Natural pozzolana as standalone photocatalyst for water treatment

Abstract

This study focuses on natural pozzolana (volcanic ash) as standalone photocatalyst for removal of organic water pollutants under solar irradiation. Natural pozzolana has been modified and investigated using various techniques (XRD, EDS, FTIR, TGA, and BET surface area). The investigated pozzolana material has worked as metal oxide heterojunctions with SiO2 (35.45 %), Al2O3 (12.56 %), Fe2O3 (14.15 %) and CaO (7.89 %) in a majority, besides other oxides (MgO (5.75 %), TiO2 (3.25 %), Na2O (2.15 %), K2O (1.23 %), and MnO (0.34 %)). The XRD results showed that pozzolana materials contains different crystalline forms such as Albite, Quartz, Biotite, Hematite and Magnesio hornblende. The performance of the prepared pozzolan material has been evaluated for photocatalytic degradation of BPB dye as model water pollutant and the photocatalytic activity was related to the characterization results. It was shown that the sieved pozzolana material (Ps) has the highest photocatalytic degradation rate (0.0175 min−1) compared to raw (P0) and calcined (Pc) samples. The photocatalytic activity of Ps was also higher than that of TiO2 anatase (0.0121 min−1) used under the same experimental conditions, which was attributed to the diversity of pozzolana compositions from various oxides, with a cascade transference of charge carriers leading to effective charge separation and transfer, hence enhancing the photocatalytic activity. Based on this, natural pozzolan could be used as cost effective and green material for sustainable photocatalytic applications.