Preparation And Photocatalytic Performance Of Nano-TiO₂/diatomite Composites By Mechanochemical Method

Diatomite has large surface area and special pore structure. Due to the adsorptionproperties of diatomite, it became a good support of the catalyst. Nano-TiO₂hasreceived special attention in the field of photocatalysis because of its low-cost,non-toxicity and so on. However, some limitations such as its easy agglomeration intolarge particles and difficult recovery from the wastewater limit its further industrialapplications. So we need fix nano-TiO₂on supports. We make the nano-TiO₂particlesonto natural minerals to resolve the problem. And it can improve the photo-catalyticproperties by means of adsorption properties of minerals. Compared with othertraditional methods of preparation, methano-chemical method has many advantagessuch as easy operation, low-cost, no pollution, and it has gradually become a hottopic in the material preparation method.In this paper, the changes of diatomite’s structure and performance in the wetgrinding process were investigated. A series of experiments have been performed inorder to analyze the effect of operational parameters such as grinding time, solidconcentration and the ratio of ball to powders. According to particle size analysisresults, the optimal conditions was as follows: ball to powders ratio6:1, solidconcentration25%.And then, the following experiment was carried out to investigatethe change in particle size, surface area, adsorption ability and structure with theincrease of grinding time. The experiment results show that the properties of grounddiatomite are related to the grinding time. Wet grinding changed the particle size andspecific surface area. d50and d90decreases rapidly during the first60min and thenappears to slow down. SEM studies show that the reduction in particle size with theprolonged grinding time, but agglomeration of the particle is not observed. Adsorptionof kinetics of methylene blue onto diatomite indicate that the adsorption capacityinitially increases with the increase of grinding time, while the adsorption capacityhas no so much change with prolonged grinding time. By means of controllinggrinding time, the diatomite with high adsorption capacity could be obtained.This paper studies the dispersion of nano-TiO₂in water system. And the optimalconditions is followed:0.5%of triethanolamine, pH for4, dispersion time for20min.Preparation and characterization of nano-TiO₂/diatomite has been completed. A series of experiments have been performed with four operational parameters, such asball to powders, reaction time, content of TiO₂and solid concentration. The optimalconditions were as follows: ball to powders4:1, reaction time60min, ratio-solidconcentration15%. Further experiments show that the sample has the bestphotocatalytic properties when the content of TiO₂is60%and the photo-catalyticproperties are about89.39%. The degradation rate of the sample is better than that ofpure TiO₂. XRD test shows that anatase TiO₂exists on the surface of diatomite. SEMstudies shows that TiO₂powders exists the surface and pore of diatomite. IR test showthat the Si-O-Ti bond was not obtained in this composite material.In order to discuss the performance of photo-catalytic properties, single factorexperiments have been performed, such as dosage of powders, irradiation time, pHvalue, the initial concentration of methylene blue solution and the number of reuse.And the results show that after dark-box mixing20min and irradiation40min, thedegradation rate of methylene blue solution is about95%. And the performance ofcomposites powders remains unchanged after being used for five times.