Source Profiles and Chemical Reactivity of Volatile Organic Compounds from Surface Coating of Aluminum Products in Foshan, China

Abstract

Volatile organic compounds (VOCs) samples were collected and analyzed for the surface coating processes of aluminum products in Foshan. The concentration levels of VOCs from solvent-based coating (63.90-149.67 mg·m-3) are much higher than that from water-based, electrophoretic, and powder coating (2.99-21.93 mg·m-3). With respect to the VOC composition, aromatics are the main VOC group of solvent-based coating emission, ranging from 52.32%-71.55%. Typical species include toluene, ethylbenzene, xylene, and ethyl acetate. The VOCs emitted from water-based coating are mainly oxygenated VOCs, such as ethyl acetate (48.59%) and tetrahydrofuran (8.43%), while the percentage of aromatics (11.32%) is lower than that of solvent-based coating. Isopropanol is the most abundant species of electrophoretic coating emissions, accounting for up to 81.19% of the VOCs. The major VOC compounds of powder coating processes are acetone (30.25%), propane (15.48%), ethylene (12.15%), ethane (9.35%), and n-butane (5.16%). The calculation of the ozone formation potential (OFP) shows that the solvent-based coating has the highest OFP (3.89 g·g-1), followed by powder coating (2.53 g·g-1), while water-based and electrophoretic coating have lower OFPs (1.31 and 0.85 g·g-1, respectively). The most important contributor to OFP of solvent-based coating are aromatics, especially C7-C10 aromatics. The major contributors of water-based coating are ethyl acetate, m/p-xylenes, and toluene, with contributions of 23.24%, 21.76%, and 17.07%, respectively. The key reactive components of powder coating are ethylene, propene, and 1-butene; the sum of alkenes accounts for 71.11% of the OFP. With respect to the contribution of VOCs emitted from electrophoretic coating to the OFP, the percentage of isopropanol (65.08%) is significantly larger than that of other species (<6%).