Initial Arsenic Concentration Research Articles

Removal performance and adsorption behaviour on Mg-based adsorbents in As(III) and F simultaneous removal as in comparison with As(V)

In this study, simultaneous removal tests, with fixed initial arsenic (As) concentration of 1 mg l −1 , for arsenite [As(III)] and fluoride (F) were performed using three types of Mg-based adsorbents. Their As(III) removal performance was of the order of MgCO 3 << Mg(OH) 2 < MgO. MgO met the environmental standards for As (0.01 mg l −1 ) at initial F concentrations ( C F0 ) of 15 and 30 mg l −1 . MgO and Mg(OH) 2 met the As effluent standard (0.1 mg l −1 ) even at C F0 = 60 mg l −1 . In contrast, MgCO 3 did not meet the effluent standards under the test conditions. The F removal performance of the Mg-based adsorbents followed the order of MgCO 3 < Mg(OH) 2 < MgO. MgO and Mg(OH) 2 met the environmental standard of F (0.8 mg l −1 ), whereas MgCO 3 met the effluent standards for F in non-marine areas (8 mg l −1 ) at C F0 = 15 and 30 mg l −1 , and in marine areas (15 mg l −1 ) even at C F0 = 60 mg l −1 . The As(III) adsorption data fit the Langmuir model for MgO and the Freundlich model for MgO and Mg(OH) 2 , but not MgCO 3 for either model. Notably, the As(III) adsorption behaviour of MgO was strongly influenced by C F0 . Meanwhile, the F adsorption data fit both the Langmuir and Freundlich models for all Mg-based adsorbents.

Turning waste into wonder: Arsenic removal using rice husk based activated carbon

In this study, rice husk activated carbon (RHAC) was synthesized by physicochemical activation, which consists of heat treatment with CO2 gasification and KOH chemical treatment to eliminate arsenic (As) from the polluted water. Initial arsenic concentrations, solution pH, solution temperature and contact time are the parameters that have been tested in this study. The characterization study showed that RHAC has a high BET surface area (815.52 m2/g) and its pore structure was found to be mesoporous with an average pore diameter of 2.96 nm. Characterization studies, including X-ray diffraction analysis (XRD), Raman spectroscopy and scanning electron microscopy (SEM) were employed to determine the RHAC’s performance. The adsorption of As towards RHAC followed the Freundlich isotherm model and pseudo-first order with adsorption process was favorable at higher arsenic concentrations. The mechanism study also signified that the adsorption of As-RHAC was limited by film-diffusion. Thermodynamic studies indicated that the As-RHAC adsorption system was endothermic, random, spontaneous, feasible in nature and governed by the chemisorption process. Desorption and regeneration studies of RHAC showed that it can be utilized up to 5 cycles and is stable for the water treatment facilities.

Concurrent elimination of arsenic and nitrate from aqueous environments through a novel nanocomposite: Fe3O4-ZIF8@eggshell membrane matrix

The high concentration of nitrate and arsenic as potentially toxic elements (PTEs) with carcinogenic properties in many groundwater sources worldwide is a concern for health and the environment. This work checked the capacity of a novel nanocomposite, Fe3O4-ZIF8@eggshell membrane matrix (F-ZIF8@EMM) for concurrently eliminating arsenic and nitrate, two of the most encountered hazardous pollutants in drinking water. Contact time (30–120 min), pH (3–10), initial arsenic concentration (25–100 μg/L), initial nitrate concentration (60–120 mg/L) and adsorbent dose (0.25–5 mg/L) as various operating influences were investigated on the co-adsorption of arsenic and nitrate from water by a new nanocomposite thru diverse experimental tests. Characteristics of F-ZIF8@EMM were determined through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR) and Brunauer–Emmett–Teller (BET) analyses. Taguchi model was used to determine the optimal co-adsorption conditions. The results revealed that the optimal conditions for the simultaneous adsorption of 94.32 % of these two elements were at pH = 7, adsorbent dose 1 mg/L, primary nitrate concentration 120 mg/L, initial arsenic concentration 100 μg/L, and contact time 90 min. Correspondingly, the simultaneous adsorption of arsenic and nitrate best fit the Langmuir isotherm, and the pseudo-second-order (PSO) model was the best model that fitted with experimental kinetic data (R2 = 1). The maximum experimental adsorption capacity of F-ZIF8@EMM was 128.5 mg/g. This study indicated that the efficiency of nanocomposite F-ZIF8@EMM in the co-adsorption of arsenic and nitrate was promising.

Simultaneous Removal of As(iii) and As(v) from Aqueous Solution by Using Iron-Functionalized Polythiophene: A Novel Approach toward Water Treatment.

Arsenic contamination in groundwater poses a significant threat to human health, affecting millions worldwide. This study presents a novel approach for simultaneous remediation of both As(III) and As(V) by using iron-functionalized polythiophene (PTh@Fe) composites. The PTh@Fe composite was synthesized by a reduction process involving FeCl2/FeCl3 byproducts of polymerization, resulting in a highly efficient adsorbent for both As(III) and As(V) species. The investigation systematically examined key parameters influencing arsenic removal, including adsorbent dosage, pH, initial arsenic concentration, and contact time. The composite exhibited exceptional adsorption capacities, with maximum removal percentages of 98.7% for As(III) and 98.8% for As(V) under the optimized conditions. Thermodynamic and kinetic analyses suggested endothermic and spontaneous adsorption processes following a pseudo 2nd-order mechanism. Furthermore, the Langmuir isotherm model provided an excellent fit to the experimental data, with maximum adsorption capacities of 8.62 mg/g for As(V) and 7.57 mg/g for As(III). Density functional theory (DFT) calculations confirmed the feasibility of arsenic adsorption onto iron species in various oxidation states, offering valuable theoretical insights into the process. Furthermore, the composite demonstrated good reusability over multiple adsorption-desorption cycles and tolerance to coexisting anions, highlighting its practical applicability for water purification. This research demonstrates the potential of iron-functionalized polythiophene composites as a promising solution for addressing arsenic contamination in water sources, bridging the gap between innovative materials and theoretical understanding in environmental science and water treatment technologies.

Impact of silicate on the microstructure of β-FeOOH and its adsorption of As

The structural and chemical properties of iron oxides are usually pertinent to the high affinity of silicon and iron in the environment, which further influences the retention of As. Previous work mainly focused on the Fe-Si interactions in Si-rich environments, while there is a dearth of both structural alteration of iron oxide in low-silicate conditions and the mechanistic understanding on the adsorption As process in Si-Fe oxide (Si-FeOOH). Herein, we investigated the adsorption of As on Si-FeOOH, proceeding from the physical and chemical properties of low-silicate co-precipitated β-FeOOH. Additionally, the effect of initial concentration of arsenic, oxygen, pH, and electrolyte concentration were discussed. SEM, TEM, XPS, FTIR, XRD and Rietveld refinement, BET and Zeta potential were used to characterize the structure and surface properties of Si-FeOOH; atomic fluorescence spectrometer were used to determine the residual As solution. DFT-calculated adsorption energies and electron localization function distribution for (310) facet is consistent with the analytical results obtained from experiments, demonstrating that the little dopped silicate stabilized the crystal microstructure of β-FeOOH, and strengthened the combination of As by generating the intramolecular hydrogen bonding and promoting electron transfer.

Mechanism of arsenic removal using brown seaweed derived impregnated with iron oxide biochar for batch and column studies

Water contaminated with arsenic presents serious health risks, necessitating effective and sustainable removal methods. This article proposes a method for removing arsenic from water by impregnating biochar with iron oxide (Fe2O3) from brown seaweed (Sargassumpolycystum). After the seaweed biomass was pyrolyzed at 400 °C, iron oxide was added to the biochar to increase its adsorptive sites and surface functional groups, which allowed the binding of arsenic ions. Batch studies were conducted to maximize the effects of variables, including pH, contact time, arsenic concentration, and adsorbent dosage, on arsenic adsorption. The maximum arsenic adsorption efficiency of 96.7% was achieved under optimal conditions: pH 6, the adsorbent dosage of 100 mg, the initial arsenic concentration of 0.25 mg/L, and a contact time of 90 min. Langmuir and Freundlich’s isotherms favored the adsorption process, while the kinetics adhered to a pseudo-second-order model, indicating chemisorption as the controlling step. Column studies revealed complete saturation after 200 min, and the adsorption behavior fits both the Adams–Bohart and Thomas models, demonstrating the potential for large-scale application. The primary mechanism underlying the interaction between iron-modified biochar and arsenic ions is surface complexation, enhanced by increased surface area and porosity. This study highlights the significant contribution of iron-modified biochar derived from macroalgae as an effective and sustainable solution for arsenic removal from water.

Application of green solvents for arsenic removal from petroleum produced water: Statistical, DFT and McCabe-Thiele determination

This work presents the novel application of green oils to extract arsenic ions from petroleum produced water via liquid-liquid extraction (LLE). In the experiment, the removal of arsenic ions from synthetic petroleum produced water is investigated, using five green oils: canola oil, corn oil, linseed oil, rice bran oil, and sunflower oil, in place of petroleum-based solvents: toluene and kerosene. Both extraction and stripping optimizations are examined. For extractants, Aliquat 336 and Cyanex 921 are implemented. The initial arsenic concentration (3.984 mg L−1) of petroleum produced water is examined. Results demonstrate that Aliquat 336 in corn oil proved to be most effective for arsenic removal. At optimal conditions via response surface methodology (RSM), the highest extraction and stripping percentages reached 99.95 % and 100.00 %, respectively. In accordance with the World Health Organization (WHO) levels of ≤0.01 mg L−1, arsenic concentration remaining in the extracted water (0.002 mg L−1), is seen to fulfill the requirement needed. The extraction and stripping kinetics are of first and second-order. Mechanisms of arsenic removal are evaluated via density functional theory (DFT). Further, selectivity, recycling of the organic phase, and the number of stages via McCabe-Thiele theory are determined under optimal conditions.

Enhanced Adsorption of Arsenate from Contaminated Waters by Magnesium-, Zinc- or Calcium-Modified Biochar—Modeling and Mechanisms

The adsorption of arsenate from wastewaters was investigated by applying Mg-, Zn- or Ca-modified nut residue biochar activated by nitrogen/steam. The parameters studied were the contact time, adsorbent dose, initial arsenate concentration and solution pH. The adsorption mechanism was investigated. Various analyses of the material before and after arsenate adsorption were carried out, and experimental data were simulated by applying two isotherm models. The results indicated that the maximum removal efficiency of arsenate was 29.4% at an initial concentration of 10 mg/L. The modification of biochar by Mg, Zn or Ca oxides increased the removal rate significantly, from 49.4% at 100 mg/L As5+ up to 8%, 97% and 97%, respectively. Zn-modified biochar presented an excellent performance for both low and high As5+ concentrations. All experimental data were accurately fitted by the Freundlich isotherm model (R2 = 0.94–0.97), confirming a multilayer adsorption mechanism. For a biochar dose of 2 g/L, the maximum capacity of adsorption was enhanced after Mg-, Zn- or Ca-modification from 12.4 mg/g to 35 mg/g, 50 mg/g and 49 mg/g, respectively. The potential mechanisms of adsorption were ligand exchange, chemical complexation, surface precipitation and electron coordination.

Adsorption and estimation of As (III) from wastewater using cross linked Chitosan-STPP nanoparticles with voltammetric analysis computrace, isotherms, and kinetic study

Chitosan (CS) is a naturally occurring polycationic linear amino polysaccharide produced commonly through the deacetylation of chitin. This study describes the synthesis of Chitosan (CS) modified with sodium tripolyphosphate (STPP) using an efficient coated Cross-linked method. The study investigated the efficacy of chitosan-tripolyphosphate (CS-STPP) nanoparticles for the efficient adsorption of As (III) ions from a wastewater solution. The effect of initial Arsenic (III) ion concentration, solution pH, and temperature on adsorption efficiency was thoroughly investigated. The highest adsorption capacity of CS-STPP nano adsorbents for As (III) was found to be 39.8 mg/g and 39.6 mg/g, respectively, at pH 5.5, and a temperature of 30 °C. The FESEM, SEM, HRTEM, XRD, FTIR, DLS, and TGA results indicated that the adsorption process of As (III) was chemically dominating. As (III) Determine with the anodic linear sweep voltammetry 797 VA Computrace (Metrohm). The Langmuir parameters of 40.9 mg/g and 1000 L/mg were found for maximum adsorption capacity, which indicated monolayer adsorption on a homogeneous site, Freundlich isotherm is applicable for multilayer adsorption onto heterogeneous sites. The thermodynamic study showed that the adsorption of As (III) by CS-STPP was spontaneous, feasible, and exothermic at temperatures ranging from 30 °C to 50 °C. The kinetic model indicated that the adsorption processes persist well to the pseudo-second-order kinetics model. The reaction is suitable for a pseudo-second-order model, it indicates an inclination for chemisorption. Adsorption-desorption processes are determined efficiency of bio adsorbent by several physicochemical cycles. All results indicate that the prepared CS-STPP nanoparticles might be considered a cost-effective adsorbent for removing As (III) from wastewater.

Comparative evaluation of diffusion kinetics of arsenic adsorption on iron (oxy) hydroxides containing biopolymer nanocomposite beads

Exposure to arsenic-contaminated water poses great health risks to mankind. Nanocomposite beads have been proven to be an effective alternative for large-scale treatment of arsenic-loaded water. The larger size of the beads makes the adsorbent retrieval process less energy-intensive and prevents accidental leaching of nanoparticles into the surrounding environment. Adsorption using macroporous beads is predominantly a diffusion-controlled process. Therefore, in the present study, the shrinking core model (SCM) was used to compare and evaluate the diffusion kinetics of arsenic adsorption using in-situ precipitated iron (oxy)hydroxide alginate (IIAB) and chitosan beads (IICB). Simulated dynamic nondimensional liquid phase arsenic concentration profiles fit well with the experimental data (SSE = 0.018–0.025). External mass transfer coefficient (kf) and effective diffusivity coefficient (De) for both kinds of beads at different initial arsenic concentrations (C0 ∼ 1 mg.L−1 and 5 mg.L−1) were derived. By comparison of diffusivity values and the simulated concentration front profiles, it was observed that chitosan provided a better porous polymer template with more easily accessible adsorption sites covering up to 85 % of the beads’ volume. Comparison with progression conversion models has also been made to test the effectiveness of SCM fitting.

Formation processes of iron-based layered hydroxide in acid mine drainage and its implications for in-situ arsenate immobilization: Insights and mechanisms

The immobilization of arsenate in transformed minerals depends on their states in acid mine drainage (AMD). In this study, an iron-based layer hydroxide mineral was derived from the transformation of ferrihydrite under co-existing Mg2+ ions in AMD. The immobilization behavior of arsenate on the mineralized LDHm and pre-prepared LDHad was distinguished. 99 % immobilization efficiency was achieved from the mineralized LDHm, maintaining stability without subsequent releases, across initial arsenate concentrations ranging from 10 to 60 mg/L. LDHm outperformed the pre-prepared LDHad, which was synthesized from AMD for arsenate adsorption. Electron energy loss spectroscopy line profiles revealed predominant incorporation of arsenate in the LDHm structure, supported by higher bulk As signals within LDHm. Density functional theory calculations indicated primary arsenate incorporation into LDHm, forming stable bonds with lower energy activation barriers. Importantly, LDHm exhibited a superior electron rearrangement configuration, resulting in enhanced electron state activity and affinity for arsenate. In contrast, arsenate adsorption predominantly occurred on the pre-prepared LDHad, with notable As signals detected particularly at the edges. Adsorption energy evaluation indicated arsenate preference for bonding to Fe3+ sites on LDHad. These findings provide important insights into the role of stable LDH-like minerals for long-term arsenate immobilization in the natural AMD attenuation processes.

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.