盾构渣土基碳复合陶粒的制备及除磷性能

Phosphate Removal by Using Shield Residues/Carbon Composite Ceramsite

以固体废弃物地铁盾构渣土、稻草秸秆和氧化镁为主要原料,通过烧结法制备了一种盾构渣土基碳复合陶粒。考察了陶粒吸附磷的主要影响因素及平衡吸附量,并采用模型对实验数据进行拟合分析。结果表明,当盾构渣土、稻草秸秆粉末和氧化镁质量比为7∶2∶1,在最佳烧结条件700℃烧结可得到除磷性能最佳的陶粒。当吸附pH=6.3时,陶粒具有较高的磷吸附性能。吸附在12 h内基本能达到吸附平衡,该过程适合准二级动力学方程。盾构渣土基碳复合陶粒对磷酸盐的吸附符合Temkin等温模型,随温度升高吸附量逐渐增大,40℃下最大吸附量为12.76 mg/g。热力学参数ΔH=5.64 k J/mol>0,ΔS=8.00 J/(K·mol)>0,ΔG=3.16 k J/mol>0,呈吸热、非自发的热力学特征,陶粒吸附磷后可通过2.0 mol/L的氢氧化钠溶液重新解吸回收。

Composite ceramsite was prepared by sintering solid waste residue of shield residues, powdered rice straw and magnesium oxide. The effects of pH, sorption time and temperature were investigated. The results show that the optimal sintering temperature of the composite ceramsite is 700℃ with the mass ratio of shield residue to powdered rice straw and to magnesium oxide as 7：2： 1. The optimum adsorption pH is 6.3, and phosphate can reach adsorption equilibrium within 12 hours. The Lagergren pseudo second order kinetics and the Temkin isotherm model fit the experimental data well. The adsorption capacity increases with increasing the sorption temperature, and the maximum adsorption of ceramsite is 12. 76 mg/g at 40℃. The adsorption is confirmed as a nonspontaneous endothermic process according to the results of ΔH = 5.64 kJ/mol 〉0, AS = 8.00 J/（ K·mol） 〉 0, AG = 3.16 kJ/mol 〉 0. Meanwhile, the adsorbed phosphate on ceramsite can be recovered by using 2. 0 mol/L NaOH.