| The development and application of fertilizers,pesticides and agricultural irrigation has resulted in more and more serious pollution to farmland wastewater.Agricultural pollution has become one of the most serious environmental problems in China and threatened food safety and human health,so it was urgent to take effective ways to prevent and control agricultural pollution.With the development of nanotechnology,researchers paid attention to the application of nanoscale iron in the environments.High reactivity properties of NZVI and NZVI/CDt were successfully prepared by liquid phase reduction method.Then,the removal rate of NO3--N、Cu2+ and CIP were evaluated by simulation experiment.This study provided theoretical basis to remove contaminants using new functional materials.This issue was studied from the following several aspects:(1)The NZVI and NZVI/CDt were prepared by using sodium borohydride as reducing agent via the liquid phase reduction method.The NZVI/CDt was characterized by X-ray diffraction(XRD),scanning electron microscope(SEM),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS)and Zeta potential to observe the crystal composite,surface and internal structure,sample elements.This study provided theoretical based on removal efficiencies and mechanisms of pollutants.XRD and XPS characterization showed that NZVI/CDt composites were successfully prepared in this experiment.SEM and TEM characterization showed that bare NZVI were severely agglomerated with chain but iron nanoparticles were highly dispersed on the surface of diatomite after supported on the diatomite and several iron nanoparticles were embedded within the diatomite porous.Iron nanoparticles had a nearly spherical shape with the range of 100nm and agglomeration and instability of iron nanoparticles was decreased,indicating that diatomite is good support.The Zeta potential result showed the zero point potential of the NZVI/CDt was 6.7.(2)The removal efficiency of NO3--N by NZVI and NZVI/CDt was investigated.Based on the experimental data,the kinetics,the reaction mechanism and material reuse were studied.The results showed that the NZVI/CDt showed efficient removal of nitrate nitrogen and the removal efficiency could reach 90.05%after 60 min at proper conditions:pH 7,initial 20 mg/L concentration of nitrate nitrogen,0.5141 g NZVI/CDt at the room temperature.The removal rate of NO3--N was decreased with the increase of pH value,and the removal of NO3--N was more favorable under acidic conditions.For NZVI/CDt,NZVI/CDt had a good effect on NO3--N at different pH conditions.The final product of NZVI/CDt removal NO3--N is mainly NH4+-N.Kinetic studies showed that the reduction of nitrate nitrogen by NZVI/CDt followed pseudo-first-order kinetics.The reusability of NZVI/CDt is more stable than NZVI.(3)The removal efficiency of Cu2+ by CDt,NZVI and NZVI/CDt was investigated.The influence NZVI/CDt dosage,pH and initial concentration of Cu2+ on removing Cu2+ was discussed.Based on the experimental data,the adsorption model and kinetic analysis of Cu2+by NZVI/CDt were established.The the final products was studied by XPS.The results indicated that NZVI/CDt demonstrated high removal abilities of Cu2+.When the dosage 0.075 g,the 20 mg/L initial concentration of Cu2+,pH=5,and the reaction time 4 h,the removal efficiency of Cu2+ reached 98.52%.The experiment datas were fitted well with the Langmuir(R2=0.998)adsorption isotherms,and the maximum adsorption capacity was 74.29 mg/g.When initial concentration was 60 mg/L and 100 mg/L,the adsorption behaviors of Cu2+on NZVI/CDt conformed to pseudo-second-order kinetics equation(R2=1 and 0.999).Finally the adsorbed Cu2+ was reduced by Fe0 to Cu2O and Cu0.(4)The effect of pH initial concentration of CIP and different materials on removing ciprofloxacin(CIP)was discussed.Based on the experimental data,the adsorption model and kinetic analysis of CIP by NZVI/CDt were established.The reaction mechanism was studied by HPLC-TOF-MS.The results showed that the adsorption capacity of NZVI/CDt on CIP was higher than that of NZVI.Under the conditions of pH=6,CIP initial concentration 20 mg/L and NZVI/CDt dosage 0.5 g,the removal efficiency of CIP reached 93.50%.NZVI and NZVI/CDt were in accordance with the pseudo-second-order kinetics model,and the correlation coefficients were 0.999 and 0.997,respectively.The datas were fitted well with Langmuir model,indicating that the adsorption is a monomolecular layer adsorption.The correlation coefficient R2 was 0.986 and the maximum adsorption capacity of 8.242 mg/g.NZVI/CDt and CIP reaction is mainly based on adsorption. |
