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羟基磷灰石(HAP)是一种高容量、环保型饮用水除氟材料。以氢氧化钙和磷酸为原料采用沉淀法合成了羟基磷灰石,并用红外光谱和XRD图谱进行了表征。研究了接触时间、pH值和温度等因素对羟基磷灰石吸附氟性能的影响。通过对吸附过程中的热力学动力学参数的计算来判断吸附的实质过程。研究结果表明,60 min以内吸附速率较快,在约70 min时吸附过程趋于平衡;酸性环境中的吸附效果要比在碱性环境中要好;升高温度有利于吸附的进行。吸附过程更符合Langmuir吸附模型,说明化学吸附占主导地位;吸附过程是一个自发的吸热过程,其中ΔGo<0,ΔHo为13.10 kJ/mol,Ea为15.24 kJ/mol,ΔSo为31.42 J/(mol.K);吸附过程符合拟二级动力学模型。
Hydroxyapatite (HAP) is a high-capacity, environmentally friendly drinking water fluoride removal material. Hydroxyapatite was synthesized by precipitation method using calcium hydroxide and phosphoric acid as raw materials, and characterized by IR and XRD. The effects of contact time, pH value and temperature on the adsorption capacity of hydroxyapatite were investigated. Through the calculation of thermodynamic kinetic parameters in the adsorption process to determine the adsorption process. The results showed that the adsorption rate was faster within 60 min, and the adsorption process tended to be balanced at about 70 min. The adsorption in acidic environment was better than that in alkaline environment. The higher temperature was favorable for the adsorption. The adsorption process is more consistent with the Langmuir adsorption model, indicating that chemisorption predominates. The adsorption process is a spontaneous endothermic process with ΔGo <0, ΔHo of 13.10 kJ / mol, Ea of 15.24 kJ / mol and ΔSo of 31.42 J / mol.K). The adsorption process accords with the second-order kinetic model.