Prepartion And Zeolitization Of A Sludge Ceramsite For Processing Heavy Metals Contained Sewage

In this investigation, using sludge produced in the process of sewage treatment as a major raw material and fly ash as an additive to sinter porous ceramsites, and then the obtained ceramsites were zeolitized to process heavy metals contained sewage, thus eventually attaining the purpose of "using solid waste treat wastewater”.The main results are as follows:1. The raw materials such as the sludge have been chemically analyzed and analyzed by TG-DTA, XRD as well. Based on the water absorption、porosity and bulk density, the best mixture ratio of raw materials was as follows, sewage sludge: fly ash:feldspars:feldspars=5:3:1:1. The optimized preheating temperature, preheating time, sintering temperature, soaking time and heating rate were 550℃, 20 min, 1050℃, 30 min and 10 ℃ /min, respectively. Under this condition, the properties of the prepared ceramsite were as follows:the water absorption was 85.43%, the porosity was 89.26% and the bulk density was 0.642g/cm3.2. On the basis of the above investigation, the ceramsite was zeolitilized through the reaction of alkaline fluid, therefore its porous structure has been optimized and absorption performance has been improved. During the process of ceramsite sintering, theoretically the phase transformation under high temperature could improve the reactivity significantly, which is the premise condition for zeolitization. Zeolitized ceramites could be achieved through controlling reaction conditions such as alkali concentration, reaction temperature. Through SEM morphology analysis, the suitable reaction conditions were confirmed:the alkaline concentration was 3 ~ 4 molar, the reaction temperature was 160℃. The results of SEM, XRD and FTIR analysis have shown that the structure of zeolitization was formed on the surface of the ceramsite, where there was a complex pore structure and considerable surface area.3. For the ceramsites and the zeolitilized ceramsites, their toxic heavy metal leaching test revealed that the heavy metal contents in lixivium were much lower than the limits of the national standards. The adsorption experiments of sewage(Ba、 Co、Ni、Se、Sr、Cu、Mn) from Jiaozuo sewage treatment plant showed that removal rate of heavy metals was above 99%,therefore, using zeolitilzed ceramsite to process heavy metals contained sewage is safe and effective.4. Considering Ni as an objection, effects of the absorption time、the pH value、the quantity of absorbing material and the initial concentration of Ni on the removal rate were investigated. The results are as follows: between 0 to 2 hours, Ni2+ adsorption rate increased rapidly and the removal rate achieved at 87.12% at 2 hours. With the increase of absorption time, the absorption rate became slower and eventually was at steady state; with the increase of initial concentration of Ni2+,the removal rate of Ni2+ decreased, the removal rate reached the value of 100% roughly when the initial concentration is less than 300 mg/L; when the pH value was 4-10, the Ni2+ adsorption ability of the zeolitilized ceramsite became stronger; Ni2+ adsorption capacity gradually was reduced from 18.4 mg/g to 3.3 mg/g when the quantity of zeolitilized ceramsite increased from 0.1 g/L to 3 g/L. The removal rate was nearly close to 100% when its quantity was 2g/L.