Preparation Of Composite Nano Pd/nZVI/GAC Materials And Study On The Degradation Mechanism Of Refractory Organic Pollutantants

Based on the study of the remove of organic refractory pollutants in the water environment,selected the new technology of environment pollution control and remediation – zero-valent iron reduction technology,on this basis using impregnationliquid phase reduction-reductive deposition method and loading nZVI particle on the activated carbon.In order to enhanced its stability and chemical efficiency,then introduced heavy metal palladium,then synthesized one supported composite Pd/nZVI/GAC material.Through designing orthogonal experimental to optimization of preparation parameters.The morphologies,properties and reactivity of the as-prepared clay supported nZVIs were further analyzed using a series of characterization techniques such as scanning electron microscope(SEM),BET and energy dispersive spectrometer(EDS).Using methylene blue and nitrobenzene as object pollutants to detected the marerials chemical properties,Variables influencing the methylene blue and nitrobenzene removal efficiency(e.g.different active carbon material,metal loading content,composite Pd/nZVI/GAC material dosage,pH,and initial concentration)were also investigated to achieve an optimal application of the composite materials,and study the kinetics,removal mechanism removal opproaches.Through orthogonal experiment obtained the optimal preparation conditions: the nZVI loading capacity was 5 %,the Pd loading rate was 0.3 %,the calcination temperature of 200 ℃,and the G-60 DARCO as the carrier;The characterization results show that the nZVI and Pd was successfully loaded on activated carbon.Through the experiment,the composite Pd/nZVI/GAC material can effectively reduce the concentration of methylene blue and nitrobenzene,and the remove efficiency is Pd/nZVI/GAC>nZVI/GAC>GAC,it is proved that loading the ZVI onto active carbon and introducing the inert metal can improve the enhanced reaction activity and chemical efficiency.Metal loading content,material dosage,initial concentration of pollutants and pH are the main factors affecting the removal rate of pollutants during the reaction.The results show that 93.17 % of methylene blue was removed after 10 minutes using Pd/nZVI/GAC material at initial concentration of 100 mg/L and dosage of 0.5 g/L;The kinetics depicted that the degradation process of methylene blue fitted well the first order reaction kinetics.According to the scanning spectrum and ion chromatographic analysis,confirmed that the degradation of methylene blue by Pd/nZVI/GAC including both physical adsorption and chemical degradation process.The chromophore and aromatic heterocyclic structure was gradually reduced to small molecules,and eventually completely degraded.89.33 % of nitrobenzene was removed after 180 minutes using Pd/nZVI/GAC material at initial concentration of 100 mg/L and dosage of 0.3 g/L;Nitrobenzene can be reduced by Pd/nZVI/GAC materials through varieties of ways to aniline which was lower toxicity and biodegradability,inrerred that during the reaction process exist both adsorption and reduction effect,in the early stage of the reaction,adsorption was dominant.