纳米SiO_2对Pb^(2+)污染水源水混凝过程的影响

Effects of SiO_2 on coagulation process in treatment of source water polluted by Pb^(2+)

随着纳米材料的广泛应用,越来越多的纳米材料会泄露到水环境中,但目前关于纳米材料对混凝过程的影响还缺乏充分的研究。针对不同浊度,不同纳米SiO2浓度,不同p H以及腐殖酸对混凝去除Pb2+的影响进行了一系列的研究。结果表明,在低投加量(40 mg/L)条件下,Pb2+的去除率受浊度影响较大,然而在高投加量(80 mg/L)条件下,Pb2+的去除率受浊度的影响反而较小,且随着浊度从15.0 NTU增加到90.0 NTU,Pb2+的去除率从70.172%下降到63.925%。当浊度为45.0 NTU,投加量为40 mg/L时,铅离子的去除率在SiO2投加量达到0.8 mg/L时达到最高(92.34%)。由于在低浊度条件下絮体形成不充分,以至于生成的絮体对SiO2的吸附去除率较低,所以吸附在SiO2表面的Pb2+会悬浮在溶液体系中,造成Pb2+去除率的下降。随着p H的升高,Pb2+去除率呈先升高后降低的趋势,且在偏碱性条件下达到最高。p H对Pb2+去除率的影响主要体现在其对纳米SiO2表面电荷的影响,SiO2表面负电荷增多可有效提高Pb2+的去除率,说明纳米SiO2的吸附作用在去除Pb2+的过程中起重要的作用。在高混凝剂投加量(80.0 mg/L)下腐殖酸对Pb2+的去除有促进作用,且当腐殖酸存在时,SiO2的含量对Pb2+的去除率无明显影响。

More and more nano particles may be found in the aquatic environment due to the widely application,but the effects of nano particles on the coagulation process have not been investigated well. The effects of SiO2 on the removal efficiency for Pb2 ＋in the coagulation process were investigated under different coagulation conditions. The results indicated that the turbidity had a larger effect on the removal efficiency for Pb2 ＋under the lower coagulant dosage（ 40 mg / L）. The removal efficiency of Pb2 ＋under the larger coagulant dosage decreased from 70. 172% to 63. 925% with the increasing turbidity from 15. 0 NTU to 90. 0 NTU. The removal efficiency of Pb2 ＋reached the highest（ 92. 34%） under 40 mg / L coagulant dosage when the turbidity was 45. 0 NTU. The Pb2 ＋which was adsorbed on the surface of SiO2 particles would be left in the solution under low turbidity conditions,so the removal efficiency decreased. The p H values affected the surface charges of SiO2,and the removal efficiency increased with the increasing negative surface charges. HA molecules could enhance the removal efficiency of Pb2 ＋under the larger coagulant dosage（ 80. 0 mg / L）,and the dosage of SiO2 had no significant effects on the removal efficiency of Pb2 ＋.