Sulfur/zinc co-doped biochar for stabilization remediation of mercury-contaminated soil: Performance, mechanism and ecological risk.

In this study, a novel sulfur/zinc co-doped biochar (SZ-BC) stabilizer was successfully developed for the remediation of mercury-contaminated soil. Results from SEM, TEM, FTIR and XRD revealed that biochar (BC) was successfully modified by sulfur and zinc. In the batch adsorption experiments, the sulfur-zinc co-pyrolysis biochar displayed excellent Hg(II) adsorption performance, with the maximum adsorption capacity of SZ-BC (261.074 mg/g) being approximately 16.5 times that of BC (15.855 mg/g). Laboratory-scale static incubation, column leaching, and plant pot experiments were conducted using biochar-based materials. At an additional dosage of 5 % mass ratio, the SZ-BC exhibits the most effective stabilization of mercury in soil, leading to a significant reduction in leaching loss compared to the control group (CK) by 51.30 %. Following 4 weeks of incubation and 2 weeks of leaching with SZ-BC, the residual mercury in the soil increased by 27.84 %. As a result, potential ecological risk index of mercury decreased by 92 % compared to the CK group. In the pot experiment, SZ-BC significantly enhanced the growth of Chinese cabbage, with biomass and root dry weight reaching 3.20 and 2.80 times that of the CK group, respectively. Additionally, the Translocation Factor (TF) and Bioconcentration Factor (BF) were reduced by 44.86 % and 74.43 %, respectively, in the SZ-BC group compared to the CK group. Moreover, SZ-BC can effectively improve enzyme activities and increase microbial communities in mercury-contaminated soils. The mechanisms of adsorption and stabilization were elucidated through electrostatic adsorption, ion exchange, surface complexation, and precipitation. These findings provide a potentially effective material for stabilizing soils contaminated with mercury.

Phosphorus-modified biochar cross-linked Mg-Al layered double-hydroxide stabilizer reduced U and Pb uptake by Indian mustard (Brassica juncea L.) in uranium contaminated soil.

The decommissioning of uranium tailings (UMT) is usually accompanied by uranium (U) contamination in soil, which poses a serious threat to human health and ecological security. Therefore, the remediation of uranium pollution in soil is imminent from ecological and environmental points of view. In recent years, the use of biochar stabilizers to repair uranium tailings (UMT) soil has become a research hotspot. In this study, a novel phosphorus-modified bamboo biochar (PBC) cross-linked Mg-Al layered double-hydroxide composite (PBC@LDH) was prepared. The hyperaccumulator plant Indian mustard (Brassica juncea L.) was selected as the test plant for outdoor pot experiments, and the stabilizers were added to the UMT soil at the dosage ratio of 15 g kg-1, which verified the bioconcentrate and translocate of U and associated heavy metal Pb in the UMT soil by Indian mustard after stabilizer remediated. The results shown that, after 50 days of growth, compared with the untreated sample (CK), the Indian mustard in PBC@LDH treatment possessed a better growth and its biomass weight of whole plant was increased by 52.7%. Meanwhile, the bioconcentration factors (BF) of U and Pb for PBC@LDH treatment were significantly decreased by 73.4% and 34.2%, respectively; and the translocation factors (TF) were also commendable reduced by 15.1% and 2.4%, respectively. Furthermore, the Tessier available forms of U and Pb in rhizosphere soil showed a remarkably decrease compared with CK, which reached by 55.97% and 14.1% after PBC@LDH stabilization, respectively. Complexation, precipitation, and reduction of functional groups released by PBC@LDH with U and Pb described the immobilization mechanisms of biochar stabilizer preventing U and Pb enrichment in Indian mustard. As well as, the formation of U-containing vesicles was prevented by the precipitation of -OH functional groups with free U and Pb ions around the cell tissue fluids and vascular bundle structure of plant roots, thereby reducing the migration risk of toxic heavy metals to above-ground parts. In conclusion, this research demonstrates that the PBC@LDH stabilizer offers a potentially effective amendment for the remediation of U contaminated soil.

Highly efficient photocatalytic oxidation of antibiotic ciprofloxacin using TiO2@g-C3N4@biochar composite.

In this present study, a novel indirect Z-scheme TiO2@g-C3N4@biochar (TiO2@g-C3N4@BC) composite photocatalyst was successfully fabricated and characterized with SEM, TEM, EDS, XRD, FTIR, PL, XPS, and UV-vis DRS. The photocatalytic degradation behavior of ciprofloxacin (CIP) on the TiO2@g-C3N4@BC was evaluated under UV-vis and visible light irradiation, and the possible reaction mechanism of photocatalytic oxidation of CIP on the TiO2@g-C3N4@BC was explained. The TiO2@g-C3N4@BC composite photocatalyst exhibited stronger photocatalytic oxidation activity for CIP in comparison with TiO2, g-C3N4, TiO2@BC, and TiO2@g-C3N4. After 60 min of UV-vis and visible light irradiation, the photocatalytic removal efficiency of CIP by TiO2@g-C3N4@BC was 99.3 and 89.2%, respectively. The photocatalytic removal performance of CIP was affected by the initial concentration of CIP, catalyst dosage, and pH value. The composite photocatalyst presented excellent stability and reusability after five cycles. An indirect Z-scheme principle of the CIP photocatalytic oxidation reaction on TiO2@g-C3N4@BC was clearly proposed, and the whole process of photocatalytic degradation was the results of the interaction between CIP and reactive active species (·O2-, h+, and ·OH), of which ·O2- is the main active substance. Four CIP degradation pathways were proposed. This work may provide an effective strategy to remove antibiotics in wastewater.

Enhanced phytoremediation of uranium-contaminated soils by Indian mustard (Brassica juncea L.) using slow release citric acid.

In this study, a novel slow release carrier for the controlled release of citric acid (CA), hydroxypropyl chitosan-graft-carboxymethyl-ß-cyclodextrin (HPCS-g-CMCD) was synthesized by the grafting reaction of carboxymethyl-ß-cyclodextrin (CMCD) with hydroxypropyl chitosan (HPCS), and the structural characteristics of HPCS-g-CMCD were confirmed by FT-IR, TGA, and NMR. Based on HPCS-g-CMCD and CA, slow release citric acid (SRCA) was prepared by a spray drying method. HPCS-g-CMCD carrier has a better slow release performance for CA compared to HPCS and CMCD, and CA release mechanism was attributed to a Fickian diffusion. Furthermore, the release behavior of uranium in contaminated soil could be effectively controlled by SRCA. The effects of SRCA on improving the phytoremediation capacity in uranium-contaminated soil were investigated using Brassica juncea, which were grown in pots containing soil with uranium at 56 mg kg-1. After 50 days of growth, 5 mmol kg-1 of CA, SRCA I, SRCA II, and SRCA III was applied, respectively. The results showed that slow release citric acid could enhance the uptake of uranium in Indian mustard. Uranium concentration in the root with SRCA I treatment was increased by 80.25% compared to the control, and the uranium removal efficiency of the SRCA I treatment was 1.66-fold greater than that of the control. Simultaneously, the leaching loss of uranium in SRCA I-treated soil was decreased by 37.35% compared to CA-treated soil. As a promising remediation strategy, SRCA-assisted phytoremediation may provide a kind of feasible technology with low leaching risk for remediation of uranium-contaminated soils.

Phosphorus-modified biochar cross-linked Mg-Al layered double-hydroxide composite for immobilizing uranium in mining contaminated soil.

The decommissioning of uranium mill tailings (UMTs) is usually accompanied by uranium (U) contamination in soil, which poses a serious threat to human health and ecological safety. In this study, a novel phosphorus-modified bamboo biochar (PBC) cross-linked Mg-Al layered double-hydroxide (LDH) composite ("PBC@LDH") was successfully prepared by phosphate pre-impregnation and a hydrothermal method with Mg-Al LDH. Physicochemical analysis revealed that phosphorus-containing functional groups and Mg-Al LDH were grafted onto the pristine biochar (BC) matrix. Laboratory-scale incubation and column leaching experiments were performed on the prepared BC, PBC, and PBC@LDH. The results showed that, at a dosage of 10%, the PBC@LDH composite had a commendable ability to immobilize U in soil. After 40 days of incubation with the stabilizer, the more mobile U was converted into immobilized species. Furthermore, during a column leaching experiment with simulated acid rain, the cumulative loss and leaching efficiency of U were remarkably reduced by PBC@LDH treatment compared with the control, reaching 53% and 54%, respectively. Surface complexation, co-precipitation, and reduction described the adsorption and immobilization mechanisms. In conclusion, this research demonstrates that the PBC@LDH composite offers a potentially effective amendment for the remediation of U contaminated soil.

Adsorption of dichromate ions from aqueous solution onto magnetic graphene oxide modified by ß-cyclodextrin.

In this work, the ß-cyclodextrin modified magnetic graphene oxide (ß-CD/MGO) composite was fabricated by the in situ co-precipitation method and characterized by Fourier transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), vibrating sample magnetometer (VSM), and particle size analysis. The adsorption behavior of dichromate ions on the ß-CD/MGO was investigated, and the mechanism of adsorption was also studied using FT-IR and XPS. The results from SEM and TEM showed that the graphene oxide (GO) layer became rough, and many fine particles were attached after compounding with ferroferric oxide and ß-cyclodextrin. The characterization results of FT-IR and XPS show that that ß-cyclodextrin and ferroferric oxide have been perfectly compounded to the graphene oxide layer and ß-CD/MGO has a particle size of about 460 nm, a specific surface area of 252.3 m2g-1, and a saturation magnetization of 73.5 emu g-1. The adsorption amount of dichromate ions on the ß-CD/MGO is affected by pH, adsorbent dosage, and adsorption time. Kinetic studies showed that the adsorption process followed a pseudo-second-order kinetic model. Equilibrium data agreed very well with the Langmuir model, the maximum adsorption amount of dichromate ions on the ß-CD/MGO was 49.95 mg g-1. After five successive adsorbent reuses, the reuse rate is still 73%, indicating the excellent potential reusability of ß-CD/MGO adsorbent. ß-CD/MGO exhibits excellent adsorption performance for dichromate ions. As an environmentally friendly magnetic adsorbent, ß-CD/MGO is suitable for the treatment of dichromate-containing wastewater.

Enhanced photocatalytic New Coccine degradation and Pb(II) reduction over graphene oxide-TiO2 composite in the presence of aspartic acid-ß-cyclodextrin.

In this work, aspartic acid-ß-cyclodextrin (ACD) was synthesized by the reaction of ß-cyclodextrin with aspartic acid and epichlorohydrin, and graphene oxide-TiO2 (GO-TiO2) composite catalyst was prepared by a hydrothermal method. The complexation of ACD with New Coccine (NC) and Pb2+ was characterized with FT-IR and XPS, respectively, the results show that ACD can simultaneously complex NC and Pb2+. XRD analysis and SEM images of GO-TiO2 show that TiO2 platelets are well distributed on both sides of the graphene oxide sheets, and display a similar XRD pattern to the pure TiO2 nanoparticles with the typical diffraction peak of anatase phase. The effects of ACD on the photocatalytic degradation of NC and photocatalytic reduction of Pb2+ were investigated in the single pollution system, and the synergistic effects on the simultaneous photocatalytic NC degradation and Pb2+ reduction in the presence of ACD were also evaluated. The results showed that the presence of ACD was favorable to the acceleration of photocatalytic oxidation of NC and photocatalytic reduction of Pb2+ in the single pollution system, and the photocatalytic reaction rate constants of NC and Pb2+ in the presence of ACD increased 58% and 42%, respectively. For the combined pollution system, the synergistic effects on the simultaneous conversion of NC and Pb2+ in aqueous solutions were also further enhanced. ACD enhanced photocatalytic activity was attributed to the improvement of the electron transfer and mass transfer at the GO-TiO2 interface.

Cysteine-ß-cyclodextrin enhanced phytoremediation of soil co-contaminated with phenanthrene and lead.

It is necessary to find an effective soil remediation technology for the simultaneous removal of hydrophobic organic contaminants and heavy metals from contaminated soils. In this work, a novel cysteine-ß-cyclodextrin (CCD) was synthesized by the reaction of ß-cyclodextrin with cysteine, and the structure of CCD was confirmed by (1)H-NMR, (13)C-NMR, FT-IR spectroscopy and elemental analysis. Pot-culture experiments were conducted to investigate the effects of CCD on the phytoremediation of soil co-contaminated with phenanthrene and lead. The results showed that CCD can enhance the phytoremediation of soil co-contaminated with phenanthrene and lead. When CCD was added to the co-contaminated soil, the concentrations of phenanthrene and Pb in roots and shoots of ryegrass (Lolium perenne L.) significantly increased, the presence of CCD is beneficial to the accumulation of phenanthrene and Pb in ryegrass, and the residual concentrations of phenanthrene and Pb in soils significantly decreased. Under the co-contamination of 500 mg Pb kg(-1) and 50 mg PHE kg(-1), the bioconcentration factor of phenanthrene and Pb in the presence of CCD was increased by 1.43-fold and 4.47-fold, respectively. After CCD was added to the contaminated soils, the residual concentration of phenanthrene and Pb in unplanted soil was decreased by 18 and 25%, respectively. However, for the planted soil, the residual concentration of phenanthrene and Pb was decreased by 48 and 56%, respectively. CCD may improve the bioavailability of phenanthrene and Pb in co-contaminated soil; CCD enhanced phytoremediation technology may be a good alternative for the removal of hydrophobic organic contaminants and heavy metals from contaminated soils.

ß-Cyclodextrin's orientation onto TiO2 and its paradoxical role in guest's photodegradation.

This work revealed that ß-cyclodextrin was attached onto the surface of TiO(2) predominately by its secondary ring side, which caused paradoxical functions of ß-cyclodextrin in the photodegradation of the four bisphenols. The equilibrium between the guest adsorbed through ß-cyclodextrin onto TiO(2) and the one locked in ß-CD in water could also change the role of ß-cyclodextrin in the degradation of a certain guest.

Photodegradation of E2 in the presence of natural montmorillonite and the iron complexing agent ethylenediamine-N,N'-disuccinic acid.

In this work, the photochemical degradation process of 17ß-estradiol (E2) in a suspension of natural montmorillonite (NM) has been studied. The addition of the iron complexing agent ethylenediamine-N,N'-disuccinic acid (EDDS) to the suspension was investigated and compared with the system without EDDS. The effects of the main physicochemical parameters (pH, EDDS, oxygen and NM concentrations) on E2 degradation in NM suspensions were also investigated. In order to better understand the photochemical process, experiments were carried out in the presence of 2-propanol. In general, the photochemical efficiency of the E2 degradation is better in EDDS-NM suspensions than in NM suspensions, especially at higher pH. This work demonstrated that the NM-EDDS system is an interesting and valuable research area and could be considered as a promising photochemical system for wastewater treatment.

Intermediates in photochemistry of Fe(III) complexes with carboxylic acids in aqueous solutions.

The primary processes in the photochemistry of Fe(III) complexes with carboxylic acids (glyoxalic, tartaric, pyruvic and lactic) were studied by means of laser flash photolysis. The inner-sphere electron transfer with the formation of Fe(II) complex and an escape of an organic radical to the solution bulk was shown to be a minor channel of the photolysis. The main channel was proposed to be the formation of a long-lived radical complex [Fe(II)···Ë™OOC-R](2+). Spectral and kinetic parameters of the radical complexes are determined.

Efficient photodegradation of dyes using light-induced self assembly TiO(2)/ß-cyclodextrin hybrid nanoparticles under visible light irradiation.

A novel ß-cyclodextrin (ß-CD) grafted titanium dioxide (TiO(2)/ß-CD) was synthesized through photo-induced self assembly methods, and its structure was characterized. The TiO(2)/ß-CD hybrid nanomaterial showed high photoactivity under visible light irradiation (λ ≥ 400 nm and/or λ ≥ 420 nm) and simulated solar irradiation (λ ≥ 365 nm). Photodegradation of Orange II followed the Langmuir-Hinshelwood kinetics model. The initial rate R(0) of Orange II degradation increased by 6.9, 2.6 and 1.9 times in the irradiation conditions of λ ≥ 420nm, λ ≥ 400nm and λ ≥ 365 nm, respectively. ß-CD increased the lifetimes of the excited states of the unreactive guests and facilitated the electron transfer from the excited dye to the TiO(2) conduction band, which enhanced the dye pollutant degradation. Superoxide radicals were shown to be the main reactive species that caused the degradation of Orange II under visible irradiation.

Simultaneous removal of phenanthrene and lead from artificially contaminated soils with glycine-ß-cyclodextrin.

Preparation of glycine-ß-cyclodextrin (GCD) was carried out by the reaction of ß-cyclodextrin with glycine in the presence of KOH and epichlorohydrin. The enhanced solubilization behavior of phenanthrene and lead carbonate by GCD was studied, and the desorption behavior of phenanthrene and lead from co-contaminated soil was also investigated. The results showed that GCD has obvious solubilization for phenanthrene and lead carbonate. The solubility of phenanthrene in 30 g/L of GCD was enhanced about 30-fold. And the apparent aqueous solubilities of lead carbonate are also obviously increased with increasing GCD concentration, when the concentration of GCD reached 20 g/L, the aqueous lead concentration was 2945 mg/L. GCD could simultaneously increase the apparent aqueous solubility of phenanthrene and complex with lead. The desorption process of GCD for phenanthrene and lead from co-contaminated soil followed the pseudo-second-order kinetic model. The removal efficiencies of phenanthrene and lead in soil increased dramatically with increasing GCD concentrations. At concentration of 40 g/L, GCD has a removal efficiency of 85.8% and 78.8% for lead and phenanthrene, respectively, from the combined contaminated soil. The use of GCD as an extractant to enhance the removal of heavy and hydrophobic organic contaminants (HOCs) from co-contaminated soils appears as a promising remediation method.

Photo-induced transformations of Hg(II) species in the presence of Nitzschia hantzschiana, ferric ion, and humic acid.

Effects of algae Nitzschia hantzschiana, Fe(III) ions, humic acid, and pH on the photochemical reduction of Hg(II) using the irradiation of metal halide lamps (lambda > or = 365 nm, 250 W) were investigated. The photoreduction rate of Hg(II) was found to increase with increasing concentrations of algae, Fe(III) ions, and humic acid. Alteration of pH value affected the photoreduction of Hg(II) in aqueous solution with or without algae. The photoreduction rate of Hg(II) decreased with increasing initial Hg(II) concentration in aqueous solution in the presence of algae. The photochemical kinetics of initial Hg(II) and algae concentrations on the photoreduction of Hg(II) were studied at pH 7.0. The study on the total Hg mass balance in terms of photochemical process revealed that more than 42% of Hg(II) from the algal suspension was reduced to volatile metallic Hg under the conditions investigated.

Photodegradation of chloroform in aqueous solution: impact of montmorillonite KSF particles.

In this work, photodegradation of chloroform in water suspensions of montmorillonite KSF (KSF) under a black light lamp (lambda=365 nm) was investigated. The results showed that KSF induced the photodegradation of chloroform by producing hydroxyl radical (OH) that oxidized chloroform in the heterogeneous clay-water systems. The photodegradation of chloroform in KSF suspensions was greatly influenced by the concentration of KSF and the pH of KSF suspensions. The photodegradation of chloroform by KSF followed the Langmuir-Hinshelwood Model. Furthermore, the removal efficiency of chloroform can be enhanced by the presence of carboxylates (oxalate and citrate) and humic acid (HA). This work demonstrates that KSF can be used as a new and efficient photocatalyst in oxidation and removal of organic compounds.

Photoinduced degradation of 2,4-dichlorophenol in water: influence of various Fe(III) carboxylates.

Fe(III)-carboxylate complexes were investigated with respect to tri-carboxylic (citric), di-carboxylic (tartaric) and mono-carboxylic (pyruvic) acids. In agreement with the chemical structure, results demonstrated that Fe(iii) was complexed by citric acid with a ratio of 1 : 1 (Fe/ligand), tartaric acid (d or l) with a ratio of 1 : 2 and by pyruvic acid with a ratio of 1 : 3. The iron concentration was fixed at 0.3 mmol L(-1) and the ligand concentration ranged from 0 to 1.0 mmol L(-1). The primary stage of 2,4-dichlorophenol (2,4-DCP) degradation photoinduced by these Fe(iii) complexes was investigated under monochromatic irradiation (lambda = 365, 313 and 296 nm). The values of initial quantum yields of 2,4-DCP disappearance (between 0.01 and 0.135) and Fe(ii) formation (between 0.002 and 0.47) were evaluated and are presented in detail. Short irradiation wavelength (296 nm), low pH (3.0) and high oxygen concentration favoured the pollutant degradation. The disappearance of 2,4-DCP was complete under these favourable conditions.

Degradation of atrazine photoinduced by Fe(III)-pyruvate complexes in the aqueous solution.

The composition and photochemical properties of the Fe(III)-Pyr complexes in the aqueous solution was studied in this work. Fe(III) was complexed by Pyr in the ratio of 1:3. The photochemical processes occurred in the Fe(III)-Pyr system was studied in detail. Fe(II) was the main intermediate product. DMPO was used as scavenger to determine the active radicals, such as *OH, CO3*-, CO2*-, H and RCO2* by ESR. Photodegradation of atrazine induced by the photolysis of Fe(III)-Pyr was studied and the reaction kinetics fitted the first order reaction. Parameters such as pH, the initial concentrations of Fe(III), pyruvate (Pyr) and atrazine were all investigated. Photoproducts were detected by the LC-MS and the photodegradation scheme was proposed. *OH radical was the main pathway of atrazine degradation.

Adsorption of uranium (VI) from aqueous solution onto cross-linked chitosan.

Cross-linked chitosan (CCTS) was synthesized by the reaction of chitosan with epichlorohydrin under alkaline conditions. Adsorption of uranium (VI) from aqueous solution onto cross-linked chitosan was investigated in a batch system. Adsorption isotherm and adsorption kinetic studies of uranium (VI) onto cross-linked chitosan were carried out. The influence factors on uranium (VI) adsorption were also investigated and described in detail, such as contact time, pH value and initial uranium (I) concentration. Langmuir and Freundlich adsorption models were used for the mathematical description of the adsorption equilibrium. Equilibrium data agreed very well with the Langmuir model. Adsorption kinetics data were tested using pseudo-first-order and pseudo-second-order models. Kinetic studies showed that the adsorption followed a pseudo-second-order kinetic model, indicating that the chemical adsorption was the rate-limiting step. Results also showed that cross-linked chitosan was favourable adsorbent.

Influence of marine phytoplankton, transition metals and sunlight on the species distribution of chromium in surface seawater.

The photoreduction of Cr(VI) to Cr(III) by marine phytoplankton (diatoms, red and green algae), with or without the presence of transition metals (Fe(III), Cu(II) and Mn(II)) was studied. The direct influence of marine phytoplankton on the photochemical reduction of Cr(VI) was confirmed for the first time, and two kinds of mechanisms were suggested to be responsible for the species transformation: (a) Cr(VI) in excited state could be reduced by the electron donor in its ground state via photo produced electrons; and (b) the solvated electrons reduce the CrO(4)(2-) anions in their ground state. The conversion ratio of Cr(VI) to Cr(III) increased with increasing algae concentration and irradiation time. Different species of marine phytoplankton were found to have different photo-reducing abilities. The photochemical redox of transition metals could induce the species transformation of chromium. After photoreduction by marine phytoplankton and transition metals, the ratio of Cr(VI) to Cr(III) was in the range of 1.45-2.16 for five green algae (Tetraselmis levis, Chlorella autotrophica, Dunaliella salina, Nannochloropsis sp., and Tetraselmis subcordiformis), and only 0.48 for Phaeodactylum tricornutum (diatom) and 0.71 for Porphyridium purpureum (red alga). The species distribution of chromium in the sunlit surface seawater was greatly affected by combined effects of marine phytoplankton (main contributor) and transition metals; both synergistic and antagonistic effects were observed. The results provided further insights into the species distribution and the biogeochemical cycle of chromium, and have significant implications for the risk assessment of chromium in the sunlit surface seawater.

Fenton-like oxidation of Rhodamine B in the presence of two types of iron (II, III) oxide.

The catalytic efficiency of iron (II, III) oxide to promote Fenton-like reaction was examined by employing Rhodamine B (RhB) as a model compound at neutral pH. Two types of iron (II, III) oxides were used as heterogeneous catalysts and characterized by XRD, Mössbauer spectroscopy, BET surface area, particle size and chemical analyses. The adsorption to the catalyst changed significantly with the pH value and the sorption isotherm was fitted using the Langmuir model for both solids. Both sorption and FTIR results indicated that surface complexation reaction may take place in the system. The variation of oxidation efficiency against H(2)O(2) dosage and amount of exposed surface area per unit volume was evaluated and correlated with the adsorption behavior in the absence of oxidant. The occurrence of optimum amount of H(2)O(2) or of exposed surface area for the effective degradation of RhB could be explained by the scavenging effect of hydroxyl radical by H(2)O(2) or by iron oxide surface. Sorption and decolourization rate of RhB as well as H(2)O(2) decomposition rate were found to be dependent on the surface characteristics of iron oxide. The kinetic oxidation experiments showed that structural Fe(II) content strongly affects the reactivity towards H(2)O(2) decomposition and therefore RhB decolourization. The site density and sorption ability of RhB on surface may also influence the oxidation performance in iron oxide/H(2)O(2) system. The iron (II, III) oxide catalysts exhibited low iron leaching, good structural stability and no loss of performance in second reaction cycle. The sorption on the surface of iron oxide with catalytic oxidation using hydrogen peroxide would be an effective oxidation process for the contaminants.