Impact of the interaction between hematite and halloysite on environmental fate of organic pollutants

Abstract Clay minerals and iron oxide usually coexist in soil. This work revealed the effect of the interaction between halloysite (HNTs) and hematite on the environmental fate of organic pollutants. Methylene blue (MB) was used as a probe molecule to investigate the effect of this interaction on the adsorption and degradation of MB in the presence of H2O2. The experimental results showed that the presence of hematite changed the Zeta potential of HNTs and weakened the adsorption capacity of HNTs to MB, but the existence of HNTs improved the dispersion of hematite and hence enhanced the performance for activating H2O2 to degrade MB. The adsorption and degradation of other organic pollutants (e.g. 2,4-dichlorophenol, phenol, sulfadiazine, sodium) were similar to MB. The hydroxyl radicals (·OH) were the dominant reactive species confirmed by quantitative experiments, radical scavenging studies and ESR spectra. In addition, with the participation of hematite, the adsorbed methylene blue on the halloysite surface was also removed via activating H2O2. Consequently, these findings are of significance to understand the migration, enrichment, degradation of organic pollutions.