Studies On The Recovery Of Serpentine In Dawu Prefecture, Hubei

This paper examines the feasibility techno-economy project of the recovery of serpentine. Our country is abundant in serpentine resources. A mass of serpentine waste, called breeze or tailings, which produced in exploitation and utilization account for about one-third to two-third amount in serpentine exploited. The serpentine of breeze or tailings as waste in exploited not only covering huge area and pollution of environment but also destroyed natural and have influence of the normal life and productive activities. The serpentine is also abandoned as solid waste from natural asbestos exploited that exploitable amount is reached 200, 000 tons every year in our country. The asbestoide-bearing content in asbestos is about 8ï¼…. The serpentine that amount to over 90ï¼…in asbestos is abandoned as asbestos tailings which the utilization rate at present is only 2ï¼…of the discharge value. As a result, the amount of the serpentine as waste is enormous. The tiny asbestos-fabric contented in tailings could embalmed the air and produce disastrous influence on ecological environment and the health of human beings. The utilization of the serpentine at present is still in its infancy. The most mine sell natural ore or primary products for a few dozens of yuan per ton. In the area of picking up the beneficial constituent and composing of new advanced industrial product, Japan, Australia and American leaped to the first place in the world. But our country is still in its infancy.The valuable elements in serpentine are magnesium and iron. It also contains iron, nickel, cadmium and so on. There're two methods of picking up valuable elements form serpentine: (1) calcinations-extraction; (2) pickling process, which is mostly reported for vitriol extraction. But the research of the serpentine extraction is mainly about technology and it has some deficiencies like the slow speed of vitriol leaching process and the low leaching efficiency of magnesia. The low leaching efficiency of magnesium could bring about two problems: First, it lead to low utilization rate of metal ion as magnesium. Next, the not pure leaching residue that silica must be made by the alkali soak, adjustment, acid analyzes, rinse, drying, the ignition effect the application performance and has long processes of the utilization of silica. These shortcomings lead to large consumption of raw material and the low economic efficiency. The results from laboratory research indicated that the max rate of dry leaching is 4%;The rate of wet leaching of vitriol is higher than hydrochloric acid, when the concentration of vitriol is 40%, measuring Ratio of Solid to Liquid of serpentine and vitriol is 4:1.,and joined helper leaching agent: HF (The amount put in is 1.2%-1.5% of the 40% vitriol), the rate of leaching of magnesia could over 98%. After using ammonia to trash extraction, basic magnesium carbonate is acquired by ammonium hydrocarbonate. Basic magnesium carbonate to calcine at 900℃,3h. Magnesia content is over 98%, the other indicators meet national standards GB9004-88. In the process of purification by ammonium, Fe³⁺,Fe²⁺,Al³⁺,Cr³⁺,Ni²⁺ could be separated for their different solubility product. Iron is recovered in the form of jarosite and ferric hydroxide that the concentrations of them determinate with dichromate method are 72.37%, 62.0% . Nickel is recovered in the form of nickel sulfide. The other trace elements is to solidify and then to landfill.Common technology of picking up magnesia of serpentine has low gain at present. For the complete cleavage of serpentine's leaching process, the silicon residue achieves the standard of silica after water cleaning. It provides practicable solution to the recovery of serpentine.The environmental problem from silicon fluoride (SiF₄)could be solved by using water to absorb from hollow spray tower. The water from cleaning silicon residue could be used as water-confected in refining epsom salt. Mixed the redundant portion of it and other waste water, joins the sodium hypochlorite, limewater and polymerization aluminum chloride coagulant mix precipitates, could discharged after reaching the standards. For the alkaline air that comes from evaporation of cleaning waste water of magnesium carbonate could reuse. The solid from filtration could be used as magnesium-contained fertilizer.The whole process is proved feasible after technical economic evaluation and promoted clean production. The process provide feasible industrialized program on the recovery of serpentine.