Adsorptive removal of thorium(IV) from aqueous solutions using poly(methacrylic acid)-grafted chitosan/bentonite composite matrix: Process design and equilibrium studies

A novel composite matrix, poly(methacrylic acid) -grafted composite/bentonite (PMAA-g-CTS/B) was prepared through graft copolymerization reaction of methacrylic acid and chitosan in the presence of bentonite and N,N′-methylenebisacrylamide as cross linker. The composite was well characterized using FTIR, XRD, XPS, SEM, TG/DTG, surface area analyzer and zeta potential measurements. The adsorption behavior of the composite towards thorium(IV) from water and sea water was studied under varying operating conditions of pH, concentration of Th(IV), contact time, and temperature. The effective range of pH for the removal of Th(IV) was 5.0–6.0. Kinetic data followed a pseudo-second-order model. The equilibrium data were correlated with the Langmuir isotherm model. The equilibrium Th(IV) sorption capacity was estimated to be 110.5 mg/g at 30 °C. For the quantitative removal of 100 mg/L Th(IV) from 1.0 L simulated sea water, a minimum adsorbent dosage of 2.0 g PMAA-g-CTS/B was required. Adsorption–desorption experiments over four cycles illustrate the feasibility of the repeated uses of this composite for the extraction of Th(IV) from aqueous solutions. Counter current process design was done by using operational lines.