Decomposition of Wastewater Containing Isopropyl Alcohol Using the Gamma-ray/hydrogen Peroxide Process

Isopropyl alcohol (IPA) is the major organic ingredient in wastewater of semiconductor manufacturing industry. The efficiency of traditional wastewater treatment processes using physicalchemical or microorganism decomposition approaches is limited. Wastewater containing organic solvents that are not decomposed deteriorates the quality of water in the environment, while its volatile nature results in air pollution that affects the health of factory workers and residents in the neighborhood. Hence, it is of urgent need to develop more efficient pollution reduction technology. In this study, gamma-rays were induced using a Co-60 radiation source to treat IPA alone or in combination with hydrogen peroxide. Experimental results reveal that the combined γ-ray/H2O2 process shows better decomposition efficiencies than the use of γ-ray or H2O2 alone. *Corresponding author Email: [email protected] INTRODUCTION Semiconductor manufacturing and other hightech electronic industries contribute greatly to Taiwan’s economic development over the past 20 years. Numerous organic solvents are used in the semiconductor manufacturing process. The organic compounds present in wastewater of semiconductor manufacturing and other photo-electric industries have become more complicated due to the intricate manufacturing processes. Isopropyl alcohol (IPA), acetone, propylene glycol monomethyl ether acetate, ethyl lactate, phenol, benzene, toluene and xylene are the common organic reagents present at high concentrations in the wastewater [1] and most of them are volatile in nature. These organic compounds pose direct or indirect harm to the liver, kidney, central nervous system and skin, and some of them have already been verified as carcinogen, teratogenic agent and gene mutagen for humans. Traditional wastewater treatment approaches involving physical-chemical decomposition or microorganisms have shown only limited efficiencies [2]. Chemicals that are not removed enter the environment producing detrimental impact on soil and water resources, agriculture, animals, plants and the climate. For example, workers and local residents in areas with pesticide factories, chemical factories and high-tech industries suffer from cancer. It is therefore necessary and urgent to develop more efficient methods for eliminating harmful chemicals from wastewater. Many advanced oxidation processes have been developed to treat pollutants that are hard to decompose [3-10]. This study proposes a new technique; the γ-ray/H2O2 process, for treating IPA. The γ-ray generated using Co-60 is often employed to treat cancers, 152 J. Environ. Eng. Manage., 20(3), 151-156 (2010) Table 1. The IPA residues after H2O2 oxidation treatment Irradiation time (min)/IPA Residual percentage (%) IPA