LDH层间限域生长PBA催化PMS降解磺胺嘧啶研究

Degradation of sulfadiazine by PMS activated with PBA synthesized in confined space of LDH interlayers

为了探讨PBA-LDH/PMS体系对磺胺嘧啶的降解性能、影响因素以及机理,运用共沉淀法制备出Mg/Al–LDH水滑石,再利用Na Cl-HCl法在氮气保护下去除Mg/Al–LDH层间部分的CO32-,使得PBA前驱物[Co(CN)6]3-更易置换LDH层间的Cl-,最后在LDH层间生成钴普鲁士蓝衍生物Co(II)-Co(III) PBA,形成复合物PBA-LDH,与PMS(Peroxymonosulfate,过硫酸氢钾)组成PBA-LDH/PMS非均相催化体系,产生硫酸根自由基,用于降解PPCPs类污染物磺胺嘧啶。结果表明,相较于在LDH限域层间之外形成的普通PBA,限域生长的PBA-LDH/PMS体系对SDZ具有更高的降解速率。PBA-LDH/PMS体系在p H=3.0~9.0、催化剂投量为0.05 g/L的情况下,SDZ在10 min内能降解80%以上。循环试验表明,在4次循环试验过后,PBA-LDH/PMS体系对SDZ的降解效果仍能维持在80%以上。

The present paper has first of all successfully prepared a fully-crystalline Mg/Al layered double hydroxide via the coprecipitation method.And,then,it has fruitfully intercalated Cl-into the interlayer of Mg Al-LDH through ion-exchange with the hydrochloric acid so as to remove the CO32-and make it more efficient for[Co(CN)6]3-exchange.And,subsequently,the hexacyanocobaltate PBA precursor has to be intercalated into the interlayer of LDH through ion-exchange to cultivate and grow PBA in the interlayer of Mg Al-LDH.By taking advantage of somewhat characteristic methods,such as SEM,FTIR,XRD,BET and XPS analysis,it is demonstrated that PBA is successfully synthesized in the confined space of LDH interlayer.The brand-new prepared PBA-LDH is used to activate peroxymonosulfate to generate reactive radicals to degrade sulfadiazine(SDZ).The effects of the initial p H value,the PBA-LDH dosage and the peroxymonosulfate concentration on the SDZ degradation can then all further be determined through systematic investigation.The experiment and investigation results of the given paper can thus verify that,as compared with the pristine PBA,whose pseudo-1-st order rate constant (k) can be found equal to 0.015 min-1,in which PBA-LDH (0.281 min-1) tends to exhibit much higher degradation efficiency toward SDZ.And,meanwhile,higher dosage of PBA-LDH or PMS can also lead to more appreciable degradation efficiency of SDZ and speed up its corresponding rate constant (k).And,correspondingly,it would be possible for the SDZ degradation efficiency to be gone up and reach beyond 80%in 10 minutes in a wide range of initial p H value (3.0-9.0) and low catalyst dosage (0.05 g/L).And,thus,quenching experiments suggest that the sulfate radical is likely to serve as the main oxidant.And,so,the mechanism of SDZ degradation and the intermediates of SDZ can then be determined by the LC-MS system,with a few products gained in the reaction found and illustrated in the paper in the likely pathways.Besides,recycling tests also reveal that the SDZ degradation can still be made left over nearly 80%within 10 min through 4 consecutive experiments.Thus,the XPS results can also indicate the perfect stability of PBA-LDH in the catalytic process.Hence,the paper may include and suggest that PBA-LDH could be taken as a promising catalyst to promote the PMS for the SDZ degradation.