Treatment Of Hexavalent Chromium In Groundwater Using Zero-Valent Iron Nanoparticles

With the fast development of economy and society, the problem of groundwater pollution has become increasingly prominent issues, and the negative impact of polluted groundwater is also becoming more serious. It is extremely urgent to control contaminated groundwater and explore remediation technology.Hexavalent chromium, Cr(VI), is a pollutant in groundwater and hazardous to human health. In the residual water of mining, tanning, electroplating and other industries, the concentration of Cr(VI) is hundreds times more than limitation value of national standards. Cr(VI) could infiltrate into the groundwater and cause serious security risks because of its high mobility and toxicity.This thesis aimed to remove hexavalent chromium by zero-valent iron nanoparticles. Through the batch experiments, first-hand data were got and these could provide the basis for the in-site groundwater remediation using nano zero-valent iron.The effect factors of Cr(VI) removal contain Fe0 particle size, Fe0 dosage, initial Cr(VI) concentration, reaction temperature and Fe0 aging time. Single factor experiments and orthogonal experiments were both designed for reduction of Cr(VI) from water by nano zero-valent iron (nZVI). The factors of nZVI particle size, nZVI dosage, initial concentration of Cr(VI), temperature, nZVI aging time were discussed and optimized.The results showed in the following.(1) Smaller Fe0 particles, larger Fe0 dosage, higher temperature, and fresh Fe0 can stimulate the reaction.(2) For the granular zero-valent iron (average particle size 0.5-1mm), when its dosage is ten times of nZVI, removal efficiency of Cr(VI) only reaches 2-3% by nZVI.(3) From three factors and three levels in orthogonal experiments, the importance order of factors for Cr(VI) removal is nZVI dosage, initial Cr(VI) concentration and the temperature. The optimal removal conditions is that when the water contains 50mg/L Cr(VI), 2g/L nZVI at 25℃was added.