矿山酸性废水中微量有害重金属元素的中和沉淀去除

石灰中和及其衍生方法是处理矿山酸性废水最常用的方法,但该法对废水中微量有害重金属元素的去除作用通常不被了解.该文用石灰石、石灰中和处理某硫铁矿露天采场的酸性废水,考察了废水中微量有害重金属元素的沉淀去除效果.结果表明:对大多数重金属离子而言,pH值越高,重金属离子的去除效果越好,但若重金属离子生成两性化合物沉淀,则存在一个最适宜的pH值.石灰石中和法对在酸性条件下生成沉淀的重金属离子去除效果及沉渣的沉降性能较好,但最高pH值为6,对其他的重金属离子的去除效果有限;石灰法的pH值有较大的调节范围,处理效果明显优于石灰石;石灰石-石灰二段中和法的处理效果在总体上与石灰法相当,在达到与石灰相同的处理效果时,能够降低约1/3的石灰投加量和沉渣的产生量,沉渣的含水率相比石灰法更低,沉降性能更好.废水中微量有害重金属元素的中和沉淀去除效果与pH值密切相关,因此在工艺的选择之外,中和剂的投加量和投加方式,处理设施更为精准的掌控和运作非常关键,研究可为确立石灰石-石灰法处理矿山酸性废水的最佳工艺和过程控制条件提供依据.

Neutralization Sediment Treatment of Minim Harmful Heavy Metal Elements in Acid Mine Drainage

Although treating the acid mine drainage by the neutralization method of limestone and lime is the most common practice,few researches have done to analyze the removal effects on those minimal amounts of toxic heavy metal elements in it.In our series of experiments the acid mine drainage of some pyrite excavating plant has been treated by neutralization of lime and limestone.And the sedimentation performance and removal effects on those minim harmful heavy metal ions are studied carefully.The experiments show that in terms of most heavy metal ions,the greater the pH values are,the better sedimentation removal effects will be.But if the metal ion will produce amphoteric compound deposits,there will be a better pH value which will result the best removal effect.The neutralization method of limestone has better removal effects to those metallic ions produced in acid conditions and has better sedimentation performance.But the highest pH value required by this method is 6,and its removal effects to other kinds of metal ions are not so satisfactory.In contrast,the neutralization of lime can have more flexible pH value ranges and its removal effects are better than limestone.The experiments further discover that the two stage neutralization of limestone and lime can reduce about a third lime dozing quantity and sediment,causing better sedimentation performance and lower water ratio in produced sediment compared with lime treatment method.Since the sedimentation performance and removal effects of those minim harmful heavy metal elements are closely related to the pH value,the accurate operation of equipment,the feeding pattern and feeding quantity of neutralizer are critical besides the careful design of processing.These study results provide valid basis for establishing optimum technology and process controlling conditions in treating the acid mine drainage by the neutralization sediment treatment of limestone and lime.