Abstract
In this study, Box-Behnken design (BBD) in response surface methodology (RSM) was employed to optimize As(V) removal from an aqueous solution onto synthesized crosslinked carboxymethylchitosan-epichlorohydrin/Fe3O4 nanaocomposite. The factors like solution pH, adsorbent dose, contact time and temperature were optimized by the method which shows high correlation coefficient (R2=0.9406), and a predictive quadratic polynomial model equation. The adequacy of the model and parameters were evaluated by analysis of variance (ANOVA) with their significant factors of Fischer's F - test (p<0.05). Seven significant parameters with interaction effects in the experiment with p-value < 0.0001 was observed, having a maximum removal efficiency of As(V) is 95.1%. Optimal conditions of dosage, pH, temperature, initial ion concentration and contact time in the process were found to be 0.7 g, pH 6.5, 308K, 10 mg/L and 60 min respectively. Langmuir isotherm model fitted better than the Freundlich model having a maximum adsorption capacity of 28.99 mg/g, a high regression value of 0.9988, least chi-square value of 0.1781. The process was found to follow monolayer adsorption and pseudo-second-order kinetics. Thermodynamic parameters indicate the process is spontaneous, endothermic and physisorption in nature. Successful regeneration of the adsorbent implies its applicability to the removal of arsenic from real life wastewater.
Highlights
Several adsorbents have been found suitable for arsenic removal counting activated carbon,[7] activated alumina,[8] red mud,[9] etc., In the last decade developments in the knowledge of biosorption exposed high adsorption capacities, low costs and regenerability of natural biosorption materials.[10]
At position C-5 of Carboxymethyl chitosan (CMC)’s pyranose ring indicated that the amino (-NH2) group plays a major role in the adsorption of arsenic anion by electrostatic attraction.[25]
Statistical analysis system software was used for the study of Analysis of variance (ANOVA), response surface studies and 3D surface plot generation
Summary
Arsenic is a pervasive element in the environment and has been known as a notorious toxic substance to man and living organisms for centuries.[1]. Long term exposure to arsenic in drinking water causes skin diseases (pigmentation, dermal hyperkeratosis, skin cancer), cardiovascular, neurological, renal, respiratory and black foot diseases, as well as lung, liver, kidney and prostate cancers.[4]. World Health Organization has set a provisional guideline limits of 10 μg/L for arsenic in drinking water which was afterward adopted by the European Union and India.[5]. The removal of Arsenic by Co-precipitation, flotation, ion-exchange, ultra-filtration, and reverse osmosis[6] have been received more attention due to its high concentration efficiency.[6]. Several adsorbents have been found suitable for arsenic removal counting activated carbon,[7] activated alumina,[8] red mud,[9] etc., In the last decade developments in the knowledge of biosorption exposed high adsorption capacities, low costs and regenerability of natural biosorption materials.[10]. Challenges encountered for biosorbents with high uptake, low cost and as well as in understanding the mechanism of reaction.
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