Study On Modified Zeolite Containing Zinc Oxide Nanoparticles In Removing Heavy Metal Ions In Waste Water

With the development of industry in China,the influence of heavy metal ions on pollution of water quality is becoming more and more serious.Thus,the effective removal of heavy metal ions in water has become an urgent task for environmental governance,especially lead and cadmium ions in water,which are the most representative polluted heavy metal ions.This paper is based on the characteristics of zinc oxide nanoparticles containing environment-friendly,large specific surface area,catalytic and adsorption properties,and the peculiarity of natural zeolites including multi-pore structure,good adsorption and ion-exchange properties,low price and easy recovery.Therefore,in this paper,a novel environmentally friendly modified material is prepared by loading zinc oxide nanoparticles on the surface of a natural zeolite with a porous structure.It could effectively remove lead and cadmium ions in polluted water,and characterizes samples by X-ray diffraction?XRD?,scanning electron microscopy?SEM?,measurement of specific surface area?BET?and energy dispersive X-ray spectrometry?EDS?.Results demonstrated:?1?.Comparing with the natural zeolite,the adsorption effect of zinc oxide nanoparticle-modified zeolite with a porous structure on heavy metal ions Cd²⁺and Pb²⁺was obviously improved.Especially when the conditions reach a degree?25?,particle size within 30-40 mesh,dosage of 0.5g,initial concentration 100mg/L,PH within 6-7and adsorption time of 2h?,the saturated adsorption capacity of zinc oxide nanoparticle-modified zeolite for Cd²⁺reaches 5.35 mg/g,while the capacity of natural zeolites was only 3.89 mg/g.However,when the above temperature,PH and dosage keep constant,only the particle size is changed to 20-30 mesh and initial concentration50mg/L,the adsorption time is increased to 4h,the saturated adsorption capacity of zinc oxide nanoparticle-modified zeolite on Pb²⁺reaches 34.28 mg/g,while the capacity of natural zeolite was 33.3 mg/g.?2?.The clear characteristic peaks of zinc oxide nanoparticles in the map demonstrates that the zinc oxide nanoparticles has been successfully loaded onto the natural zeolite through analysis of XRD.Whereas,there is no obvious change in other peaks,which indicates that the modification process dose not affect the structure of zeolite.The experiment of SEM reveals that the surface area and adsorption sites are increased after the successful loading of zinc oxide nanoparticles onto zeolite.The detection of BET shows that the specific surface area of zinc oxide nanoparticle-modified zeolite is 2.4 times that of natural zeolite,the aperture of zinc oxide nanoparticle-modified zeolite was 1.3 times that of natural zeolite,and the pore volume of zinc oxide nanoparticle-modified zeolite was 1.4 times that of natural zeolite.?3?.The adsorption mechanisms of zinc oxide nanoparticle-modified zeolite and natural zeolite on heavy metal Cd²⁺and Pb²⁺are studied,in which the removal process of Cd²⁺and Pb²⁺by zinc oxide nanoparticle-modified zeolite is a combination of adsorption and ion exchange.Fitting using Langmuir and Freundlich isothermal formulas demonstrates that the adsorption isotherms of natural zeolite and zinc oxide nanoparticle-modified zeolite adsorbing Pb²⁺could be well fitted by Langmuir equation.And the adsorption isotherm of natural zeolite adsorbing Cd²⁺could be well fitted by Freundlich isothermal equation,however the R² is 0.95 when the adsorption of nano zinc oxide modified zeolite on Cd²⁺is fitted by Freundlich isotherm formula.This indicates that the adsorption of Cd²⁺on the modified zeolite has multi molecular layer adsorption.At 25°C,the kinetic equation is fitted to find that the adsorption process of Cd²⁺and Pb²⁺by nano-zinc oxide modified zeolite is described better with pseudo-second-order kinetic equation,in which the value of R² reaches 0.985 and0.972,respectively.?4?.The effect of zinc oxide nanoparticle-modified zeolite on the removal of Pb²⁺,Cb²⁺,Cu²⁺and Ni²⁺from simulated waste water is studied.The final results show that zinc oxide nanoparticle-modified zeolite could better remove Cd²⁺,Pb²⁺,Cu²⁺and Ni²⁺in waste water,with a removal rate of over 90%.The zinc oxide nanoparticle-modified zeolite could be reused through the regenerative cycle experiment,and the number of effective recycling is 3 times.