水化普通硅酸盐水泥颗粒吸附水中磷酸盐研究

Behavior of Phosphate Adsorption to the Hydrated Ordinary Portland Cement

以水化普通硅酸盐水泥颗粒为吸附剂,研究了时间、温度和粒径等因素对其吸附PO34-效果的影响.结果表明:在20℃,粒径0.51.0mm,初始PO34-质量浓度100mg/L条件下,水化普通硅酸盐水泥颗粒吸附平衡时间为192h,平衡吸附量高达16.06mg/g;经0.25mol/L盐酸活化后,水化水泥颗粒对PO34-的平衡吸附量增至18.54mg/g;粒径2.03.0mm的颗粒对PO34-的吸附效果优于0.51.0mm和5.06.0mm的颗粒.吸附过程遵循假二级动力学模型,符合Freundlich等温方程.热力学解析的结果表明:酸活化水化水泥颗粒吸附PO34-时焓变ΔH=7.56kJ/mol,熵变ΔS=0.041 6kJ/(mol.K);4,20℃的吉布斯自由能ΔG分别为-3.98,-4.65kJ/mol;酸活化水化水泥颗粒对PO34-的吸附是一个以吸热、化学吸附为主,熵推动且自发的过程.

Effects of time, temperature and particle size on phosphate adsorption by the hydrated ordinary Portland cement（HPC） were studied. The results show that the adsorption equilibrium reach in 192 h and the adsorption capacity is higher than 16.06 mg/g when the temperature is 20℃, particle size is 0. 5 - 1.0 mm and the initial concentration is 100 mg/L. The acid activation of HPC can enhance phosphate re- moval and the adsorption capacity of HPC subject to the treatment of 0.25 mol/L of hydrochloric acid, re- sulting in the adsorption capacity increased to 18.54 mg/g. Adsorption capacity of HPC with particle size of 2.0-3.0 mmis better than that of 0.5-1.0 mmand 5.0-6.0 mm. Kinetics data are fitted with pseu- do-second-order model, the behaviour of phosphate adsorption on the particle of HPC could be appropri- ately fitted as Freundlich isotherm. Results of thermodynamic analysis on the phosphate adsorption to the particle of HPC subjected to the acid activation indicated that the adsorption heat AH is 7.56 kJ/mol, the entropy AS is 0. 041 6 kJ/（mol K） and the Gibbs free energy AG at 4 ℃and 20 ℃ are --3.98 kJ/mol and--4.65 kJ/mol, respectively. It means that the adsorption is an endothermic and spontaneous process with entropy increase and chemisorption.