Efficient extraction of heavy metals from collagens by sulfonated polystyrene nanospheres

This work reports the feasibility of utilizing sulfonated polystyrene nanospheres (SPS NSs) to extract heavy metals from collagen solutions. We have endeavored to present a detailed study on the adsorption characteristics and mechanism of heavy metals including Pb2+, Mn2+, Cr3+ and Cd2+. The adsorption isotherms were fitted by the Langmuir and Freundlich models while the adsorption kinetics data were described by the pseudo-first-order, pseudo-second-order and intraparticle diffusion equations. The adsorption isotherms were better fitted by the Langmuir model, leading to theoretical maximum capacities of 50.7, 15.0, 8.7 and 39.0 mg g−1 for the adsorption of Pb2+, Mn2+, Cr3+ and Cd2+, respectively. Isothermal titration calorimetry (ITC) measurements were conducted to detect the heat exchange of the adsorption processes. As a proof of concept, SPS NSs were practically applied in sequestrating heavy metals from Talapia-fish-scale derived collagen. The effects of pH of the collagen solutions in the removal of metals were investigated. By a single treatment, the concentrations of the metal ions were decreased to the regulatory standards whilst the concentration of collagen proteins was well maintained.