Low-cost ternary composite photocatalysts consisting of TiO2, kaolinite and cement for an efficient organic waste decontamination in water

Abstract

 The present study demonstrates the fabrication of heterogeneous ternary composite photocatalyst consisting of TiO2, kaolinite and cement (TKCe), which is essential to overcome the practical barriers that are inherent to currently available photocatalysts. TKCe is prepared via a cost-effective method, which involved the mechanical compression and thermal activation as a major fabrication steps. Clay-cement ratio primarily determines TKCe mechanical strength and photocatalytic efficiency where TKCe with the optimum clay-cement ratio, which is 1:1 results in uniform matrix with fewer surface defects. The composites that have clay-cement ratio below or above the optimum ratio account for comparatively low mechanical strength and photocatalytic activity due to inhomogeneous surface with more defects, including particle agglomeration and cracks. The TKCe mechanical strength is mainly from clay-TiO2 interactions and TiO2-cement interactions. TiO2-cement interactions result in CaTiO3 formation, which significantly increases matrix interactions; however, the maximum composite performance is observed at the optimum titanate level; anything above or below this level deteriorates composite performance. Over 90% degradation rates are characteristic to all TKCe, which follow pseudo first order kinetics in methylene blue decontamination. The highest rate constant is observed with TKCe 1-1, which is 1.57 h−1 and being the highest among all the binary composite photocatalyst that were fabricated previously. The TKCe 1-1 accounts for the highest mechanical strength, which is 6.97 MPa, while the lowest is observed with TKCe 3-1, indicating that clay-cement ratio has direct relation to composite strength. TKCe is a potential photocatalyst, which can be obtained in variable sizes and shapes, complying with real industrial wastewater treatment requirements.