住房和城乡建设部科学技术项目计划(2012 k7 21);国家水体污染控制与治理科技重大专项(2009ZX07212 002 004 003);国家自然科学基金资助项目(50830303)
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 192h and the adsorption capacity is higher than 16.06 mg/g when the temperature is 20℃, particle size is 0.51.0mm and the initial concentration is 100mg/L. The acid activation of HPC can enhance phosphate removal and the adsorption capacity of HPC subject to the treatment of 0.25 mol/L of hydrochloric acid, resulting in the adsorption capacity increased to 18.54 mg/g. Adsorption capacity of HPC with particle size of 2.03.0 mm is better than that of 0.51.0 mm and 5.06.0 mm. Kinetics data are fitted with pseudo second order model, the behaviour of phosphate adsorption on the particle of HPC could be appropriately 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 ΔH is 7.56 kJ/mol, the entropy ΔS is 0.0416kJ/（mol·K） and the Gibbs free energy ΔG 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.