Degradation of Hexachlorocyclohexanes (HCHs) by Stable Zero Valent Iron (ZVI) Microparticles

Abstract

During the production of lindane (γ-HCH) large volumes of wastes containing α-, β-, and δ-HCH isomers were generated. Hexachlorocyclohexanes (HCHs) are carcinogens and teratogen compounds. Although their production and use are currently banned in most countries, many landfills and sites remain polluted by these compounds. This paper studies a promising and novel alternative for the HCH abatement: dechlorination by zero valent iron microparticles. Synthetic wastewater (0.5 mg/L of α-, β-, γ-, and δ-HCH or 6 mg/L of γ-HCH) and five types of commercial iron microparticles (here named mFe-1, mFe-2, mFe-3, mFe-4, and mFe-5) were used in batch (5 g/L) and continuous (W mFe/Q L = 167 g · h/L) operation mode at room temperature. Iron microparticles were characterized (before and after reaction) by N2 adsorption/desorption isotherms and X-ray diffraction. HCH isomers showed different behavior vs. dechlorination (γ > α > δ > β) according to the axial/equatorial position of the chlorines. The most active iron source among those tested was mFe-1, presenting small particle diameter (70 μm), moderate BET area (35 m2/kg), low oxygen content, and traces of manganese. mFe-1 exhibited high activity and stability both in continuous (X γ-HCH = 70%, W mFe/Q L = 167 g · h/L) and discontinuous (X γ-HCH = 100%, 48 h) operation. Contribution of HCH adsorption over iron microparticles was found negligible being benzene and Cl− the final dechlorination products.