Malachite green dye adsorption from wastewater using pine gum-based hydrogel: Kinetic and thermodynamic studies

Abstract

In this study, a novel Pn-g-poly(AAm) hydrogel was synthesized via free radical polymerization, using pine gum as the backbone material and polyacrylamide as the monomer. By employing response surface methodology and central composite design, various process parameters were optimized, achieving an optimum 1325 % maximum swelling. The optimized quantities were 0.085 g of initiator, 1.4 g of monomer, 0.013 g of crosslinker, and 14 ml of solvent. The physio-chemical characterizations were conducted using XRD, FE-SEM, FTIR, BET, and TGA. BET analysis showed a specific surface area of 34.973 m²/g and a pore volume of 0.104 cc/g. In adsorption studies, the highest removal (97 %) of malachite green (MG) dye was observed at pH 7, a temperature of 25 °C, a contact time of 5 h and 30 min, an adsorbent dose of 0.08 g, a dye concentration of 50 mg/L, and a shaking speed of 150 rpm. The adsorption data followed pseudo-second-order kinetics and Langmuir isotherm models, with a maximum adsorption capacity of 120.772 mg g−1. Furthermore, thermodynamic studies yielded ΔH° at 106.123 KJ/mol and ΔS° at 382.618 J/mol. These results collectively demonstrate the potential of this adsorbent for effectively treating industrial wastewater pollutants.