Adsorptive potential of agricultural wastes for removal of dyes from aqueous solutions

•Novel green adsorbents were explored for removal of dyes from waste water.•Proposed an economic incentive to industrial practice for waste management.•Possibility of mass transfer resistance and kinetic aspects was investigated.•More than 90% dye removal was obtained for all investigated dye-adsorbent systems.•Isotherms and kinetics were examined to look into adsorbate-adsorbent interaction.

Present work aims to investigate the adsorptive characteristics of agricultural wastes (Citrus Limetta Peel and Zea Mays Cob) for effective removal of dyes from aqueous solutions. Batch adsorption experiments were carried out in order to analyse sorption behaviour of dye-adsorbent systems at different adsorbent dosage and initial dye concentration. Possibility of mass transfer resistance was investigated to improve the diffusion rate, whereas kinetic aspects were examined to achieve thermodynamic equilibrium for the proposed adsorption process. Solution pH was observed to significantly affect the adsorption efficiency by regulating degree of ionization of the adsorbate's functional groups. More than 90% removal of dyes was attained for all dye-adsorbent systems under optimum reaction conditions. Characterization studies were performed to examine the changes in morphology and functional groups of the adsorbents before and after adsorption process. Kinetic study suggested the pseudo-secondorder kinetic model with normalized standard deviation Δqt (%) <5% and regression coefficient >0.999 as being able to better describe kinetic data than pseudo first order and elovich kinetic models. Adsorbate-adsorbent interaction was investigated by looking into the applicability of Langmuir, Freundlich and Dubinin-Radushkevich isotherms for the proposed adsorption process. Maximum adsorption capacity Q° was observed to be highest for malachite green dye (8.733 mg/g and 16.72 mg/g) using CLP and ZMC respectively. Findings obtained from thermodynamic studies indicated endothermic and spontaneous nature of the proposed process. This work offers an economic incentive to the industrial practice for waste management and eofriendly approach for removal of toxic dyes from textile waste water.

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