| Heavy metal ions have great harm to human body,especially lead and cadmium pollution have caused great threat to the environment.As one of the main sources of heavy metal pollution,the source of heavy metal wastewater is one of the most important sources of heavy metal pollution.And it Has been become a matter of great concern to people.First,the heavy metal ions in the waste water have been fixed in the mineral,and then the solid solution has been separated by filtration to achieve the national standard of wastewater discharge,which is one of the effective methods for treating heavy metal wastewater.Ceramic membrane technology has been widely used in solid-liquid separation and has the advantages of continuous,high efficiency and energy saving.Silicon carbide ceramic membrane is a new type of non oxide inorganic membrane,it not only has high mechanical strength,pore size distribution,good thermal shock resistance and long service life,etc,but also has a prominent advantage at the membrane flux,high temperature stability and resistance to strong acid,strong alkali,etc.It is a kind of beneficial attempt to use silicon carbide ceramic membrane for heavy metal wastewater treatment.In this paper,two methods of reaction sintering and particle deposition were used to prepare silicon carbide ceramic membrane.The reaction sintering was sintered after carbonization with phenolic resin and nano-silica as the main raw materials.It was found that reaction at 1300 ° C generated only tiny amounts of silicon carbide,and the nano-silica is recrystallized to cristobalite form.The reaction was basically complete at 1400 C,forming the 3C type silicon carbide,but due to the coarse particle size of the phenolic resin,the average pore diameter was about 1?m silicon carbide ceramic membrane.In the preparation of silicon carbide ceramic membrane by solid state sintering method,the stability of the silicon carbide slurry has been studied first.The result turned out that when tetramethyl ammonium hydroxide content was 0.6 wt % the stability of the slurry is accord with the requirement of coating.After two days of membrane slow drying,the sintering temperature system was optimized by optimizing the sintering temperature system,and the average pore diameter was about 0.45?m,which was suitable for the treatment of the silicon carbide ceramic membrane.In recent years,the treatment of heavy metal wastewater with apatite has been widely studied.The mineral materials used include synthetic hydroxyapatite and natural apatite,China has abundant phosphorus resources,and a large number of tailings are produced after the annual phosphate ore dressing.There is a certain amount of natural apatite,which is a low cost environment mineral material,but the removal rate of heavy metal ions is low.This topic with strong biological toxicity of lead and cadmium ions as the main research object,first research on modification phosphorus tailings activation,and found a can significantly improve phosphorus tailings of lead and cadmium ion removal modification methods.When the pH value of the wastewater solution is 3~11,the modified phosphate tailings can effectively remove lead and cadmium ions.the removal rate is positively correlated with pH value.The removal rate of lead ions is over 99% when the pH value is higher than the weak acidity of 4,and in alkaline conditions,cadmium removal rate is more than 99%.The modified phosphate tailings have a buffer effect on the acid and alkalinity of the solution,and the pH value of the solution will increase under acidic conditions,while the pH value will decrease under alkaline conditions.Finally,the tubular membrane was prepared according to the process conditions of 0.45?m silicon carbide ceramic membrane.The solid-liquid separation of the heavy metal wastewater treated by modified phosphorus tailings was carried out by using the method of cross flow filtration.The membrane treatment flux,membrane fouling and membrane cleaning were discussed under different transmembrane pressure difference.It was found that with the increase of transmembrane pressure difference,the flux of membrane treatment increased significantly,and membrane fouling is harder to clean.The removal rate of the suspended solids(SS)in the filtered water was 100%,and the content of lead and cadmium was lower than 0.1mg/L,which was in line with the requirements of China's wastewater discharge standard(GB8978-1996).In this study,a new modification method of phosphate tailings was used,which significantly improved lead ion and cadmium removal rate of phosphate tailings,found a new way for the utilization of phosphorus tailings solid waste.The treatment of lead and cadmium wastewater treated by modified phosphate tailings with silicon carbide ceramic membrane has achieved the standard discharge of wastewater,and the application prospect in the treatment field of heavy metal wastewater will be good. |
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