Upcycling of waste concrete powder into a functionalized host for nano-TiO2 photocatalyst: Binding mechanism and enhanced photocatalytic efficiency

Abstract

Recycled concrete powder (RCP) is not reutilized well and thus causes a huge environmental issue. In this paper, to improve the added value of RCP and mitigate the environment burden, RCP is recycled to replace natural mineral as carrier for nano-TiO2. RCP/TiO2 composites are prepared by a mechanical chemical method and applied in photocatalytic degradation of dye wastewater as an eco-friendly material. The microstructure of RCP/TiO2 composites and binding mechanism are revealed by microscopic characterizations. The results show that nano-TiO2 particles are homogenously immobilized on RCP surface by chemical bonds and physical adsorption, confirming the feasibility of RCP as the carrier for TiO2. The photocatalytic degradation experiment result shows that the photocatalytic efficiency of net TiO2 is significantly improved by the form of RCP/TiO2 composites, as the apparent rate constant of RCP/TiO2 composites (A24RCPT20) is 43.9% of that of TiO2 (P25), while the TiO2 content of A24RCPT20 is only 20% by mass of P25. The enhanced photocatalytic efficiency is caused by surface hydroxylation. RCP/TiO2 composites also have excellent reusability and high stability in cyclic tests. Thus, RCP is proved to be a valuable carrier for nano-TiO2 in terms of cost and photocatalytic efficiency. The implementation of RCP/TiO2 composites leads to huge ecological benefit by reducing the consumption of natural mineral resource and improving the added value of RCP. Our work has developed a new application field for RCP, which can promote the upward circulation of RCP.