Study On The Adsorption Of Heavy Metals With Modified Diatomite

Water is the vital factor of people's living.With the development of economic and rapid urbanization , many industries , including the electroplating,metal finishing,metallurgical,tannery,chemical manufacturing,mining,and battery manufacturing industries,produce aqueous effluents containing heavy metal contaminants,causing serious soil and water pollution.Various techniques have been used to remove the heavy metals from waste water,including chemical precipitation,ion exchange,electrolytic methods,chemical coagulation,membrane processes and adsorption.Today,numerous approaches have been studied for the development of cheaper metal sorbents,such as fly ash,peat,microbial biomass,clays and related minerals.The diatomite is the biologic quartzite that be constitute by the diatom and the silicon quality remains of the other microorganisms,having the huge ratio surface area and strong surface adsorption.As a kind of new flocculant,the diatomite has extensive sources,good effection of treating sewage and simple equipment for subsequent sludge disposal,so it has a great future for application.First,this paper introduces the structure and some properties of diatomite,the application and research development of diatomite materials to heavy metal waster water treatment are also summarized. diatomite are used to treat heavy metal waste water. The article studies the adsorption characteristic and the mechanisms of modified diatomite which adsorbs the heavy metals(Pb2+,Cu2 +,Zn2 +,Cd2+)from the wastewater(the artificial prepare).Using CaCO3 to change the characteristic of diatomite, after that,using modified diatomite to deal with heavy metals wastewater. After modified, the surface area have improved. The properties and optimal condition for CaCO3-diaomite to adsorb heavy metal Pb2+,Cu2 +,Zn2 +,Cd2+ were investigated under static state in the laboratory. The experiment indicated that diatomite dosage, adsorb time and the temperature of adsorption,the pH value of aqua,the beginning concentration of heavy metals about the aqua,etc.are main factors that affect the adsorption characteristic of heavy metals wastewater. It determined the optimal adsorption conditions. At th esuitable condition,PH=5.1,m=10g/L,T=20oC,t=25min, 1.5mmol/L heavy metal solution, it can remove 97.43%,99.78%,83.91%和71.72% Cu2 +,Pb2 +,Zn2 + and Cd2 + in waste water.The adsorption isotherms model and kineties model of heavy metal onto diatomite were then proposed in the paper.The adsorption isotherms were studied using Langmuir and Freundlieh models.It showed that the Langmuir models was the best one.The adsorption process of dye can be better described by the pseudo-second-order model than the pseudo-first-order model.In a mixed system experiment, because the four ions interacted together, diatomite adsorption capacity of units declined. The most obvious decline appeared in zinc and cadmium.A fixed bed was designed and manufactured,and the breakthrough curves are determined for fixed bed with diatomite. Thomas model can be used to describe the adsorpition column performance in this experiment.The experiment which was eluted by hydrochloric acid was indicated that the modified diatomite adsorbing the heavy metal ion was eluted easily,which reached above 97%.Then the modified diatomite eluted was carried on the regeneration adsorption experiment,and it indicated the modified diatomite has the good reuse. According to all experiment dates and analysis of theory,the modified diatomite play a great role on the wastewater treatment and environment remediation.In a word,the modified diatomite have extensive prospect on the treatment of contaminate environment.