Investigation On Preparation Of Pyrite Tailings-based Mineral Admixture With Photocatalytic Activity And It's Application In The Cementitious Materials

In this work,the pyrite tailings-based mineral admixture with the feature of photocatalysis was made by sol-loaded method using butyl titanate as titanium source and acidleach-loaded method using high titanium slag as titanium source,respectively.The optimum technical parameters was investigated for the mentioned two method.The photocatalytic property of the mineral admixture and mechanical property of cement paste blended with the resulting mineral admixture was studied.The degradation mechanism of methylene blue(MB)in alkaline solution which observed in the experiment was also preliminarily discussed in this paper.Results show that: As far as the sol-loaded method(butyl titanate as titanium source)is concerned,the optimum technical parameters is as follows: the loading titanium content is 11%,the loading temperature is 45 ?,the calcination regime is 800 ? for 2h.The photo-degradation rate of MB of the prepared admixture reached94.87% after irradiation for 5h with the initial MB concentration of30mg/L and the ratio of admixture and MB of 0.5%.The white cement paste incorporated with the resulting mineral admixture has not only greater compressive strength and perfect photocatalytic performance.As far as the acidleach-loaded method(high titanium slag as titanium source)is concerned,the optimun technical parameters is as follows: the mass ratio of acid and slag is 8:1;the temperature of acid leaching is 85 ?;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 ?;the loading time is 3.5 hours;at last,the precursor of admixture is calcined in 800 ? for 2 hours.The admixture prepared in this method showed a superior crystallinity of anatase with the particle size 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 by40.92%,44.57% and 37.74%,respectively.The photocatalyticdegradation rate of MB reached 95.28% after irradiation for 5 hours,and white cement with the admixture manifested perfect photocatalytic performance under irradiation by 300 W high-pressure mercury lampBy means of contrasting the admixture prepared in different methods,the photocatalytic activity of the acid leach-loaded admixture is superior to sol-loaded admixture in the early stage of irradiation and have no significant difference in the later stage.Whether the compressive strength of cement paste or photo-degradation property to MB of the cement paste blended with acid leach-loaded admixture is higher than with sol-loaded admixture.It is obtained from the experiment that the degradation rate of methylene blue in solution increases with the alkalinity of the solution,irradiation light energy intensity and illumination time.but it decreased with the increasing MB concentration.While the strong alkali solutin with the concentration of 0.2mol/L,the degradation rate of methylene blue are more than 99% after exposed to high pressure mercury lamp light irradiation for 10 h.