Enhancement of Removal of VOCs and Odors from Wood by Microwave-Activated Persulfate

Abstract

Since traditional methods for removing volatile organic compounds (VOCs) from wood consume large amounts of energy and generate environmental pollution, it is desired to develop a convenient and green treatment method. Oxidation by microwave-activated persulfate (MW-PS) is a promising alternative method that has been used to eliminate VOCs from wood. The penetration of microwave energy can destroy the wood pit membranes and increase VOC emissions. The VOCs are further degraded by •OH and SO 4•− , which are generated via the activation of microwaves. This phenomenon can be detected by the electron paramagnetic resonance spectrometry. The 35 types of main VOCs of natural wood were determined, including alkanes/ terpenes, alcohols/ethers, esters, aldehydes/ketones, and others. In the MW-PS system, 23 compounds were removed with an efficiency of 100%. Specifically, as one of the major compounds, the content of alkanes/terpenes was sharply decreased, and no alcohols/ethers and esters were detected. It was found that the optimal conditions of the MW-PS system for the minimum release of VOCs from wood were the microwave power of 462 W, irradiation time of 30 min, and PS dosage of 0.5 mmol/L.

Thermal and Radiation Based Catalytic Activation of Persulfate Systems in the Removal of Micropollutants: A Review

“…Microwave (MW) energy is a band of the electromagnetic spectrum of alternating electric and magnetic fields with a frequency of 300 MHz–300 GHz. The interaction of microwave radiation with various substances occurs via the three steps of penetration, reflection, and absorption, which result in direct internal heating. , About 85% of the electrical energy is converted to heat energy . The various advantages offered by microwave radiation include minimal energy requirement and activation energy, shorter reaction time, higher selectivity in terms of reaction, energy of high utilization efficiency, comparatively high power density, intensive molecular level heating, homogeneous environment, and an eco-friendly and cost-effective process. ,− In recent decades, microwave irradiation has received extensive research attention, as energy is transformed by irradiation, resulting in the rotation of dipolar molecules (i.e., dielectric material/water molecules) .…”

“…It has been proposed that microwave heating provides faster and low activation energy to activate the persulfate resulting in an increased rate of degradation compared to conventional heating methods . In general, persulfate (the oxidant) has a high dielectric loss factor (ε″) value and is also known to exhibit ultrafast realignment rates, thereby rapidly increasing the temperature . Most of the experimental data suggest that the rate of generation of sulfate radicals from persulfate is considerably low at minimal temperatures and progresses as the temperature increases.…”

“…The interaction of microwave radiation with various substances occurs via the three steps of penetration, reflection, and absorption, which result in direct internal heating. 63,64 About 85% of the electrical energy is converted to heat energy. 65 The various advantages offered by microwave radiation include minimal energy requirement and activation energy, shorter reaction time, higher selectivity in terms of reaction, energy of high utilization efficiency, comparatively high power density, intensive molecular level heating, homogeneous environment, and an eco-friendly and cost-effective process.…”

“…68 In general, persulfate (the oxidant) has a high dielectric loss factor (ε″) value and is also known to exhibit ultrafast realignment rates, thereby rapidly increasing the temperature. 63 Most of the experimental data suggest that the rate of generation of sulfate radicals from persulfate is considerably low at minimal temperatures and progresses as the temperature increases.…”