Removal of Phosphate in Water Using Blast Furnace Slag

In order to evaluate the feasibility of the removal of phosphate in water by the blast furnace slag, purification experiments were conducted with the slag particles and phosphate aqueous solution under stirring.In the experiments, the influences of particle size of slag, pulp density, initial concentration of phosphate in the solution and stirring time on the removal ratio of phosphate were investigated. As a result, the smaller particle was used, the higher removal ratio was obtained in a short stirring time. In the case of the particle size of slag was less than 0.21mm, the removal ratio of 97% was attained by stirring of 5min, when the initial concentration of phosphate and pulp density were 50mg/l and 1%, respectively. However, the phosphate concentration after the stirring time of 5min was 1.8mg/l that was still higher than environmental standards. On the other hand, the removal ratio of 100% was obtained after 5min, when the initial concentration of phosphate was 2mg/l.It was suggested that the removal of phosphate was due to the formation of calcium phosphate by the reaction between phosphate in the solution and Ca ion dissolved from the slag particle

Separation and Recovery of Valuable Metals from Automobile Shredder Residue (ASR) Fly Ash by Wet Processing

The amount of automobile shredder residue (ASR) reaches 0.6-0.7 million tons per year in Japan, approximately. One of the effective processes to reduce the amount of ASR was the incineration process, generally carried out in smelting and refining plant. During the process, however, large amounts of ASR fly ash containing chloride (Cl) compounds and some valuable metals (e.g. copper, zinc) were produced. In this contribution, the recycling of copper, zinc and Ca/Na chloride compounds from ASR fly ash was investigated by using a process consisting of cementation, sulfide precipitation and distillation. The experimental results showed that high-grade copper (metal and oxide) and zinc (sulfide) were separated with recovery rate >97% from the HC1 washing solution of ASR fly ash by cementation and precipitation. CaCl2･9H2O and NaCl were obtained from the washing solution of ASR fly ash by vacuum distillation