淀粉改性混凝剂复合硅酸盐对微污染水强化混凝性能研究

传统混凝工艺对微污染地表水净化效果有限,此外,近年来淀粉等天然高分子混凝剂由于绿色环保等特点而备受关注.本研究采用一种阳离子改性淀粉材料(淀粉-3-氯-2-羟丙基三甲基氯化铵,St-CTA)为混凝剂,分别与实验室自制的聚硅酸(PSA)及聚硅酸钛锌(PSTZ)进行复合强化混凝,应用于处理微污染水体.首先以高岭土-腐殖酸(HA)混合液为模拟水样,基于表观混凝性能、絮体特征及混凝后上清液ζ电位等,详细考察了强化混凝工艺的净水效果及混凝机制.结果表明,St-CTA分别复合两种不同硅酸盐的强化混凝工艺均对模拟水样具有良好的净水效果;St-CTA与PSTZ复合优于其与PSA组合工艺的混凝性能,且St-CTA/PSTZ复合工艺能缓解St-CTA过量引起的再稳定效应,具有较宽的有效混凝范围.St-CTA通过电中和作用与污染物结合,可有效压缩表面双电层;而带正电性的PSTZ,相比于负电性的 PSA,不仅具有粘结架桥强化效应,还具有电中和作用,且与HA可形成Zn-HA复合物,实现高效净水效果.除模拟水样外,还考察了两种强化混凝工艺对实际微污染地表水的混凝效果,其均表现出良好的混凝性能,有效弥补单一混凝剂对有机微污染水体混凝效率较低的不足,进一步证实了该强化混凝工艺的有效性.此外,与处理模拟水样效果一致,St-CTA复合PSTZ的净化效果更佳,但PSA具有更低的应用成本.本研究提供了一种绿色环保的强化混凝工艺,可有效净化微污染水体,具有良好的应用前景.

Coagulation performance of a modified starch-based coagulant combined with silicates in treating micro-polluted water

Traditional coagulation is inefficient to treat micro-polluted surface water; besides, natural polymeric coagulants including starch-based ones have recently received considerable attention due to their environmentally-friendly characteristics. In this work, a cationic modified starch-based coagulant (starch-3-chloro-2-hydroxypropyl trimethyl ammonium chloride, St-CTA) coupled with polysilicic acid (PSA) and laboratory-developed polysilicic-titanium-zinc (PSTZ), respectively, has been tried to coagulate the micro-polluted water bodies. An aqueous mixture of kaolin and humic acid (HA) were first used as a simulated water sample, and the purification effects and enhanced coagulation mechanisms of St-CTA in combination with silicates were studied and discussed in detail based on the apparent coagulation performance, floc properties, and zeta potentials of supernatants. This enhanced coagulation showed a good purification effects on the simulated water body. St-CTA in conjunction with PSTZ had better coagulation performance than the starch-based coagulant with PSA. The synergistic effects of St-CTA and PSTZ could significantly weaken the re-stabilization effect when St-CTA was overdosed, thus St-CTA coupled with PSTZ had a wider effective coagulation range. St-CTA can interact with contaminants through charge neutralization and effectively compress its electric double layer; while, in comparison to anionic PSA, the cationic PSTZ can not only have an effective adsorption-bridging effect, but also charge neutralization and adsorption of HA through the formation of Zn-HA complex, causing a higher purification effect of PSTZ. In addition to simulated water sample, the validation of this enhanced coagulation technique was further confirmed by its good coagulation performance in treating a real surface water, which technique can overcome the inefficiency of single coagulant in purification of organic micro-polluted water bodies. Similarly to the simulated water sample, St-CTA in conjunction with PSTZ had better performance in coagulation of real surface water, but the starch-based coagulant with PSA had lower cost. This work provides an environmental-friendly strategy to effectively purify micro-polluted wastewater, and has a good application prospect.