Fast removal of methylene blue and Hg(II) from aqueous solution using a novel super-adsorbent containing residues of glycine and maleic acid.

The alternate cyclo-copolymerization of diallylammonioethanoate [(CH2=CHCH2)2NCH2CO2-] and maleic acid in the presence of a cross-linker afforded a novel pH-responsive resin (90% yield). The resin has turned out to be a super-adsorbent for methylene blue (MB) removal with a qMax of 2101 mg g-1. The adsorption of the dye followed pseudo second-order kinetics with an energy of activation (Ea) of 31.5 kJ mol-1. The process showed an extraordinarily fast adsorption rate owing to faster film diffusion; the resin (250 mg) was able to trap 78 and 99.4% MB from its 3000 mg L-1 solution (100 mL) within 3 and 30 min, respectively. Equilibrium constants from Langmuir nonlinear isotherm model in the range 288-328 K gave ΔGo ΔHo, and ΔSo values of ≈ -25 kJ, -13 kJ and 39.5 J mol-1 K-1, respectively. Immobilization mechanism was discussed using FTIR, SEM, and Elovich kinetic model. The presence of the chelating glycine residues was exploited for the removal of Hg(II) ions; the qHg was determined to be 263 mg g-1. The resin also removed MB and Hg(II) simultaneously from industrial wastewater with remarkable efficacy. The very impressive performance along with efficient recycling conferred the resin a top position among many sorbents.