磁种絮凝-磁分离法处理含锌废水的研究

Treatment of zinc-containing wastewater by magnetic seeding flocculation and magnetic separation

采用磁种絮凝-磁分离方法对模拟某锌盐制造企业的排放废水进行处理,研究了废水pH值对其Zn^2＋去除效果的影响、絮凝剂聚丙烯酰胺（PAM）和磁种（Fe3O4）对氢氧化锌沉淀物沉降性能的影响以及外加磁场对磁种-氢氧化锌絮凝体沉降性能的影响。结果表明,有利于Zn^2＋沉淀的最佳废水pH值为9-12;PAM与磁种同时使用能改善Zn（OH）2的沉降性能;在外加磁场作用下,废水中的磁种-氢氧化锌絮凝体由于受到与重力方向一致的磁力,其沉降速度加快,污泥压缩得更快、更实,上清液中锌的质量浓度降至0.83 mg/L;磁性矾花絮凝体经硫酸溶液或氢氧化钠溶液浸泡后,过滤得到的磁种可循环使用,滤液中的锌可回收利用。

The zinc-containing wastewater was treated by magnetic seeding flocculation and magnetic separation.First,the effect of pH value on the precipitation of Zn2＋ ion and that of flocculatant（PAM） and magnetic seed（Fe3O4） on the settlement of Zn（OH）2 were investigated.Secondly,a contrasting test of the settlement of magnetic seed-Zn（OH）2 aggregation inside and outside a designed magnetic field was carried out.The results indicate that the pH value best for Zn2＋ ion precipitation is from 9 to 12;the settlement properties of Zn（OH）2 can be improved by the combined use of PAM and Fe3O4;the magnetic seed-Zn（OH）2 aggregation sink faster and the sludge becomes more easily compressed because the magnetic force accords with the gravity.Under the external magnetic field,the sludge settlement ratio declines to 32% after 8-minute settlement and to 29% after 28-minute settlement,and the zinc content of the upper clear liquid is 0.83 mg/L.It is also demonstrated that the Fe3O4 and Zn can be separated completely and reused after the magnetic seed-Zn（OH）2 aggregation is soaked with sulfide acid or sodium hydroxide solution and filtered.