Microwave-assisted synthesis of a β-cyclodextrin/TEMPO-oxidized cellulose/Fe3O4 adsorbent for Pb and Cu remediation in soil

Abstract

β-cyclodextrin (β-CD)-grafted and TEMPO-mediated oxidized cellulose (O-NC_MW@β-CD) was synthesized by microwave-assisted synthesis technique for remediating Pb and Cu contaminated soil. The results indicated that TEMPO-mediated oxidation altered the structure of pristine cellulose, which was beneficial for successfully grafting β-CD onto the cellulose through microwave-assisted method. The adsorption performance of O-NC_MW@β-CD was significantly superior to that of the pristine cellulose, achieving maximum adsorption capacities of 377.26 mg/g for Pb(II) and 249.63 mg/g for Cu(II) within 60 min. Notably, at a soil pH of 7.0 and a moisture content of 40%, the concentrations of bioavailable Pb and Cu were decreased to 54.64 and 45.68 mg/kg, respectively, after 30 days of remediation with 5% O-NC_MW@β-CD. Furthermore, the labile fractions of Pb and Cu were almost entirely converted into stable fractions, with the residual fractions of Pb and Cu increasing to 34.24% and 46.08%, respectively. In addition, O-NC_MW@β-CD enhanced the abundance and diversity of soil microbial communities, especially those associated with heavy metal resistance and soil carbon and nitrogen cycling. The mechanisms for stabilizing Pb and Cu in soil via O-NC_MW@β-CD were primarily influenced by electrostatic attraction, followed by pore filling, hydrogen bonding, as well as complexation.