Data from: Simultaneous removal of fluoride and arsenic in geothermal water in Tibet using modified yak dung biochar as an adsorbent

Fluoride (F) and arsenic (As) are two typical and harmful elements that are found in high concentrations in geothermal water in Tibet. In the present work, yak dung, an abundant source of biomass energy in Tibet, was made into biochars (BC1, BC2 and BC3) by pyrolysis under different conditions, and the better biochar was modified by FeCl2 (Fe-BC3). The adsorption conditions were optimized to adsorb F and As in geothermal water. The results showed that BC3 can remove 90% F- and 20% As(V), which is the best effect of the three initial biochars. Fe-BC3 could remove 94% F- and 99.45% As(V) under the same conditions as BC3, which was an adsorbent dosage 10 g/L, pH 5-6 and temperature of 25 °C. It was also demonstrated that the removal rate did not decrease at 80 °C. A quasi-second-order kinetic model best described the adsorption behavior of ions on the surface of the biochar. The maximum adsorption capacity of F- and As(V) on Fe-BC3 was 3.928 mg/g and 2.926 mg/g, respectively. The features of Fe-BC3 were characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR), Brunauer-Emmett-Teller (BET), Energy Dispersive Spectrometer (EDS), and Scanning Electron Microscopy (SEM) to understand the adsorption process.

氟（F）与砷（As）是两类典型有害元素，在西藏地热水中浓度偏高。本研究以西藏储量丰富的生物质能源原料牦牛粪为对象，通过不同热解工艺制备了三种生物炭（biochars，BC1、BC2、BC3），并选取吸附效果最优的生物炭经氯化亚铁（FeCl₂）改性得到Fe-BC3。为吸附地热水中的氟与砷，研究团队优化了吸附工艺条件。实验结果表明，未改性的BC3对氟离子（F⁻）与五价砷（As(V)）的去除率分别可达90%与20%，为三种初始生物炭中吸附性能最佳者。在吸附剂投加量10 g/L、pH值5~6、反应温度25℃的相同实验条件下，Fe-BC3对氟离子与五价砷的去除率分别提升至94%与99.45%。进一步验证发现，该吸附体系在80℃下仍未出现去除率下降的情况。准二级动力学模型可最优拟合离子在生物炭表面的吸附行为。Fe-BC3对氟离子与五价砷的最大吸附容量分别为3.928 mg/g与2.926 mg/g。为深入解析吸附过程机制，本研究通过X射线衍射（X-Ray Diffraction, XRD）、傅里叶变换红外光谱（Fourier Transform Infrared, FTIR）、布鲁诺尔-埃米特-泰勒比表面积分析法（Brunauer-Emmett-Teller, BET）、能量色散光谱（EDS）以及扫描电子显微镜（SEM）对Fe-BC3的物化特性进行了表征。