改性钢渣吸附氨氮和磷的特性研究

利用钢渣与氢氧化铝以4∶3质量配比混合,在700℃下进行2 h煅烧,得到改性钢渣。通过批次吸附实验,研究了改性钢渣在不同初始pH值、振荡时间和温度下对水溶液中氨氮和磷酸根的吸附情况,进而分析了改性钢渣对氨氮和磷酸根的吸附等温线、热力学和动力学特性。结果表明,改性钢渣脱氮除磷能力比原钢渣显著增强,且最适pH值为4～8。改性沸石对氨氮和磷酸盐的吸附均符合Langmuir等温吸附方程,氨氮(以N计)最大吸附量在10、20和30℃下分别为1.67、2.59和3.24 mg/g,磷酸根(以P计)的最大吸附量在10、20和30℃下分别为1.02、1.19和1.37 mg/g。热力学参数ΔG0、ΔH0和ΔS0表明,该吸附是一个自发、吸热、熵增型反应过程,且磷的吸附是化学吸附为主,氨氮的吸附是以离子交换吸附和物理吸附为主。改性钢渣对磷和氨氮的吸附动力学符合伪二级方程(R2>0.999)。

Adsorption characteristic of modified steel-making slag for simultaneous removal of phosphorus and ammonium nitrogen from aqueous solution

A modified steel-making slag was prepared from mixture of steel-making slag with Al(OH)3(4∶ 3 mass ratios) calcined at 700 ℃.Effects of initial pH,contact time and temperature on adsorption of NH+4 and PO3-4 were investigated by batch experiments.And the adsorption characteristics of NH+4 and PO3-4 from aqueous solution onto modified steel slag were studied.The results showed that the adsorption capacity of modified steel slag could exceed clearly those of untreated slag.The optimum pH range was 4~8.The adsorption of NH+4and PO3-4 follows the Langmuir isotherm model,and the maximum adsorption capacities of NH+4 was 1.67,2.59 and 3.24 mg/g at 10,20,30 ℃ respectively,and the maximum adsorption capacities of PO3-4 was 1.02,1.19,1.37 mg/g,as well.And the thermodynamic parameter of ΔG0,ΔH0 and ΔS0 values showed that the adsorption process was a spontaneously endothermic process,and implied that PO3-4 adsorption might be chemisorption,and NH+4 adsorption might be exchange adsorption and physisorption.The NH+4 and PO3-4 adsorption by the modified steel-making slag fit well with the pseudo second-order kinetics.