不同生物炭对水中氟离子的吸附特征研究

Study on Adsorption Characteristics of Fluorine Ions in Water by Different Biochars

地下水中过高浓度的氟化物会对人体和环境产生较大危害,如何有效去除水体中氟污染备受人们关注。生物炭作为优良的吸附剂已广泛应用于水体污染治理及生态修复领域。选取花生壳、玉米秸秆和枫杨树枝为原料制备生物炭材料,进行了生物炭对水中F−的批量吸附解吸实验,并讨论了其吸附解吸的热力学和动力学过程。利用SEM、BET、FTIR与XRD等方法表征其结构特性。探究了生物炭投加量、溶液pH和平衡温度对生物炭吸附水中F−作用的影响。结果表明,3种生物炭对水体中F−有较强的吸附作用,其吸附和解吸的热力学过程与Langmuir模型拟合有较好的相关性。花生壳生物炭(PB)对溶液中F−的吸附效果最好,其对水体中F−的最大吸附量和解吸量分别可达1.18、0.92 mg·g−1。准二级动力学模型对生物炭吸附F−的过程拟合效果优于准一级动力学模型。总体上,3种生物炭对F−的吸附过程近似于单分子层的化学吸附,且生物炭具有一定的可重复利用的再生能力。PB对F−的吸附作用受生物炭投加量、溶液pH和平衡温度影响。影响因素大小依次为:平衡温度>投加量>pH。当pH值为5.0,平衡温度为25℃,投加量为0.10 g时,PB对F−的去除率可达70.55%。该研究可为探究生物炭对水体氟化物的吸附规律和机理提供基础数据,为含氟水体的污染控制提供理论依据。

Excessive concentration of fluoride in groundwater can impose a serious threat to human health and the environment.The treatment technologies which can effectively remove fluoride in water have attracted people's wide attention.Biochar as an excellent adsorbent has been widely used in the field of water pollution control and ecological restoration.In this study,the Peanut shell,corn straw,and the branch of Pterocarya stenoptera were selected as raw materials to prepare biochar.The adsorption and desorption experiments of F−in water by biochar were carried out,and the mechanism of adsorption and desorption were discussed by thermodynamics and kinetics.The structure and properties of biochar were characterized by SEM,BET,FTIR,and XRD.The effects of biochar dosage,solution pH,and equilibrium temperature in sorption and desorption experiments were investigated.The results have shown that the three biochar had a strong adsorption effect on F−in water,and the adsorption thermodynamic process has a good correlation with the fitting of Langmuir models.Among three biochars,peanut shell biochar(PB)has the best adsorption effect of F−in water,and the maximum adsorption and desorption capacity were 1.18 mg·g−1 and 0.92 mg·g−1,respectively.The adsorption kinetics fitted the pseudo-second order model.In general,F−was adsorbed onto the biochar by chemical interactions via monolayer,and the biochars have a certain renewable capacity.The adsorption capacity of F−by PB was affected by the amount of biochar,pH of solution and equilibrium temperature.The order of influencing factors was:equilibrium temperature>dosage>pH.PB has the best adsorption effect on F−in water and the removal rate of F−can reach 70.55%when the pH value is 5.0,the equilibrium temperature is 25℃,and the biochar dosage is 0.10 g.This study provided the basic data for exploring the adsorption mechanism of fluoride by biochar,and provide the theoretical basis for controlling the fluoride pollution in water.