Mechanism-Enhanced Active Attapulgite-Supported Nanoscale Zero-Valent Iron for Efficient Removal of Pb(2+) from Aqueous Solution

In this study, attapulgite-supported nano zero-valent iron (nZVI@ATP) was synthesized by a liquid-phase reduction method using active attapulgite (ATP) as raw material, and used for Pb(2+) remediation in aqueous solution. To understand the mechanism of Pb(2+) removal, various techniques were used to characterize nZVI@ATP. The results showed that spherical nZVI particles were uniformly dispersed on the surface of ATP, and the agglomeration of nZVI particles was significantly weakened. The adsorption performance of nZVI@ATP for Pb(2+) was greatly improved compared with that of ATP ore, in which the Fe/ATP mass ratio of 1:2 was the best loading ratio. Under the conditions of a temperature of 25 °C and a pH of 5.00, the initial concentration of Pb(2+) was 700 mg/L, and the Pb(2+) removal rate of nZVI@ATP was 84.47%. The adsorption of nZVI@ATP to Pb(2+) was mainly a spontaneous endothermic reaction of heterogeneous surfaces, and the adsorption rate of nZVI@ATP to Pb(2+) was proportional to pH in the range of 2–5.5. The presence of Na(+), Mg(2+), and Ca(2+) can inhibit the removal of Pb(2+), and Ca(2+) has the strongest inhibition effect on the removal of Pb(2+). The removal mechanism of Pb(2+) by nZVI@ATP obtained from SEM-EDS, BET, XRD, FTIR and XPS included reduction, precipitation, and the formation of complexes.