A study on the removal of heavy metals and anionic dyes from aqueous solution by amorphous polyamide resin containing chlorobenzalimine and thioamide as chelating groups

Abstract

Poly(chlorobenzalimino thiourea amide) (PCBA) resin was synthesized by using the phosphorilation poly condensation method. PCBA was characterized by analytical techniques, and it was used for the adsorption of heavy metals (Ni2+ and Zn2+) and anionic dyes (methyl orange (MO) and acid orange (AO)). The variables which affect the adsorption efficiency, such as pH, adsorbate concentration, adsorbent dose and contact time were studied. The results show that the adsorption of Ni2+, Zn2+, MO and AO follows the pseudo-second order kinetic model. The maximum monolayer adsorption capacity of PCBA for Ni2+, Zn2+, MO and AO, calculated using Langmuir isotherm is 191.2, 247.1, 153.8, 149 mg/g, respectively. Surface area (21.1m2/g) and crystal size are 21.1m2/g and 0.35 nm, respectively. High efficiency of the polymeric resins may be due to their amorphous nature and the presence of strong binding sites in the polymer structure. Thermodynamic parameters such as change in standard free energy change, enthalpy and entropy ΔG0, ΔH0 and ΔS0 were evaluated, and the adsorption process was found to be feasible, exothermic and spontaneous. Desorption studies show that adsorption efficiency of PCBA was retained even after four cycles.