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This study compared arsenic removal from drinking water by two different adsorbents: iron-impregnated chitosan beads (Fe-ICB) and iron-doped chitosan beads (Fe-dCB). Scanning electron microscopy, X-ray diffraction (XRD), Fourier transform infrared, and Raman spectroscopy were applied to characterize the materials produced. The As(V) adsorption capacity of both types of materials was evaluated by batch tests, followed by a column test using the most promising material. The XRD and the Raman spectroscopy confirmed the presence of 2-line ferrihydrite in the produced Fe-dCB, and no specific iron oxy-hydroxide was identified in the Fe-ICB. Both types of materials followed either the Langmuir or the Freundlich isotherm adsorption models. The Fe-dCB were more efficient in removing As(V) than the Fe-ICB. The actual maximum capacity of the produced Fe-dCB ranged from 0.27 to 0.61 mg/g under the conditions tested (concentration: 1 mg/L; pH: 7.0; 100 rpm). The Fe-dCB with the better adsorption capacity at low concentrations (<0.1 mg/L) were used in a column test using an As(V) influent concentration of 0.060 mg/L. The Fe-dCB produced close to 91,000 BVs, meeting the standard for drinking water (0.01 mg/L). Therefore, the material exhibits promising adsorbent properties for filtration applications with low arsenic concentrations. [ABSTRACT FROM AUTHOR]

Low‐cost adsorbents from agricultural by‐products are intensively studied in water treatment, especially in arsenic removal for obtaining safe drinking water. Here, it is reported that a cheap and effective nano‐composite of iron–manganese oxide incorporated active rice husk silica (FMRS) for efficient removal of arsenic (As(III) and As(V)) from water, which is fabricated using a one‐pot synthesis. Fe3+ and Mn4+ in their oxides supported silica structure are successfully characterized. The FMRS (qe = 11.9 mg g−1) shows a remarkable enhancement of arsenic removal compared with the original rice husk ash (qe = 0.4 mg g−1) at initial [As(V)] = 5 mg L−1. The As(III) and As(V) adsorption are in good agreement with both Langmuir and Freundlich non‐linear isotherm models (R2 > 0.98), where the maximum adsorption capacities at pH 7 are found up to 19.1 and 20.3 mg g−1, respectively. The role of Mn4+ in enhancing the As(III) adsorption is also discussed. The FMRS exhibits high selectivity toward arsenic under the influences of other co‐existing anions in water (e.g., chloride, sulfate, and bicarbonate) and sustains a good arsenic removal efficiency during four cycles of the reusability test, suggesting a high potential of the fabricated adsorbent for long‐term removal of arsenic in field application. [ABSTRACT FROM AUTHOR]

We have explored the use of two different iron-based porous materials for arsenic uptake from neutral pH aqueous solutions. Both materials are reminiscent of a material known as MIL-100(Fe), a Metal Organic Framework (MOF) built upon the coordination of Fe(III) ions with trimesate organic linkers (benzene tricarboxylic acid). Aside from the proverbial high surface area with extended microporosity/mesoporosity, the presence of Fe(III) centers offers the possibility of specific strong interactions with arsenic, therefore making it appealing for its use in detection and purification technologies. Our approach tackles the characterization of the system from both physical and chemical perspectives. We report equilibrium isotherms and time dependent arsenic uptake for the determination of adsorption capacity and kinetics; and also, by means of synchrotron-based X-ray absorption techniques, we probe possible changes in coordination environments and oxidation states of Fe and As in the porous network occurring upon adsorption at high and low loadings. The results presented bring further insight on the nature and diversity of adsorption sites present and confirm the suitability of the proposed adsorbents for the intended use. [ABSTRACT FROM AUTHOR]

Presence of arsenic ion [As(V)] in ground water at different locations of India is a big health concern in present days. In this work, effort was made to remove As(V) ions from tap water by electrocoagulation (EC) using iron (Fe) electrodes having an effective surface area of 38.67 m2/m3. Investigation was focused on studying the effects of various process parameters of EC like solution pH, current density (CD), inter-electrode distance (IED) initial arsenic concentration (Co), electrical conductivity of water on removal of As(V) in efficient ways. Experimental results reveal that initial pH of 7, CD of 0.431 mA/cm2, IED of 0.5 cm, agitation speed of 200 rpm and NaCl dose of 0.33 g/L are optimal conditions to reduce As(V) ion concentration from 100 µg/L to below 10 µg/L. Overall, 99.4% As(V) removal was achieved at 30 minutes of EC treatment. Different quality parameters for drinking water such as TDS, turbidity, salinity, electrical conductivity were also assessed during the EC, to verify drinking water quality in several aspects. Kinetic analysis infers that As(V) removal by EC follow the first order reaction model. Present study affirms that, EC is an effective technique for efficient As(V) removal from drinking water with an estimated energy consumption of 8.33 × 10−3 Kwh/m3, electrode utilization of 0.0486 kg/m3, and operational cost of 0.0488 US$/m3. [ABSTRACT FROM AUTHOR]

The present study is devoted to arsenic sorption on hydrous bismuth oxide (HBO) through batch and column studies. Advantage of the adsorbent includes arsenic removal in addition to the simultaneous removal of nitrate and fluoride from aqueous solution. Both the forms of arsenic tested by adsorbent in which affinity for arsenic (V) was found better than arsenic (III). Langmuir isotherm and pseudo-secondorder kinetic models were found a fit with the experimental data. Calculation of adsorption energy and increased level of chloride in treated water indicated the possible role of physical adsorption and ion exchange phenomenon in arsenic(V) sorption. A fixed bed column study gave 615 mL of treated water [As (V) < 0.01mg/L] from 0.085 mg/L arsenic (V) spiked influent with a sorption potential of 13.1-19.6 μg/g. XRD and EDS analyses confirmed the adsorption of arsenic (V) and the presence of chloride in the exhausted bed of adsorbent. The thermodynamic parameter has shown the endothermic and spontaneous process of adsorption. [ABSTRACT FROM AUTHOR]

Drinking water sludge (DWS) contains organic carbon and metal ions with the potential to prepare adsorbents. In this research, DWS was separated into two parts by acid leaching, i.e., an acid leaching carbonization sludge (ALCS) and an acid leaching solution. Iron and aluminum were extracted from the acid leaching solution and loaded onto ALCS by sedimentation and liquid-phase reduction to prepare a carbon/Al2O3/nZVI magnetic adsorption material (ALCS-Al-Fe). The optimum arsenic removal conditions, adsorption kinetics, and isotherm were determined, and the characteristics of the adsorbent ALCS-Al-Fe were investigated. The results showed that the composite exerted a favorable arsenic removal effect due to the electrostatic adsorption of nanometer zero-valent iron as well as ion exchange and complexation between the OH− groups on the surface of ALCS-Al-Fe and As(V). The pH change had a slight effect on the adsorption capacity, while the common anions SO42− and SiO32− showed obvious inhibitory effects. Considering that alkalinity is beneficial to arsenic ion desorption, NaOH was used in desorbing to conduct 6 cycles of regeneration experiments, and the final removal rate could still reach 90.5%. Therefore, the concept of green development of preparing magnetic adsorbents by using whole component of DWS is significant to the exploitation of sludge recycling. [ABSTRACT FROM AUTHOR]

Arsenic is a toxic element that is often found in drinking water in developing countries in Asia, while arsenic poisoning is a serious worldwide human health concern. The objective of this work is to remove arsenic (V) (As(V)) from water by using an adsorbent material prepared from mine waste, called MIRESORBTM, which contains Fe, Al. The performance of the MIRESORBTM adsorbent was compared with granular ferric hydroxide (GFH), which is a commercial adsorbent. Adsorbents were characterized by using scanning electron microscopy (SEM), X-ray fluorescence spectroscopy (XRF), X-ray diffractometry (XRD), and N2 sorption with Brunauer–Emmett–Teller (BET) analysis. The kinetics, isotherms, and pH-dependency of arsenic adsorption were interrogated to gain insights into arsenic adsorption processes. The maximum adsorption capacity of MIRESORBTM was 50.38 mg/g, which was higher than that of GFH (29.07 mg/g). Moreover, a continuous column test that used environmental samples of acid mine drainage was conducted to evaluate the MIRESORBTM material for practical applications. The column could be operated for more than 5840 bed volumes without a breakthrough. Successful operation of a pilot plant using MIRESORBTM adsorbent was also reported. Thus, these studies demonstrate MIRESORBTM as a highly efficient and economical adsorbent derived from recycled mine sludge waste. [ABSTRACT FROM AUTHOR]

The processing of fine metallurgical dust by pyrometallurgical methods leads to the accumulation of impurities and deterioration in the quality of blister copper. Fine dust contains copper, zinc, lead, arsenic and iron. A hydrometallurgical method for the separation of the main components into the following products is proposed: copper-zinc residue, iron-arsenic residue, lead residue. The hydrometallurgical scheme consists of three stages of leaching: neutral and using sulfuric and nitric acids. When processing metallurgical dust according to the proposed scheme, a solution containing copper, zinc, iron and arsenic is formed, as well as a lead containing precipitate. Arsenic and iron are removed from the solution in the form of iron (III) arsenate, after which zinc and copper are precipitated. Lead in sediment is in carbonated form. The developed technology allows the extraction of: 87% copper, 88% zinc, 83% iron, 83% arsenic, 99% lead in individual products. [ABSTRACT FROM AUTHOR]

Substantial quantities of openly dumped slag contribute to the absence of recovery and utilization of valuable metals as well as potential environmental pollution to water and soil. Owing to the excessively high arsenic content present in iron extracted from copper smelting slag, we propose a new arsenic removal process in this paper. The results indicate that arsenic sulfides in copper smelting slag can be significantly removed at 1100 °C in an N2 atmosphere, leading to a 0.15% residual arsenic content. Furthermore, undecomposed arsenate in the slag can be reduced in an N2–CO atmosphere. During a coal-based direct reduction process, under optimal conditions, the removal efficiency of arsenic is relatively low. Subsequently, under optimal conditions, the arsenic content drops significantly from 0.18 to 0.080%. This new removal process engenders lower arsenic content in iron extracted from slag than the standards of pig iron and direct reduced iron in steelmaking. [ABSTRACT FROM AUTHOR]

Natural groundwater from the towns of Wabana and Freshwater and treated well water from the town of Wabana in Newfoundland and Labrador, Canada were tested separately and together in sand columns to study the removal of arsenic. The most ideal conditions for arsenic removal appeared to include an arsenic concentration of approximately 35 µg/L and lower, an Fe:As mass ratio in the order of 65 and lower, and aeration of the sand media. Active aeration by pumping air though the filter, passive aeration by scraping off top layers of sand and virtual aeration by diluting the strength of the water being treated, were employed and compared. For tests where groundwater from the towns of Wabana and Freshwater was combined, arsenic removal was optimized and other elements, in addition to iron, were also correlated with effluent arsenic. Further, for these same tests there was a gradual increase in effluent pH that could have been due to oxygen depletion or gradually more reducing conditions in the sand column. Where Ni, Mn and Zn were correlated with effluent arsenic it was concluded that the increase in pH increased heavy metal removal and arsenic release. In the test where the treated Wabana water made up a greater proportion of the mix than the Wabana groundwater, lithium was also correlated with arsenic. [ABSTRACT FROM AUTHOR]

In this study, a hybrid arsenic adsorbent was synthesized through intercalation inorganic and organic surfactant cations onto kaolin clay interlayers. The synthesized adsorbent was characterized X-ray fluorescence (XRF), Fourier Transform Infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET). Batch studies were conducted to determine As(III) and As(V) removal capacity of hybrid sorbent synthesized. It is found that As(III) removal is optimum at pH range of 4-6 while As(V) removal is optimum at pH range 4-8. The data for adsorption kinetics fitted to pseudo second order model implying that adsorption of As(III) and As(V) is chemisorption. The isotherm studies showed a better fit to Langmuir isotherm model indicating that adsorption of both As(III) and As(V) occurred on a mono-layered surface. The maximum adsorption As(III) and As(V) capacity at room temperature as determined by Langmuir model were found to be 7.99 and 7.32 mg/g, respectively. Thermodynamic parameters, ΔG° and ΔH° were found to be negative indicating that adsorption process occurred spontaneously and exothermic. Inorgano-organo modified kaolin clay was successfully regenerated for up 7 adsorption-regeneration cycles using 0.01 M HCl as regenerant. This study concluded that hybrid sorbent synthesized in this study is suitable for arsenic removal from groundwater.

Mesoporous pellet adsorbent developed from mixing at an appropriate ratio of natural clay, iron oxide, iron powder, and rice bran was used to investigate the optimization process of batch adsorption parameters for treating aqueous solution coexisting with arsenate and arsenite. Central composite design under response surface methodology was applied for optimizing and observing both individual and interactive effects of four main influential adsorption factors such as contact time (24-72 h), initial solution pH (3-11), adsorbent dosage (0-20 g/L) and initial adsorbate concentration (0.25-4.25 mg/L). Analysis of variance suggested that experimental data were better fitted by the quadratic model with the values of regression coefficient and adjusted regression coefficient higher than 95%. The model accuracy was supported by the correlation plot of actual and predicted adsorption efficiency data and the residual plots. The Pareto analysis suggested that initial solution pH, initial adsorbate concentration, and adsorbent dosage had greater cumulative effects on the removal system by contributing the percentage effect of 47.69%, 37.07% and 14.26%, respectively. The optimum values of contact time, initial solution pH, adsorbent dosage and initial adsorbate concentration were 52 h, 7, 10 g/L and 0.5 mg/L, respectively. The adsorption efficiency of coexisting arsenate and arsenite solution onto the new developed adsorbent was over 99% under the optimized experimental condition.

A plethora of technologies has been developed over decades of extensive research on arsenic remediation, although the technical and financial perspective of arsenic removal plants in the field requires critical evaluation. In the present study, focusing on some of the pronounced arsenic-affected areas in West Bengal, India, we assessed the implementation and operation of different arsenic removal technologies using a dataset of 4000 spatio-temporal data collected from an in-depth field survey of 136 arsenic removal plants engaged in the public water supply. Our statistical analysis of this dataset indicates a 120% rise in the average cumulative capacity of the plants during 2014–2021. The majorities of the plants are based on the activated alumina with FeCl3 technology and serve about 49% of the population in the study area. The average cost of water production for the activated alumina with FeCl3 technology was found to be ₹7.56/m3 (USD $1 ≈ INR ₹70), while the lowest was ₹0.39/m3 for granular ferric hydroxide technology. A machine learning-based framework was employed to analyze the impact of water quality and treatment plant parameters on the removal efficiency, capital, and operational cost of the plants. The artificial neural network model exhibited adequate statistical significance, with a high F-value and R2 of 5830.94 and 0.72 for the capital cost model, 136,954, and 0.98 for the operational cost model, respectively. The relative importance of the process variables was identified through random forest models. The models indicated that flow rate, media, and chemicals are the predominant costs, while contaminant loading in influent water and a coagulating agent was important for removal efficiency. The established framework may be instrumental as a decision-making tool for water providers to assess the expected performance and financial involvement for proposed or ongoing arsenic removal plants concerning various design and quality parameters.

A cationic polymer gel (N-[3-(dimethylamino)propyl]acrylamide, methyl chloride quaternary)(DMAPAA-Q gel)-supported oxidising agent (KMnO4 or K2Cr2O7) was proposed to remove As from water. The gel could adsorb arsenite, As(III), and arsenate, As(V), through the ion exchange method, where the oxidising agent oxidised As(III) to As(V). theoretically speaking, the amount of oxidant in the gels can reach 73.7 Mol%. The maximal adsorption capacity of the D-Mn gel (DMAPAA-Q gel carrying MnO4−) and D-Cr gel (DMAPAA-Q gel carrying Cr2O72−) for As(III) could reach 200 mg g−1 and 263 mg g−1, respectively; moreover, the As(III) removal rate of the gels could still be maintained above 85% in a neutral or weak acid aquatic solution. Studies on the kinetic and adsorption isotherms indicated that the As adsorption by the D-Mn and D-Cr gels was dominated by chemisorption. The thermodynamic parameters of adsorption confirmed that the adsorption was an endothermic process. The removal of As is influenced by the co-existing high-valence anions. Based on these results, the gels were found to be efficient for the As(III) adsorption and could be employed for the As(III) removal from the industrial wastewater.

Natural zeolites are used as adsorbents in purification processes due to their cation-exchange ability and molecular sieve properties. Surface modified natural zeolites (SMNZs), produced by attaching cationic organic surfactants to the external surface, can simultaneously act as ionic exchangers and organic molecule adsorbents. In this paper, SMNZs were produced and investigated as adsorbents for As(V) removal from wastewater: two natural zeolites, clinoptilolite and phillipsite, were modified using HDTMA-Br and HDTMA-Cl as surfactants. The obtained samples were then characterized under static and dynamic conditions. Results showed that As(V) removal follows a pseudo-second order kinetic, with fast adsorption rates: every sample reached 100 % removal in 2 h, while equilibrium data showed a Langmuir-like behavior, with a greater anion uptake by the HDTMA-Br modified SMNZs due to the formation of a compact and complete micellar structure. Finally, fixed-bed tests were performed to characterize the samples under dynamic conditions assessing the effect of severe operating parameters on the dynamic exchange capacity, selectivity and efficiency of the process. The obtained results demonstrate a good ability of the tested materials to adsorb As(V) from wastewater, confirming the effectiveness of the proposed surface modification technique in expanding the possibility of using natural zeolites in these processes. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Water bamboo shellis one of the agricultural wastes and its cellulose can be used to produce source of bioresource. In this work, a composite (FeOOH/Cuo@WBC) based on water bamboo cellulose (WBC) was controllable synthesized and employed for the removal of arsenic(III) from aqueous solution. The tests of SEM, XRD, FT-IR and XPS were used to characterize the materials, and the results showed that arsenic was successfully adsorbed by the prepared FeOOH/CuO@WBC. Additionally, the influence of different factors on the adsorption capacity was studied. It was found that when the pH was adjusted to about 3.5, the maximum adsorption capacity was 76.1 mg/g at 150 mg/L initial concentration. In order to further explore the adsorption mechanism, the adsorption isotherms and kinetic were studied, and the correlation coefficient (R²) value after fitting revealed that the adsorption of arsenic by FeOOH/CuO@WBC is a combination of physical and chemical reactions. The comparison with other adsorbents and the results of recycling experiments declared that the synthetic FeOOH/CuO@WBC can effectively remove arsenic from aqueous solution based on the idea of "treating waste with waste", and has the advantages of environmental friendliness, economy and recyclability. [ABSTRACT FROM AUTHOR]

Arsenic contamination in groundwater and its consequences to the human health has been reported as one of the world’s biggest natural groundwater calamity to the mankind. People in these affected states have chronically exposed to drinking Arsenic contaminated hand tube-wells water. One of the urgent steps towards mitigation of arsenic contamination in groundwater is supply of arsenic free or arsenic safe water. The main objective of this study was selection of suitable electrode for efficient removal of arsenic from groundwater using the method of electrocoagulation, which is a useful technique of contaminant removal. The batch mode experiments were carried out in rectangular glass cell, using different electrode combination of locally available materials such as mild steel (MS), aluminium (Al) and stainless steel (SS). The anode-cathode electrode combinations were MS-SS, MS-MS, MSAl, Al-MS, Al-Al and Al-SS. These critical examinations had been performed under different operating condition including varying inter electrode distance, current, electrical charge loading and As (III) to As (V) ratio. The others parameters on treated water such as Fe, pH and TDS also investigated. MS anode showed 81 - 95% As removal, performed significantly well as compared to Al anode with 21 - 27% As removal for similar conditions. MS-SS was more efficient than MS-MS and MS-Al for higher arsenite to arsenate ratio. Decreasing of inter electrode distance increased arsenic removal and energy consumption. In treated water, the concentration of Fe, pH, TDS varied 0.414 - 0.057 mg/L, 7.42 - 7.60, and 391 - 413 mg/L, respectively. Fe and TDS concentration decreased whereas pH increased from initial value. [ABSTRACT FROM AUTHOR]

In the present study, we have reported the synthesis of nano porous carbon material (GC) by the thermal treatment of the commonly available Bermuda grasses, and metal oxides doped bio‐compatible polymer chitosan‐GC based porous cross‐linked composites (CHGCCZ) as adsorbent materials for the removal of total dissolved solids (TDS) and efficient removal of arsenic (As(V)) ions from aqueous medium, respectively. The synthesized adsorbents have been characterized by FTIR, PXRD, FESEM, TGA, and the systematic investigations have shown that the incorporation of GCs into cross‐linked matrix makes them porous, more resistant to degradation, and suitable adsorption matrix for the toxic As(V) removal. The presence of As(V) ions is quantified by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP‐OES) measurements. The amount of TDS and arsenic concentration was reduced to the minimum value of 103 ppm (average value∼119 ppm) from 414 ppm and 7.7 ppm from very high concentration of 10.15 ppm, respectively. The recyclability test has also been performed after regeneration of the CHGCCZ and the initial findings has been found to be promising. Therefore, we have systematically investigated the efficacy of TDS removal by GCs and As(V) adsorption properties of metal oxide doped cross‐linked CHGCCZ composite from the aqueous system and demonstrated the regeneration process for CHGCCZ in our study. [ABSTRACT FROM AUTHOR]

BACKGROUND Arsenic pollution of water supplies is a global problem of environmental concern. Among inorganic species, trivalent arsenite, As(III), is the most toxic and difficult to remove. Conventional treatments usually involve the pre‐oxidation to pentavalent arsenic, As(V); however, this study is focused on the direct removal of aqueous arsenite species by selective adsorption. RESULTS: Sulfur‐containing adsorbents were prepared from mesostructured SBA‐15 silica by functionalization with propylthiol chains. The sulfur content of the synthetized materials, denoted as SBA‐15‐SH‐x, reached 4 mmol g−1. Kinetics and equilibrium batch experiments showed that all materials were excellent As(III) adsorbents, with maximum capacity as high as 0.46 mmol g−1, superior to literature values for comparable materials. The pH influence was significant and the best performance occurred at pH 8. A complementary pelletized material was designed and synthetized to explore the potential use of the adsorbents in the treatment of water streams polluted with arsenic through fixed‐bed column experiments. The breakthrough curves obtained in different operative conditions evidenced the viability of the process. CONCLUSIONS: SBA‐15‐SH‐x materials evaluated in this work exhibited very good performance for aqueous As(III) removal by direct adsorption without previous oxidation to As(V). The suitability of the materials was demonstrated through kinetics, equilibrium, and fixed‐bed column adsorption experiments. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

A series of microporous Zn doped Fe3O4 spheres were successfully fabricated by a simple method. The characteristic of the obtained products was studied using the X-ray diffraction (XRD), Raman spectroscopy, (SEM) scanning electron microscopy, UV-vis reflectance, FTIR techniques. The photo-oxidation of As(III) to As(V) by as-synthesised samples under visible light was examined. The results exposed that with Zn doped Fe3O4 photocatalyst, the complete oxidation of As(III) to As(V) was observed, in which 1.05% mol of Zn doped into Fe3O4 showed the best photocatalytic performance. The proposed mechanism of photocatalytic activity enhancement was also investigated, indicating the introduction Zn content act as a trapping electron-centre resulting in the decreasing in the recombination rate of the photogenerated electron/hole pairs thus improving the photocatalytic performance. Photocatalytic tests were presented also in real groundwater and complete oxidation of As(III) to As(V) by 1.05 Zn doped Fe3O4 photocatalyst was achieved in 180 min under visible light irradiation. [ABSTRACT FROM AUTHOR]

This study focuses on the synthesis of nanocomposites named CCA and CZA that were prepared by the incorporation of cellulose (CL) in the Ca/Al and Zn/Al layered double hydroxide (LDH), respectively. These materials were then used for the uptake of As(III) and As(V) from aqueous medium. Characterization of both nanocomposites (CCA and CZA) was done using FTIR and Raman analysis to identify the functional groups, N 2 adsorption-desorption isotherms to determine the specific surface area and pore geometry and XPS analysis to obtain the surface atomic composition. Some other characters were investigated using simultaneous TGA and DTA and elemental chemical analysis (CHNS/O). The crystallinity of the prepared nanocomposites was displayed by XRD patterns. Furthermore, the sheet-like structure of the LDHs and the irregularity of surface morphology with porous structure were observed by TEM and SEM microphotographs. Optimization of maximum adsorption capacity was adjusted using different parameters including pH, contact time and adsorbent dosage. The pseudo-second-order model was in good fitting with kinetics results. The adsorption isotherm results showed that CZA exhibits better adsorption capacity for As(III) than CCA and the Langmuir isotherm model described the data well for both nanocomposites. Thermodynamic studies illustrated the endothermic nature of CCA and exothermic nature on CZA, as well as the fact that the adsorption process is spontaneous. A real water sample collected from well located in Gabes (Tunisia), has also been treated. The obtained experimental results were confirmed that these sorbents are efficient for the treatment of hazardous toxic species such as. Image 1 [ABSTRACT FROM AUTHOR]

Since arsenic is highly toxic and carcinogenic, it now causes serious health problems all over the world. Therefore, there is an urgent need to develop new techniques that are cost-effective and easily applicable to remove arsenic from contaminated waters. Layer double hydroxides have the potential to be a good adsorbent to remove arsenic from contaminated waters due to high surface area and high anion exchange capacity. In this paper, arsenic removal from water by calcined Fe–hydrotalcite (CFeHT) known as layered double hydroxide and prepared synthetically with coprecipitation method was researched. The study brings out that the effect of initial solution pH values was limited for the adsorption. The experimental study indicates that the adsorption of arsenic rapidly occured in comparison with other studies. It was determined that the pseudo-second-order kinetic model was more suitable than the first order. In isotherm studies, it was seen that the experimental data were compatible with Langmuir model. In this study was determined that CFeHT has a high arsenic removal potential. And also the concentration of the arsenic solution (600 µg/L) has been reduced below the allowable value by the World Health Organization (< 10 µg/L). The desorption test indicates that the desorption ratio of As(V) was obtained as 72.7. [ABSTRACT FROM AUTHOR]

Microporous carbon fibers prepared by controlled carbonization of cellulose proved promising carrier of nano- and microparticles of solid active substances. The average pore size of the carbon fibers ranges from 0.5 to 0.6 nm and, therefore, molecules of many low- molecular substances are excluded. Consequently, the nano- and microparticles formed by precipitation of a solution in the presence of fibers are deposited exclusively on their outer surface. In this way, composite materials with favorable macro-structure can be created because large surface of appropriate active substance remains easily accessible for the desired action. Technical problems connected with the direct application of nano- and microparticles are avoided. The practical advantages of the microporous carbon fibers prepared from cellulose comprise feasibility of their preparation, as well as general availability and low price of the raw material. Moreover, compared to particulate carriers with identical diameter, fibrous carriers exhibit reduced resistance against flow of liquids and gases. The pertinence of carriers based on the microporous carbon fibers prepared from delignified cellulose has been tested with the deposition of nano- and microparticles of hydrated ferric hydroxide, Fe(OH)3·(H2O)n. Compared with particulate ferric hydroxide, the resulting heterogeneous composite showed increased efficiency in adsorptive removal of harmful arsenic from water. [ABSTRACT FROM AUTHOR]

Combined effects of some cations such as calcium (Ca2+), iron (Fe2+), manganese (Mn2+), and magnesium (Mg2+) and operating time on the removal of arsenic by air-injected electrocoagulation (EC) reactor with aluminum (Al) ball electrodes were investigated. The operating conditions were optimized with the Box–Behnken design of response surface methodology (RSM). The response variables were selected from the program as removal efficiency, residual arsenic concentration, energy consumption and operating cost (OC) in the EC process. A total of 46 experimental run was performed. The removal efficiency of arsenic increased with an increase in iron concentration (0.5–4.5 mg/L). The rest of the cations showed no noticeable effect on arsenic removal efficiency. The maximum arsenic removal efficiency and minimum OC at the optimum operating conditions (CCa: 305 mg/L, CMg: 42 mg/L, CFe: 3.3 mg/L, CMn: 2.34 mg/L, initial pH of 7.5 applied current of 0.15 A, Al ball size of 7.5 mm, 5.0 cm of Al ball anodes height in the EC reactor, air-fed rate of 6.0 L/min and tEC: 16.83 min) in the EC process were 99.9% and 0.0332 $/m³ for initial arsenic concentration of 200 μg/L, respectively. The removal mechanism of As(III) by EC seems to be oxidation of As(III) to As(V) and subsequent removal by adsorption/complexation with aluminum hydroxides generated in the process. The results showed that the air-injected EC reactor can be used effectively for arsenic and hardness removal simultaneously from real groundwater sources. [ABSTRACT FROM AUTHOR]

The calcined ground oyster shell was used as the adsorbent to remove As(III) from contaminated water under the presence of anions. The solubility and precipitation tests indicated that As(III), NO3−, and SO42- were removed by adsorption process whereas HPO42- was removed by precipitation and adsorption processes. The adsorption results showed that, in bi-solutes, HPO42- strongly interfered with As(III) removal. In the case of tri- and tetra-solutes, the adsorption performances of As(III) and anions depended on (1) the binding affinity between the sorption sites and adsorbates, (2) observed adsorption rate constant of adsorbates, (3) electrostatic interaction, and (4) adsorbates interaction. [ABSTRACT FROM AUTHOR]

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This study discusses synthesis and characterization of iron-incorporated activated carbon (MAC) from biomass mixture by FeSO4 impregnation and subsequently pyrolysis, and its application in arsenic adsorption from aqueous solution. The textural, morphological, and structural properties were determined with BET surface area, total pore volume, average pore size, pHpzc, XRD, VSM, and SEM-EDX analysis. The results showed that the MAC has 375.32 m2/g surface area and 0.2391 cm3/g of total pore volume and contains a single iron compound in the magnetite structure. Arsenic removal efficiency was evaluated depending on MAC dosage, pH, contact time, and As(V) concentration. The data was analyzed by Freundlich and Langmuir isotherms. Also, pollution potential of the adsorption residue was examined by TCLP. 10 mg/l of As(V) in the solution could be removed in the presence of 1.5 g/l of MAC at pHs above 2.5 for 60 min. As(V) adsorption fitted better to the Langmuir isotherm, and adsorption capacity was found to be 42.92 mg/g. It has been found that the adsorption residue has no potential pollutants; thus, they are safe for regular landfill waste disposal. The results suggested that FeSO4 impregnation and subsequently pyrolysis were suitable process for synthesis of MAC from biomasses for arsenic adsorption. [ABSTRACT FROM AUTHOR]

Selective removal of trace arsenic is crucial for obtaining safe drinking water. Here, the selective adsorptive performance of arsenate (As(V)) on a hybrid ZMAE (nanoscale zirconium molybdate embedded a macroporous anion exchange resin) was examined. It was found that the As(V) adsorption efficiency of ZMAE was almost retained in the presence of competing ions (NO3− or SO42−) up an [SO42−]/[As] or [NO3−]/[As] ratio of 150/1, whereas that of bare AE (anion exchange resin) was negligible for [SO4]/[As] over 15/1. In addition, the As(V) maximum adsorption capacity of ZMAE was found to be 41.2 mg/g, which is in contrast with the negligible adsorption of bare AE under sulfate-rich condition. The enhanced arsenate selectivity of ZMAE can be attributed to the excellent selectivity of ZM NPs (zirconium molybdate nanoparticles), which contributed up to 45% of the adsorption capacity of ZMAE. The behavior of ZMAE towards arsenate was compared with that towards phosphate showing similar adsorption performances between them, which indicates the similar affinity of ZMAE towards arsenate and phosphate. Finally, ZMAE examined for fixed-bed column adsorption for As(V) removal from synthetic As(V) water was effective for up to 5100 BVs, treating As(V) from 0.1 mg/L to below 0.01 mg/L (meeting the WHO guidelines). [ABSTRACT FROM AUTHOR]

Modified activated carbon cloth is prepared by mechanochemical modification of viscose rayon carbon cloth. The effects of different milling atmospheres, in the air and inert conditions, were investigated. Changes in kind and number of acidic and basic surface groups on the surface of activated carbon cloth, upon modification, as well as before and after the sorption of arsenic were determined. Higher number of basic groups responsible for the removal of arsenic ions was achieved by modification under inert conditions. Breakage and collapse of cylindrical fibers, decrease of particle sizes, change in the shape and consistency of the particles, as well as increase of microstructural disorder i.e. the loss of turbostratic structure occurred upon milling. pH PZC values increased from 4.46 to 5.04 and 5.77 after the air and inert milling, respectively. Adsorption followed pseudo second order kinetics with chemisorption as rate-controlling step. Langmuir isotherm best fit the equilibrium data and maximum adsorption capacity is 5.5 mg g−1 at a pH value close to 7.0, typical for groundwater. The mechanism of arsenic adsorption onto activated carbon cloth milled in inert atmosphere involved electrostatic and dispersive interactions between arsenic ions and carbon particles in wide pH range (from 2 to 10). [ABSTRACT FROM AUTHOR]

• A controllable preparation method for removing As(III) from wastewater is proposed. • Rod-like NZVI can be distributed evenly orderly on the surface of cotton fibers. • The synergistic effect of cotton fiber, NZVI, silica protective layer effectively improves the removal efficiency. • The adsorption mechanism of FBC on As(III) was systematically proposed. From the perspective of basic human health, arsenic is extremely toxic and highly lethal, which will enter surface water and groundwater through industrial production and eventually enter human beings through the food chain, causing immeasurable harm. Herein, a new composite material, namely NZVI@SiO 2 @ celluloses (FSC), was successfully synthesized by hydrothermal and reduction methods based on cotton fiber as the carrier, nanoscale zero-valent iron (NZVI) as the active component of arsenic removal and silica as the protective layer. The crystal structure, morphology and chemical elements of the composite were characterized and determined by SEM, XPS, TEM, and XRD techniques. The results demonstrated that rod-like NZVI with the diameter of 50–80 nm was distributed evenly on the surface of cotton fiber, and the coating of silica forming a 10–20 nm transparent shell can effectively prevent the oxidation of NZVI from losing its effectiveness on the surface. In addition, the optimal adsorption conditions by FSC were investigated by concentration, controlling pH value, interfering ions and temperature. The obtained results show that the prepared materials have better adsorption capacity for sodium arsenite under acidic conditions of pH at 2.8–4; and the maximum adsorption capacity could reach about 70 mg/g when the concentration was 300 mg/L at 30 °C. The pseudo-first-order and pseudo-second-order kinetic models were all in good agreement with the experimental data, further identifying the adsorption kinetics mechanism of FSC on arsenic. Because NZVI alone is easily oxidized in the air, and agglomeration is also likely to occur, the combination of NZVI, silica and cotton fiber perfectly solved these defects and further improved the adsorption performance in this work. Moreover, the comparison on removal effects of various adsorbents simultaneously indicates that FSC will have a great application prospect in the future water pollution treatment. [ABSTRACT FROM AUTHOR]

An adsorbent material arranged in a ceramic monolith (CM) obtained by extrusion technique using natural bentonite and alumina (as raw materials) is presented. Ceramic and raw materials were characterized by X-ray fluorescence, thermal analysis, X-ray diffraction, and textural analysis (with N2 adsorption–desorption at 77 K and Hg intrusion–extrusion porosimetry) to determine their chemical and physical properties. Then, As (V) adsorption capacity of the CM at different pH (3–9) using arsenic aqueous solution (with 2000 µg As (V) L−1) was evaluated. Additionally, studies of kinetics and equilibrium of As (V) adsorption on CM were performed. It was found that: (i) the As (V) removal capacity is favored at acidic pH, reaching an average value of 15 µg As (V) per gram of CM; (ii) from kinetic studies, As (V) adsorption on CM occur in two stages, the first of them reaching a lower As uptake in a short time period, followed by an slow second stage with a subsequent higher As uptake, which continued for a longer time period, reaching equilibrium conditions in approximately 24 h; and (iii) the As (V) adsorption isotherm is a type-Langmuir, indicating that the CM present an homo quantity of fixed sites to adsorb the As (V). [ABSTRACT FROM AUTHOR]

PVA/ZnO nanofibrous composite polymer was synthesized as a novel sorbent via electrospinning method at ambient conditions. Physicochemical characteristics of the samples were analyzed using XRD, SEM, EDS, TGA/DSC, and BET techniques. Efficiency of the composite samples for arsenic removal [i.e., As (III) and As (V) anions] was studied under different conditions using RSM optimization approach. Experimental results of adsorption tests indicated that the synthesized PVA/ZnO polymer with the maximum removal of 97% is a highly efficient sorbent for arsenic comparable with other sorbents studied for arsenic removal. The effect of some cations on arsenic removal was also studied in this research. Results showed that the tested ions do not cause a significant reduction in the removal rate. PVA/ZnO composite polymer, which is highly biocompatible, can be considered as a new adsorbent for removal of arsenic from contaminated water. [ABSTRACT FROM AUTHOR]

A new method to remove arsenic from aqueous chloride solution by using lead oxide was proposed, and the effects of the lead(II)/arsenic(V) molar ratio (nPb(II):nAs(V)), initial pH of solution, initial concentrations of chloride ion (Cl−) and arsenic(V) on arsenic removal were investigated. The results showed that nPb(II):nAs(V), initial pH and initial Cl− concentration had great influence on arsenic removal. The suitable conditions of arsenic removal were initial pH of 1.8–2.4 and initial Cl− concentration of 0.52–2.00 g L−1 for 200 mg L−1 As(V) solution. Initial As(V) concentration had little influence on arsenic removal when the appropriate nAs(V):nCl− was controlled in the solution at nPb(II):nAs(V) of 1.52. Based on these conditions, As(V) removal efficiency reached up to 99.99% and As(V) concentration decreased from 200 mg L−1 to less than 0.01 mg L−1 at initial pH of 1.8 with nPb(II):nAs(V) of 2.12. Various characterizations confirm that the formed precipitate was mimetite (Pb5(AsO4)3Cl) and had better thermal stability within 500 °C. For the prevalent problem of lead dissolution by forming mimetite, Pb residual concentration reduced from 337.6 to 0.07 mg L−1 using sodium sulfide in the solution after arsenic removal. Therefore, lead oxide could be used as an effective reagent of arsenic removal to remove As(V) from aqueous chloride solution. [ABSTRACT FROM AUTHOR]

Developing affordable and efficient materials for the removal of arsenic from drinking water is crucial for human and environmental safety. In the present study, the adsorptive performance of magnetic GO/ZnFe2O4 nanocomposite and ZnFe2O4 nanospinel for arsenic removal from aqueous water was analyzed. The adsorbents were characterized using Fourier-transform infrared spectroscopy, X-ray powder diffraction, transmission electron microscopy, selected area electron diffraction and vibrating sample magnetometer. The conditions were optimized by response surface methodology (RSM) by considering the main factors as adsorption time, arsenic concentration, dose of adsorbent and pH. The optimum condition for the removal of arsenic was observed at pH 9.76, 30 min of contact time, 13.4 mg L−1 of initial arsenic concentration and 0.048 g of adsorbent dosage. The predicted arsenic removal percent under optimized conditions was noted as 98%; on the other hand, the experimental values at optimized conditions were observed as 96%. The Pareto analysis predicted that pH of the polluted water is the major factor in adsorptive arsenic removal and the relative importance of the process factors was found in the following order: pH > arsenic concentration > contact time > adsorbent dosage. Thus, introduced compositions form a promising material for the decontamination of polluted water or using in environmental remediation programs. [ABSTRACT FROM AUTHOR]

Combining adsorption with other technologies holds great potential in fast and deep arsenic ion removal. Herein, chitosan‑zirconium composite adsorptive membranes (CS-Zr CM) were successfully prepared using simple casting and sodium hydroxide coagulation strategies, which was demonstrated the use in arsenic ion-capture electrodialysis based on their good adsorption performance. In the batch adsorption tests, the maximum adsorption capacities of CS-Zr CM for As(III) and As(V) were 134.2 mg/g and 119.5 mg/g, respectively. CS-Zr CM also exhibited satisfying adsorption selectivity and good reusability toward As(III) and As(V). However, the adsorption kinetics showed that they needed 48 h to reach the adsorption equilibrium and the adsorption ability toward trace arsenic ion was ineffective. Furthermore, CS-Zr CM was applied as the adsorptive membrane in the electrodialysis process. Under the influence of electric field, the As(III) and As(V) removal equilibrium time was shortened to 12 h and the concentrations of As(III) and As(V) ions could be efficiently reduced to below the WHO limit in drinking water (10 μg/L), which far surpassed the physicochemical adsorption method. Such good arsenic ion removal ability of CS-Zr CM together with the ease scalable fabrication, low cost, and biodegradable properties shows its huge prospects in arsenic-containing wastewater treatment. Biodegradable chitosan‑zirconium composite adsorptive membrane was used in the arsenic ion-capture electrodialysis configuration which exhibited fast and deep arsenic ion (As(III) and As(V)) removal. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Integral material for easy recycling. • Nanomaterial loading for enhanced adsorption and oxidation properties. • Easy and convenient preparation method. The remediation of geogenic high arsenic groundwater is of great significance for environmental protection. In this study, a feasible strategy for in-situ growth of MnO 2 and FeOOH on a three-dimensional (3D) porous carbon foam skeleton was developed by simple calcination carbonization and activation treatment of modified carbon foams. This work demonstrates that arsenic in aqueous solution can be efficiently removed by the dual function of "oxidation and adsorption" from the composite of MnO 2 -FeOOH co-loaded carbon foam (CF). The prepared 3D monolithic has the advantages of low cost, easy preparation, and independent integrity. It can be innovatively used for arsenic remediation of groundwater systems. The MnO 2 serves as the oxidizer to convert highly toxic As(III) into less toxic As(V), the FeOOH acts as the adsorbent for the capture of As(V), and CF offers an interconnected porous network for efficient mass transfer as well as a robust skeleton for facile recycling. The maximum adsorption capacity of As(III) and As(V) for MnO 2 -FeOOH@CF can reach 63 and 78 mg g−1, respectively. After repeatedly utilizing the free-standing adsorbent three times, its adsorption capacity for As(III) and As(V) can still reach 84 % and 85 % of the initial adsorption capacity, respectively. The low cost, high efficiency of arsenic removal, and easy preparation and recycling endow the MnO 2 -FeOOH@CF to be a promising adsorbent in practical application. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3DNF@MOF adsorbent was successfully prepared for smelting wastewater treatment. • Molecular dynamics and adsorption site modeling have well verified the adsorption mechanism. • The NF@MOF was found to be dominated by chemical monolayer adsorption by curve fitting. A significant challenge in environmental remediation involves designing adsorbents that can effectively remove arsenic from smelting wastewater. This study aimed to address issues related to Metal-Organic Framework (MOF) pore blockage and insufficient active sites. To do this, we prepared MIL-101(Fe) and MIL-101(Cr) directly on three-dimensional nickel foam (NF) using a sustainable hydrothermal one-pot method. Using the NF as a carrier allowed for a uniform distribution of MIL-101(Fe) and MIL-101(Cr). This increased their contact area with the solution and enhanced the exposure of active sites. We investigated the adsorption capacities of trivalent and pentavalent arsenic by NF/MOFs through experiments and computational simulations. Our findings indicated that NF/MIL-101(Fe) and NF/MIL-101(Cr) adsorbed arsenic at concentrations of 152.65 mg/g and 132.615 mg/g, under conditions of room temperature and pH levels of 7 and 4, respectively. Analysis of the adsorption kinetics and thermodynamics revealed that the adsorption process for both adsorbents was chemical in nature, with monolayer adsorption being predominant. Molecular dynamics results indicated diffusion coefficients of 0.556667 × 10–6 for Fe3+ ions and 0.44 × 10–6 for Cr3+ ions. This suggests that NF/MIL-101(Fe) has a strong adsorption capacity. The proposed adsorption site model accurately predicted arsenic adsorption on the NF/MIL-101(Cr) and NF/MIL-101(Fe) structures. Given these properties, NF/MIL-101(Cr) and NF/MIL-101(Fe) are versatile materials with specificity and storage capacity for arsenic removal from smelting wastewater. Their potential in industrial wastewater purification is promising. [ABSTRACT FROM AUTHOR]

[Display omitted] • As 2 O 3 adsorption on CaO(0 0 1), γ-Al 2 O 3 (0 0 1) and α-Fe 2 O 3 (0 0 1) is mainly chemisorption. • The d-band center of Fe atom influence the adsorption reactivity significantly. • SO 2 exhibits obvious competitive adsorption with As 2 O 3 on CaO(0 0 1) surface. • As 2 O 3 structure will change on SO 2 pre-adsorbed γ-Al 2 O 3 (0 0 1) and α-Fe 2 O 3 (0 0 1). Arsenic (mainly As 2 O 3) removal is one of the key concerns in the ultra-clean emissions of coal-fired flue gas. Facing the no consensus on the adsorption mechanism of As 2 O 3 on typical metal oxides (CaO, γ-Al 2 O 3 and α-Fe 2 O 3) and the influence mechanism of SO 2 on that, this work adopted the DFT calculation to conduct the systematic study from multiple perspectives, including adsorption energy, EDD, PDOS, Gibbs free energy and FMO. The results show As 2 O 3 adsorption on CaO (0 0 1), γ-Al 2 O 3 (0 0 1) and α-Fe 2 O 3 (0 0 1) surface are mainly chemisorption, where that on CaO (0 0 1) surface is strongest. The adsorption ability of the metal oxides to As 2 O 3 under 0–1173.15 K satisfies CaO (0 0 1) > γ-Al 2 O 3 (0 0 1) > α-Fe 2 O 3 (0 0 1). SO 2 competes with As 2 O 3 for adsorption active sites, and that on CaO is greater than α-Fe 2 O 3 (0 0 1) and γ-Al 2 O 3 (0 0 1). The newly formed adsorption sites are less active for As 2 O 3 adsorption after SO 2 adsorbed on the three metal oxides surfaces. The γ-Al 2 O 3 (0 0 1) and α-Fe 2 O 3 (0 0 1) surface with pre-adsorbed SO 2 decreases the stability of hexahedral As 2 O 3 , which benefits for the adsorption occurrence. [ABSTRACT FROM AUTHOR]

World's highest arsenic (As) contamination is well-documented for the groundwater system of southwestern region (mainly Jashore district) of Bangladesh, where the majority of inhabitants are underprivileged. To mitigate As poisoning in southwestern Bangladesh, numerous steps have been taken so far by the government and non-governmental organizations (NGOs). Among them, digging deep tube wells and As removal by naturally deposited Fe(OH) 3 species are being widely practiced in the contaminated areas. However, these actions have been left unmonitored for decades, making people unaware of this naturally occurring deadly poison in their drinking water. Hence, water samples (n = 63, both treated and untreated) and soil samples (n = 4) were collected from different spots in Jashore district to assess the safety level of drinking water and to understand the probable reasons for high As(III) contamination. About 93.7% of samples were found to contain As(III) above 10 μg/L; among them, 38% contained above 50 μg/L. The study shows that current As(III) removal strategies in the study area are ineffective. In this connection, a simple low-cost As(III) removal adsorbent is proposed that can be prepared with very cheap and locally available materials like iron sludge and charcoal. The adsorbent was characterized in terms of SEM, EDX, and XPS. The optimal dosage of the adsorbent was investigated for real-life application concerning several vital water quality parameters. The Fe–C adsorbent exhibited a maximum As(III) removal efficiency of 92% in real groundwater samples. The study will allow policymakers for informed decision-making regarding water body management as well as enable the local people to avail As-safe water in a way that aligns with their economic factors. [Display omitted] • Southwestern Bangladesh has high As(III) concentrations reaching up to 194 μg/L. • The northern part of the study area has a higher As(III) concentration. • 49% of the widely anticipated arsenic-safe deep tube wells were found ineffective. • The average performance of JICA-installed arsenic removal plants is only 12(±8.05)%. • A locally sourced novel adsorbent achieved 89.26 ± 3.13% As(III) removal efficiency. [ABSTRACT FROM AUTHOR]

The efficient removal of arsenic from wastewater is still a challenge. In this paper, a heterojunction consisting of in-situ carbon-doped TiO 2 and nitrogen deficiency g-C 3 N 4 (C/TiO 2 @ND-C 3 N 4) 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 TiO 2 (75.0%) and nitrogen deficiency g-C 3 N 4 (50.5%). The good photocatalytic oxidation and adsorption performances of C/TiO 2 @ND-C 3 N 4 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 TiO 2 and hydrogen bonds with high content pyrrole nitrogen derived from ND-C 3 N 4 , 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. [Display omitted] • C–O–Ti interfacial bonds promote the photocatalytic oxidation efficiency of As(III). • Enhanced arsenic adsorption by hydrogen bonds with pyrrole nitrogen and As–O bonds. • C/TiO 2 @ND-C 3 N 4 material achieved 95% removal of total arsenic. [ABSTRACT FROM AUTHOR]

Arsenic (As) contamination poses a significant threat to human health, ecosystems, and agriculture, with levels ranging from 12 to 75% attributed to mine waste and stream sediments. This naturally element is abundant in Earth's crust and gets released into the environment through mining and rock processing, causing ≈363 million people to depend on As-contaminated groundwater. To combat this issue, introducing a sustainable hydrochar system has achieved a remarkable removal efficiency of over 92% for arsenic through adsorption. This comprehensive review presents an overview of As contamination in the environment, with a specific focus on its impact on drinking water and wastewater. It delves into the far-reaching effects of As on human health, ecosystems, aquatic systems, and agriculture, while also exploring the effectiveness of existing As treatment systems. Additionally, the study examines the potential of hydrochar as an efficient adsorbent for As removal from water/wastewater, along with other relevant adsorbents and biomass-based preparations of hydrochar. Notably, the fusion of hydrochar with nanoparticle-centric approaches presents a highly promising and environmentally friendly solution for achieving the removal of As from wastewater, exceeding >99% efficiency. This innovative approach holds immense potential for advancing the realms of green chemistry and environmental restoration. Various challenges associated with As contamination and treatment are highlighted, and proposed solutions are discussed. The review emphasizes the urgent need to advance treatment technologies, improve monitoring methods, and enhance regulatory frameworks. Looking outlook, the article underscores the importance of fostering research efforts, raising public awareness, and fostering interdisciplinary collaboration to address this critical environmental issue. Such efforts are vital for UN Sustainable Development Goals, especially clean water and sanitation (Goal 6) and climate action (Goal 13), crucial for global sustainability. [Display omitted] [ABSTRACT FROM AUTHOR]