Synergistic construction of green tea biochar supported nZVI for immobilization of lead in soil: A mechanistic investigation

Abstract

Biochar-based nanocomposites with functional materials provide an excellent prospect in reactivity and stability. Most biochar reported have no reusability upon aging and offer the risk of release of immobilized components after short-term immobilization. To overcome this, we developed nano zero-valent iron (nZVI) impregnated magnetic green tea biochar ([email protected]) and studied its performance in immobilizing Pb and long-term effectiveness in the soil. The reactive nZVI units were obtained from iron oxide solution by reducing with polyphenol solution (green tea extract) and were successively stabilized by impregnation onto the remaining green tea waste matrix through co-precipitation technique. Finally, the magnetic biochar was developed from the above nZVI impregnated green tea waste through oven drying and slow pyrolysis technique in different temperature range (150–650 °C). The synthesized [email protected] biochar was characterized and studied by XRD, FTIR, Raman, UV–Vis, TG/DSC, XPS, SEM, and TEM. The [email protected] obtained with a particle size of 130 nm and surface charge of +2.8 C/m2 at 450 °C. Moreover, colloidal stability and mobility experiments were considered to explain the transport behavior and stability of bare nZVI and magnetic [email protected] in the soil. The immobilization of Pb by pristine nZVI, GTBC, and [email protected] was compared and explained under different soil pH conditions. The bioavailability of Pb content before and after immobilization was investigated through leaching experiments. Further, thirty days of soil incubation were carried out to examine different species of Pb according to the Tessier sequential extraction scheme. The study suggested that [email protected] enhanced the immobilization efficiency by 19.38% in comparison with pristine nZVI and 57.14% in comparison with bare GTBC biochar.