Study On The Purification Of Aldehydes And Ketones VOCs By Absorption-photocatalysis

As an important precursor for the formation of PM_2.5and ozone,the prevention and control of volatile organic compounds（VOCs）has received considerable attention.Volatile aldehydes and ketones,as an important type of VOCs gas,have the characteristics of wide sources and strong harmfullness.In this study,characteristic pollutant acetone gas of the pharmaceutical industry and characteristic pollutant formaldehyde gas of the board processing industry were selected as representative aldehydes and ketones VOCs to investigate the purification performance of the"absorption-photocatalysis"combined process and the"absorption-photocatalysis"co-processing method on VOCs,respectively.And the purified products were analyzed by GC-MS.On this basis,the purification mechanism and reaction kinetics process of aldehydes and ketones VOCs in the research system were preliminary studied.The research results are as follows:1)The study of the“absorption-photocatalysis”combined process to purify acetone gas showed that,when the UV power was 60 W and the light time was 55 min,the single“photocatalysis”has the highest removal rate of acetone gas（84.2%）;When water was used as the absorbent,the liquid-gas ratio was 5 L·m^-3,and the residence time was 6 s,the removal rate of acetone gas by single“absorption”was the highest（88.4%）.The purification efficiency of different purification processes for acetone gas increased in the sequence of“photocatalysis-absorption”>“absorption-photocatalysis”>“absorption”>“photocatalysis”.Among them the removal rate of the“photocatalysis-absorption”combined process was the highest（93.7%）.In the products,in addition to the unreacted acetone gas,a small amount of acetic acid was generated.The reaction mechanism of“photocatalysis-absorption”combined purification of acetone gas has been preliminarily established,and the degradation process of“photocatalysis-absorption”combined purification of acetone gas degradation can be described by quasi-first order reaction kinetics.2)The study of“absorption-photocatalysis”synergistic purification of formaldehyde gas showed that,when the UV power wass 40 W,the H₂O₂concentration was controlled to 10 mol·L^-1,the p H of the solution was 5,the oxidation-reduction potential was 300 m V,and the liquid-gas When the ratio was 7 L·m^-3and the residence time is 8.5 s,the removal efficiency of formaldehyde gas was the highest（97.1%）.No other intermediate products were detected in the purified exhaust gas except for formaldehyde,and a small amount of formic acid was detected in the circulating absorption liquid besides formaldehyde.On this basis,the reaction mechanism of“absorption-photocatalysis”purification of formaldehyde gas established.The degradation process of“absorption-photocatalysis”synergistic purification of formaldehyde gas can be also described by quasi-first order reaction kinetics.