Sorptive potential of a cationic exchange resin of carboxyl banana stem for mercury(II) from aqueous solutions

A cationic exchange resin of carboxyl banana stem (CBS) was fabricated through the hydrolysis of graft copolymer of banana stem (BS) with acrylonitrile that was made using ceric ammonium nitrate (CAN) initiator. Infrared spectroscopy and acid–base titration were used to confirm graft copolymer formation and carboxylate functionalization. SEM studies of CBS clearly indicated that adsorbent has rough and porous surface caused by rigid and hydrophobic nature of acrylonitrile cross-links. Thermal stability of the CBS was studied using thermogravimetry. The cationic exchange capacity (CEC) of the CBS was determined to be 1.68 mequiv. g−1. The sorptive potential of the CBS for mercury(II) from aqueous solutions was examined by the batch technique. The optimum pH range for the maximum removal of mercury(II) was 6.0–9.0. The CBS was observed to have high adsorptive capacity for mercury(II) with 99.3% from a solution containing 10 mg L−1 of mercury(II) with 0.2% (w/v) concentration of CBS. The experimental kinetic data for the mercury(II)–CBS system were analyzed using the linearised form of the Elovich model, a second-order kinetic equation. The isotherm data were correlated reasonably with the Langmuir isotherm and the mercury(II) adsorption capacity was found to be 90.88 mg g−1 at 30 °C. The quantitative removal of 10 mg L−1 mercury(II) in 50 mL chlor-alkali industry wastewater by 125 mg of CBS was observed at pH 6.0. The mercury(II)-loaded CBS can be regenerated by 0.1 M HCl treatment without altering the adsorbent properties.