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).

Automated summary

In this study, an environmentally friendly adsorbent, sodium lignosulfonate modified illite (LS-ILT), was prepared by hydrothermal modification. The adsorption behavior of Pb(II) and Cd(II) by LS-ILT and the effects of pH, sorbent dosage, and initial concentration were extensively investigated. The results showed that the adsorption of Pb(II) and Cd(II) followed quasi-second-order kinetics and the Freundlich model, with maximum adsorption capacities of 42.3 mg/g and 17.0 mg/g, respectively. The optimal conditions for adsorption equilibrium were a dosage of 4 g/L and a reaction pH of 5.5-5.8. LS-ILT exhibited better stability in Pb(II) adsorption compared to Cd(II), and the presence of coexisting cations did not significantly inhibit the removal of Pb(II) and Cd(II). Furthermore, LS-ILT met the ultra-low emission standard, maintaining over 50% adsorption capacity after four cycles, which has important implications for the treatment of wastewater with ultra-low concentrations of Pb(II) and Cd(II).