Highly efficient preferential adsorption of Pb(II) and Cd(II) from aqueous solution using sodium lignosulfonate modified illite

In this study, sodium lignosulfonate modified illite (LS-ILT), an environmentally friendly adsorbent, was prepared by hydrothermal modification. An extensive study of Pb(II) and Cd(II) adsorption behavior and the mechanisms were conducted by evaluating the effects of initial pH value, sorbents dosage, and initial concentration of Pb(II) and Cd(II). Results showed that the adsorption characteristics of Pb(II) and Cd(II) by LS-ILT were well described by quasi-second-order kinetics and the Freundlich model, and the maximum adsorption capacity of Pb(II) and Cd(II) was 42.3 mg/g and 17.0 mg/g, respectively. The optimal application conditions for adsorption equilibrium were the dosage of 4 g/L and reaction pH = 5.5-5.8. The adsorption stability of Pb(II) by LS-ILT was better than that of Cd(II), and most of the existence of coexisting cations had no obvious inhibitory effect on the removal of Pb(II) and Cd(II). Furthermore, the dynamic adsorption results showed that LS-ILT can meet the ultra-low emission standard, and the adsorption capacity could maintain over 50% after four cycles, further providing certain guiding significance for the treatment of wastewater with ultra-low concentrations of heavy metals Pb(II) and Cd(II).