酸性矿山废水中Zn²⁺、Fe²⁺、Mn²⁺的分离及处理新工艺研究

【作者】 彭映林；

【导师】 郑雅杰；

【作者基本信息】 中南大学 ， 环境工程， 2010， 硕士

【摘要】 酸性矿山废水pH值低,水量大,金属离子含量高,如果直接排放,将对水体产生严重污染,破坏生态环境,危害人类健康。本论文采用两种方法对含Fe2+、Fe3+、Mn2+、Zn2+浓度分别为2742mg·L-1、158 mg·L-1、315 mg·L-1、150 mg·L-1的酸性矿山废水进行处理,结果表明,废水经处理后均达到国家污水综合排放标准(GB8978-1996),并实现了资源化。采用石灰与氢氧化钠二段中和法处理酸性矿山废水。用石灰调节废水pH值至5时,铁锰锌去除率分别为11.96%、5.97%、12.43%,一段中和渣为石膏(CaS04-2H20)。再采用氢氧化钠二段中和,当废水pH值为10.20,曝气流量为50mL-min"’,反应时间为20min,反应温度为12℃时,废水中铁锰锌去除率均达到99.7%以上,废水中TFe、Mn2+、Zn2+残留浓度分别为0.08 mg·L-1、0.81mg·L-1、0.03mg·L-1。XRD分析表明二段中和渣为锰锌铁氧体(Fe2Mn0.5Zn0.5O4·nH2O)和四氧化三铁(Fe304)。石灰与氢氧化钠二段中和法与石灰中和法比较,二段中和渣量少,二段中和渣具有综合利用价值。采用机械活化硫精矿吸附,氧化沉淀以及氢氧化钠沉淀法处理酸性矿山废水,使废水中锌、铁、锰得到分离与回收。结果表明,硫精矿活化的最佳条件是：球料质量比为8：1,球磨时间为4h,液固比为2：1。当废水pH值为1.83,在10升酸性矿山废水中加入活化硫精矿975g,反应20min后,铁、锰、锌浓度分别为5466.84 mg·L-1、353.04 mg·L-1、1.33 mg·L-1。废水经除锌后,取10L废水,当废水pH值为6.92,空气流量为500mL·min-1,反应时间为2.5h,搅拌速度为300r·min-1时,铁、锰残留浓度分别为97.96 mg·L-1.290.55 mg·L-1。XRD分析表明氧化沉淀渣为Fe3O4,渣中铁含量为52.73%。废水经除铁后用氢氧化钠溶液调节pH至11.01,反应时间为30min时,废水中锰残留浓度为1.15 mg-L-’,所得锰渣含锰达到34.47%。除锰废水经硫酸调节pH为7后达标排放。硫精矿经球磨后粒度变小,比表面积增大,反应活性提高,在活化过程中生成SO42-、OH,增强其亲水性,溶解度增大。研究表明活化硫精矿在酸性条件下溶解产生S2-,S2-与废水中Zn2+发生化学沉淀反应,产物为ZnS,继而ZnS被活化硫精矿吸附共沉淀。因此,活化硫精矿除锌机理主要为化学沉淀反应和吸附共沉淀。更多还原

【Abstract】 Acid mine drainage has the characteristics of low pH, large quantity and high content of metal ions. If it is discharged into natural environment without being treated, it will make the water body polluted badly, the ecological environment damaged, even it will endanger human health.Two methods were used to treat acid mine drainage, in which the concentrations of Fe2+, Fe3+, Mn2+ and Zn2+ are 2742 mg·L-1,158 mg·L-1, 315 mg·L-1 and 150 mg·L-1 respectively. The results show that the treated wasterwater can reach the Chinese standards of wastewater discharge (GB8978—1996) and realize the reclamation.The treatment of acid mine drainage by two-steps neutralization method of lime and sodium hydroxide was studied. After the pH of the wastewater is adjusted to about 5 with lime, the removal rates of total iron(TFe), Mn and Zn are 14.14%,5.94% and 13.91% respectively. The first-step sediment is gypsum(CaSO4·2H2O). In the second-step, sodium hydroxide was used as neutralizing agent. Under the conditions that pH is 10.20, airflow is 50mL·min-1, reaction time is 20 min,reaction temperature is 12℃, the removal rates of TFe, Mn and Zn are all up to 99.7%, and the concentrations of TFe, Mn and Zn are 0.08 mg·L-1,0.81 mg·L-1 and 0.03 mg·L-1 respectively. XRD shows that the second-step sediment are Fe2Mn0.5Zn0.504·nH20 and Fe3O4. Comparing two-steps neutralization method with lime neutralization method, the two-steps neutralization method produces less slag which has comprehensive utilization value.Separation and recovery of Zn, Fe and Mn from acid mine drainage were researched by applying absorption with mechanically activated pyrite, oxidation-precipitation and sodium hydroxide neutralization. The results show that the optimum conditions of mechanically activated pyrite are as follows:ball-to-pyrite weight ratio is 8:1, grinding time is 4h, liquid-solid ratio is 2:1. The concentrations of TFe, Mn and Zn are 5466.84 mg·L-1, 353.04 mg·L-1 and 1.33 mg·L-1 respectively when the pH of the acid mine drainage is 1.83, the dosage of activated pyrite is 975g in 10L wastewater, reaction time is 20 min. In 10 L wastewater after removing Zn, the residual Fe and Mn are 97.96 mg·L-1 and 290.55 mg·L-1 respectively when the pH of the wastewater is 6.92, airflow is 500mL·min-1, reaction time is 2.5h, stirring speed is 300r·min-1. XRD shows that the product of oxidation-precipitation is Fe3O4, in which the content of Fe is 52.73%. The residual Mn is 1.15 mg·L-1, and the Mn content in the sediment is 34.47% when the pH of the wastewater is adjusted to about 11.01 with sodium hydroxide solution, reaction time is 30min. The effluent quality can meet the Chinese standards of wastewater discharge (GB8978—1996) after the pH of the Mn removing wastewater is adjusted to 7 with sulfuric acid.After griding, pyrite particle size became smaller, specific surface area increased, reaction activity increased, SO42- and OH which can improve its hydrophilicity were produced, and the solubility of pyrite increased. Research shows that under the acidic conditions, activated pyrite dissolves and produces S2-,S2- reacts with Zn2+ and produces ZnS, which is adsorbed and co-precipitates with activated pyrite. The main mechanism of removing Zn by activated pyrite is chemic precipitation reaction and absorption co-precipitation.更多还原