L-半胱氨酸修饰秸秆纤维吸附水体中磺胺甲恶唑行为研究:XPS定性分析和DFT定量计算

Adsorption behavior of sulfamethoxazole onto L-cysteine modified straw fiber:XPS qualitative analysis and DFT quantitative calculation

通过碱化、醚化和接枝反应成功地研制了L-半胱氨酸修饰秸秆纤维(TNCS),并开展材料的表征分析和吸附水体中磺胺甲恶唑(SMZ)的性能测试.同时,结合X射线光电子能谱(XPS)分析和密度泛函理论(DFT)计算具体揭示了TNCS的吸附行为机制.结果显示:pH值对TNCS的吸附性能影响较大,在pH=5时其最大理论吸附容量达到38.51 mg·g^(-1),吸附过程符合Langmuir吸附等温模型和伪二级动力学模型.此外,TNCS具有良好的抗干扰吸附性能和循环再生性能.XPS分析定性地表明了TNCS结构中-NH-、-COOH和-SH基团发挥了重要的化学吸附作用,主要涉及氢键作用、路易斯酸碱中和反应和π+-πEDA相互作用;从不同吸附位点的结合能和电势密度的角度,DFT计算定量地阐明了TNCS的基团与不同形态的SMZ(SMZ+、SMZ0和SMZ-)的作用关系,即当吸附SMZ+时—NH—发挥最主要的作用,而当吸附SMZ0和SMZ-时—COOH的作用最稳定.

L-cysteine modified straw fiber(TNCS)was successfully prepared by alkalization,etherification and grafting reaction,and the characterization and adsorption performance test of sulfamethoxazole(SMZ)from aqueous solution were carried out.Meanwhile,combined with X-ray photoelectron spectroscopy(XPS)analysis and density functional theory(DFT)calculation,the adsorption mechanism of TNCS was revealed in details.The results showed that pH had a remarkable influence on the adsorption performance of TNCS,and its maximum theoretical adsorption capacity reached 38.51 mg·g^(-1) at pH 5.The adsorption process accorded with the Langmuir adsorption isotherm model and the pseudo-second-order kinetic model.In addition,TNCS had favorable anti-interference adsorption and recycling regeneration performance.XPS analysis qualitatively showed that-NH-,-COOH and-SH groups in TNCS exerted crucial influence over chemisorption,mainly involving hydrogen bonding,Lewis acid-base neutralization reaction and π^(+)-πEDA interaction.From the perspective of binding energy and potential density of different adsorption sites,DFT calculation quantitatively elucidated the interaction relationship between TNCS groups and different forms of SMZ(SMZ^(+),SMZ^(0) and SMZ^(-)),i.e.-NH-elaborated the most important effect in SMZ+adsorption,while-COOH performed the most stable role in SMZ0 and SMZ^(-)adsorption.