牛粪生物炭对磷的吸附特性及其影响因素研究

以牛粪生物炭为吸附剂,采用平衡吸附法研究了牛粪生物炭对磷的吸附特征.研究了pH值、共存离子、反应温度、投加量、热解温度等对牛粪生物炭吸附磷的影响.结果表明,牛粪生物炭吸附磷的最佳初始pH值为7.0;共存离子的存在对生物炭吸附磷的影响有限;反应温度升高不利于磷的吸附;当投加量为0.1g时,对磷的去除率较为理想;热解温度升高不利于对磷的吸附.通过对实验数据进行动力学、吸附等温线及热力学分析,发现牛粪生物炭对磷的吸附动力学数据符合拟二级吸附动力学方程,Langmuir-Freundlich(R2=0.9705)和Temkin(R2=0.9556)方程能很好地描述磷在牛粪生物炭上的吸附行为.热力学分析结果显示25,35,45℃下的吉布斯自由能变化(ΔG0)分别为-17.43,-15.98,-15.89kJ/mol,表明牛粪生物炭对磷的吸附是自发的过程.

Characteristics phosphate adsorption onto biochars derived from dairy manure and its influencing factors

Characteristics phosphate adsorption onto biochars derived from dairy manure was investigated by batch adsorption experiments, and the influences of pH, coexisting anions, temperature, dosage of biochar, and pyrolysis temperature on the phosphate adsorption were studied. The results indicate that the optimal initial pH value for phosphate adsorption was 7.0, and low temperature favored the adsorption of phosphate. The coexisting anions had little effect on the adsorption and the optimal dosage of biochar for removing phosphate was 0.1g. The adsorption kinetic was well described by Pseudo-second kinetic model, whereas adsorption isotherm results elucidated that Langmuir-Freundlich (R2=0.9705) and Temkin (R2=0.9556)model provided the best fit for the equilibrium data. Furthermore, with regard to thermodynamic parameters, it was found that Gibbs free energy change or adsorption energy (ΔG0), -17.43at 25℃, -15.98at 35℃, and -15.89kJ/mol at 45℃ is negative indicating the spontaneous nature of the adsorption process.