Enhanced adsorption of aqueous acetone by modified powdered activated carbon

Acetone, a small molecule organic compound, is freely soluble and volatile. To improve the removal rate of acetone, three different types of powdered activated carbon (PAC) were compared and then modified with formic acid and NaOH to optimize the adsorption capacities of PAC. The adsorption mechanism and the effect of physical-chemical properties of PAC to the adsorption were clarified. Results show that PAC produced from wood performed best adsorption capacities. The pseudo-second-order model and the Freundlich model accurately described the adsorption behaviour, while lower temperature was more conducive to the adsorption process. PAC giving a higher acetone adsorption capacity had a larger specific surface area, a richer micropore structure, a larger micropore volume, a smoother surface, with more acidic, oxidizing functional groups. The adsorption removal efficiency of modified PACs with formic acid was improved from 60.89% to 82.93%, while NaOH modification decreased the adsorption capacity. The positive effect of formic acid was attributed to the formation of novel acidic oxygen-containing functional groups, which was supported from the NaOH treatment that removed original acidic oxygen-containing functional groups, contrarily the formation of novel alkaline reducing functional groups did not restore the acetone adsorption capacity. We conclude that wooden PAC is a suitable adsorbent for acetone, in particular after pretreatment with formic acid.