镁浸渍生物炭吸附氨氮和磷:制备优化和吸附机理

Adsorption of ammonia nitrogen and phosphorus by magnesium impregnated biochar:preparation optimization and adsorption mechanism

利用废弃的木薯杆制备了载镁的生物炭吸附剂。以氨氮、磷为目标污染物,采用控制变量法研究了不同镁盐改性、MgCl2浓度、碳化温度、固液比和碳化时间对氨氮、磷吸附性能的影响,制备最具吸附性能的载镁木薯秆基生物炭(Mg-BC),进行批量吸附氨氮和磷实验。利用等温模型(Langmuir和Freundlich模型)和动力学模型(准一级动力学、准二级动力学和颗粒内扩散模型)探究其吸附特性,在其吸附特性研究的基础上,运用FTIR、XRD、SEM-EDS、XPS等表征手段对其吸附机理进行探讨。结果表明,Mg-BC对氨氮和磷的吸附过程均符合Freundlich模型和准二级动力学模型,为多分子层的化学吸附,理论饱和吸附量分别为43.48 mg·g^-1和96.00 mg·g^-1。结合表征结果推测,Mg-BC吸附氨氮、磷主要通过官能团作用、络合沉淀和离子交换等多过程协同完成。

Magnesium-loaded biochar adsorbent was prepared from waste cassava stalks.The effects of modification of different magnesium salts,MgCl2 concentration,carbonization temperature,solid-liquid ratio and carbonization time on the adsorption of ammonia-nitrogen and phosphorus were studied using the controlled variable method.Samples of magnesium-loaded cassava stalk-based biochar(Mg-BC)using the process with the best adsorption performance were prepared and batch adsorption experiments for ammonia-nitrogen and phosphorus were carried out.The adsorption characteristics were studied using isothermal models(Langmuir and Freundlich model)and kinetic models(quasi-first-order kinetics,quasi-second-order kinetics and intra-particle diffusion model).The adsorption mechanism was also studied using FTIR,XRD,SEM-EDS and XPS.The results show that the adsorption process of ammonia-nitrogen and phosphorus by Mg-BC conforms to the Freundlich model and quasi-second-order kinetic model,and is multilayer chemisorption.The theoretical saturated adsorption capacities were 43.48 mg·g-1 and 96.00 mg·g-1 for ammonia-nitrogen and phosphorus respectively.Combined with the characterization results,it is speculated that magnesium-titanium-based biochar(Mg-BC)adsorbs ammonia nitrogen and phosphorus mainly through functional groups,complex precipitation and ion exchange and other processes.