改性玉米芯生物碳对氨氮的吸附特性

Adsorption characters of ammonium-nitrogen in aqueous solution by modified corn cob biochars

以农业废弃物玉米芯为原料,采用限氧热解法(600℃)制备生物碳,分别采用盐酸、双氧水和硝酸对其进行改性。通过元素分析、FTIR、BET-N2、Boehm滴定法及扫描电镜等手段表征了生物碳的组成与结构。通过序批实验,研究了生物碳对氨氮的吸附性能及影响因素,探讨了其吸附机理,为生物碳在污水处理中更好的应用提供参考。结果表明,未改性生物碳和经过盐酸、硝酸和双氧水改性的生物碳其比表面积分别为17.74、212.89、208.74和209.15 m2·g?1;表面酸性含氧官能团数量分别为0.11、0.95、5.73和2.15 mmol·g?1。等温吸附曲线符合Freundlich方程。动力学研究表明,生物碳对氨氮吸附行为符合准二级动力学方程。且经硝酸改性生物碳由于表面酸性含氧官能团的增加,其对氨氮的吸附能力显著提高。

Biochars produced by pyrolysis of corn cob（600℃） which is agricultural waste, and modified with hydrochloric acid, hydrogen peroxide and nitric acid separately. Elemental analysis, BET-N2 surface area （SA）, scanning electron microscopy, Boehm titration and FTIR spectra were used to characterized their physicochemical properties. Batch experiments were conducted to investigate ammonium adsorption process of corn cob biochars. The results revealed that acid modification can significantly improve biochars＇ specific surface area, which were 17.74, 212.89, 208.74 and 209.15 m2 . g^-1 for without modified and modified with HC1, HNO3 and H202 samples, respectively; while the amounts of acidic functional groups were 0.11, 0.95, 5.73 and 2.15 mmol.g^-1, respectively. The results for fitting experimental data of adsorption process with isotherm models showed that it is better for Freundlich isotherm model than Langmuir isotherm model. Moreover, the adsorption process can be well described by pseudo-second-order kinetic model. The results obtained demonstrated that biochars modified with nitric acid have the highest adsorption capacity because of more acidic functional groups.