Simultaneous adsorption-photocatalytic treatment with TiO2-Sep nanocomposites for in situ remediation of sodium pentachlorophenol contaminated aqueous and soil

Sodium pentachlorophenol (NaPCP) is a highly toxic and persistent organic pollutant. With sepiolite as the support, a series of TiO₂-Sep nanocomposites (NCs) with different Ti/Sep ratios were developed. The objective was to understand the effect of Ti/Sep ratio on the structure and activity of the NCs in aqueous and soil systems and to evaluate the feasibility of the NCs for in situ soil remediation. The prepared NCs were characterized with XRD, SEM, TEM, and N₂ adsorption–desorption, respectively. The results showed that high surface area and good dispersion of TiO₂ on sepiolite surface were obtained. The photocatalytic activities in aqueous and soil of the as-developed NCs were examined using NaPCP as a model pollutant. Compared with bare sepiolite and TiO₂, the heterogeneous NCs showed significantly higher photocatalytic performance in decomposing NaPCP, and the photocatalytic activities varied with the content of TiO₂ in the NCs. In aqueous media, treatment with TiO₂-S-30 showed excellent degradation efficiency with about 90% NaPCP decomposed in 140 min. Nevertheless, the sample TiO₂-S-20 promotes maximum rate reduction of NaPCP with above 90% within 20-h irradiation in soil. The results indicate that an appropriate Ti/Sep ratio could significantly enhance the activities of NCs on NaPCP remediation and the role of carrier sepiolite is more important in soil media than that in aqueous phase. The excellent performance of the TiO₂-Sep in wastewater degradation and soil remediation can be attributed to the synergistic effects between the high photocatalytic activity of TiO₂ nanoparticles and the strong adsorption capacity of sepiolite nanofibers. This work revealed that sepiolite adsorption coupled with TiO₂ photocatalysis can be one promising technique for in situ remediation of NaPCP-contaminated soil.