镁硅改性烟秆炭吸附特性和能力研究

Study on adsorption characteristics and capacity of Mg/Si modified tobacco stalk carbon

【目的】研究镁硅改性烟秆炭吸附特性和能力,解决水体中过量的氮和磷造成的水体富营养化,并实现废弃生物质烟草秸秆的资源化利用。【方法】将烟草秸秆通过热解制备烟秆生物炭,再由MgCl 2和Na 2 SiO 3对其浸渍改性,用于吸附水体中的氮、磷并研究其吸附特性。【结果】改性后烟秆炭对氮和磷的吸附量分别为4.26和37.93 mg·g-1,分别是改性前的5和11.6倍;改性后烟秆炭镁、硅含量分别是改性前的26.5和4.5倍;烟秆炭的BET测定结果表明,改性提高了烟秆炭的比表面积和平均孔径,孔隙结构更加发达;改性后的烟秆炭出现新的衍射峰,改性引入了新的表面官能团。改性烟秆炭在中性或弱碱性环境下对氮具有较高的吸附能力,吸附磷的pH值范围相对较宽。改性烟秆炭对氮和磷的吸附过程分别符合颗粒内扩散和准二级动力学方程,吸附方式主要为化学吸附;吸附类型均符合Langmuir模型,为单分子层吸附;改性烟秆炭在双溶质溶液中对氮、磷的吸附量相比在单溶质溶液中有显著提升,说明氮和磷在水中共存时对烟秆炭吸附产生协同作用。【结论】镁硅改性烟秆生物炭可以高效去除水体中的氮和磷,是一种高效除氮磷吸附剂。

【Objective】The adsorption characteristics and capacity of Mg/Si modified tobacco stalk carbon were studied to solve the eutrophication caused by excessive nitrogen and phosphorus in water and realize the resource utilization of waste biomass tobacco straw.【Method】This study prepared tobacco stalk biochar by pyrolysis,and then impregnated modified it by MgCl 2 and Na 2 SiO 3 for the adsorption of nitrogen and phosphorus in water to study its adsorption characteristics.【Result】The results showed that the adsorption capacities of nitrogen and phosphorus were 4.26 and 37.93 mg·g-1 after modification,which were 5 and 11.6 times of those before modification.After modification,the contents of magnesium and silicon in tobacco stalk biochar were 26.5 and 4.5 times of those before modification.BET test results showed that the modified tobacco stalk carbon increased the specific surface area and average pore size,and the pore structure was more developed.New diffraction peaks appeared in tobacco stalk biochar and new surface functional groups are introduced by modification.The modified tobacco stalk biochar had high adsorption capacity for adsorption nitrogen under neutral or weakly alkaline environment and relatively wide pH range for adsorption phosphorus.The adsorption processes of nitrogen and phosphorus from modified tobacco stalk biochar conformed to the intra-particle diffusion and second-quasi-order kinetic equations,and the adsorption methods were mainly chemisorption.The adsorption types were consistent with Langmuir model and were monolayer adsorption.The adsorption of nitrogen and phosphorus by modified tobacco straw biochar in two-solute solution had a significant enhancement compared to that in single-solute solution,suggesting a synergistic effect on tobacco straw biochar adsorption when nitrogen and phosphorus coexist in water.【Conclusion】The above results indicate that magnesium-silicon modified tobacco straw biochar can efficiently remove nitrogen and phosphorus from water bodies and is an efficient nitrogen and phosphorus removal adsorbent.