膨润土负载纳米零价铁去除废水中Cr(Ⅵ)的动力学特性研究

Reduction kinetics of Cr(Ⅵ) in wastewater by nanoscale zerovalent iron loaded on bentonite

利用液相还原法制备膨润土负载纳米零价铁(B-nZVI)并将其应用于含Cr(Ⅵ)废水的处理,研究了B-nZVI投加量、反应时间和溶液初始pH等3个因素对Cr(Ⅵ)处理效果的影响,探讨了B-nZVI对不同初始浓度的含Cr(Ⅵ)废水的降解动力学规律,通过扫描电镜和X射线衍射仪对反应前后的B-nZVI进行形貌分析。结果表明:膨润土能有效提高纳米零价铁(nZVI)的分散性并阻止其氧化。三因素对Cr(Ⅵ)去除率影响均达到显著水平(p<0.05),其中投加量的影响达到极显著水平(p<0.01);其显著性大小依次为:投加量>溶液初始pH>反应时间。在投加量为2.0g/L、反应40min、溶液初始pH=6的最佳工艺条件下,初始浓度为20mg/L的含Cr(Ⅵ)废水中Cr(Ⅵ)去除率可达99.15%。B-nZVI去除Cr(Ⅵ)的反应在不同Cr(Ⅵ)初始浓度下均能较好地符合准一级动力学模型,且可用L-H动力学模型描述;B-nZVI对Cr(Ⅵ)去除是吸附和还原共同作用的结果,且nZVI对Cr(Ⅵ)的还原作用是其去除的主要作用机制。

Cr（Ⅵ）containing wastewater is always an environmental problem with carcinogenicity,teratogenicity and mutagenicity.Nanoscale zerovalent iron loaded on bentonite（B-nZVI）was produced by liquid-phase reduction and used for the treatment of containing Cr（Ⅵ）wastewater.The influence factor of reaction system,such as B-nZVI dosage,reaction time and initial pH for Cr（Ⅵ）removal efficiency was studied,and the degradation kinetics was investigated.The morphology of B-nZVI before and after the reaction was characterized by scanning electron microscopy（SEM）and X ray diffraction（XRD）.The results indicated that bentonite could improve the dispersion of nZVI and prevented the oxidation of it.The effect of B-nZVI dosage on Cr（Ⅵ）removal rate tended to be very significant,while the effect of reaction time and initial pH were also significant.The important effect of three factors on Cr（Ⅵ）reduction can be shown in the following descending order：B-nZVI dosage〉initial pH〉reaction time.For Cr（Ⅵ）wastewater contained 20 mg/L Cr（Ⅵ）,the optimum operational conditions were set as follows：B-nZVI dosage=2.0 g/L,reaction time=40 min and initial pH=6.0.At which,the measured average value of 3 times of Cr（Ⅵ）removal rate were99.15%.The removal of Cr（Ⅵ）was in accord with the pseudo first order reduction kinetics model and could be described by L-H dynamic model.The removal of Cr（Ⅵ）by B-nZVI was the common effect of adsorption and reducing action while the reducing action of nZVI was the major action.