新型固体聚硅硫酸铁混凝剂的制备及结构表征

聚硅酸基混凝剂是重要的水处理剂之一,在混凝过程中扮演重要的作用,但易于产生自聚反应、形成硅胶、失去稳定性。因此,制备稳定的聚硅酸基混凝剂受到广泛关注。为获得一种稳定的聚硅酸基混凝剂,提出一种新型稳定的固体硅酸基混凝剂(PSPF)的制备方法。采用红外光谱与扫描电镜表征PSPF的结构与形貌;Ferron逐时络合比色分光光度法分析PSPF中Fe的形态;通过微污染源水的处理评估PSPF的混凝性能。以硫酸亚铁、硅酸钠、磷酸二氢钾、碳酸钠等为原料,确定硅铁摩尔比(n_(Si)/n_(Fe))、磷铁摩尔比(n_p/n_(Fe))与碱化度(n_(OH)/n_(Fe))对PSPF的制备影响。结果显示在60℃水浴30 min条件下,PSPF最优合成条件为:n_(Si)/n_(Fe)为1:4,n_P/n_(Fe)为1:6与n_(OH)/n_(Fe)为1:10。表征分析显示,PSPF是一种高分子聚合物,含有的新基团键(例如,Si—O—Si与Fe—O—Si),其有助于增大PSPF分子量与分子链与增强PSPF的混凝性能;PSPF形貌团簇,呈网状结构,有助于吸附架桥和网捕卷扫;Si含量增加提高了PSPF中Fe(b)和Fe(c)的含量,增强了PSPF的聚合度与固化效果。PSPF的混凝性能受PSPF投加量与水环境pH影响显著;在pH为6与投加量为8 mg·L~(-1)时,残余浊度和UV254去除率分别可达0.33 NTU与58.6%。实验研究显示,混凝剂多因素(Si,Fe与P)调控对增强固体聚硅酸基混凝剂的固化效果、稳定性以及混凝性能具有良好的效果。

The Preparation and Characterization of a New Solid Coagulant:Polymeric Ferric Silicate Sulfate

As one of the most important water treatment agents,polysilicate coagulant,has been playing an important role in co-agulation-flocculation,but it is prone to lose stability due to self-polymerization and the forming of silica gel.Therefore,re-search on the preparation of stable polysilicate coagulant has attract great attention.A new method to prepare a stable polysili-cate coagulant (PSPF),was proposed in this paper.Its structure and morphology were characterized by using Fourier transform infrared (FTIR)spectroscopy and scanning electron microscopy (SEM)respectively.Fe species in PSPF was analyzed via Fe-Ferron complexation timed spectrophotometric method.The performance of PSPF was assessed by measuring micro-polluted wa-ter treatment efficiency.Primary chemicals,such as ferrous sulfate,sodium silicate,potassium dihydrogen phosphate,sodium carbonate,were used.The influence of those parameters affecting the preparation of PSPF,such as n Si/n Fe ,n P/n Fe and n OH/n Fe molar ratios were examined.The results showed that n Si/n Fe of 1 ∶4,n P/n Fe of 1 ∶6 and n OH/n Fe of 1 ∶ 10 under 60 ℃ water bath for 30 min was the optimum condition for preparation.The FTIR spectrum indicated that PSPF was a kind of high molecu-lar polymer,containing new groups (e.g.,Si—O—Si and Fe—O—Si),which could increase the molecular weight,molecular chain and coagulation-flocculation efficiency.PSPF presented a cluster appearance similar to a network structure,which was conductive to adsorption-bridging capacity and precipitation sweeping.The increase of Fe(b)and Fe(c)as a result of Si increas-ing in PSPF improved the polymerization and solidification.The coagulation behaviors of PSPF that were largely affected by the coagulant dosage and pH,indicated that for pH and dosage at 6 and 8 mg·L-1 ,respectively,the residual turbidity and UV254 removal efficiency could achieve 0.33 NTU and 58.6%,respectively.