赵天赐,周世真,马小龙,马子川.负载铁锰氧化物的玉米芯炭对Pb2+的吸附作用[J].环境科学学报,2019,39(9):2997-3009
负载铁锰氧化物的玉米芯炭对Pb2+的吸附作用
- Study on the adsorption of Pb2+ by MnFeOx-loaded corncob biochar
- 基金项目：国家重点研发计划项目（No.2018YFC0506901）；河北省自然科学基金（No.B2017205146）
- 赵天赐
- 河北师范大学化学与材料科学学院, 石家庄 050024
- 周世真
- 河北师范大学生命科学学院, 石家庄 050024
- 马小龙
- 河北师范大学生命科学学院, 石家庄 050024
- 马子川
- 1. 河北师范大学化学与材料科学学院, 石家庄 050024;2. 河北省无机纳米材料重点实验室, 石家庄 050024
- 摘要：采用两步浸渍-草酸盐热解法制备了均匀负载铁锰氧化物的磁性玉米芯炭（MnFeOx@CCBC），通过X射线衍射（XRD）、扫描电子显微镜（SEM）、比表面积分析仪和pH漂移实验等表征，证明制备的MnFeOx@CCBC材料表面由MnFe2O4和无定形态的δ-MnO2或水合氧化锰组成，pHZPC约为6.0，比表面积为3.9 m2·g-1.同时，比较研究了MnFeOx@CCBC和原始玉米芯炭（CCBC）对Pb2+的吸附动力学和热力学行为.结果表明：吸附过程均符合准二级动力学方程和Langmuir等温吸附模型，在实验条件下，MnFeOx@CCBC对Pb2+的吸附速率和吸附量都明显优于CCBC，准二级动力学速率常数大3.3倍，理论平衡吸附量高6.95倍；在30℃时，MnFeOx@CCBC和CCBC的饱和吸附量分别为99.60和15.66 mg·g-1；Pb2+的吸附过程是熵驱动和吸热的.傅里叶变换红外光谱（FTIR）和X射线光电子能谱（XPS）等分析表明，MnFeOx@CCBC的主要吸附位是Mn—OH，其主要吸附机理是Pb2+对Mn—OH中H+的置换，并形成内层表面络合物.
- Abstract：Magnetic MnFeOx-loaded corncob biochar (MnFeOx@CCBC) was obtained by combining two-step impregnation of corncob biochar (CCBC) with the pyrolysis of oxalate. MnFeOx@CCBC and CCBC were characterized by XRD, SEM, specific surface area as well as by the measurements of pHZPC. The results revealed that Fe-Mn binary oxide is composed of microcrystal MnFe2O4 and amorphous δ-MnO2/hydrous manganese oxide which cover uniformly on the surface of CCBC. The as-prepared MnFeOx@CCBC demonstrates a pHZPC of about 6.0 as well as a specific surface area of 3.9 m2·g-1. The adsorption dynamics and thermodynamic behavior of MnFeOx@CCBC and CCBC for Pb2+ were investigated. The results showed that the adsorption of Pb2+ by MnFeOx@CCBC or CCBC is completely consistent with the pseudo-second-order kinetics model and the Langmuir model could correctly describe the adsorption isotherms. Under the experimental conditions, MnFeOx@CCBC displayed excellent performance in both the adsorption rate and adsorption capacity towards Pb2+, in which the fitted rate constant (k2) and equilibrium adsorption capacity (qe) were 3.3-fold and 6.95-fold, respectively higher than CCBC. From Langmuir isotherms, maximum adsorption capacity (qm) of MnFeOx@CCBC and CCBC towards Pb2+ was determined at various temperatures, which indicates that qm increases with an increase in temperature, which were 99.60 mg·g-1 of MnFeOx@CCBC and 15.66 mg·g-1 of CCBC at 30 ℃. The thermodynamic parameters exhibited that the adsorption process of both materials was endothermic and entropy driven. XPS and FTIR analysis revealed that the adsorption mechanism could mainly be ascribed to the replacement of Pb2+ for H+ in Mn—OH as the predominant adsorption site of MnFeOx@CCBC to form the inner surface complexes.
