Abstract
•Cross-linked pH-responsive cycloterpolymeric resin was synthesized.•Analyzed by FTIR, TGA, XRD, BET, SEM/EDX.•Superb qmax of 1509 mg/g for malachite green removal.•Kinetic, equilibrium, and thermodynamic evaluations.•The resin demonstrates excellent recyclability.
Malachite green (MG) dye and leucomalachite green (its major metabolite present in fish tissue) are suspected genotoxins and carcinogens, and despite its ban, it is being illegally used in aquaculture. As a cationic dye, MG is anticipated to have enhanced removability by a polymer equipped with a plethora of negative charges. Thus, this work reports the synthesis of a cross-linked cycloterpolymer that is pH-responsive and zwitterionic-anionic (±=) in nature. The resin was characterized by FTIR, TGA, XRD, BET, SEM, and EDX. Zeta potential measurement of the polymer was also performed at the pH range 2–8, and the obtained values at pH 2, 8, as well as the point of zero charge are 17 mV, –32.3 mV, and 2.2, respectively. The polymer showed an excellent qmax of 1509 mg/g for MG with removal efficiencies of 100% and 95% with just 5 mg dosage at 50 mg/L and 100 mg/L MG concentrations, respectively at pH 8 and 25 °C. The batch adsorption data was evaluated by Langmuir, Freundlich and Temkin, Toth and Redlich-Peterson (R-P) models. The kinetics of the process was evaluated by Pseudo-first order (PFO) and Pseudo-second order (PSO) models. Thermodynamics studies suggest that MG uptake is endothermic and spontaneous. The adsorbent shows excellent reusability even after five regeneration cycles; the efficiencies obtained in the 1st-3rd, 4th, and 5th cycles were ∼ 100%, 98%, and 96% respectively. This suggests the suitability of the polymer for use industrially in the treatment of dye polluted water.