Removal Of VOCs From Wood Based On Sulfate Radical Advanced Oxidation Process

Wood is popular as the main raw material used in furniture manufacturing and interior decoration.However,volatile organic compounds(VOCs)with unpleasant odors are emitted from wood,which lead to indoor air pollution.In this study,SO₄^·--based advanced oxidation processes(AOPs),as a green,low-energy and efficient method,was used to eliminate VOCs from wood.The Chinese fir and poplar were selected as the research objects.Firstly,Chinese fir was treated using thermal activated persulfate(H-PS),which was used to verify the feasibility of VOCs removal from wood by AOPs.Then,the method of microwave activated persulfate(MW-PS)was applied to oxidize Chinese fir to improve the removal efficiency of VOCs.Considering the excellent VOCs removal efficiency in Chinese fir,MW-PS system was used to treat poplar,in order to compare the removal efficiency and mechanism of VOCs in hardwood and softwood.The removal mechanism of VOCs was investigated by gas chromatography-mass spectrometry(GC-MS),ultraviolet visible spectrophotometer(UV-vis),electron spin resonance(EPR),scanning electron microscopy(SEM).And the properties of wood after being treated by SO₄^·--based AOPs was investigated by contact angle,thermogravimetric analysis(TG)and fourier transform infrared spectroscopy(FTIR).The main conclusions are as follow:(1)It was feasible to remove VOCs from Chinese fir by H-PS system.The 35 types of main VOCs of Chinese fir were determined,including alkanes/terpenes(67.7%of main VOCs),alcohols/ethers(13.5%of main VOCs),esters(11.0%of main VOCs),aldehydes/ketones(2.3%of main VOCs),and others(5.5%of main VOCs).In the H-PS system,the removal efficiency of TVOCs was 62.6%.Additionally,alkanes/terpenes,alcohols/ethers,esters,and others were efficiently decreased,while aldehydes/ketones were increased.The SO₄^·-and·OH were continually produced by decomposition of PS.In H-PS system,the pit membranes of wood were swelling,which was conducive to the infiltration of free radicals and the removal of VOCs.Being treated under 60?,70?,and 80?had slight effect on the removal of VOCs from wood.The chemical structure and thermal stability of wood were slightly influenced after the wood was treated by H-PS system.(2)The removal efficiency of TVOCs was improved by the MW-PS system,which reached 89.4%.Moreover,alkanes/terpenes,aldehydes/ketones and others were significantly removed,and no alcohols/ethers and esters were detected.The SO₄^·-and·OH were continually produced by rapid decomposition of PS under MW irradiation.MWs destroyed the pit membranes,which promoted the permeability of wood,accelerating the transfer of more free radicals into the wood interior for oxidation.In MW-PS system,the removal of VOCs was significantly influenced by the treatment conditions(MW power,treatment time,and PS dosage).The optimal conditions of the MW-PS system for the minimum release of VOCs from wood were a microwave power of 462 W,an irradiation time of 30 min,and a PS dosage of 0.5 mmol/L.Being treated by MW-PS system had few effect on the chemical structure and the thermal stability of wood.(3)The MW-PS system also exhibited a high removal efficiency of the VOCs for poplar.The 32types of main VOCs of poplar were determined,including alkanes/terpenes(68.2%of main VOCs),alcohols/ethers(3.5%of main VOCs),esters(3.3%of main VOCs),aldehydes/ketones(15.8%of main VOCs),and others(9.2%of main VOCs).The TVOCs from poplar was less than Chinese fir.The removal efficiency of TVOCs in poplar was 88.5%after being treated by MW-PS system.In addition,the content of alkanes/terpenes,esters,aldehydes/ketones,and others obviously decreased,and no alcohols/ethers were detected.The removal of VOCs was slightly influenced by the reaction conditions of MW-PS system.Unlike Chinese fir,MW destroyed the pit membranes of poplar,while slightly affected on the permeability of wood,because of the complex microstructure of the hardwood.The effect of MW-PS system on the chemical structure and thermal stability of poplar and Chinese fir was similar.