Study On Preparation Of Modified Nanoscale Zero-valent Iron And Removal Of Mixed Contaminants In Water

Nanoscale Zero Valent Iron(nZVI) particles with small particle size, large surface area and high reaction activity, can effectively remove a variety of pollutants in water. And its application in environmental remediation had caused great attention. Many scholars studied modified nZVI in order to overcome the aggregation and oxidation of nZVI. In this paper, the removal of common heavy metal pollutants(Cd2+) and chlorinated organic pollutants(HCB) in wastewater were studied, using prepared attapulgite loaded nano-iron material(ATP-nZVI) and nanoscale nickel iron bimetal(Nano-Ni/Fe) in laboratory. The mass ratio of Ni/Fe was 2%. Batch experiments were carried out to study the influencing factors and removal efficiency of the pollutants, as well as mixed contaminant(Cd2+、Zn2+ and Pb2+or Cd2+、Zn2+ and HCB), which ultimately provides theory and data support for the remediation of actual contaminated sites.The main research results are as follows: 1. nZVI dispersed well on the attapulgite clay and reactivity was greatly improved. Adsorption kinetics experiments showed that ATP-nZVI dosage was 10.34 g/L, temperature was 25 ℃, fluctuating frequency was 130 rpm, initial concentration of Cd2+ was 92.26 mg/L, the reaction could reach equilibrium after 5 h, and the adsorption reaction adapted to the secondary reaction kinetics model well. 2. Batch experiments showed that the dosage ATP-nZVI, the initial concentration of Cd2+ and pH could affect the removal of Cd2+ from water, and higher dosage, higher initial pH(3~7) and lower concentration of Cd2+ was conducive to the removal efficiency. The addition of heavy metals(Pb2+、Zn2+) would reduce the removal efficiency. It was bad to the removal of Cd2+ from water. 3. Remediaton of heavy metals and chlorinated organic pollutants showed that hexachlorobenzene could be removed rapidly from water by sorption when the initial concentration was 400 ug/L and the dosage of Nano-Ni/Fe was 7.5 g/L in different reaction system. The degradation process followed stepwise degradation well and the main products were pentachlorobenzene(PCB), 1,2,3,4-tetrachlorobenzene(1,2, 3,4-TeCB), 1,2,3–trichlorobenzene(1,2,3-TCB) and 1,2-dichlorobenzene(1,2-DCB). And the addition of heavy metals could influence the degradation rate of HCB and its products. The degradation process will be slower due to the competetive adsorption between heavey metals and products.