新型复合聚硅酸钛锌混凝剂的合成、表征及混凝性能

Synthesis,characterization,and coagulation performance of a novel polysilicic-titanium-zinc composite coagulant

采用聚硅酸(PSA)、钛盐及锌盐以不同摩尔比合成了一系列新型聚硅酸钛锌(PSTZ)混凝剂,并使用胶体滴定、扫描电子显微镜、透射电子显微镜、X射线衍射和傅立叶变换红外对药剂进行了结构表征。以高岭土悬浊液和腐殖酸(HA)水溶液为模拟水样,详细考察了各组成含量及pH对PSTZ混凝性能及絮体结构的影响,同时与聚硅酸钛(PST)和聚硅酸锌(PSZ)进行性能对比。结果表明,由于PSTZ具有层状和多孔的表面结构,PSTZ混凝性能优于PST和PSZ,形成絮体尺寸也大;进一步研究发现具有适中Si/Ti物质的量比(1:0.53)的PSTZ混凝剂具有更佳的电中和与粘结架桥作用;对Zn离子而言,特别是在pH 9.0—10.0下,易于与HA形成Zn-HA络合物,同时减轻Ti水解产物Ti(OH)_(5)^(-)的负面影响,进一步增强PSTZ混凝性能。此外,PSTZ在近中性pH条件下对高岭土悬浊液混凝性能最佳,而在酸性条件下对HA水溶液净化效果最优,这是由于PSTZ对不同污染物具有不同混凝机制所造成的。除模拟水样外,还考察了PSTZ对实际微污染地表水的混凝效果,并与传统混凝剂聚合氯化铝(PACl)进行对比,PSTZ表现出优于PACl的混凝性能,进一步证实了该复合混凝剂的有效性。该工作提供了一种绿色环保、可回收再利用的无机复合混凝剂,可有效地净化微污染地表水,提高用水安全。

A series of new composite coagulants,polysilicic-titanium-zinc(PSTZ)was synthesized by polysilicic acid(PSA),titanium salt,and zinc salt with different molar ratios,which was characterized by colloidal titration,scanning electron microscopy,transmission electron microscopy,x-ray diffraction and fourier transform infrared spectra.The kaolin suspension and humic acid(HA)aqueous solution were used as simulated water samples,and the effects of the composition contents in PSTZ and pH on the coagulation performance and floc structure were investigated in detail,which were compared with those of polysilicic-titanium(PST)and polysilicic-zinc(PSZ).PSTZ exhibited better coagulation performance than PST and PSZ due to its porous surface structural characteristics,and the size of the flocs formed by PSTZ was larger.PSTZ with moderate Si/Ti molar ratio of 1:0.53 had better charge neutralization and adsorption-bridging effects;besides,especially at the pH of 9.0—10.0,Zn could adsorb HA to form Zn-HA complexes,and simultaneously alleviate the negative effect of Ti hydrolysis product Ti(OH)_(5)^(-),causing the improved coagulation performance of PSTZ.In addition,PSTZ showed better effects at the natural pH in coagulation of kaolin suspension but at the acidic condition in removal of HA due to their different coagulation mechanisms in removal of various pollutants.In addition to simulated water,the performance of PSTZ in coagulation of a real surface water sample was also investigated and compared with a conventional coagulant,polyaluminum chloride(PACl).The coagulation performance of PSTZ was better than that of PACl,further confirming the effectiveness of this composite coagulant.This work provides a green,environmentally friendly,recyclable inorganic composite coagulant,which can effectively purify micro-polluted surface water and improve water safety.