载镧生物炭对水体氟离子的去除性能

Characteristics of fluoride ion removal from waterbody by lanthanum-loaded biochar

以花生壳为原料、LaCl_(3)·7H_(2)O为镧前驱体,通过一步热解法制备了载镧生物炭(La-BC),确定了最佳制备条件,考察了溶液pH、吸附时间、La-BC投加量、F^(−)初始质量浓度、共存离子等因素对La-BC吸附性能的影响,评估了La-BC在真实地下水中的应用潜能。结果表明:在pH为5~8时,La-BC表现出稳定的除氟性能。吸附过程符合准二级动力学和Langmuir等温线模型;在25℃和35℃下,La-BC的最大理论吸附容量分别为29.50 mg·g^(−1)与33.17 mg·g^(−1)。SO_(4)^(2-)、HCO_(3)^(−)与CO_(3)^(2−)对吸附过程存在不同程度的影响,Cl^(−)、NO_(3)^(−)和NH_(4)^(+)影响较小。加标地下水经酸化预处理后,La-BC对工业园区地下水和农村饮用井水均表现出优异的除氟性能。La-BC上的含镧物种包括La(OH)_(3)、LaOCl、La(OH)_(2)Cl以及少量La_(2)(CO_(3))_(3)和LaPO_(4),其中La(OH)_(2)Cl为主要的除氟活性物种,F^(−)主要通过静电作用和化学沉淀转化为LaF_(3)沉淀去除。

In this work,lanthanum-loaded biochar(La-BC)was prepared by one-step pyrolysis method with peanut shells and LaCl_(3)·7H_(2)O as precursors,and the optimal preparation conditions were determined.The effects of solution pH,adsorption time,La-BC dosage,F^(−)initial concentration and coexisting ions on F^(−)removal were tested.Meanwhile,the application potential of La-BC in real groundwater was evaluated.Results showed that La-BC exhibited a stable F^(−)removal ability at pH 5~8,and the adsorption process conformed to the pseudosecond-order kinetics and Langmuir isotherm model.At 25 and 35℃,the maximum theoretical adsorption capacities of La-BC were 29.50 and 33.17 mg·g^(−1),respectively.Except SO_(4)^(2−),HCO_(3)^(−)and CO_(3)^(2−),the influence of the coexisting anions including Cl^(−),NO_(3)^(−)and NH_(4)^(+)was negligible.After acidification pretreatment of the spiked groundwater samples,La-BC showed an excellent defluorination performance for both industrial park groundwater and rural drinking well water.XRD results showed that the lanthanum-containing species on the La-BC included La(OH)_(3),LaOCl,La(OH)_(2)Cl and a small amount of La_(2)(CO_(3))_(3) and LaPO_(4).F^(−)was removed mainly by reaction with La(OH)_(2)Cl and converted to LaF_(3) by electrostatic interaction and chemical precipitation.