High adsorption capacity and selectivity of layered metal sulfide (KZTS) for effective removal of lead ions from wastewater

A novel layered metal sulfide (K 1.87 Zn 0.13 Sn 6.4 S 12.67 , KZTS) with high adsorption capacity was synthesized by hydrothermal method for selective removal of Pb 2+ ions from wastewater. Scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, thermogravimetric analysis and BET were used to characterize the synthesized materials. The removal efficiency of KZTS for Pb 2+ and effects of various factors including the solution pH, adsorption time and initial concentration on the adsorption behavior were evaluated. Under an optimal condition, the maximum adsorption capacity is as high as 431.26 mg·g −1 . Moreover, the KZTS exhibited excellent adsorption selectivity against competitive ions such as Ca 2+ , Cd 2+ , Co 2+ , Al 3+ and Mn 2+ . The adsorption kinetics and isotherms were also studied. The adsorption process is in good agreement with the Langmuir adsorption isotherm and conforms to the pseudo-second-order model, indicating that the adsorption of Pb 2+ by KZTS is a monolayer chemisorption process. Namely, the adsorption of Pb 2+ is mainly caused by the chemical bonding interaction between S 2− and Pb 2+ , accompanying the exchange of K + ion with Pb 2+ ion. The excellent properties of KZTS enable it to be a promising adsorbent for the removal of Pb 2+ from heavy metal wastewater. Graphical abstract