生物炭/铁酸镧磁性复合材料的制备及对亚甲基蓝的吸附性能

为获得吸附性能良好、便于回收利用的新型吸附剂以处理染料废水,采用超声辅助溶胶-凝胶法将铁酸镧(LaFeO3)经过一步热解负载于生物炭制得生物炭/LaFeO3磁性复合材料(BC/FL)。其表面形态、结构和组成分析表明:BC/FL的比表面积、总孔容及平均孔径分别为34.67m2/g、0.041cm3/g和7.82nm,磁饱和强度达到40.283A/m,表面含有C=O、C=C=N、C≡C等官能团。批量吸附实验表明,25℃下,当亚甲基蓝(MB)的初始质量浓度为30mg/L时,BC/FL的最佳投加量为1.5g/L,吸附反应在120min达到平衡,去除率可达92.3%,且吸附效果基本不受pH影响。BC/FL对MB的吸附符合准二级动力学模型,Langmuir模型可描述其等温吸附过程。化学吸附占主导地位,主要机理为静电吸附、氢键和π-π共轭作用。吸附反应为单分子层吸附且为自发的吸热过程。

Preparation of biochar/LaFeO3 magnetic composite material and adsorption properties for methylene blue

In this study,biochar/LaFeO3 magnetic composite material(BC/FL),a new adsorbent with good adsorption performance and easy recycling capability to dispose dye wastewater,was synthesized by ultrasoundassisted sol-gel method,with LaFeO3 loaded on biochar through one step pyrolysis.The characterization of composition,morphology and structure indicated that the specific surface area,total pore volume and average pore diameter were 34.67 m2/g,0.041 cm3/g and 7.82 nm,respectively,and the saturation magnetization could reach40.283 A/m.At the same time,C=O,C=C=N and C≡C were observed on the material surface.Batch experiment results showed that the optimum dosage of BC/FL was 1.5 g/L at 25℃ when the initial concentration of methylene blue(MB)was 30 mg/L.When adsorption reaction reached equilibrium in 120 min,the removal rate of MB could reach 92.3% and pH had little impact on the adsorption effect during this process.The adsorption of MB on BC/FL conformed to the quasi-second-order kinetic model,and Langmuir model could be used to describe the isothermal adsorption process.Chemical adsorption played a dominant role among many mechanisms,such as electrostatic adsorption,hydrogen bond and π-π conjugate.Moreover,the adsorption took place in monolayer and was an endothermic and spontaneous process.