改性芦苇生物炭对水中硫酸盐的吸附性能及机理

水中过高浓度硫酸盐赋存会对水生环境产生一定的影响。为此，选取芦苇秸秆作为生物炭原料，通过添加煤矸石共热解对生物炭进行了改性，采用扫描电子显微镜(SEM)、氮气吸附脱附法(BET)和傅里叶红外光谱(FTIR)等手段对生物炭的物理化学性质进行了分析，考察了pH、吸附剂投加量、吸附时间和初始浓度对水中硫酸盐吸附性能的影响。结果表明：改性后生物炭(MBC)的吸附效果优于未改性生物炭(OBC)；MBC的粗糙程度大于OBC，MBC拥有更大的比表面积和更多的孔隙结构，其比表面积为改性前的2.4倍；对吸附过程进行吸附动力学和吸附等温模型拟合，发现准一级动力学模型和Langmuir模型可以更好的描述MBC对硫酸盐的吸附行为，表明吸附过程以静电吸附和单分子层吸附为主。当pH为2、投加量为8 g·L^-1时改性材料吸附效果最好，最大吸附量可达29.69 mg·g^-1，且经过5次再生吸附后，硫酸盐去除率仍能达到50%以上。因此，改性后的生物炭可作为去除水体中硫酸盐的良好材料。

Adsorption performance and mechanism of modified reed biochar towards sulfate in water

Excessive sulfate concentration in water will have a certain impact on the aquatic environment. In this study, reed straw was selected as the raw material of biochar, and the biochar was modified by co-pyrolysis with addition of coal gangue. The physicochemical properties of biochar were analyzed by means of scanning electron microscope (SEM), nitrogen adsorption desorption (BET) and Fourier infrared spectroscopy (FTIR). The effects of pH, adsorbent dosage, adsorption time and initial concentration on the adsorption performance of sulfate in water were investigated. The results showed that the adsorption effect of modified biochar (MBC) was better than that of unmodified biochar (OBC); The roughness of MBC was greater than that of OBC, and MBC had larger specific surface area and more pore structure, and its specific surface area was 2.4 times of that before modification; The adsorption kinetics and adsorption isotherm model fitting of the adsorption process showed that the quasi-first-order kinetic model and Langmuir model could better describe the adsorption behavior of MBC to sulfate, indicating that the adsorption process was dominated by electrostatic adsorption and monolayer adsorption. When the pH was 2 and the dosage was 8 g·L-1, the modified material had the best adsorption effect, and the maximum adsorption amount could reach 29.69 mg·g-1. After five times of regeneration adsorption, the sulfate removal rate could still reach higher than 50%. Therefore, the modified biochar can be used as a good material to remove sulfate from water.