REMOVAL OF HEXAVALENT CHROMIUM FROM SYNTHETIC WASTE WATER USING SYNTHETIC NANO ZERO VALENT IRON (NZVI) AS ADSORBENT

摘要

Hexavalent chromium is toxic, carcinogenic, probably mutagenic and highly soluble. The harmful effects of chromium include lung and throat cancer. Since chromium is an important heavy metal used in various industrial processes, it finds its way into the industrial effluents causing lethal environmental hazards. The impacts of chromium on human health and the environment is matter of concern. Remediation of Cr (VI) contaminated water poses both technological and economic challenges, as conventional methods are often too expensive and difficult to operate. Therefore, it is imperative that Cr (VI) be removed from contaminated water by using new material. NZVI particles are considered to be one of the important reducing agent to Cr (VI), transforming the same into non toxic Cr(III).The NZVI particles were prepared by chemical reduction method using Ferric chloride hexa hydrate (FeCl3.6H2O) with sodium borohydride (NaBH4).Removal of hexavalent chromium using NZVI particles as a Cr (VI) reducing agent was studied in synthetic waste water, containing 20 mg/L of hexavalent chromium. Chromium recovery batch study indicated that better recovery is achieved at lower pH and it increased with lowering of the pH of the aqueous solution. The optimum removal of the Cr (VI) and metal ions occurred at low pH (pH=3) and at maximum temperature of 250C.Chromium recovery of 99.9% was achieved within 2 min. at pH=3. After treatment, the Cr (VI) concentration was determined by UV–vis spectrophotometer by 1, 5-diphenyl carbazide method. This study demonstrates that NZVI particles have the potential to become an effective agent for the removal of Cr (VI) from synthetic model wastewater. Cleaning up of synthetic waste water has been successfully done by rapid removal of chromium Cr (VI) by NZVI particles from aqueous solution. Langmuir and Freundlich adsorption isotherm were used to explain the phenomena of adsorption.