氯化锌改性玉米秸秆生物炭对Cr(Ⅵ)的吸附特性研究

为了提高对废水中Cr （Ⅵ）的去除效率，获得高效且成本低廉的吸附剂，以农业废弃物玉米秸秆为原材料制备生物炭，并采用氯化锌对其进行改性。实验表明，在固液比为2 g/L、pH为2、Cr （Ⅵ）溶液初始质量浓度为100 mg/L、吸附时间为6 h时，最佳改性剂比例条件下改性炭的去除率能够达到99.3%，比未改性的生物炭高73.7%。此外，考察了单一因素改性剂比例、溶液pH、吸附温度、离子强度对吸附效果的影响。同时研究了改性炭对Cr（Ⅵ）的吸附动力学和吸附等温线。结果说明该吸附是自发、熵增的吸热过程且吸附反应符合准二级动力学方程和Langmiur等温模型，最大饱和吸附容量为72.46 mg/g。通过扫描电镜（scanning electron microscopy）、傅里叶红外光谱（Fourier transform infrared spectroscopy）、X射线衍射（X-ray diffraction）等方法对原炭（biochar）和改性生物炭（modified biochar）进行表征，分析表明改性炭微孔结构明显，表面粗糙，吸附位点增加，芳香化程度提高，从而提高了吸附性能，且锌以氢氧化物颗粒形式存在于生物炭表面。

Study on adsorption property of Cr(VI) by zinc chloride modified corn stalk biochar

To improve the removal efficiency of chromium in the water and obtain a kind of adsorbent with low-cost and high efficiency, corn stover biochar was produced and modified by zinc chloride(ZnCl₂). The experimental results show that when the dosage of modified carbon is 2 g/L, the initial pH is 2, the initial concentration of Cr(VI) is 100 mg /L and the adsorption time is 6 h,the Cr(VI) removal rate can reach 99.3% under the optimal modifier ratio, which is 73.7% higher than that of unmodified biochar. Furthermore, the effects of single factors such as modifier ratio, solution pH, adsorption temperature and ionic strength on the adsorption performance were investigated. The adsorption kinetics and adsorption isotherms of modified carbon on Cr(VI) were also studied. The results indicate that the adsorption is a spontaneous endothermic process and the adsorption reaction is in accordance with the quasi-second-order kinetic equation and the Langmiur isothermal model. The maximum saturated adsorption capacity is 72.46 mg/g. The biochar(BC) and modified biochar(MBC) were characterized by scanning electron microscopy(SEM), Fourier transform infrared spectroscopy(FTIR) and X-ray diffraction(XRD). The analysis shows that the surface of the modified carbon is rough with obvious microporous structure, increased adsorption sites and aromatization, thereby improving the adsorption performance, and zinc is present on the surface of the biochar as hydroxide particles.