Arsenic Removal Research Articles

Synthesis, characterization and adsorptive performances of functionalized clay minerals and red mud for aqueous arsenic removal

Water pollution due to elevated arsenic (As) levels is a very serious health issue worldwide. Employing adsorbent substances to remove As from an aqueous environment presents a viable solution to this pressing concern. The As adsorption behavior onto modified clay (kaolinite, bentonite) and red mud in aqueous media was investigated in this study. Specific surface area (SSA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) studies confirmed successful modification of kaolinite, bentonite, and red mud through Fe-impregnate and dimethyl sulfoxide (DMSO)-intercalation. The incorporation of iron and DMSO improved the ability to remove As. The kinetic study showed that the adsorption equilibrium for both clay minerals and red mud products was reached within approximately 120 min, and the data fitted well to the simple Elovich, power function, and pseudo-second-order equation. Of all the products, Fe-Bentonite exhibited the highest As adsorption capacity, with a value of 581.2 μg g−1 (initial As concentration = 50 μg mL−1). Revealed in this study is that Fe-Bentonite, DMSO-Bentonite, and Fe-Red mud were the best-screened products for removing As from the aqueous system.

Synergetic interactions between zero-valent iron and schwertmannite for enhanced arsenic (III) removal: Role of morphological variations

Although the enhanced removal of heavy metals using zero valent iron (ZVI) assisted by schwertmannite (Sch) was achieved in previous studies, their interactions between Sch and ZVI seems to be bidirectional and impact on the As(III) removal by ZVI/Sch mixture remains elusive. This study investigated As(III) removal in the mixed suspensions of ZVI and Sch with various premixing times and mass ratios. Batch experiments demonstrated that ZVI/Sch mixture with the premixing time of 3 h and mass ratio of 2:1 exhibited excellent performance in As(III) removal. The results indicated that synergetic interactions between ZVI and Sch during premixing process played crucial roles, particularly in terms of morphological variations. Results of FTIR and XPS revealed the mass and electron transfer occurred between Sch and ZVI during the premixing process, resulting in the accelerated recrystallization of Sch and the corrosion process of ZVI. Furthermore, the premixing process was found to significantly improve the As(III) removal capacity of ZVI/Sch mixture without altering the As(III) removal pathway, including the adsorption/precipitation/oxidation processes of ZVI and surface complexation/ion exchange/channels inlay of Sch. These findings shed light on the complex interactions between ZVI and Sch in As(III) removal and offer promising opportunities for the development of efficient treatment strategies in As(III)-contaminated environments.

Process optimization of rice straw-derived activated biochar and biosorption of heavy metals from drinking water in rural areas

The Indo-Gangetic plain of northern India is known for prevalent rice farming. Due to the lack of a rice straw waste management system, a large volume of rice straw is burned in the field. Therefore, we add value to rice straw by converting it into activated biochar and utilizing it to remove toxic metals from natural water. In this work, single-step physical activation (CO2 and H2O) of rice straw was planned and optimized the activation process parameters to get better biochar yield and surface area. The biochar activation parameters were optimized using the central composite design method. The CO2 activated biochar has an optimum surface area and product yield of 399.99 m2/g and 26.79 %, whereas H2O activated biochar has an optimum product yield and surface area of 31.53 % and 300 m2/g. The SEM analysis shows that CO2 activated biochar has a more uniform porous structure than H2O activated biochar. Cost analysis revealed that CO2 and H2O activated biochar had a lower manufacturing cost of 1.287 and 1.672 U.S. $/kg, respectively compared to other adsorbents. Arsenic and manganese removal efficiency in natural water was found to be greater than 95 % for both activated biochar.

Arsenic Removal and Iron Recovery from Arsenic-Bearing Iron Ores by Calcification-Magnetic Roasting and Magnetic Separation Process.

Extracting iron while minimizing the health and environmental risks associated with arsenic contamination necessitates the removal of arsenic from arsenic-bearing iron ores to ensure a safe and sustainable supply of this metal for industries. The beneficiation of iron minerals and arsenic-bearing minerals from arsenic-bearing iron ores with a calcification-magnetizing roasting and low-intensity magnetic separation (CMR-LMS) process is investigated in this work. The results show that the process is successful in extracting iron minerals and eliminating arsenic-containing minerals. The roasting involves two key steps: calcification and magnetizing, which change hematite and goethite into magnetite and arsenic-bearing minerals into calcium arsenates. The process's separation efficiency of the CMR-LMS is closely linked to the parameters such as roasting temperature, roasting time, coke, alkalinity, and the liberation of gangue minerals from iron minerals. Through grinding and secondary magnetic separation, the iron minerals and gangue components, as well as arsenic, in roasted sand can be further separated. The optimum procedure results in a high-grade iron concentrate with an iron assay of 65.65%, an Fe recovery rate of 80.07%, and an arsenic content of 0.085%, while achieving a 93.29% As removal rate from the original ore that has 45.32% Fe and 0.70% As.

Carbon Dots-Embedded Silica Tubes: An Excitation-Independent Yellow-Emitting Turn-On Probe for Simultaneous Detection and Removal of Inorganic Arsenic with In Vivo Tracking in Living Organisms.

The environmental monitoring and remediation of highly toxic inorganic arsenic species in natural water are needed for the benefit of the ecosystem. Current studies on arsenic detection and removal often employ separate materials, which exhibit blue luminescence with fluorescence quenching, making them unsuitable for biological and environmental samples. In this study, carbon dot-embedded mesoporous silica tubes functionalized with melamine are synthesized to address these limitations and enable specific and turn-on probing of inorganic arsenic. The newly synthesized material demonstrates excitation-independent yellow luminescence and can effectively detect both As (III) and As (V) at low detection limits (11 × 10-9 m, 11.2× 10-9 m), well below the prescribed threshold limits in drinking water. It also exhibits a high adsorption capacity (≈125, 159mg g-1 ) with fast kinetics. The material's applicability in environmental samples is validated through the successful quantification of arsenic in real samples with satisfactory recoveries. Moreover, the material shows recyclability for reuse, as demonstrated by its arsenic adsorption and desorption for several cycles under basic conditions. Additionally, the material's capability for monitoring arsenic in a biological sample (Artemia salina) is demonstrated through fluorescence imaging. The encouraging outcomes underscore the material's potential use in monitoring and mitigating arsenic in aqueous systems.

Simultaneous removal of cadmium(II) and arsenic(III) from aqueous solutions using pyrite-modified biochar: Effects and mechanisms

Simultaneous removal of cadmium [Cd(II)] and arsenic [As(III)] from aqueous systems is still a great challenge. Through mechanical ball milling and thermal activation, pyrite-modified biochar (PMB) was successfully prepared and used to evaluate its synchronous removal effect and mechanism of Cd(II) and As(III) from aqueous solutions. PMB exhibited a maximum adsorption capacity of 51.0 mg·g−1 for Cd(II) (pH=6) and 65.9 mg·g−1 for As(III) (pH=4) at 25 °C, surpassing that of biochar by 1.5 and 5.7 times, respectively. Interestingly, in the mixed Cd-As system, the presence of Cd(II) hindered the adsorption of As(III) onto PMB, while the presence of As(III) enhanced the adsorption of Cd(II). Additionally, the removal of Cd(II) and As(III) by PMB remained in the range of 70%− 80% under the competition of cations (K+, Mg2+) and anions (NO3-, SO42-), except for the severe inhibition of Cd(II) and As(III) removal by Ca2+ and PO43- due to their specific physicochemical properties. The adsorption of Cd(II) by PMB followed the Langmuir and pseudo-second-order models, involving ion exchange (formation of CdS) and complexation as the main removal mechanisms. And the adsorption of As(III) followed the Freundlich and pseudo-second-order models, involving oxidation of As(III) to arsenic(V) and further complexation as the primary removal mechanisms. After four adsorption-desorption cycles, the adsorption performance of PMB for Cd(II) and As(III) could still reach 78% and 68% of the initial performance. Overall, the results demonstrated that PMB was the preferred eco-friendly material for efficiently removing Cd(II) and As(III) from co-pollution aqueous solutions.

Removal of Arsenate by Fixed-Bed Columns Using Chitosan-Magnetite Hydrogel Beads and Chitosan Hydrogel Beads: Effect of the Operating Conditions on Column Efficiency.

Fixed-bed columns packed with chitosan-magnetite (ChM) hydrogel and chitosan (Ch) hydrogel were used for the removal of arsenate ions from aqueous solutions at a pH of 7.0. The effect of flow rate (13, 20, and 25 mL/h), height of the columns (13 and 33 cm), and initial arsenate concentration (2, 5 and 10 mg/L) on the column's efficiency for the removal of As(V) is reported. The maximum adsorption capacity (qb), obtained before the allowed concentration of contaminant is exceeded, the adsorption capacity (qe) when the column is exhausted, and the mass transfer zone were determined. With this information, the efficiency of the column was calculated, which is given by the HL/HLUB ratio. The higher this ratio, the higher the efficiency of the column. The highest efficiency and the highest uptake capacity value at breakthrough point were obtained when using the lower flow rate, lower initial arsenate concentration, and longer bed length. When 33 cm-high columns were fed with a 10 mg As(V)/L solution at 13 mL/h, the maximum uptake capacity values at exhaustion obtained for Ch and ChM were 1.24 and 3.84 mg/g, respectively. A pH increase of the solution at the column's exit was observed and is attributed to the proton transfer from the aqueous solution to the amino and hydroxyl groups of chitosan. The incorporation of magnetite into Ch hydrogels significantly increases their capacity to remove As(V) due to the formation of complexes between arsenic and the magnetite surface. Experimental data were fitted to the Thomas model, the Yoon-Nelson model and the Bohart-Adams model using non-linear regression analysis.

Removal of arsenic and metal ions from acidic effluents via the Fenton reaction method

Arsenic-bearing acidic effluent from hydrometallurgical processes contains many harmful metal ions and must be appropriately treated before discharge. In the present study, arsenic, copper, zinc, aluminum, and magnesium were co-precipitated by means of the Fenton reaction. The precipitates obtained under different conditions were investigated to determine their stability. The results indicate that pH value and hydrogen peroxide (H2O2) dosage have significant effects on the removal of various elements. Arsenic, copper, zinc, and aluminum (but not magnesium) can be removed at pH 5-6 and anH2O2/As mole ratio of 2 at ambient temperature. The precipitates were mainly amorphous and granular with particle size in the micrometre range. The arsenic concentration in leachate from the toxicity characteristic leaching test was 3.6 mg/L, which proves that the precipitates are effective in fixing arsenic.

The Significance of Polymeric Ligand Exchange (PLE) Technique for Arsenic Removal from Polluted Groundwater: A Review

The Significance of Polymeric Ligand Exchange (PLE) Technique for Arsenic Removal from Polluted Groundwater: A Review

Amorphous Fe–Mn binary oxides nanoparticles decorating waste bamboo biomass-based monolith for efficient arsenic removal with column adsorption

The removal of naturally occurring arsenic from aqueous media remains a challenging endeavor for the protection of public health and ecosystems. Herein, we devised a workable fresh-biomass-based monolith adsorbent by in situ generation of amorphous Fe–Mn binary oxides nanoparticles (Fe–Mn–O) on a waste bamboo biomass (MB) via a simple procedure of pre-oxidation plus co-precipitation. In the pre-oxidation process of MB, the surface underwent roughening and the manganese ions permeated deeply inside the biomass, both of which facilitated the loading of Fe–Mn–O (25.06 wt%). As a result, the Fe–Mn–O/MB had outstanding adsorption capacities of 33.41 and 36.88 mg g−1 for As(III) and As(V), respectively. XRD and FTIR analyses show that the amorphous structure of Fe–Mn–O with low-coordinated active centers provides numerous hydroxyl functional groups that enhance arsenic adsorption, moreover, oxidation of As(III) was realized. In different water matrix, the Fe–Mn–O/MB composite exhibited a retention of 87.33 % and 89.53 % of its original adsorption capacity for As(III) and As(V) after five cycles of reuse as well as enabled continuous operation in a fixed-bed system with a bed volume of around 1150. Therefore, this work provides a promising approach for efficient abatement of inorganic arsenic-caused water pollution.

Rapid and selective removal of trace As(III) from water using Fe[sbnd]Mn binary oxide

The rapid removal of trace arsenic is crucial for ensuring the safety of drinking water. However, achieving the rapid removal of trace arsenic poses a significant challenge. In this study, we aim to enhance the removal efficiency of trace arsenic by increasing the specific surface area of the adsorbent material while maintaining its micrometer size. The material design allowed for the rapid removal of trace amounts of As(III) in groundwater within 10 s, resulting in a concentration as low as 0.281 μg L−1, which meets the WHO drinking water standard (<10 μg L−1). Our experimental results demonstrated that the FeMn binary oxide could partially oxidize As(III) into As(V), achieving a removal efficiency exceeding 99 %. Furthermore, we investigated the influence of common cations and anions, such as K+, Mg2+, Ca2+, Cl−, NO3−, SO42−, and PO43−, which may be present in natural water, on As(III) removal. Our findings indicated that the FeMn binary oxide exhibited remarkably high separation factors (ranging from 10 to 103) for other coexisting ions, indicating its exceptional selectivity for As(III) even in the presence of other ions. The outstanding arsenic uptake capability and selectivity of the FeMn binary oxide make it a highly promising adsorbent for the efficient removal of trace As(III) from aqueous solutions.

Removal of heavy metals from domestic wastewater using Beneficiated Kaolin Clay, Silver Oxide and zinc Oxide nanocomposite

This study describes the removal of total iron, cadmium, lead, copper, manganese, arsenic, mercury silver and zinc from domestic wastewater disposed of via sewers, using Beneficiated Kaolin Clay (BKC), BKC/Ag, BKC/ZnO and BKC/Ag/ZnO nanocomposite adsorbents produced by blending Silver Oxide (Ag) and Zinc Oxide (ZnO) nanoparticles with kaolin clay. High Resolution Transmission Electron Microscope (HRTEM) results showed that the produced adsorbents were polycrystalline in nature, while the interplanar spacing and average crystalline sizes are 1.775 – 4.712 nm and 26. 834 – 40.258 nm respectively, according to X-Ray Diffractometer (XRD) analysis. The Dispersive X – Ray Fluorescence (XRF) analysis indicated that SiO2/Al2O3 ratios for BKC/Ag, BKC/ZnO and BKC/Ag/ZnO nanocomposites adsorbents were 1.5170, 1.4818 and 1.5231 respectively. Brunauer – Emmett – Teller (BET) analysis showed that the desorption average pore sizes fell in the mesopore widths of 13.8994 – 16.9233 nm and surface areas of 1.0545 - 14.5126 m2.g-1. The removal efficiencies of the produced adsorbents followed this trend: BKC/Ag/ZnO &gt; BKC/Ag &gt; BKC/ZnO &gt; BKC. These adsorbents were excellent in the removal of total iron, cadmium, lead, copper, manganese, arsenic, mercury silver and zinc pollutants from domestic wastewater, and hence, recommended for large scale production.

Tuned bimetallic MOFs with balanced adsorption and non-radical oxidizing activities for efficient removal of arsenite

The removal of arsenic from contaminated water is important for environmental protection and drinking water safety worldwide. In this study, bimetallic metal–organic frameworks (MOFs) with catalytic and adsorptive effects were synthesized and combined with peroxymonosulfate (PMS) for efficient As(III) oxidation and As(III)/As(V) removal. The molar ratio of Fe and Mn precursor was adjusted to balance the adsorption and catalytic processes of As(III) in the system. The results showed that among the Fe/Mn-MOFs and MIL-88(Fe) tested, the Fe/Mn-MOFs with an Fe/Mn molar ratio of 1:1 (Fe0.3Mn0.3-MOFs) could achieve the best catalytic and adsorption performance with 98% removal of As(III). The performance of Fe0.3Mn0.3-MOFs in natural contaminated water was also verified. Electron spin resonance detection and quenching experiments have revealed that trivalent arsenic oxidation is facilitated primarily by a non-radical process through singlet oxygen. Density-functional theory, XPS and FTIR analyses reveal the structures, corresponding binding energies and binding sites for the adsorption of As(III)/As(V) by Fe0.3Mn0.3-MOFs. The coupling of Fe0.3Mn0.3-MOFs to the PMS system was still able to achieve 78% arsenic removal after five cycles, showing good reliability and effectiveness in arsenic removal. This study provides a new insight into the catalytic and adsorption mechanisms in MOFs/PMS systems and provides a theoretical basis for the application of MOFs in the remediation of arsenic contaminated water.

Synergistic photocatalytic oxidation and adsorption boost arsenic removal by in-situ carbon-doped TiO2 and nitrogen deficiency C3N4 heterojunction

The efficient removal of arsenic from wastewater is still a challenge. In this paper, a heterojunction consisting of in-situ carbon-doped TiO2 and nitrogen deficiency g-C3N4 (C/TiO2@ND-C3N4) has been constructed, which can completely oxidize As(III) (10,000 μg/L, 40 mL) to As(V) within 12 min under visible light and simultaneously adsorb total As (95.0%) with the pseudo-secondary kinetic equation, superior than in-situ carbon-doped TiO2 (75.0%) and nitrogen deficiency g-C3N4 (50.5%). The good photocatalytic oxidation and adsorption performances of C/TiO2@ND-C3N4 on As(III) removal can be attributed to the successful synthesis of heterojunction. On one hand, the building of C–O–Ti interfacial chemical bonds enable rapid electron transfer and improve the efficiency of photocatalytic oxidation. On the other hand, the decreased As(V) adsorption energy resulted from the synthesized heterojunction boost the adsorption capability of As(V), which was completed by the generation of O–As bonds with oxygen-containing functional groups on the surface of TiO2 and hydrogen bonds with high content pyrrole nitrogen derived from ND-C3N4, respectively. The results manifest that the preparation of bifunctional materials with both photocatalytic oxidation and adsorption properties provides a new strategy to achieve the removal of As.

Artificial Intelligence Modelling to Support the Groundwater Chemistry-Dependent Selection of Groundwater Arsenic Remediation Approaches in Bangladesh

Groundwater arsenic (As) still poses a massive public health threat, especially in South Asia, including Bangladesh. The arsenic removal efficiency of various technologies may be strongly dependent on groundwater composition. Previously, others have reported that the molar ratio [Fe]−1.8[P][As], in particular, can usefully predict the potential efficiency of groundwater As removal by widespread sorption/co-precipitation-based remediation systems. Here, we innovatively extended the application of artificial intelligence (AI) machine learning models to predict the geospatial distribution of [Fe]−1.8[P][As] in Bangladesh groundwaters utilizing our analogous AI predictions for groundwater As, Fe, and P. A comparison between the predicted geospatial distribution of groundwater As and [Fe]−1.8[P][As] distinguished high groundwater As areas where (a) sorption/co-precipitation remediation technologies would have the potential to be highly effective in removing As without Fe amendment, as well as from those areas where (b) amendment with Fe (e.g., zero-valent Fe) would be required to promote efficient As removal. The 1 km2 scale of the prediction maps provided a 100-fold improvement in the granularity of previous district-scale non-AI models. AI approaches have the potential to contribute to informing the appropriate selection and amendment of appropriate groundwater contamination remediation strategies where their effectiveness depends on local groundwater chemistry.

Effective removal of arsenic from contaminated groundwater using an iron-based metal-organic framework

This study investigates the potential of an iron-based metal–organic framework (MOF) material, Fe-benzene-1,3,5-tricarboxylate (Fe-BTC), for arsenic removal from water. We conducted batch and column experiments to evaluate the effects of varying mass dosages of MOF and pH ranges on arsenic adsorption. Our batch experiments revealed that increasing the mass of Fe-BTC MOF led to higher adsorption capacity. Furthermore, within the range of pH values analyzed, Fe-BTC demonstrated stable arsenic adsorption capacity, suggesting that pH conditions did not significantly affect its performance. In the column experiments, we used granitic material amended with compost and compared arsenic concentration breakthrough curves with and without the presence of MOF to assess its efficiency in arsenic removal. Without MOF, we observed rapid arsenic arrival followed by a slow increase in concentration, indicating anomalous transport dynamics induced by the compost. The addition of MOF resulted in prolonged arsenic arrival and a stabilized lower concentration, indicating effective arsenic adsorption. Fe-BTC MOF exhibited a six-fold increase in arsenic adsorption compared to its absence when added to the soil material. We employed a fractional order advection–dispersion equation model to characterize and predict the physical and chemical dynamics in the column experiments. The transport model accurately matched the arsenic breakthrough curves in the column experiments by capturing the non-Fickian transport and sorption chemical dynamics. The model indicated that compost had an insignificant impact on arsenic adsorption due to flow heterogeneity, while higher dosages of MOF resulted in increased arsenic adsorption and non-Fickian dynamics.

Arsenic Removal Using Unconventional Material with Iron Content: Batch Adsorption and Column Study.

The remediation of arsenic contamination in potable water is an important and urgent concern, necessitating immediate attention. With this objective in mind, the present study investigated arsenic removal from water using batch adsorption and fixed-bed column techniques. The material employed in this study was a waste product derived from the treatment of groundwater water for potable purposes, having a substantial iron composition. The material's properties were characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier-transformed infrared spectroscopy (FT-IR). The point of zero charge (pHPZC) was measured, and the pore size and specific surface area were determined using the BET method. Under static conditions, kinetic, thermodynamic, and equilibrium studies were carried out to explore the influencing factors on the adsorption process, namely the pH, contact time, temperature, and initial arsenic concentration in the solution. It was found that the adsorption process is spontaneous, endothermic, and of a physical nature. In the batch adsorption studies, the maximum removal percentage was 80.4% after 90 min, and in a dynamic regime in the fixed-bed column, the efficiency was 99.99% at a sludge:sand = 1:1 ratio for 380 min for a volume of water with arsenic of ~3000 mL. The kinetics of the adsorption process conformed to a pseudo-second-order model. In terms of the equilibrium studies, the Sips model yielded the most accurate representation of the data, revealing a maximum equilibrium capacity of 70.1 mg As(V)/g sludge. For the dynamic regime, the experimental data were fitted using the Bohart-Adams, Thomas, and Clark models, in order to establish the mechanism of the process. Additionally, desorption studies were conducted, serving as an essential step in validating the practical applicability of the adsorption process, specifically in relation to the reutilization of the adsorbent material.

An affordable bioadsorbent system to treat arsenic-contaminated drinking water in the developing world: Prototyping and economic assessment

The contamination of surface and groundwater with arsenic is an urgent problem in many countries where the population does not have any other water sources. A new renewable/recoverable sugarcane bagasse anion adsorbent (SBAA) for arsenic removal was prepared using a greener, cleaner, and sustainable synthesis method in a mini-pilot reactor. SBAA was prototyped for the treatment of arsenic-contaminated groundwater. Tests carried out with the prototype connected to household clay ceramic water filters showed that SBAA achieved 95 ± 3% arsenic removal, reaching arsenic levels below the WHO’s limit of 10 µg L−1. SBAA obtained the NSF/ANSI 61–2016 safety certification, which allows its safe and commercial use. Comparing the performance of the SBAA with commercial materials demonstrates its potential to compete with other technologies in the market. The SBAA is efficient, even in the presence of interfering contaminants. The technology validation classified it at technology readiness level 4. The financial analysis of the proposed business model considered a total sale of 180,000 units in 5 y (semi-industrial process), 4% of the Latin American market, and a sales price of USD $6.95 per unit. A Net present value of USD $52,690.51, internal return rate of 28%, payback of 3.0 y, discounted payback of 3.4 y, and breakeven point of 1.6 y were obtained. The upscaling potential of the SBAA technology was demonstrated, considering technical and market aspects for the development of competitive renewable-based technologies not yet available in the market for the treatment of water contaminated with arsenic.

Arsenic removal using iron oxide nanoparticles produced employing a green synthesis approach

AbstractSeveral adsorbents were prepared employing co‐precipitation, urea, ascorbic acid, and natural plant extracts and evaluated for the removal of arsenic from groundwater. Several parameters affecting adsorption, namely, initial arsenic concentration, pH, adsorbent dose, and contact time were studied in batch experiments. pH was found to be one of the most important parameters which affected adsorption, and it was most effective in the acidic pH range of 2–6. The optimum adsorbent dose varied from 0.24 g/L to 1.0 g/L for various methods and a contact time of 120 min. Maximum removal efficiency varied from 92% to 98% for various methods. Isotherms and kinetics studies were performed to determine the adsorption capacity and rate of reaction, respectively. The maximum adsorption capacities of 79.36 μg/g, 69.44 μg/g, 243.90 μg/g, and 101.01 μg/g could be obtained by the adsorbents produced through co‐precipitation, urea, ascorbic acid and natural plant extracts, respectively. The adsorbents prepared through co‐precipitation, urea and ascorbic acid followed Langmuir isotherm and adsorbents prepared using plant extracts followed Freundlich isotherm. Various characterization techniques, including XRD, BET, and SEM were employed for analysis of the adsorbents.

Facile preparation of maghemite based on iron sludge for arsenic removal from water

In this study, we demonstrated the effective acquisition of magnetic iron oxide (MIO) for As(V) adsorption by high-temperature pyrolysis of waste iron sludge from the water treatment plant under a confined environment without adding extra chemical reagents. The operating temperature and time in the pyrolysis process were optimized to improve the yield of MIO and its As(V) adsorption capacity. MIO500–2(500 °C, 2 h) had both relatively high yield and arsenic adsorption efficiency, which was characterized by XRD and XPS as mainly γ-Fe2O3 with small particle size (100–900 nm), significant mesopore (12.43 nm), high specific surface area (65.25 m2/g), and effective saturation magnetization intensity (14.45 emu/g). The maximum adsorption capacity was 14.2 ± 0.4 mg/g, and the removal rate could still reach about 80 % after five times of adsorbent regeneration. Considering this facile preparation route and its high yield, large-scale production of MIO from waste iron sludge is feasible, which is expected to provide a low-cost and efficient adsorbent for the treatment of arsenic-containing water in less economically developed areas.