Studies On A Modified ACF Sampling Multigas Pollutant

Current passive samplers mostly are used to collect a single gaseous pollutant. Ifa multigas passive sample for several criteria air pollutants regulated in the air qualitystandard is developed, the sampling cost and analysis time can be significantlyreduced. The purpose of this paper is to develop an adsorbent for a passive samplerwhich can collect formaldehyde, nitrogen dioxide, sulfur dioxide, benzene andtoluene simultaneously with low blank value and high recovery rate. Compared withthe other commonly used adsorbents, active carbon fiber (ACF) has the advantage ofhaving large specific surface areas, well-developed micropores, good acid andalkaline resistance, thermostability, easy regeneration and being able to be modifiedby a wide range of methods. Therefore, the aim of this study is to develop an ACF fora multigas passive sampler.The research contents include development of methods of removing the ACFblank interferences and analyzing sample components simultaneously to get lowblank value and high recovery rate. Select a suitable ACF modification method amongair oxidation, hydrogen peroxide, potassium hydroxide, triethanolamine, potassiumhydroxide/microwave, hydrogen peroxide/potassium hydroxide to achieve highsampling rates of formaldehyde, sulfur dioxide, nitrogen dioxide, benzene and toluenein a series of an indoor chamber experiments and the experimental results indicatethat ACF modified by hydrogen peroxide/potassium hydroxide solution has highsampling rates of formaldehyde, sulfur dioxide, nitrogen dioxide, benzene and toluenewith relatively low blank value and high recovery rate. Draw the sampling rate curveof formaldehyde, nitrogen dioxide, sulfur dioxide, benzene and toluene using ACFmodified by hydrogen peroxide/potassium hydroxide solution as adsorbent and thesampling time should be8h. Select the optimal modified conditions by orthogonalexperiments on the basis of results from variance analysis and intuitive analysis ofexperimental data. According to orthogonal experiments, the optimal ACF wasmodified using the following method: the purified ACF is oxidize in30%H2O2at60℃for5h and washed multiple times by small amount of ultrapure water. TheACF is then oxidized in2.5mol/L KOH solution at50℃for1h and washedmultiple times by small amount of ultrapure water until the pH of the effluent waterbecomes around7.0and then is N2-dried at300℃for30mins. The conclusion ofthis study is that ACF modified by hydrogen peroxide/potassium hydroxide solutioncan adsorb formaldehyde, sulfur dioxide, nitrogen dioxide, benzene and toluene withhigh sampling rates and the multicomponents in the samples can be treated and analyzed simultaneously. Such a passive sampler with the modified ACF by hydrogenperoxide/potassium hydroxide can reduce the cost of sampling and analysis time andhas wide application prospects.