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In this study, adsorption of As(III) removal on iron oxide-coated quartz, iron oxide-coated lignite sand, and iron oxide-coated silica sand were investigated. Batch studies were performed to evaluate the influences of various parameters like initial pH, adsorbent dose, and initial concentration for the removal of As(III). Optimum conditions for As(III) removal on the three adsorbents were found to be pH 7, adsorbent dose 20 g/l of solution, and equilibrium time 6 h. The kinetics study of As(III) removal have also been determined using a pseudo-first-order, pseudo-second-order, Weber and Morris, and Elovich model. Among the conventional models, the q e,exp and the q e,calc values from the pseudo-second-order kinetic model are very close to each other and followed by Weber-Morris and Elovich model for all adsorbents. In this system, the effective diffusion coefficient (D e ) value of As(III) is more than the order of 10 À9 cm 2 /s. This order shows in the literature that pore diffusion is the rate-limiting step for all the adsorbents. Equilibrium isotherms for the adsorption of As(III) on all the three adsorbents were analyzed by Langmuir, Freundlich, Redlich-Peterson (R-P), and Temkin isotherm models using nonlinear regression technique. R-P and Freundlich isotherm was found to be the best to represent the data for As(III) adsorption on all the adsorbents. The parameters obtained in this study for different kinetic and equilibrium models of all adsorbents are very comparable with other reported values for sand-based and other adsorbents.

The present research aimed to analyse the impact of economical Fe impregnated PET char (PETC-Fe) for adsorption of As (III) through series of column experiments. For an inlet arsenite concentration of 1,000 μg/L, PETC-Fe exhibits excellent uptake capacity of 1,892 μg/g. CCD (central composite design) in response surface methodology (RSM) was used to evaluate the influence of various process variables on the response function (breakthrough time) for optimization and assessment of interaction effects. The breakthrough time is more responsive to influent As (III) concentration and bed height than inlet flow rate, according to the perturbation plot. Adams–Bohart, Bed Depth Service Time model, and Thomas models were used to model the dynamics of the adsorption system. The BDST model suited the experimental data well in the early part of the breakthrough curve, but there were minor variations over the breakpoints. Despite the fact that the experimental values and the data sets estimated using the Adams–Bohart model followed a similar pattern, they differed slightly. The PETC-Fe was found to be a sustainable and highly economical adsorbent, with a desorption performance of more than 97 percent indicating the adsorbent's reusability. This adsorbent's excellent As (III) uptake capacity and regeneration performance imply that it might be used in industrial/domestic applications, and the information obtained could aid in future scaling up of the adsorption system.

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As(III) removal from aqueous solution was conducted using low-cost adsorbents like unmodified raw coconut husk (RCH) and modified iron impregnated coconut husk (IICH). Prepared both adsorbents was characterisation by using elemental analyses, FTIR, TGA, SEM and EDX. The analysis behaviour indicates, both adsorbents are highly suitability for As(III) removal. The effects of operational parameters, such as pH, adsorbent dose and initial concentration on these adsorbents were investigated and compared with other agriculture based adsorbent. The result reveals that the As(III) removal capacity is effective in the pH range of 6.2–7.8 and the optimum pH and adsorbents dose was found as 7.0 and 40 g l−1, for RCH and IICH, respectively. Kinetic and equilibrium studies over a wide range of operating conditions are tested to evaluate the effectiveness of RCH and IICH to remove As(III) from water. The values of both kf1 and ks2 values are found to be nearly same and same trend was observed at higher 50 mg l−1 and lower arsenic concentration 25 mg l−1 for RCH and IICH. But the kinetic data is fitted better in the pseudo-second-order kinetic model than the pseudo-first order model. The effective intraparticle diffusion coefficient of As(III) ions in RCH and IICH is observed to be 2.145×10−9 cm2 s−1 and 1.838×10−10 cm2 s−1, which indicates that the overall As(III) adsorption on both adsorbents are intraparticle diffusion control. Equilibrium isotherms for the adsorption of As(III) on RCH and IICH were analyzed at different dose and different initial concentration. At different concentration system, Freundlich isotherm and Redlich-Peterson are best fitted followed by Langmuir and Temkin isotherm models and for varying doses, all equilibrium models give almost similar fitness.