Structural modification of acrylonitrile–butadiene–styrene waste as an efficient nanoadsorbent for removal of metal ions from water: isotherm, kinetic and thermodynamic study

Abstract

Acrylonitrile–butadiene–styrene (ABS) terpolymer waste was recycled via amidoximation of the nitrile groups using hydroxylamine hydrochloride. The resulting modified ABS (AO-ABS) nanoparticles possessing amidoxime functional groups, –C(NH₂)NOH, have been shown to be an effective adsorbent for the removal of heavy metal ions from aqueous solutions. The effect of pH, adsorbent dosage, immersion time, concentration of adsorbate and temperature on the extent of adsorption was investigated to understand adsorption isotherms, kinetics and thermodynamics. The results showed that the interaction between metal ions and –C(NH₂)NOH groups agree with the Langmuir isotherm and pseudo-second-order kinetic model and the maximum adsorption capacities (Q_m) were found in the range of 56.5, 56.18, 53.47, and 51.28 (mg g⁻¹) for the adsorption of metal ions Pb²⁺, Cu²⁺, Cd²⁺, Zn²⁺. Thermodynamic studies of metal ions indicated that the adsorption process was spontaneous and endothermic with ΔH and ΔS values in the range of 22.2–36.4 kJ mol⁻¹ and 74.7–128.6 J k⁻¹ mol⁻¹, respectively. Not having hydrolysable linkages, the desorption process of AO-ABS has been carried out in HCl (0.1 M) without losing much of its activity. It can be suggested that amidoximation is a suitable recycling method for new applications of ABS waste and it seems to be applicable in large scale water softening processes.