有机改性蒙脱石负载纳米零价铁去除水体新兴污染物双氯芬酸

Organic modified montmorillonite with loaded nano zero-valent iron for removing emerging pollutant diclofenac

双氯芬酸(DFC)作为一种典型的新兴污染物,进入环境中难以被生物降解和转化,给人类健康造成潜在危害.本研究采用阳离子表面活性剂十六烷基三甲基溴化铵(HDTMAB)改性的蒙脱石(Mt)负载自制的纳米零价铁(nZVI),得到有机改性蒙脱石负载纳米零价铁(H-Mt+nZVI)复合材料,用于去除水中的DFC.利用X射线衍射仪(XRD)、比表面积分析仪(BET)对复合材料进行了表征.结果表明,在XRD图谱中2θ=44.6°附近出现了对应于Fe0的衍射峰,证明nZVI被成功负载于Mt上;在0.5 CEC、1 CEC、2 CEC改性的Mt比表面积由49.40 m2·g-1下降到20.86、21.27、26.06 m2·g-1,且Mt的孔径由8.01 nm增大到10.93、11.60、12.40 nm,主要由于nZVI负载到Mt表面或层间,扩充了部分吸附孔洞.同时,采用批次吸附实验比较了Mt、nZVI和H-Mt+nZVI复合材料对DFC的去除效果,研究结果表明,Mt和nZVI对DFC的去除率均低于20%,复合材料对DFC的去除率明显增大,可达90%以上.复合材料对DFC的吸附等温曲线符合Langmuir和Freundlich等温模型,吸附动力学更满足准一级动力学模型.在采用1倍阳离子交换量改性蒙脱石负载纳米零价铁(1 CEC Mt+nZVI)吸附DFC时,饱和吸附量可达1922.78 mg·kg-1,吸附平衡时间为30 min.说明H-Mt+nZVI复合材料可应用于水体新兴污染物DFC的快速去除.

As a typical emerging pollutant,diclofenac(DFC)is difficult to be biodegraded and transformed into the environment,posing a potential hazard to human health.In this study,the nano-zero-valent iron(nZVI)was loaded with montmorillonite(Mt)modified with cationic surfactant cetyltrimethylammonium bromide(HDTMAB)to obtain organic modified montmorillonite loaded nano-zero.A valence iron(H-Mt+nZVI)composite is used to remove DFC from water.The composites were characterized by X-ray diffractometry(XRD)and specific surface area analyzer(BET).The results showed that a diffraction peak corresponding to Fe0 appears in the XRD pattern near 2θ=44.6°,which proved that nZVI was successfully loaded on Mt.The Mt specific surface area modified at 0.5 CEC、1 CEC、2 CEC decreased from 49.40 m2·g-1 to 20.86,21.27,26.06 m2·g-1,and the pore diameter increased from 8.01 nm to 10.93,11.60,12.40 nm,because the loading of nZVI onto the surface or interlayer of Mt,occupied part of the adsorption pores of Mt.At the same time,the removal effects of Mt,nZVI and H-Mt+nZVI composites on DFC were compared by batch adsorption experiments.Evidently,the removal rates of DFC adsorbed by Mt and nZVI were less than 20%,and the removal rate of DFC adsorbed by composites increased to 90%.The adsorption isotherm curve of the composite material to DFC accords with the Langmuir and Freundlich isotherm models,and the pesudo first order model satisfies the adsorption kinetics better.When DFC was adsorbed by montmorillonite-loaded nano-zero-valent iron(1 CEC Mt+nZVI)with 1 cation exchange capacity,the saturated adsorption capacity was up to 1922.78 mg·kg-1 and the adsorption equilibrium time was 30 min.It showed that H-Mt+nZVI composite could rapidly and effectively remove the emerging pollutants DFC in water.