3类金属离子对活性污泥吸附水体腐殖酸的影响

研究了3类金属离子对活性污泥吸附水体腐殖酸效果的影响.结果表明,盐类金属离子(Na )、硬度金属离子(Ca2 、Mg2 )和水解金属离子(Al3 、Fe3 )均能在一定程度上提高吸附效率.作为活性污泥助凝剂,以大于10-2mol/L硬度离子的促进效果为好.加入10-2mol/L Ca2 、Mg2 48 h后溶液中的腐殖酸浓度分别为(0.64±0.17)mg/L和(2.32±0.40)mg/L,其去除率分别为98.4%和94.2%;当加入10-1mol/L Ca2 、Mg2 48 h后,其去除率均接近100%,而且Ca2 离子促进作用要优于Mg2 .盐类金属离子、硬度金属离子、水解金属离子提高活性污泥吸附腐殖酸的主要作用机理可能分别是压缩双电层、架桥作用、吸附共沉淀.同时,投加金属离子也可能使活性污泥上的吸附位性质改变或失效,对腐殖酸的吸附有一定的负面影响.

Influence on Three Categories of Metal Ions on Adsorption of Humic Acid by Activated Sludge

Activated sludge, as the adsorbent of humid acid in solution, was considered as an environment-friendly material. The effects of three categories of metal ions on sorption of humic acid by activated sludge were studied. The results indicated that the salts (Na⁺), hardness (Ca²⁺, Mg²⁺) and hydrolyzing metal (Al³⁺, Fe³⁺) ions were able to increase the efficiency of adsorption. In view of coagulant aids, the hardness metal ions would be a better choice at the concentration higher than 10^-2 mol/L. Addition of 10^-2 mol/L Ca²⁺ and Mg²⁺ to the solution resulted in the concentrations of humid acid of (0.64±0.17) mg/L and (2.32±0.40) mg/L, respectively, in 48 h with corresponding removal efficiencies of 98.4% and 94.2%. Upon increasing the concentrations of Ca²⁺ and Mg²⁺ in the solution to 10^-1 mol/L, the removal efficiencies were close to 100% after 48 h. Moreover, the effect of Ca²⁺ was superior to that of Mg²⁺. Decrease in thickness of the electric double layer due to repulsion forces, cationic bridge, destabilization and precipitation might be the major mechanisms to promote the removal of humic acid in solution. On the other hand, the addition of metal irons might have resulted in physical changes in sorption site on the activated sludge, even inactivation, and might have caused negative effects on humid acid adsorption.