铁锰原位氧化产物吸附微量磷的实验

Trace Amounts of Phosphorus Removal Based on the in-suit Oxidation Products of Iron or Manganese in a Biofilter

采用小试生物滤池,分别考察了铁和锰离子原位过滤氧化产物吸附去除水中微量磷酸根的特性,并结合SEM/EDS/BET/Zeta电位等分析手段解析了二者对磷酸根的吸附机制.结果表明,铁或锰离子在滤层内氧化的同时,其氧化产物均对磷酸根具有吸附作用;进水铁或锰的去除量与磷酸根的吸附量呈正相关线性关系,其吸附关系分别为106.28μg·mg-1和77.98μg·mg-1.SEM/EDS/BET的分析结果表明,富铁氧化物和富锰氧化物的比表面积分别为96 m2·g-1和67 m2·g-1,前者主要以小颗粒形态在滤层空隙间积累,而后者则以层状或片状形式披覆于滤料表面;反冲洗过程不影响锰氧化过程对磷酸根的吸附,而对铁氧化除磷过程具有促进作用.Zeta等电点和阴离子竞争吸附结果表明,富铁和富锰氧化物吸附磷酸根后,Zeta等电点p H均降低,二者对磷酸根的吸附过程以内层配合吸附作用为主,且氯离子、硫酸根、硝酸根离子对磷酸根的竞争吸附作用影响较弱,属于特异性吸附.

In order to remove trace amounts of phosphorus from water bodies,a lab-scale biofilter was constructed to investigate the capacity of in situ oxidation products of iron or manganese for phosphorus adsorption. SEM,EDS,BET,and zeta technologies were employed to reveal the adsorption mechanisms. The results indicated that phosphorus could be removed by the oxide products generated from the iron or manganese removal process,at 106. 28 μg·mg^-1 and 77. 98 μg·mg^-1,respectively,as shown by the linear relationships between phosphorus removal and the two oxides. SEM,EDS,and BET analysis demonstrated that the BET specific surface areas for the iron-and manganese-rich oxides were 96 m^2·g^-1 and 67 m^2·g^-1,respectively,with the former accumulated between the pore spaces of the filtering sand and easily washed out of the layer by backwashing,whereas the latter coated the surface of the filtering sand. Thus,backwashing was favorable for phosphorus adsorption in the iron oxidation process to avoid overaccumulation.Moreover,the zero point of charge of the two oxides indicated electrostatic attraction may have occurred between iron-rich oxide and phosphorus; however,inner-sphere complex reactions obviously occurred for the two oxides because the zero point of charge after phosphorus adsorption decreased to a lower level. In addition,other anions were negatively complexed with the phosphorus on the surface of the oxides,it demonstrated that phosphorus adsorption on the surface of the two oxides seemed to be a specific adsorption.