Study On Emission Characteristics And Purification Technology Of Volatile Organic Compounds From Cooking Oil Fume

Cooking fumes are important volatile organic compounds（VOCs）sources of in-door air,however,emission characteristics of the commonly used oils（canola,soybean,peanut,corn and lard）in Chinese cooking and health risks of the corresponding VOCs are still not clear.At the same time,the adsorption mechanism and technology of VOCs from cooking fume are not yet clear.In this study,a stable cooking oil fume generater was developed to obtain the cooking fumes with constant VOC compositions.The spe-ciation of VOCs in the cooking fumes from five edible oils and their corresponding health risk assessments has been investigated.Using Monte Carlo molecular simulation to develop the adsorption mechanism of typical pollutants（benzene,formaldehyde）from cooking oil fume.Four typical metal-organic frameworks（MOFs）,namely MIL-101（Cr）,UiO-66,ZIF-8 and Cu-BDC were synthesized and applied to purify the indoor hexanal.The main contributions and innovations are as follows:First of all,we sprayed the oil droplets uniformly on a pre-heated wall via a nozzle in order to obtain the cooking fumes with constant VOC compositions.Our results show that emission profiles of VOCs are similar in the five oils.Aldehydes are the most abun-dant VOCs species,accounting for 42.1%-74.6%in the temperature range of 130-270℃,followed by alcohols（5.0%to 14.5%）,alkanes and alkenes（4.9%to 9.6%）,furans（2.3%to 4.3%）and benzenes（0.1%to 3.3%）.The vegetable oils rich in unsaturated fatty acids emit more VOCs than the lard oil rich in saturated fatty acids,and the VOCs emitted from the soybean oil increase with increasing cooking temperatures.Water in oils always enhances VOC emissions by steam stripping at high temperatures.Moreo-ver,oxidative radicals generated in the water-oil system facilitate oxidation of unsatu-rated fatty acids,producing carcinogenic aldehydes,benzenes and furans in the emitted VOCs.Then,this study presents a comprehensive study of benzene adsorption in carbon nano-porous materials by combining high-resolution measurement,modeling and molecular simulation.High-resolution isotherms and isosteric heats of benzene adsorption in two materials,microporous activated carbon fiber（ACF）and micro-mesoporous CMK-3were provided.It is found that CMK-3 has higher specific adsorption capacity than ACF at very low pressures(<10^-3P/P₀),making it a promising adsorbent for benzene capture in indoor environments.The Dubinin–Radushkevich model were used to fit the isotherms over the low-pressure regions.Furthermore,the experimental isotherm and the isosteric heat were analyzed with molecular simulation results,and the empha-sis is placed on the behavior at ultralow pressures of benzene,typically found in indoor environments.Suggestion on the evaluation and management of adsorbents in terms of minimizing the impacts of ambient moisture were provided.In present study,we have conducted a Monte Carlo simulation of formaldehyde and water,aiming to offer new insights into the capture of polar indoor air pollutants by adsorption.Upon the adsorption isotherms of formaldehyde in the carbon nanopores at sub-ppm level,the effects of pore size and the FGs were separately investigated using the isosteric heats at zero loading as a measure of guest–host interaction.Based on the analysis of the pairwise potential energies of formaldehyde and water as well as their cluster–mediated adsorption mechanisms,we proposed that water may act as strong achors for capturing formaldehyde,with the premise that water does not condense and block the pore.Further discussion on the development of effective water–resistant adsorbent for the polar indoor air pollutants was presentedFinally,four typical metal-organic frameworks（MOFs）,namely MIL-101（Cr）,UiO-66,ZIF-8 and Cu-BDC were synthesized and applied to purify the indoor hexanal,and their adsorption capacities to hexanal were compared with the commercial activated carbon（AC）.Our results show that the adsorption capacities of hexanal follow the order of MIL-101（Cr）(135 mg g^-1)>UiO-66(64.3 mg g^-1)>ZIF-8(40.3 mg g^-1)>AC(35.8mg g^-1)>Cu-BDC(32.5 mg g^-1),and the desorption capacities（by air）follow the order of MIL-101(55.5 mg g^-1)>UiO-66(26.1 mg g^-1)>AC(24.5 mg g^-1)>ZIF-8(19.3 mg g^-1)>Cu-BDC(5.5 mg g^-1),indicating that hexanal adsorbed on MIL-101（Cr）/UiO-66is more appropriate than the commercial AC to be desorbed.FTIR analysis confirms that O-H in Cr-OH/Zr-OH,O-C-O and aromatic C-H in H2BDC in both MIL-101 and UiO-66 are possible sites for hexanal adsorption.DFT calculations further reveal that Cr-OH/Zr-OH and aromatic C-H in H₂BDC are important sites to interact with C=O in hexanal.This study provides a possibility to purify indoor aldehyde contaminants by the highly porous MOF materials.