玉米秸秆生物炭对水中氨氮的吸附特性

Adsorption Characteristics of Ammonium onto Biochar Derived from Corn Straw

采集农林废弃物玉米秸秆制备生物炭,以批平衡试验法研究了溶液pH、粒径、投加量、温度和共存阳离子等因素对玉米秸秆生物炭吸附氨氮的影响.结果表明：在共存离子Na^＋、Ca^2＋浓度相同条件下对氨氮吸附影响大小顺序为Na^＋〉Ca^2＋;玉米秸秆生物炭对氨氮吸附的最佳pH范围为5-8;吸附动力学数据拟合结果发现准二级动力学方程能更好地拟合吸附过程,颗粒内扩散方程拟合结果表明玉米秸秆生物炭对氨氮的吸附速率由表面吸附和颗粒内扩散两个过程综合控制.Langmuir-Freundlich方程能很好地描述氨氮在玉米秸秆生物炭上的吸附行为,由Langmuir拟合所得的氨氮理论最大吸附量为3.4849 mg·g^-1.吉布斯自由能变化（ΔG^θ）、焓变（ΔH^θ）和熵变（ΔS^θ）的计算结果表明,玉米秸秆生物炭对氨氮的吸附是自发的放热过程.

The adsorption of ammonium to corn straw biochar produced at 400 ℃ was quantified.Static batch experiments were conducted to investigate the effects of various parameters such as solution pH,particle size,adsorbent dosage,temperature and competitive cations during the ammonium adsorption process.The results showed that the effect of other cations on the adsorption of ammonium followed the order of preference Na^＋〉Ca^2＋at identical concentrations.The optimum pH range for ammonium adsorption by corn straw biochar was found to be 5-8.Kinetic data correlated well with the pseudo-second-order kinetic model,and Intra-particle model also showed that there are two separate stages in sorption process,namely,external diffusion and the diffusion of inter-particle.The adsorption of ammonium on corn straw biochar could be described well by Langmuir-Freundlich isotherm equation.The maximum adsorption capacity estimated from the Langmuir equation was 3.484 9mg·g^-1.Thermodynamics parameters such as free energy（ΔG^θ）,enthalpy（ΔH^θ）and entropy（ΔS^θ）were also calculated.Based on the results,it can be concluded that the adsorption is a spontaneous and exothermic process.