铁锰氧化物/生物炭复合材料对水中硝酸根的吸附特性  

Characteristic of Nitrate Adsorption in Aqueous Solution by Iron and Manganese Oxide/Biochar Composites

作　　者：郑晓青[1] 韦安磊[1] 张一璇[1] 史良于 张潇[1] 

机构地区：[1]西北大学城市与环境学院,西安710127

出　　处：《环境科学》2018年第3期1220-1232,共13页Environmental Science

基　　金：国家自然科学基金项目(51208424)

摘　　要：热解经过氯化铁和高锰酸钾浸渍的小麦秸秆,制备铁锰金属氧化物/生物炭复合材料,用以去除水中硝酸根.通过X射线光电子能谱和扫描电镜分析,发现复合材料表面形成了Fe(Ⅲ)/Mn(Ⅳ)二元金属氧化物颗粒.制备优化结果表明,复合材料比表面积可达153.116 m2·g-1,零电荷点可达9.76.同时,还调查了固液比、溶液初始pH值和共存阴离子等因素的影响.研究发现,复合材料在溶液pH值1.00~9.05时对NO-3的去除率维持在75.40%~78.70%,且以配位交换为主要吸附机制.共存阴离子对吸附NO-3竞争吸附的影响顺序为:Cl->SO2-4>PO3-4.等温吸附实验数据符合Langmuir方程,且最大吸附量为37.361 3 mg·g-1.吸附动力学分析发现,吸附过程遵循二级动力学方程,且以化学吸附为主.热动力学分析表明,吸附过程为自发吸热过程.上述结果说明铁锰氧化物/生物炭复合材料对于去除水中NO-3具有潜在价值.In this study,we synthesized Fe/Mn bimetallic oxide coated biochar sorbents by pyrolysis of wheat straw impregnated with ferric chloride and potassium permanganate and investigated their potential to adsorb nitrate in water. X-ray photoelectron spectroscopy and scanning electron microscopy analysis suggests that Fe（Ⅲ）/Mn（Ⅳ） bimetallic oxide particles emerge on the sorbents. The optimized sorbent could achieve a specific surface area of 153. 116 m2·g^-1 and a point of zero charge of 9. 76. Batch nitrate adsorption experiments were carried out to investigate the influence of various factors,such as sorbent dosage,initial solution pH,and co-existing anions. Results show that the sorbent maintained a high adsorption capacity of 75. 40%-78. 70% over a wide range of pH from 1. 00 to9. 05,and the sorption mechanism was interpreted as ligand exchange. The effects of co-existing anions on the nitrate sorption followed the decreasing order of Cl- SO2-4 PO3-4. Furthermore,the adsorption isotherms were well described by the Langmuir model,and the sorbent could exhibit a quite competitively high capacity of 37. 361 3 mg·g^-1 for nitrate removal. In addition,the accordance of sorption kinetics with the pseudo-second order model implied that the sorption could be a multi-stage controlled chemical process. In addition,the thermodynamic parameters suggested that the sorption reaction could be a spontaneous and endothermic process. The results demonstrated that the Fe/Mn bimetallic oxide coated biochar could serve as a promising agent for nitrate removal from water.

关 键 词：生物炭 铁锰氧化物 硝酸根 吸附动力学 等温吸附 

分 类 号：X52[环境科学与工程—环境工程]