Adsorption behavior of Cu2+ from aqueous solutions onto starch-g-poly(acrylic acid)/sodium humate hydrogels

A series of starch-g-poly(acrylic acid)/sodium humate (St-g-PAA/SH) hydrogels were prepared and used to adsorb Cu2+ from the aqueous solution. The batch adsorption experiments were carried out by varying contact times (0–90 min), initial Cu2+ concentration (0.003–0.02 mol/L), and pH values (2.0–5.0). The effects of ion strength (5, 10 mmol/L NaCl) and competitive ion (5, 10 mmol/L Pb(NO3)2) on the adsorption capacity were investigated. The results indicated that the addition of 5% SH into St-g-PAA polymeric networks could not only improve the initial adsorption rate and final adsorption capacity for Cu2+, but also make a remarkable contribution to regeneration ability. St-g-PAA/SH hydrogels exhibited high adsorption capacity within a wide pH range and the adsorption data could be well described by the pseudo-second-order kinetic model and Langmuir isotherm model. FTIR spectra before and after adsorption of Cu2+ on the hydrogels revealed that complexation was considered as the main adsorption mechanism.