Evaluation of neem gum-poly(acrylic acid) based adsorbent for cationic dye removal using adsorption isotherm,...

Cationic dye pollution is detrimental to human health as it accumulates in the cytoplasm and poses toxic, mutagenic and carcinogenic effects. Many dye adsorbents report secondary waste generation, non-biodegradability, high costs and energy. Therefore, in this work, Neem gum (Ng) is utilised as a propitious candidate for water treatment due to its tuneable chemical structure, renewability, biodegradability, sustainability, non-toxicity and low cost. The Ng-g-p(AA)-cl-MBA hydrogel is synthesised via a free-radical polymerization technique to find its efficacy towards the adsorption of cationic dyes rhodamine B(RhB) and methylene blue(MB) and systematically characterized using FT-IR, TGA, XRD, BET and FE-SEM analysis. Various parameters were optimized for achieving the maximum adsorption efficiency including the initial concentration, pH, temperature, adsorbent dosage, and contact time. Adsorption Isotherm, Kinetics and Thermodynamics were studied to understand the adsorption behaviour of Ng-g-p(AA)-cl-MBA towards the dyes. The adsorption behaviour was best simulated by Langmuir's model with a maximum adsorption capacity (Q_m) of 552.49 and 421.94 mg/g towards RhB and MB respectively, it obeyed a pseudo-second-order rate of adsorption and followed an exothermic and spontaneous process. It also depicted good regeneration and reusability features making it a promising candidate for dye effluent adsorption.