Performance and mechanisms of active attapulgite-supported sulfidated nanoscale zero-valent iron materials for Pb(II) removal from aqueous solution

To inhibit the oxidation, passivation, and agglomeration of nano-zero-valent iron (nZVI), a liquid phase reduction method was used to load sulfurized nZVI onto acid-modified ATP with attapulgite (ATP) as the carrier (S-nZVI@ATP). The performance and mechanism of this material were studied for Pb ^2+ removal in water. The S-nZVI@ATP preparation prevents the agglomeration of nZVI particles and reduces nZVI oxidation. Pb ^2+ removal proceeds efficiently and stably when using S-nZVI@ATP at pH values ranging from 2.5–5.5. According to the electron sharing and transfer-based pseudo-second-order kinetic model, the Pb ^2+ is adsorbed onto S-nZVI@ATP, and the speed control step is completed by liquid film diffusion and intraparticle diffusion. The S-nZVI@ATP mediated Pb ^2+ adsorption is well-described by Freundlich’s isothermal adsorption model, which is a multilayer chemical adsorption process. The temperature and initial Pb ^2+ concentration were varied, and it was determined that Pb ^2+ adsorbs on S-nZVI@ATP in an endothermic reaction. This S-nZVI@ATP composite material has high reducibility, high surface activity, and good adsorption properties for Pb ^2+ . Tests were performed for 24 h using adsorbent (1 g l ^−1 ) in Pb ^2+ solution (30 ml). For an initial Pb ^2+ concentration of 700 mg l ^−1 , S ^−1 -nZVI@ATP removes 57.37% of the Pb ^2+ and has an adsorption capacity of 401.60 mg g ^−1 . In addition to forming PbS and Pb(OH) _2 precipitates, Pb ^2+ also complexes with the Fe/H oxide shell of S-nZVI@ATP, and Fe ^0 reduces some Pb ^2+ on the nZVI to Pb ^0 . The results exhibited that S-nZVI@ATP has excellent potential as an adsorbent for the removal of Pb ^2+ from the industrial wastewater.