纳米生物炭对铵态氮的吸附-解吸效果研究

Study on Adsorption-desorption Effects of Nano-biochar on Ammonium Nitrogen

为研究纳米生物炭对铵态氮的吸附-解吸效果,以稻草秸秆为原料制得本体生物炭,并采用球磨法制备纳米生物炭,通过室内吸附-解吸试验与模型模拟相结合的方法开展研究。结果表明:相对于本体生物炭,纳米生物炭对铵态氮的吸附-解吸效果均表现出极显著的优势。纳米生物炭对铵态氮的吸附量随其投加量和初始溶液氮浓度的增大呈增加趋势,随后趋于平衡;其在pH为7的条件下对铵态氮的吸附效果最好;吸附时间为210 min时,吸附反应达到动态平衡。纳米生物炭对铵态氮的最大吸附量为6.91 mg/g,是相同条件下本体生物炭吸附量的2倍。纳米生物炭对铵态氮的吸附等温线和吸附动力学过程更适合用Langmuir方程和准二级动力学方程描述。纳米生物炭在解吸时间为240 min时,解吸反应达到动态平衡。纳米生物炭最大解吸量为6.051 mg/g,是相同条件下本体生物炭解吸量的1.9倍。准二级动力学方程能更好地描述纳米生物炭对铵态氮的动态解吸过程。纳米生物炭对铵态氮的吸附主要为单分子层吸附,以化学吸附方式为主,解吸过程可以看作是吸附反应的逆向过程。研究结果可为田间施用纳米生物炭减少氮素流失、提高氮肥利用率提供理论依据。

In order to study the adsorption-desorption effect of nano-biochar on ammonium nitrogen, bulk biochar was prepared from rice straw, nano-biochar was prepared by ball milling method, and the study was carried out by adsorption and desorption experiment combined with model simulation. The results showed that the adsorption-desorption effects of nano-biochar on ammonium nitrogen showed significant advantages compared with bulk biochar. The adsorption capacity of nano-biochar for ammonium nitrogen improved with the increase of their dosage and initial solution nitrogen concentration, followed by a stable trend. The best adsorption effect of nano-biochar on ammonium nitrogen were found at pH 7 and the adsorption reaction equilibrium time of nano-biochar was 210 min. The maximum adsorption capacity of nano-biochar for ammonium nitrogen were 6.91 mg/g, which was twice that of bulk biochar under the same conditions. The isothermal adsorption and adsorption kinetics of ammonium nitrogen by nano-biochar could be better described by the langmuir equation and quasisecond-order kinetic equation. The desorption reaction equilibrium time of nano-biochar were 240 min. The maximum desorption capacity of nano-biochar was 6.051 mg/g, which was 1.9 times of that of bulk biochar under the same conditions. The dynamic desorption process of ammonium nitrogen by nano-biochar could be better described by the quasi-second-order kinetic equation. In conclusion, the adsorption characteristics of ammonium nitrogen by nano-biochar was mainly single-molecular layer adsorption, mainly in the form of chemical adsorption, and the desorption process could be regarded as the reverse process of the adsorption reaction. This study can provide theoretical basis for reducing nitrogen loss and improving nitrogen use efficiency by applying nano-biochar in field.