Peruíbe black mud based catalysts for the removal of organic pollutants in water

Abstract

Peruibe black mud (BM) is a natural clay found on the coast of Sao Paulo state of Brazil; in this study, it was used as an eco-friendly catalyst for environmental remediation. For this purpose, the removal of two organic pollutants [phenol and methylene blue (MB) dye] in water was studied using catalysts based on BM (calcined, and also doped with TiO2). The catalytic reactions were studied under the following conditions: adsorption, heterogeneous–photocatalysis (UV light), and photo-Fenton (UV light + traces of H2O2). The catalysts were characterized by X-ray diffraction, energy dispersive X-ray spectroscopy, scanning electron microscopy, infrared spectroscopy, and adsorption–desorption of N2. The characterization indicated that the calcined black mud (BM) is composed of muscovite and quartz (as majority components), and TiO2, among other minerals in trace amounts. The tests of removal of pollutants demonstrated that the BM has a notable photocatalytic activity to degrade the pollutants, the mixture of BM with small quantities of TiO2 increased its photocatalytic activity; there was a kind of synergy between the BM and TiO2 that was clearly observed in photo-Fenton reaction. The best way to remove phenol with the BM photocatalysts was by heterogeneous-photocatalysis and photo-Fenton reactions; while the best way for removing MB was by adsorption. In the photo-Fenton process, BM/TiO2 mixture was better than the commercial catalyst (TiO2). The catalytic tests, in general, demonstrated that the BM based catalysts could be used to remove organic pollutants in water to remediate polluted water, and consequently assist towards a better quality of the sedimentary environment.