Initial Arsenic Concentration Research Articles

Arsenate removal using chitosan-coated bentonite via fixed-bed system: a process integration by fuzzy optimization.

Groundwater contamination is a global concern that has detrimental effect on public health and the environment. Sustainable groundwater treatment technologies such as adsorption require attaining a high removal efficiency at a minimal cost. This study investigated the adsorption of arsenate from groundwater utilizing chitosan-coated bentonite (CCB) under a fixed-bed column setup. Fuzzy multi-objective optimization was applied to identify the most favorable conditions for process variables, including volumetric flow rate, initial arsenate concentration, and CCB dosage. Empirical models were employed to examine how initial concentration, flow rate, and adsorbent dosage affect adsorption capacity at breakthrough, energy consumption, and total operational cost during optimization. The ε-constraint process was used in identifying the Pareto frontier, effectively illustrating the trade-off between adsorption capacity at breakthrough and the cost of the fixed-bed system. The integration of fuzzy optimization for adsorption capacity and its total operating cost utilized the global solver function in LINGO 20 software. A crucial equation derived from the Box-Behnken design and a cost equation based on energy and material usage in the fixed-bed system was employed. The results from identifying the Pareto front determined boundary limits for adsorption capacity at breakthrough (ranging from 12.96 ± 0.19 to 12.34 ± 0.42μg/g) and total operating cost (ranging from 955.83 to 1106.32 USD/kg). An overall satisfaction level of 35.46% was achieved in the fuzzy optimization process. This results in a compromise solution of 12.90μg/g for adsorption capacity at breakthrough and 1052.96 USD/kg for total operating cost. Henceforth, this can allow a suitable strategic decision-making approach for key stakeholders in future applications of the adsorption fixed-bed system.

Enhancing the bioreduction and interaction of arsenic and iron by thiosulfate in groundwater

Thiosulfate influences the bioreduction and migration transformation of arsenic (As) and iron (Fe) in groundwater environments. The aim of this study was to investigate the impact of microbially-mediated sulfur cycling on the bioreduction and interaction of As and Fe. Microcosm experiments were conducted, including bioreduction of thiosulfate, As(V), and Fe(III) by Citrobacter sp. JH012–1, as well as the influence of thiosulfate input at different initial arsenate concentrations on the bioreduction of As(V) and Fe(III). The results demonstrate that Citrobacter sp. JH012–1 exhibited strong reduction capabilities for thiosulfate, As(V), and Fe(III). Improving thiosulfate level promoted the bioreduction of Fe(III) and As(V). When 0, 0.1, 0.5, and 1 mM thiosulfate were added, Fe(III) was completely reduced within 9 days, 3 days, 1 day, and 0.5 days, simultaneously, 72.8%, 82.2%, 85.5%, and 90.0% of As(V) were reduced, respectively. The products of As(III) binding with sulfide are controlled by the ratio of As-S. When the initial arsenate concentration was 0.025 mM, the addition of thiosulfate resulted in the accumulation of soluble thioarsenite. However, when the initial arsenate level increased to 1 mM, precipitates of orpiment or realgar were formed. In the presence of both arsenic and iron, As(V) significantly inhibits the bioreduction of Fe(III). Under the concentrations of 0, 0.025, and 1 mM As(V), the reduction rates of Fe(III) were 100%, 91%, and 83%, respectively. In this scenario, the sulfide produced by thiosulfate reduction tends to bind with Fe(II) rather than As(III). Therefore, the competition of arsenic-iron and thiosulfate concentration should be considered to study the impact of thiosulfate on arsenic and iron migration and transformation in groundwater.

Highly efficient kaolin/g-C3N4/WO3 ternary nanocomposite for the effective removal of Arsenic ions from aqueous media

The effectual removal of arsenic ions from contaminated water sources remains a significant challenge in water treatment. In this study, we propose a novel composite material consisting of kaolin, graphitic carbon nitride (g-C3N4) and tungsten trioxide (WO3) for effective arsenic removal. The composite material was prepared through a facile synthesis method, and its physicochemical properties were characterized using various analytical techniques. The effects of composite dosage, initial arsenic concentration, contact time and temperature on the adsorption capacity were systematically evaluated. The results revealed that the composite material exhibited excellent arsenic removal efficiency, with a maximum adsorption capacity of 114.63 mg/g. The adsorption isotherms such as Langmuir and Freundlich models were evaluated, and the data finds to fit well with the Langmuir model, suggesting homogeneous adsorption. The mechanism of arsenic removal follows photocatalytic oxidation of As(III) to As(V) followed by adsorption of As(V). The process of adsorption followed the pseudo-second-order kinetic model. Additionally, the composite material demonstrated good reusability and stability over multiple cycles. The findings of this study contribute to the progress of sustainable and reliable water treatment technologies for arsenic removal, addressing a pressing global environmental concern.

Mechanism and thermodynamics of scorodite formation by oxidative precipitation from arsenic-bearing solution

Arsenic pollution is a challenging environmental issue caused by arsenic-bearing wastes from nonferrous metallurgy. Oxidative precipitation via introducing O2 into an ionic Fe(II)–As(V) solution is an advanced method for arsenic immobilization. However, the underlying mechanism is still not well understood. This study proposed a mechanism for scorodite formation by oxidative precipitation, and its thermodynamics were calculated using Gaussian software. Scorodite formation was divided into three stages: precursor formation (3–90 min), oxidative conversion (90–270 min) and crystallization (270–720 min) from the variation in precipitates and solution characterization and parameters such as initial pH, arsenic concentration, and ferrous dosage. In the scorodite formation mechanism, the precursors originate from the coordination polymerization of aqueous Fe(H2O)62+ and H2AsO4−, which contributes to the oxidative conversion of coordinated polymers ([Fe(H2O)4(H2O)]nn+) to basic Fe(H2O)2AsO4 until regular octahedral crystals are formed via nucleation and growth during crystallization. The ΔrGmθ for polymerization varied from −491.96 kJ mol−1 to −33.30 kJ mol−1, and the ΔrGmθ of oxidative conversion changed from −982.16 kJ mol−1 to −224.82 kJ mol−1, demonstrating the feasibility in scorodite formation. This research is significant for understanding scorodite formation in As(V) solutions. It can provide schemes for controlling and modifying the conditions of arsenic-bearing waste immobilization in the laboratories and industries.

EFFICIENT BIOCOAGULANT Azardicta Indica BARK POWDER FOR ARSENIC (III) REMOVAL IN THE SOLUTION PHASE

This study aims to remove arsenic from groundwater by employing a series of batch studies on Azardicta Indica bark powder that vary in terms of physic-chemical factors such as contact time, dose, pH, initial arsenic content, and temperature. The rate of arsenic absorption decreased as it moved farther inside the biosorbent particles from its initial quick pace. At a pH of 4.0-6.0 and a dosage of 1.5 gm, the impact of contact duration on arsenic biosorption was investigated for 30 minutes.As the initial arsenic concentration rises, the proportion of arsenic biosorption decreases because mass transfer between the solute and solution interface is impeded at higher concentrations. Through the assessment of the biosorbent's mass transfer coefficients, the experimental outcomes were accurately documented in terms of Freundlich and to some degree Temkin isotherms with values of R2 0.998 and 0.956, respectively.

Comparative analysis of synthesis of GO, CoFe2O4 and CoFe2O4 coated GO and its removal efficiency of arsenic present in the solution

A collective process of water purification is designed to reduce or remove the existing water contaminants to make water more applicable. Nanotechnology is considered to be very effective in providing contaminants free water for use. Demand of inexpensive and effective adsorbents is increasing regularly in response to the immeasurable health effects of arsenic exposure through water. The present study covers the procedure of synthesis of Graphene oxide (GO), Cobalt ferrite (CoFe2O4) and CoFe2O4 coated Graphene oxide (GO-CoFe2O4). This study shows that in room temperature at pH of 7, adsorbent dose of 0.4 gm/lit, contact time of 15 min and initial arsenic concentration of 0.2 mg/lit in the solution can be removed with nanoadsorbents with efficiency about 19 % by GO, 79 % by CoFe2O4 and 85 % by GO-CoFe2O4 without considering any other parameters. But efficiency of arsenic adsorption of the prepared nanoadsorbents increased with pre oxidation and increased contact time. Arsenic adsorption efficiency of 40 % using GO, 97 % using CoFe2O4 and 97.5 % using GO-CoFe2O4 has been achieved with pre oxidation and 22 hrs of contact time at pH of 7, adsorbent dose of 0.4 gm/lit, and initial arsenic concentration of 0.2 mg/lit. Based on result obtained, it is established that CoFe2O4 coated GO can be an effective nanoadsorbents for arsenic removal from the solution. This result underlines the need of further study for field application of these nanoadsorbents.

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.

Statistical analysis for remediation of As(III) ions from water using pristine and derivatized Phyllanthus emblica seed coat

Abstract The aim of this study is to determine the optimal conditions for remediation of As(III) ions from water using pristine Phyllanthus emblica (PPE) seed coat and derivatized Phyllanthus emblica (DPE) seed coat, by using Box -Behnken design (BBD) and central composite design (CCD) optimization techniques. pH, initial ion concentration, dosage, and contact time were taken as process parameters while designing the experiment. The desirability factor is 1.0 for the BBD and 0.8 for CCD for both adsorbents. The regression coefficient for both adsorbents was in the range of 0.993 -0.999 for the BBD and 0.965 -0.969 for the CCD. The BBD is found to be more suitable for optimization of variables for maximum removal, and estimation of removal percentage in different conditions. The adsorption of ions at equilibrium (qe) is found to be 43.59 mg/g at pH 7.13, initial concentration of arsenic of 99.02 mg/L, contact time of 105.13 min, and dosage of 0.12 g/L for PPE using the BBD. However, the adsorption of ions at equilibrium (qe) is found to be 48.79 mg/g at pH 7.31, initial ion concentration of 98.82 mg/L, contact time of 126.99 min, and dosage of 0.12 g/L for DPE using the BBD.

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.

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.

Brevibacterium sp. strain CS2: A potential candidate for arsenic bioremediation from industrial wastewater

A multiple metal-resistant Brevibacterium sp. strain CS2, isolated from an industrial wastewater, resisted arsenate and arsenate upto 280 and 40 mM. The order of resistance against multiple metals was Arsenate > Arsenite > Selenium = Cobalt > Lead = Nickel > Cadmium = Chromium = Mercury. The bacterium was characterized as per morphological and biochemical characteristics at optimum conditions (37 ℃ and 7 pH). The appearance of brownish color precipitation was due to the interaction of silver nitrate confirming its oxidizing ability against arsenic. The strain showed arsenic processing ability at different temperatures, pH, and initial arsenic concentration which was 37% after 72 h and 48% after 96 h of incubation at optimum conditions with arsenite 250 mM/L (initial arsenic concentration). The maximum arsenic removal ability of strain CS2 was determined for 8 days, which was 32 and 46% in wastewater and distilled water, respectively. The heat-inactivated cells of the isolated strain showed a bioremediation efficiency (E) of 96% after 10 h. Genes cluster (9.6 kb) related to arsenite oxidation was found in Brevibacterium sp. strain CS2 after the genome analysis of isolated bacteria through illumine and nanopore sequencing technology. The arsenite oxidizing gene smaller subunit (aioB) on chromosomal DNA locus (Prokka_01508) was identified which plays a role in arsenite oxidation for energy metabolism. The presence of arsenic oxidizing genes and an efficient arsenic oxidizing potential of Brevibacterium sp. strain CS2 make it a potential candidate for green chemistry to eradicate arsenic from arsenic-contaminated wastewater.

Raw and modified Pakistani Kaolin as an efficient adsorbent for the removal of arsenic from groundwater

Raw and modified Nagarparkar Pakistani Kaolin (RNK) were used to remove arsenic from groundwater by adsorption technique. Both the RNK samples were analyzed by XRD and SEM to examine their crystallinity and morphology. Iron-modified kaolin showed increased Si/Al ratio of 23% compared to 14% obtained with NaCl-modified kaolin indicating the influence of iron on kaolin properties in terms of its structural de-complexation reflected by higher groundwater arsenic removal. Only 1.50 gg-1 (15%) arsenic removal efficiency was observed using raw RNK at equilibrium time; however, after treatment with NaCl (0.10 M) and FeCl3 (0.1 and 0.01M) the treated solutions exhibited arsenic removal efficiency in the range of 9.2 gg-1 (92%) and 8.6 gg-1 (86%) using iron-modified MNK-1 and MNK-2, respectively. RNK and MNK equilibrium for arsenic sorption was reached in 60 min. The process kinetics transpired that Pseudo-second-order rate equation provided better kinetics of arsenic sorption with Iron-modified MNK-1 treatment protocol depicting about 1% of an average error for the amount of arsenic adsorbed on the adsorbent compared to 89% observed with pseudo-first-order model,. The experimental results indicated that arsenic adsorption was more rapid and efficient at lower initial concentration of the modifying agent. This study demonstrated that the initial arsenate concentrations as well as the iron content in the MNK affect the quantity of arsenic adsorbed on the adsorbents.

Mechanistic insights into the structure-activity relationship of FeS for arsenic removal in strongly acidic wastewater

Sulfide precipitation is an efficient method for separation. However, its application is limited due to the significant H2S pollution caused by conventional reagents. The utilization of amorphous FeS lead to a substantial reduction in H2S escape, while concurrently enhancing the crystallization and settling characteristics of As-precipitates. Under the conditions of an initial arsenic and H2SO4 concentration in the solution of 2 g/L and 50 g/L, respectively, and a FeS dosage of 1.5 times the molar amount of S/As, the arsenic removal exhibited a significant decrease from 89.8 % to 40.8 % over a FeS aging period of 0 to 84 days. Notably, no H2S emissions were detected during the entire reaction process. XRD analysis revealed a transformation of FeS from its amorphous form to a crystalline state as it undergoes aging. This transition is primarily characterized by a reduction in interlayer spacing and FeS bond length within the FeS lattice. The lattice energy experienced a decrease from −3071 to −3688 kJ/mol, indicating the progressive stabilization of the FeS structure. FTIR and TG-DSC analyses have demonstrated the infiltration of water molecules into both the interlamellar spaces and the lattice of FeS during the process of crystallization. Additionally, As3+ ions were observed to initially adsorb onto the surface of aged FeS through the hydroxyl group, followed by their diffusion into the lattice. The products of arsenic removal undergone a transformation from As2S3 to predominantly FeAsS-like complexes, as the mechanism of arsenic removal shifted from precipitate transformation to adsorption and co-precipitation.

Copper-doped ZIF-8 nanomaterials as an adsorbent for the efficient removal of As(V) from wastewater

Arsenic pollution is an international problem that must be urgently controlled. Therefore, this study is based on a one-pot precipitation method, in which copper ions were added to a zinc organic metal framework (ZIF-8) to partially replace the zinc ions and the obtained adsorbent (Cu-ZIF-8) used to effectively remove As(V) ions from water. The successful synthesis of the Cu-ZIF-8 adsorbent and its adsorption mechanisms were confirmed using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and X-ray photoelectron spectroscopy (XPS). In addition, the effects of pH (3–11), initial arsenic concentration (10–350 mg/L), and reaction time on the adsorption performance were also characterized. Our findings demonstrate that Cu-ZIF-8 had a high As(V) adsorption capacity of 238.11 mg/g, which was significantly higher than that of most adsorbents previously reported in the literature. Moreover, this material maintained >75% of its initial adsorption capacity after four adsorption-desorption cycles. The adsorption kinetics of Cu-ZIF-8 were accurately described using the pseudo-second-order kinetic model, whereas the adsorption isotherm was fitted using the Langmuir model. Collectively, our findings have demonstrated that doping organic metal frameworks with metal ions can substantially improve their adsorption performance without changing their structural properties. Therefore, Cu-ZIF-8 is a promising adsorption material for the treatment of As(V)-contaminated water.

Arsenic removal by highly efficient MnFe2O4/TiO2/g-C3N4 and MnFe2O4/TiO2/GO adsorbents from a groundwater sample, Bardsir, Iran

In this study, MnFe2O4/TiO2/GO and MnFe2O4/TiO2/g-C3N4 spinel ferrites nanoparticles were used, and synthesized via the co-precipitation method, for the removal of arsenic from groundwater in the Bardsir region, Iran. The magnetic adsorbents were characterized by XRD, VSM, BET, FE-SEM, EDS, RAMAN, and FTIR analyses. The effects of pH, adsorbent dosage, contact time, initial arsenic concentration, and temperature on the adsorption process were investigated. MnFe2O4/TiO2/GO and MnFe2O4/TiO2/g-C3N4 were utilized to minimize the concentration of arsenic. The arsenic concentration was reduced from the initial amount of 17.8 mg/l to 197 µg/l and 177 µg/l using MnFe2O4/TiO2/GO and MnFe2O4/TiO2/g-C3N4, which indicates the adsorption capacity of 331 (mg/g) and 332 (mg/g), and the removal efficiency of 98.89% and 99.01%, respectively. Moreover, the adsorption rate for MnFe2O4/TiO2/GO and MnFe2O4/TiO2/g-C3N4 was very fast and occurred in 5 (min) and 15 (min), respectively. The results of kinetics studies were well correlated with the pseudo-second-order model, with the coefficient of determination values of 1 for both adsorbents. These nanoparticles could remove arsenic by following the Freundlich isotherm model. The thermodynamics studies showed that arsenic adsorption was an exothermic and spontaneous process. This article also presents a numerical simulation containing the second-order kinetic expression using COMSOL Multiphysics software. The experimental data and the numerical modeling results were in solid agreement. Furthermore, after five adsorption–desorption cycles, the adsorption capacity of the adsorbents remained constant as in the first cycle. Overall, a simple synthesis method, high adsorption capacity, fast kinetics, easy magnetic separation, and reusability demonstrate that MnFe2O4/TiO2/GO and MnFe2O4/TiO2/g-C3N4 are high-performance adsorbents for arsenic removal from aqueous systems.

The effects of phosphate and pH on arsenate adsorption on allophanic Andosols in Miyazaki

ABSTRACT Arsenic (As) contamination in agricultural soils is a serious problem. The mobility and bioavailability of As in agricultural soil are mainly controlled by phosphate and pH. Although there is a potential risk of soil contamination in Japan by geogenic As distributed along the volcanic front, few studies have investigated arsenate adsorption on Andosols, a typical agricultural soil in Japan. In this study, we evaluated the effects of phosphate and pH on arsenate adsorption on allophanic Andosols. The adsorption isotherms of Andosols for arsenate and phosphate were determined in batch experiments at different phosphate concentrations and pH. In addition, following the competitive adsorption experiment of arsenate and phosphate, we determined three fractions of the adsorbed arsenate by sequential extraction as easily soluble As fraction (F1; 0.01 mol L−1 NaNO3 extraction), specifically adsorbed As and As mainly bound to poorly crystalline materials (F2; 0.2 mol L−1 NH4-oxalate buffer extraction), and As mainly bound to crystalline materials (F3; 0.2 mol L−1 NH4-oxalate buffer+0.1 mol L−1 ascorbic acid extraction). Andosols adsorbed~96.0% arsenate and~98.3% phosphate at the initial arsenate concentration of 214 µmol L−1 and phosphate concentration of 323 µmol L−1, respectively in each single-anion system. The maximum arsenate adsorption on the Andosols occurred at an equilibrium pH of~3.8 and it decreased with further increasing or decreasing equilibrium pH. Upon 300 µmol L−1 of arsenate addition, the Andosols adsorbed 98.6, 99.4, 91.0, and 65.8% of arsenate at an equilibrium pH of 3.0, 3.8, 6.2, and 7.6, respectively. The effect of pH was incorporated into the parameter of the modified Freundlich model for arsenate adsorption on Andosols. The competitive adsorption experiment results indicated a greater affinity of phosphate than arsenate for Andosols. Sequential extraction revealed that competition with phosphate not only decreased the amount of adsorbed arsenate, but also increased the amount of arsenate in F1, which is mobile and readily available to plants. Thus, phosphate fertilization can increase the mobility and bioavailability of arsenate in agricultural soils.

Evaluación de dos materiales geológicos de bajo costo como adsorbentes para As

Two easily accessible local materials, kaolin, and sediments from the reservoir of a dam, were evaluated to compare their efficiencies as adsorbents for As. The kaolin sample was composed mainly by kaolinite and quartz, while the sediments contained illite, montmorrillonite and quartz. Also, iron, calcium and magnesium minerals were present as minor components. The adsorption experiments were performed using batch equilibrium techniques. The samples were chemically treated using piranha solution, and trimesic acid, to study their effects on the adsorption capacity. The piranha treatment seems to be a good alternative to improve the adsorption capacity of kaolin. However, the intact reservoir sediments showed higher efficiencies than the intact or treated kaolin. On the other hand, the initial uptake of trimesic acid showed only a slightly positive effect on the arsenic uptake of the reservoir sediments. Most of the arsenic adsorption seems to be due to the finest particles of the sediments, composed mainly of iron minerals, while the organic matter contributes scarcely to the arsenic uptake. The influences of pH, contact time, initial arsenic concentration, and chemical treatments were studied. Freundlich and Dubinin-Kaganer-Radushkevich isotherm models were used to evaluate the arsenic uptake capacity of the intact and trimesic acid treated reservoir sediments. Maximum arsenic adsorption was completed almost within five hours of reaction, reaching a measured sorption capacity of 137 mg/kg for the intact sediments, slightly lower than for the trimesic treated sediments.

What's in your water? A well-known risk for arsenic toxicity.

Arsenic cannot be tasted, seen or smelled and can vary in concentration between water wells even in condensed areas. American domestic well water is not regulated to meet the same drinking water standards as other types of water supplies and often contains arsenic. If arsenic is not detected in a well water sample, it is unlikely to be found later. Conversely, if it is detected in a new well, it is recommended to retest six months later as levels may fluctuate in the first months following well construction. It is up to the well owner to test their water and remove arsenic through commercially available water filters. If it is not detected and removed via filtration, a variety of serious, yet common, medical conditions may arise from chronic arsenic exposure, some of which are life-threatening. These include diabetes mellitus, hypertension, skin cancer, renal, bladder and lung cancers, polyneuropathy and cardiac QTc prolongation. Testing is best done through urine speciation if an initial total urine arsenic concentration is elevated. Consider a complete blood count, renal and liver function tests, an electrocardiogram as well as a urinalysis assessing for evidence of hematuria when examining patients with histories concerning for chronic arsenic exposure.

Arsenic removal from contaminated water utilizing novel green composite Chlorella vulgaris and nano zero-valent iron

Arsenic waste must be carefully managed because of the adverse effects of arsenic in wastewater on the ecosystem. In the present study, an environmentally friendly novel composite of Chlorella vulgaris microalgae and nano-zero valent iron (NZVI) was employed as an adsorbent to eliminate arsenic from the aqueous environment. Fourier Transform Infrared spectroscopy, X-ray diffraction, and scanning electron microscope images were used to characterize and analyze the CV/NZVI composites. Batch tests using initial arsenic concentrations ranging from 5 to 100 mg/L were conducted to evaluate removal efficiencies. According to kinetic analysis, the best model for fitting the experimental data was the pseudo first-order model, which had the lowest Akaike information criterion (AIC), and Bayesian information criterion (BIC) values of −23.878 and −7.902, respectively. Results alluded that physisorption is the primary mechanism influenced by As-removal by CV/NZVI composite. Due to the negative sign of the enthalpy and Gibbs free energy, the thermodynamic investigation revealed that the adsorption reaction was exothermic and spontaneous. The thermodynamic analysis also affirmed that the arsenic removal process involved primarily physisorption and slight chemisorption phenomena. Meanwhile, 1.5 g/L CV/NZVI dosage achieved 99 % As(V) removal efficiency in synthetic groundwater systems, confirming the high potential of the composite in complex aqueous systems.

Effective removal of arsenic (V) from aqueous solutions using efficient CuO/TiO2 nanocomposite adsorbent

The groundwater is one of the biggest natural resources for providing drinking water to millions of people all around the globe. However, the presence of large amount of arsenic(V) in water causes serious health hazards to the consumers which necessitates the development of cost-effective remediation. The CuO/TiO2 nanocomposites were prepared by the precipitation-deposition method for the removal of the arsenate ion (AsO43-) from water. The prepared samples were characterized by powder X-ray diffraction, Fourier transform infrared, and scanning electron microscopy to examine crystallite size and structure, material purity, textural features, morphology, and surface area. The effect of different operating parameters such as pH, contact time, initial concentration of arsenic(V) and nanocomposite dose on the removal rate of arsenic(V) was examined to optimize the adsorption performance of the CuO/TiO2 nanocomposite. In addition, the adsorption mechanism was studied by employing Langmuir and Freundlich adsorption isotherms to gain better understanding of the adsorption mechanism. The Freundlich adsorption isotherm fits well with the experimental data and the maximum adsorption capacity of the Langmuir model was found to be 90 mg/g for arsenic(V). The CuO/TiO2 nanocomposite shows remarkable adsorption performance for the treatment of arsenic(V) contaminated water samples. This study provides a cost-effective solution for the safe use of groundwater contaminated with arsenic.