Fabrication of biocompatible chitosan/graphene based nanocomposite for the competitive adsorption of heavy metal ions from wastewater in binary and ternary systems: Scale-up and upgradation studies

Abstract

Coexistence of multiple metal ions in the wastewater alters the adsorption behavior compared to single metal ion system using the existing adsorbents which are chemically driven, requires harsh operating conditions and additional energy. The present study evaluates the performance of Chitosan/Graphene based nanocomposite for the competitive adsorption of heavy metals in single, binary and ternary systems. Maximum removal efficiency was 89.35 % (As), 90.41 % (Cu), 93.22 % (Ni), 96.47 % (Cd), 95.45 % (Pb) and 88.65 % (Cr) under optimum conditions (pH 4, Temperature = 25 °C, Equilibrium Time = 90 min, Adsorbent Dosage = 1.25 g and Initial Metal Ion Concentration = 150 mg/L) in a single system. A detailed investigation on the competitive adsorption of Cadmium, Copper, and Chromium ions was performed in binary. Maximum adsorption capacity was 1.55 mg/g and 1.48 mg/g (CuCd); 2.98 mg/g and 3.21 mg/g (CuCr) and 2.21 mg/g and 1.90 mg/g (CdCr system) at 4 mM concentration. The constructed mathematical models accurately forecast the adsorption behavior and shows a good match with the experimental data. Also, fixed-bed column studies were performed for the large-scale upgradation and optimum flow rate and bed height was 1 L/h and 15 cm at 25 °C. The study proposes the fabrication of natural-polymer based composite which can significantly reduce the dependency on synthetic and chemical-based adsorbents which poses severe negative impacts such as high-cost, poor selectivity and rapid saturation due to their low recyclability or sludge generation. Such application can effectively transform wastewater into contamination free water that could be valuable to society.