matter (DOM) derived from organic amendments on HMs and microbial community dynamics in waste slag are still unclear. Here, the effect of DOM derived from organic amendments (cow manure) on the geochemical behaviour of HMs and the bacterial community dynamics in mercury (Hg)-thallium (Tl) mining waste slag were investigated. The results showed that the Hg-Tl mining waste slag without the addition of DOM continuously decreased the pH and increased the EC, Eh, SO42-, Hg, and Tl levels in the leachate with increasing incubation time. The addition of DOM significantly increased the pH, EC, SO42-, and arsenic (As) levels but decreased the Eh, Hg, and Tl levels. The addition of DOM significantly increased the diversity and richness of the bacterial community. The dominant bacterial phyla (Proteobacteria, Firmicutes, Acidobacteriota, Actinobacteriota, and Bacteroidota) and genera (Bacillus, Acinetobacter, Delftia, Sphingomonas, and Enterobacter) were changed in association with increases in DOM content and incubation time. The DOM components in the leachate were humic-like substances (C1 and C2), and the DOC content and maximum fluorescence intensity (FMax) values of C1 and C2 in the leachate decreased and first increased and then decreased with increasing incubation time. The correlations between HMs and DOM and the bacterial community showed that the geochemical behaviours of HMs in Hg-Tl mining waste slag were directly influenced by DOM-mediated properties and indirectly influenced by DOM regulation of bacterial community changes. Overall, these results indicated that DOM properties associated with bacterial community changes increased As mobilization but decreased Hg and Tl mobilization from Hg-Tl mining waste slag.

More effective application of biochar-based immobilization technology in the environment: Understanding the role of biochar

In recent years, biochar-based immobilization technology (BIT) has been widely used to treat different environmental issues because of its cost-effectiveness and high removal performance. However, the complexity of the real environment is always ignored, which hinders the transfer of the BIT from lab-scale to commercial applications. Therefore, in this review, the analysis is performed separately on the internal side of the BIT (microbial fixation and growth) and on the external side of the BIT (function) to achieve effective BIT performance. Importantly, the internal two stages of BIT have been discussed concisely. Further, the usage of BIT in different areas is summarized precisely. Notably, the key impacts were systemically analyzed during BIT applications including environmental conditions and biochar types. Finally, the suggestions and perspectives are elucidated to solve current issues regarding BIT.

A halophilic Chromohalobacter species from estuarine coastal waters as a detoxifier of manganese, as well as a novel bio-catalyst for synthesis of n-butyl acetate

Anthropogenic pollution due to ferro-manganese ore transport by barges through the Mandovi estuary in Goa, India is a major environmental concern. In this study a manganese (Mn) tolerant, moderately halophilic Chromohalobacter sp. belonging to the family Halomonadaceae was isolated from the sediments of a solar saltern adjacent to this Mandovi estuary. Using techniques of Atomic absorption spectroscopy, Scanning electron microscopy-Energy dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy and Atomic Force Microscopy, the Chromohalobacter sp. was explored for its ability to tolerate and immobilize Mn in amended and unamended media with 20% natural salt concentration (w/v). In aqueous media supplemented with 0.1 mM Mn, the Chromohalobacter sp. was capable of sequestering up to 76% Mn with an average immobilization rate of 8 mg Mn /g /day. Growth rate kinetic analysis using Gompertz mathematical functions was found to model the experimental data well. The model inferred that the maximum growth rate of Chromohalobacter sp. was at 10% natural salt concentration (w/v). The Chromohalobacter sp. was further found to be multimetal tolerant showing high tolerance to Iron (Fe), Nickel (Ni) and Cobalt (Co), (each at 4 mM), and tolerated Manganese (Mn) up to 6 mM. Morphologically, the Chromohalobacter sp. was a non-spore forming, Gram negative motile rod (0.726 μ× 1.33 μ). The adaptative mechanism of Chromohalobacter sp. to elevated Mn concentrations (1 mM) resulted in the reduction of its cell size to 0.339 μ× 0.997 μ and the synthesis of an extracellular slime, immobilizing Mn from the liquid phase forming Manganese oxide, as confirmed by Scanning Electron Microscopy. The expression of Mnx genes for manganese oxidation further substantiated the finding. This bacterial synthesized manganese oxide also displayed catalytic activity (∼50% conversion) for the esterification of butan-1-ol with CH₃COOH to yield n-butyl acetate. This Chromohalobacter sp. being indigenous to marine salterns, has adapted to high concentrations of heavy metals and high salinities and can withstand this extremely stressed environment, and thus holds a tremendous potential as an environmentally friendly "green bioremediator" of Mn from euryhaline environments. The study also adds to the limited knowledge about metal-microbe interactions in extreme environments. Further, since Chromohalobacter sp. exhibits commendable catalytic activity for the synthesis of n-butyl acetate, it would have several potential industrial applications.

Biofilm formation of Ancylobacter sp. TS-1 on different granular materials and its ability for chemolithoautotrophic As(III)-oxidation at high concentrations

The oxidation of arsenic (As) is a key step in its removal from water, and biological oxidation may provide a cost-effective and sustainable method. The biofilm-formation ability of Ancylobacter sp. TS-1, a novel chemolithoautotrophic As oxidizer, was studied for four materials: polypropylene, graphite, sand, and zeolite. After seven days under batch mixotrophic conditions, with high concentrations of As(III) (225 mg·L^-1), biofilm formation was detected on all materials except for polypropylene. The results demonstrate As(III)-oxidation of TS-1 biofilms and suggest that the number of active cells was similar for graphite, sand, and zeolite. However, the biofilm biomass follows the specific surface area of each material: 7.0, 2.4, and 0.4 mg VSS·cm^-3 for zeolite, sand, and graphite, respectively. Therefore, the observed biofilm-biomass differences were probably associated with different amounts of EPS and inert biomass. Lastly, As(III)-oxidation kinetics were assessed for the biofilms formed on graphite and zeolite under chemolithoautotrophic conditions. The normalized oxidation rate for biofilms formed on these materials was 3.6 and 1.0 mg·L^-1·h^-1·cm^-3, resulting among the highest reported values for As(III)-oxidizing biofilms operated at high-As(III) concentrations. Our findings suggest that biofilm reactors based on Ancylobacter sp. TS-1 are highly promising for their utilization in As(III)-oxidation pre-treatment of high-As(III) polluted waters.

Advanced application of nano-technological and biological processes as well as mitigation options for arsenic removal

Arsenic (As) removal is a huge challenge, since several million people are potentially exposed (>10 μg/L World Health Organization guideline limit) through As contaminated drinking water worldwide. Review attempts to address the present situation of As removal, considering key topics on nano-technological and biological process and current progress and future perspectives of possible mitigation options have been evaluated. Different physical, chemical and biological methods are available to remove As from contaminated water/soil/wastes, where removal efficiency mainly depends on absorbent type, initial adsorbate concentration, speciation and interfering species. Oxidation is an important pretreatment step in As removal, which is generally achieved by several media such as O₂/O₃, HClO, KMnO₄ and H₂O₂. The Fe-based-nanomaterials (α/β/γ-FeOOH, Fe₂O₃/Fe₃O₄-γ-Fe₂O₃), Fe-based-composite-compounds, activated-Al₂O₃, HFO, Fe-Al₂O₃, Fe₂O₃-impregnated-graphene-aerogel, iron-doped-TiO₂, aerogel-based- CeTiO₂, and iron-oxide-coated-manganese are effective to remove As from contaminated water. Biological processes (phytoremediation/microbiological) are effective and ecofriendly for As removal from water and/or soil environment. Microorganisms remove As from water, sediments and soil by metabolism, detoxification, oxidation-reduction, bio-adsorption, bio-precipitation, and volatilization processes. Ecofriendly As mitigation options can be achieved by utilizing an alternative As-safe-aquifer, surface-water or rainwater-harvesting. Application of hybrid (biological with chemical and physical process) and Best-Available-Technologies (BAT) can be the most effective As removal strategy to remediate As contaminated environments.

Cupriavidus basilensis strain r507, a toxic arsenic phytoextraction facilitator, potentiates the arsenic accumulation by Pteris vittata

As a toxic and carcinogenic metalloid, arsenic has posed serious threat to human health. Phytoremediation has emerged as a promising approach to circumvent this problem. Arsenic uptake by Pteris vittata is largely determined by arsenic speciation and mainly occurs via roots; thus, rhizospheric microbial activities may play a key role in arsenic accumulation. The aim of this study was to investigate the potential of arsenic resistant rhizobacteria to enhance arsenic phytoextraction. A total of 49 cultivable rhizobacteria were isolated from the arsenic hyperaccumulating fern, Pteris vittata, and subjected to an initial analysis to identify potentially useful traits for arsenic phytoextraction, such as arsenic resistance and the presence of aioA(aroA)-like (arsenite oxidase-like) gene. Isolated strain r507, named as Cupriavidus basilensis strain r507, was a selected candidate for its outstanding arsenic tolerance, rapid arsenite oxidation ability, and strong colonization to P. vittata. Strain r507 was used in co-cultivation trials with P. vittata in the field for six months. Results showed that the inoculation with strain r507 potentiated As accumulation of P. vittata up to 171%. Molecular analysis confirmed that the inoculation increased the abundance of aioA-like genes in the rhizosphere, which might have facilitated arsenite oxidation and absorption. The findings of this study suggested the feasibility of co-cultivating hyperaccumulators with facilitator bacteria for practical arsenic phytoremediation.

Immobilization of arsenic as scorodite by a thermoacidophilic mixed culture via As(III)-catalyzed oxidation with activated carbon

In this study we describe the immobilization of arsenic as scorodite (FeAsO₄.2H₂O) by a thermophilic iron-oxidizing mixed culture from an acidic sulfate medium containing 500 mg L^-1 of Fe(II), 500 mg L^-1 As(III) and granular activated carbon (GAC) as the main arsenite oxidant. This study shows that crystalline scorodite can only be precipitated in the presence of the ferrous iron-oxidizing mixed culture (pH 1.3 and 70 °C). The efficiency of arsenite oxidation was over 99% with a maximum specific oxidation rate of 280 mgAs(III) gGAC^-1 day^-1. Ferrous iron and arsenite were also oxidized in the absence of the mixed culture, however, no scorodite precipitated under these conditions; consequently, scorodite precipitation was biologically induced. The precipitated scorodite particles had a size between 0.5 and 10 μm with an average of 5 μm, resulting in low settling rates. Ion activity product calculations and observations by Scanning Electron Microscopy (SEM) indicated that microbial cells served as surface for heterogeneous nucleation. The potential of the thermophilic mixed culture for the scorodite formation explored in this study provides the basis of a new approach for the treatment of As(III) polluted streams.

Integrated bio-oxidation and adsorptive filtration reactor for removal of arsenic from wastewater

Recently, removal of arsenic from different industrial effluent discharged using simple, efficient and low-cost technique has been widely considered. In this study, removal of arsenic (As) from real wastewater has been studied employing modified bio-oxidation followed by adsorptive filtration method in a novel continuous flow through the reactor. This method includes biological oxidation of ferrous to ferric ions by immobilized Acidothiobacillus ferrooxidans bacteria on granulated activated carbon (GAC) in fixed bed bio-column reactor with the adsorptive filtration unit. Removal efficiency was optimized regarding the initial flow rate of media and ferrous ions concentration. Synthetic wastewater sample having different heavy metal ions such as Arsenic (As), Cobalt (Co), Chromium (Cr), Copper (Cu), Iron (Fe), Lead (Pb) and Manganese (Mn) were also used in the study. The structural and surface changes occurring after the treatment process were scrutinized using FT-IR and Scanning Electron Microscopy (SEM) analysis. The finding showed that not only arsenic can be removed considerably in the bioreactor system, but also removing efficiency was much more (<90%) for other heavy metals in real wastewater sample. The results from TCPL test confirms that solid spent media was non-hazardous and can be safely disposed of. This study verified that combination of bio-oxidation with adsorptive filtration method improves the removal efficiency of arsenic and other heavy metal ions in wastewater sample.

A Genomic Outlook on Bioremediation: The Case of Arsenic Removal

Microorganisms play a major role in biogeochemical cycles. As such they are attractive candidates for developing new or improving existing biotechnological applications, in order to deal with the accumulation and pollution of organic and inorganic compounds. Their ability to participate in bioremediation processes mainly depends on their capacity to metabolize toxic elements and catalyze reactions resulting in, for example, precipitation, biotransformation, dissolution, or sequestration. The contribution of genomics may be of prime importance to a thorough understanding of these metabolisms and the interactions of microorganisms with pollutants at the level of both single species and microbial communities. Such approaches should pave the way for the utilization of microorganisms to design new, efficient and environmentally sound remediation strategies, as exemplified by the case of arsenic contamination, which has been declared as a major risk for human health in various parts of the world.

Corynebacterium glutamicum MTCC 2745 immobilized on granular activated carbon/MnFe2O4 composite: A novel biosorbent for removal of As(III) and As(V) ions

The optimization of biosorption/bioaccumulation process of both As(III) and As(V) has been investigated by using the biosorbent; biofilm of Corynebacterium glutamicum MTCC 2745 supported on granular activated carbon/MnFe2O4 composite (MGAC). The presence of functional groups on the cell wall surface of the biomass that may interact with the metal ions was proved by FT-IR. To determine the most appropriate correlation for the equilibrium curves employing the procedure of the non-linear regression for curve fitting analysis, isotherm studies were performed for As(III) and As(V) using 30 isotherm models. The pattern of biosorption/bioaccumulation fitted well with Vieth-Sladek isotherm model for As(III) and Brouers-Sotolongo and Fritz-Schlunder-V isotherm models for As(V). The maximum biosorption/bioaccumulation capacity estimated using Langmuir model were 2584.668mg/g for As(III) and 2651.675mg/g for As(V) at 30°C temperature and 220min contact time. The results showed that As(III) and As(V) removal was strongly pH-dependent with an optimum pH value of 7.0. D-R isotherm studies specified that ion exchange might play a prominent role.

Immobilization of Ochrobactrum tritici As5 on PTFE thin films for arsenite biofiltration

Ochrobactrum tritici SCII24T bacteria is an environmental strain with high capacity to resist to arsenic (As) toxicity, which makes it able to grow in the presence of As(III). The inactivation of the two functional arsenite efflux pumps, ArsB and ACR3_1, resulted in the mutant O. tritici As5 exhibiting a high accumulation of arsenite. This work describes a method for the immobilization of the mutant cells O. tritici As5, on a commercial polymeric net after sputtered modified by the deposition of poly(tetrafluoroethylene) (PTFE) thin films, and demonstrates the capacity of immobilized cells to accumulate arsenic from solutions. Six different set of deposition parameters for PTFE thin films were developed and tested in vitro regarding their ability to immobilize the bacterial cells. The surface that exhibited a mild zeta potential value, hydrophobic characteristics, the lowest surface free energy but with a high polar component and the appropriate ratio of chemical reactive groups allowed cells to proliferate and to grow as a biofilm. These immobilized cells maintained their ability to accumulate the surrounding arsenite, making it a great arsenic biofilter to be used in bioremediation processes.

Application of granular activated carbon/MnFe₂O₄ composite immobilized on C. glutamicum MTCC 2745 to remove As(III) and As(V): Kinetic, mechanistic and thermodynamic studies

The main objective of the present study was to investigate the efficiency of Corynebacterium glutamicum MTCC 2745 immobilized on granular activated carbon/MnFe2O4 (GAC/MnFe2O4) composite to treat high concentration of arsenic bearing wastewater. Non-linear regression analysis was done for determining the best-fit kinetic model on the basis of three correlation coefficients and three error functions and also for predicting the parameters involved in kinetic models. The results showed that Fractal-like mixed 1,2 order model for As(III) and Brouser-Weron-Sototlongo as well as Fractal-like pseudo second order models for As(V) were proficient to provide realistic description of biosorption/bioaccumulation kinetic. Applicability of mechanistic models in the current study exhibited that the rate governing step in biosorption/bioaccumulation of both As(III) and As(V) was film diffusion rather than intraparticle diffusion. The evaluated thermodynamic parameters ΔG(0), ΔH(0) and ΔS(0) revealed that biosorption/bioaccumulation of both As(III) and As(V) was feasible, spontaneous and exothermic under studied conditions.

Role of indigenous arsenate and iron(III) respiring microorganisms in controlling the mobilization of arsenic in a contaminated soil sample

In this study two different treatment options were investigated for the release of arsenic from a contaminated soil sample. The first option was based on the "bioaugmentation" principle and involved addition of a pure Fe(III)-reducing culture, i.e. Desulfuromonas palmitatis. The second option consisted in the "biostimulation" of indigenous bacteria and involved simple addition of nutrients. Due to the strong association of As with soil ferric oxides, the reductive dissolution of soil oxides by D. palmitatis lead to 45 % arsenic release in solution (2.15 mM). When only nutrients were supplied to the soil, the same amounts of Fe and As were dissolved with slower rates and most aqueous As was found to be in the trivalent state, indicating the presence of arsenate reducing species. The arsenate reducing microorganisms were enriched with successive cultures, using Na2HAsO4 as electron acceptor. The phylogenetic analysis revealed that the enriched microbial consortium contained Desulfosporosinus species, which are known arsenate reducers.

Desorption of arsenic from exhaust activated carbons used for water purification

This work aims to the analysis of arsenic desorption from an exhaust activated carbon used for the purification of a natural water. This last was used to mimic the properties of common groundwater or drinking water. Different low-cost and harmless eluting solutions were considered, including distilled water, natural water, saline (NaCl, CaCl₂ and NaNO₃) and basic (NaOH) solutions. Experimental results showed that, for 1g of activated carbon with arsenic loading close to the maximum value available for the model natural water (ω ≈ 0.1 mg/g), it is possible to recover more than 80% of the arsenic using 20 ml of 0.1 M sodium chloride solution. A temperature variation within 20 and 40 °C has scarce effect on desorption efficiency. A comparison between desorption data and adsorption isotherms data suggests that arsenic adsorption is actually a reversible process. Therefore, it is virtually possible to increase arsenic recovery efficiency close to 100% by increasing the NaCl concentration or the volume of the desorption solution, but a preliminary cost benefit analysis lead to consider a NaCl 0.1M solution as an optimal solution for practical applications.

Whole-genome sequence of Cupriavidus sp. strain BIS7, a heavy-metal-resistant bacterium

Cupriavidus sp. strain BIS7 is a Malaysian tropical soil bacterium that exhibits broad heavy-metal resistance [Co(II), Zn(II), Ni(II), Se(IV), Cu(II), chromate, Co(III), Fe(II), and Fe(III)]. It is particularly resistant to Fe(II), Fe(III), and Zn(II). Here we present the assembly and annotation of its genome.

Removal of heavy metals using different polymer matrixes as support for bacterial immobilisation

Great attention is focused on the microbial treatment of metal contaminated environments. Three bacterial strains, 1C2, 1ZP4 and EC30, belonging to genera Cupriavidus, Sphingobacterium and Alcaligenes, respectively, showing high tolerance to Zn and Cd, up to concentrations of 1000ppm, were isolated from a contaminated area in Northern Portugal. Their contribution to Zn and Cd removal from aqueous streams using immobilised alginate, pectate and a synthetic cross-linked polymer was assessed. In most cases, matrices with immobilised bacteria showed better metal removal than the non-inoculated material alone. For the immobilisation with all the polymers, 1C2 was the strain that increased the removal of Zn the most, whereas EC30 was the most promising for Cd removal, especially when combined with the synthetic polymer with up to a ca. 11-fold increase in metal removal when compared to the polymer alone. Removal of individual metals from binary mixtures showed that there was differential immobilisation. There was greater removal of Cd than Zn (removals up to 40% higher than those showed for Zn). The results show that metal contaminated environments constitute a reservoir of microorganisms resistant/tolerant to heavy metals that have the capacity to be exploited in bioremediation strategies. Capsule immobilisation of bacteria in the naturally occurring alginate and pectate and in a synthetic cross-linked polymer increased the Zn and Cd removal abilities from single and binary contaminated waters; the applications with the synthetic polymer were the most promising for Cd and Zn removal in single and binary mixtures.

Removal of metals from aqueous solution and sea water by functionalized graphite nanoplatelets based electrodes

In the present wok, we have demonstrated the simultaneous removal of sodium and arsenic (pentavalent and trivalent) from aqueous solution using functionalized graphite nanoplatelets (f-GNP) based electrodes. In addition, these electrodes based water filter was used for multiple metals removal from sea water. Graphite nanoplatelets (GNP) were prepared by acid intercalation and thermal exfoliation. Functionalization of GNP was done by further acid treatment. Material was characterized by different characterization techniques. Performance of supercapacitor based water filter was analyzed for the removal of high concentration of arsenic (trivalent and pentavalent) and sodium as well as for desalination of sea water, using cyclic voltametry (CV) and inductive coupled plasma-optical emission spectroscopy (ICP-OES) techniques. Adsorption isotherms and kinetic characteristics were studied for the simultaneous removal of sodium and arsenic (both trivalent and pentavalent). Maximum adsorption capacities of 27, 29 and 32 mg/g for arsenate, arsenite and sodium were achieved in addition to good removal efficiency for sodium, magnesium, calcium and potassium from sea water.

Adsorption of arsenic(V) by iron-oxide-coated diatomite (IOCD)

PURPOSES AND AIMS: Economically efficient methods for removing arsenic from the drinking water supply are urgently needed in many parts of the world. Iron oxides are known to have a strong affinity for arsenic in water. However, they are commonly present in the forms of fine powder or floc, which limits their utility in water treatment. In this study, a novel granular adsorbent, iron-oxide-coated diatomite (IOCD), was developed and examined for its adsorption of arsenic from water.

MATERIALS AND METHODS

An industrial-grade diatomite was used as the iron oxide support. The diatomite was first acidified and dried and then coated with iron oxide up to five times. The prepared IOCD samples were characterized for their morphology, composition, elemental content, and crystal properties by various instruments. Experiments of equilibrium and kinetic adsorption of As(V) on IOCD were conducted using 0.1- and 2-L polyethylene bottles, respectively, at different pH and temperatures.

RESULTS

Iron oxide (alpha-Fe(2)O(3) hematite) coated onto diatomite greatly improves (by about 30 times) the adsorption of As(V) from water by IOCD as compared to using raw diatomite. This improvement was attributed to increases in both surface affinity and surface area of the IOCD. The surface area of IOCD increased to an optimal value. However, as the IOCD surface area (93 m(2)/g) was only 45% higher than that of raw diatomite (51 m(2)/g), the enhanced As(V) adsorption resulted primarily from the enhanced association of negatively charged As(V) ions with the partial positive surface charge of the iron oxide. The As(V) adsorption decreased when the solution pH was increased from 3.5 to 9.5, as expected from the partial charge interaction between As(V) and IOCD. The adsorption data at pH 5.5 and 7.5 could be well fitted to the Freundlich equation. A moderately high exothermic heat was observed for the As(V) adsorption, with the calculated molar isosteric heat ranging from -4 to -9 kcal/mol. The observed heats fall between those for physical adsorption and chemisorption and are indicative of the formation of a series of ion-pair complexes of As(V) ions with iron oxide surface groups.

CONCLUSIONS

This study demonstrated that the granular IOCD was successfully developed and employed to remove the As(V) in aqueous solution. The Freundlich isotherm well fitted the equilibrium adsorption data of As(V) onto IOCD, and both the pseudo-second-order model and the pore diffusion model simulated well the adsorption kinetics. Compared to other iron-oxide-based adsorbents reported in the literatures, the adsorption capacity of IOCD is relatively high and its kinetics is fast.