高盐废水反应结晶制备氢氧化镁

Preparation of magnesium hydroxide by reactive crystallization of high-salinity wastewater

以某煤化工高盐废水为研究对象,利用反应结晶制备氢氧化镁产品。研究加料方式、搅拌速率、NaOH浓度、反应计量比、加料反应时间对结晶过程及产品品质的影响,同时探究连续反应结晶过程的可行性以及有机物的影响。结果表明:在双向加料方式、室温25℃、搅拌速率300 r/min、NaOH浓度0.1 mol/L、[Mg^(2+)]/[OH^(-)]反应计量摩尔比1∶2的连续反应条件下,可得到纯度约95%符合工业氢氧化镁Ⅱ类标准的产品,且脱硬废水符合预处理要求。典型有机物L-脯氨醇的添加会降低镁收率,但对结晶过程存在促进作用,实际废水体系中产品里残留有机物,纯度仍可达92%以上。实验表明高盐废水中镁的资源化利用具有可行性。

The high-salinity wastewater from the coal chemical industry was utilized in the process of the reactive crystallization to prepare magnesium hydroxide products.The influence of feeding method,stirring rate,concentration of NaOH solution,stoichiometry ratio and feeding time on the crystallization process and the quality of products were studied.At the same time,the feasibility of continuous reactive crystallization process and the influence of organic were explored.The results showed that under the continuous reaction conditions of bidirectional feeding method,reaction temperature 25℃,stirring rate 300 r/min,NaOH concentration 0.1 mol/L and[Mg ^(2+)]/[OH^(-)]stoichiometry ratio 1∶2,the product meets the requirement of the industrial magnesium hydroxide ClassⅡstandard,which has the purity of about 95%.The dehardening wastewater meets the requirement of pretreatment.The addition of the typical organic L-prolinol reduced the magnesium yield,but it promoted the crystallization process of magnesium hydroxide.There are organic residues in the product in the actual wastewater system,its purity can reach more than 92%,which affects the quality of the product.The experiment shows that the resource utilization of magnesium in the high-salinity wastewater is feasible.