Removal Of As(Ⅴ) And As(Ⅲ) From Water Using Nanoscale Zero-valent Iron And Modified ZVI(H-nZVI And D-nZVI)

Arsenic pollution is becoming more and more harmful to human society with the development of industry. As(V) and As(III) in the water can directly harm human health. The removal of arsenic has become increasingly important. There are many kinds of traditional methods of removing arsenic, but each has its advantages and disadvantages. Zero valent iron is a traditional and excellent arsenic removal material, but this material is often difficult to avoid the shortcomings of easy to reunite, resulting in the efficiency of the removal of arsenic is not ideal. In this paper, we use the liquid phase method to synthesize a kind of nano scale zero value iron material called nZVI.meanwhile, H-nZVI and D-nZVI were synthesized by the modification of nZVI by using hydroxyapatite and diatomite as dispersant. The phase composition, morphology and structure were characterized and analyzed by means of XRD, SEM, TEM, IR and BET test. The results show that the modified nano - zero - valence iron achieves the expected goal, and its dispersion performance is greatly increased.We prepared As(V) and As(III) in aqueous solution. nZVI, H-nZVI and D-nZVI were used for arsenic removal. The effects of adding amount, initial concentration of arsenic, reaction time, pH, temperature and other factors on the adsorption were explored, and the kinetics and thermodynamics of arsenic removal in the three materials were also explored. H-nZVI and D-nZVI were used to deal with the polluted water of the Yangzonghai Lake, and the water reached the drinking water standard after that.We come to the conclusion that, the removal of As(V) using this three kinds of materials is higher than As(III) removal (D-nZVI> H-nZVI> nZVI). For the 1mg/L As(V), the optimum conditions for arsenic removal using the three kinds of materials is,adding amount (0.876g/L), the reaction time (30min), pH (3-8). For the lmg/L As(III), the optimum conditions for arsenic removal using the three kinds of materials is,adding amount (0.657g/L), the reaction time (40min), pH (3-8). As the temperature increases, the removal efficiency of arsenic using nZVI and H-nZVI increase as an endothermic reaction, while the removal efficiency of D-nZVI decreased as the exothermic reaction. Three kinds of materials of arsenic removal in the reaction was spontaneous, entropy increasing reaction with quasi two order kinetic equation.We detail the arsenic removal mechanism by nano zero valent iron, oxidation-reduction reaction and Co-precipitation play the major role, Redox reaction of As and Fe°play the primary role. However, with the increase of nZVI dispersion, co-precipitation make more contributions, leading to the better removal of arsenic.