Long-term removal characterization of trichloroethylene from groundwater using sustained-release iron-carbon composite: Investigations through batch and column experiments.

Nano-zero-valent iron (nZVI) is commonly used as a reactive material for trichloro-ethylene (TCE) remediation in groundwater systems, and the long-term removal capacity serves as a critical indicator for evaluating the material efficacy. In this study, a novel sustained-release iron-carbon composite (BC@nZVI-βCD) was synthesized by the integration of biochar (BC) matrix and β-cyclodextrin (βCD) encapsulation, and the materials before and after modification were analyzed by various characterization methods. Subsequently, the kinetics of TCE removal by different materials were investigated, and the sustained-release properties of BC@nZVI-βCD were explored by batch and column experiments. Finally, the long-term TCE removal mechanism was discussed carefully. The results showed that the incorporation of BC increased the specific surface area and dispersion of nZVI, while βCD successfully encapsulated nZVI and formed abundant nanocracks on the surface. The removal of TCE by BC@nZVI-βCD was in accordance with the pseudo-second-order kinetic equation, and the removal rate of TCE was as high as 97 % within 3 h, and 92.7 % of TCE was degraded within 14 d. Moreover, BC@nZVI-βCD maintained a stable removal efficiency of TCE in long-term sand column experiments, with the removal rate remaining above 94 % for the first 32 d, and the removal rate also reached 78.6 % by 86 d. In conclusion, the synergistic effect of both BC and βCD breaks through the limitation of pure nZVI, improves the sustained-release performance of the BC@nZVI-βCD composite and the degradation effect of TCE, which can have great application prospects on the long-term remediation of TCE contaminated sites.