海藻酸钠对鸟粪石结晶的影响及机理研究

摘要

鸟粪石结晶沉淀法回收剩余污泥中磷工艺具有良好应用前景,然而污泥中的一些有机物,特别是胞外聚合物(EPS)将对鸟粪石结晶产生一定的影响.海藻酸钠(SA)在物化性质上接近于EPS,为较深入地探究此影响机理,以SA作为EPS的代用化合物采用恒组分、恒pH实验来考察EPS对鸟粪石结晶的影响,并借助红外光谱(FTIR)和X射线光电子能谱(XPS)分析来探讨SA与鸟粪石晶体之间的作用机理.结果表明,在SA浓度0～250mg/L范围内,随其浓度的增大鸟粪石结晶生长速率降低,鸟粪石晶体的尺寸有所减小,其原因是海藻酸阴离子吸附并掩蔽鸟粪石表面生长活性点上阻碍晶体生长.这种吸附作用是由鸟粪石表面Mg2+、磷酸羟基团(POH)分别与SA中COOH、C=O、COC键合共同引起的,而鸟粪石表面的NH4+并未参与反应.%The recovery of phosphorus from excess sludge by the crystallization of struvite has a good prospect. However, it may be influenced by some organic matter in excess sludge, especially by extracellular polymeric substances (EPS). To elucidate the effect mechanism of EPS, struvite crystallization from supersaturated solutions was investigated in the presence of sodium alginate (SA) presenting similar properties to EPS based on the characterization of Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis. The results indicated that the growth rate and crystal size of struvite crystals significantly decreased with an increase of the SA concentration in a range of 0mg/L to 250mg/L. This phenomenon was assigned to the adsorption of SA on the growth site of struvite. Moreover, the adsorption was attributed to the interaction between Mg2+, POH in struvite crystals and the groups of COOH, C=O, COC in SA, whereas NH4+ was not involved in the interaction.