Adsorptive and photocatalytic behaviour of PANI/TiO2/metakaolin composites for the removal of xanthate from aqueous solution

In this study, novel PANI/TiO2/metakaolin composite was successfully synthesized through sol-gel and in-situ polymerization. The microstructure, crystal structure, surface properties and pore structure of the ternary composites were comprehensively investigated. The influencing factors such as pH, pollutant concentration, light intensity and catalyst dosages were studied. The possible photocatalytic enhancement mechanism of the synthesized composite was proposed as well. As for the pore structure characteristics, the specific surface area and pore volume increased from 63.2 m(2)/g and 0.221 cm(3)/g to 78.0 m(2)/g and 0.258 cm(3)/g after the incorporation of PANI and metakaolin, which makes the composite materials have excellent adsorption capacity for butyl xanthate. The band gap decreased from 3.10 eV to 1.93 eV since the mediation effect of PANI. And the grain size of TiO2 decreased from 15.3 to 10.3 nm due to the assisted dispersion of metakaolin. Under visible light irradiation, 94.8% of xanthate was removed by PANI/TiO2/metakaolin within 4 h. In addition, the stronger visible light absorption ability and higher photogenerated electron-hole pairs' separation efficiency of PANI/TiO2/metakaolin could be attributed to the successful construction of unique heterojunction structure. This study provides new insight into the combination of conducting polymer, inorganic semiconductor and natural mineral in the field of photocatalytic decontamination.