Synthesis Of Iron/ZIF-8 Based Nanomaterials And Removal Of As Species In Wastewater

Zero-valent iron nanoparticles（nZVI）,as a highly reactive nanomaterial,have greater advantages in the field of environmental remediation,but the highly reactive and easy oxidation characteristics becomes a bottleneck problem for applications.In addition,ZIF-8,as a metal organic framework materials（MOFs）with high specific surface area and porosity,can be widely used as adsorbent for wastewater treatment.Therefore,this paper constructs a new functional composite material based on ZIF-8 and iron nanosystem materials to investigate its performance and the treatment of arsenic（As）species in wastewater.The main contents are as follows.Firstly,the liquid-phase reduction method was used to synthesize nZVI for the removal of As（III）and As（V）from water.The effect of the experimental conditions,such as p H,temperature,initial concentration of pollutants and dose,on the adsorption performance of nZVI was investigated by regulating the experimental conditions.The results show that the removal of As（III）and As（V）by nZVI involves oxidation and chemisorption as a spontaneous and heat-absorbing process.In addition,the application of nZVI in the groundwater of mining areas with the presence of different contaminants showed a high removal effect;and the coexisting ions experiments also showed that,except for PO₄^3-and CO₃^2-,other ions had less influence on the performance of nZVI.Secondly,in order to improve the dispersibility of nZVI,nZVI@ZIF-8 functional composite was prepared using ZIF-8 as a carrier and used for the removal of As（III）and As（V）.The results showed that the removal rates of As（III）and As（V）were 45.69%and96.33%,respectively.The removal process followed the pseudo-second-order kinetic model and Langmuir isothermal adsorption model as a chemisorption process.Meanwhile,p H experiments showed that electrostatic forces influenced the removal effect.That is,the removal of Arsenic species by nZVI@ZIF-8 is mainly achieved by coordination and electrostatic interactions.In addition,nZVI@ZIF-8 was applied to remove As（V）from mine wastewater and also showed a high removal rate of 94.27%.Finally,in order to further reduce nanoparticle agglomeration and increase the catalytic activity of the material,bimetallic nanoparticles FePd doped with the active component Pd were introduced into the ZIF-8 cavity to prepare FePd@ZIF-8 composites and used for the simultaneous removal of As（III）and As（V）from water.The results show that FePd@ZIF-8 composites have equally high removal rates（44.86 as well as 93.35%）for As（III）and As（V）in solution,and the removal process is a chemisorption process in which arsenic ions are adsorbed on the material mainly through surface complexation,and the electrostatic effect has little effect on the removal.Among them,Pd mainly embodies the catalytic effect in the removal process,and also stimulates the production of more reactive groups on the material surface,which increases the adsorption amount and reduces the effect of electrostatic effect.In addition,SEM,XRD,FTIR and other characterization analyses show that the FePd@ZIF-8 has good stability.