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Temperature affects the emission behavior of formaldehyde from coatings. Initial emittable concentration (C0), diffusion coefficient (Dm) and partition coefficient (K) are three key parameters for characterizing the formaldehyde emission from coatings. However, recent research concerning temperature effect on volatile organic compound (VOC) emission from coatings mainly focused on the influence on gas-phase concentration or emission rate, and few studies were conducted on the correlation between temperature and key emission factors (C0, Dm and K). In this work, formaldehyde emission from a solvent-based coating was measured at 10, 15, 20 and 25°C in a 30 L environmental chamber. From 10 to 25°C, C0 increased by 2.35-fold, and positive linear correlation was observed between ln(C0*T0.5) and 1/T. An empirical equation characterizing temperature effect on K was derived. Temperature effects on Dm were negligible. Through the obtained equations that can characterize the correlation between temperature and the key parameters, C0 and K at different temperatures from this work can be easily calculated. This study would be useful for predicting emission behavior of formaldehyde from solvent-based coatings and better understanding the influence of temperature.

Volatile organic compounds (VOCs) from solvent-based architectural coatings (SBACs) play an important role in photochemical air pollution with increasing consumption of architectural coatings in China. In this study, we collected 148 typical SBACs of 3 types in China. The TVOC emission factors and source profiles were established, the contributions of SBACs to ozone and secondary organic aerosol (SOA) formation were investigated. The VOC emissions and O3 and SOA amounts formed in chemical reactions from SBACs in 2017 were estimated. Key organic groups and VOC species with high reactivity were identified. According to the results, the TVOC emission factors were 507.17 g L−1 for solvent-based anticorrosive coatings, 381.34 g L−1 for solvent-based floor coatings and 459.68 g L−1 for solvent-based fire-retardant coatings. The VOC emissions were 186,902.11 t, 88,225.41 t and 71,352.32 t; the O3 amounts formed were 742,001.39 t, 397,896.60 t and 244,738.46 t; the SOA amounts formed were 3934.29 t, 2488.04 t and 1104.61 t, respectively, from 3 types of SBACs in 2017. The O3 production factors were 1781.82 g O3 (kg paint)−1, 1457.50 g O3 (kg paint)−1 and 1176.63 g O3 (kg paint)−1, the SOA production factors were 9.45 g SOA (kg paint)−1, 9.11 g SOA (kg paint)−1 and 5.31 g SOA (kg paint)−1, for 3 types of SBACs. Priority should be given to organic group of aromatics and top 17 VOC species with high reactivity for O3 and SOA eliminating strategies, especially three xylenes (o-xylene, m-xylene and p-xylene), ethylbenzene, trimethyl benzenes (1,3,5-trimethyl benzene, 1,2,3-Trimethyl benzene) and toluene.

This study was conducted to investigate the effect of inorganic salts on the mass-transfer coefficient of O3 and decolorization of azo dye (Acid Red 14, AR14) solution through ozonation in a microporous tube-in-tube microchannel reactor (MTMCR). The overall volumetric mass-transfer coefficient (KGa) of O3 in the MTMCR was deduced by material balance. The effects of different salts on the KGa of O3 and decolorization efficiency of the AR14 solution were studied, and results show that both were significantly affected by the inorganic salts. Although the KGa of O3 and the decolorization efficiency of AR14 increased with increasing salt concentration and pH, the effect of NaNO3 was much weaker than that of NaCl, Na2SO4, Na2CO3, and NaHCO3. The enhanced KGa of O3 and decolorization could be due to the generation of species with high oxidizing ability in the presence of the salts.

The ozonation of synthetic wastewater containing azo dye Acid Red 14 (AR 14) was investigated in a high-throughput microporous tube-in-tube microchannel reactor. The effects of design and operating parameters such as micropore size, annular channel width, liquid volumetric flow rate, ozone-containing gas volumetric flow rate, initial pH of the solution and initial AR 14 concentration on decolorization efficiency and ozone utilization efficiency were studied with the aim to optimize the operation conditions. An increase of the ozone-containing gas or liquid flow rate could greatly intensify the gas–liquid mass transfer. Reducing the micropore size and the annular channel width led to a higher mass transfer rate and was beneficial to decolorization. Decolorization efficiency increased with an increasing ozone-containing gas volumetric flow rate, as well as a decreasing liquid volumetric flow rate and initial AR 14 concentration. The optimum initial pH for AR 14 ozonation was determined as 9.0. The degradation kinetics was observed to be a pseudo-first-order reaction with respect to AR 14 concentration. The difference between the decolorization and COD removal efficiency indicated that many intermediates existed in AR 14 ozonation. The formation of six organic intermediates during ozonation was detected by GC/MS, while the concentration of nitrate and sulfate ions was determined by ion chromatography. The possible degradation mechanism of AR 14 in aqueous solution was proposed.