Investigation on preparation of pyrite tailings-based mineral admixture with photocatalytic activity

In this study, we prepared a mineral admixture with photocatalytic activity by acid leaching-hydrolyzation and single calcination method, using industrial waste pyrite tailings and high titanium slag as raw materials in which pyrite tailings were substrate and high titanium slag was the source of titanium. The compressive strength of the cementitious materials with the admixture, and the photocatalytic activity of the admixture and white cement with admixture were also studied. The results demonstrated that the optimum conditions for preparing admixture were that the mass ratio of acid and slag is 8:1; the temperature of acid leaching is 85 °C; the time of acid leaching is 250 min; the content of distilled water is 40%; the mass ratio of filtrate and tailings is 8:1; the loading temperature is 105 °C; the loading time is 3.5 h; at last, the precursor of admixture is calcined in 800 °C for 2 h. The admixture prepared in this method showed a superior crystallinity of anatase with the particle size of about 100 nm. Comparing with the cement paste without the admixture, the 3, 7 and 28 days compressive strength of the cement paste with 30% admixture were found to be increased by 40.92%, 44.57% and 37.74%, respectively. The photocatalytic degradation rate of methylene blue(MB) reached 95.28% after irradiation for 5 h, and white cement with the admixture manifested perfect photocatalytic performance under irradiation by 300 W high-pressure mercury lamp.