The effect of filter cake structure on adsorption of perfluoroalkyl substances

Compared to fixed bed adsorbers, cake filtration of adsorbents to remove dilute impurities offers flexibility and the possibility to simultaneously remove solid impurities. Here, we show the influence of adsorbent bed structure deposited by cake filtration, on the adsorption of perfluoroalkyl substances. Cake structure was varied by using the filter aid cellulose as either a precoat layer or by simultaneous filtration. Precoat filtration showed on average a ≈ 20% better kinetic adsorption performance compared to simultaneous filtration of filter aid and adsorbent. Additionally, we found that increasing the amount of filter aid used during filtration has adverse effects on the subsequent kinetic adsorption performance, but no influence on the adsorption equilibrium. These findings should be taken into consideration when designing processes where either an adsorbent is filtered using a filter aid or a filter aid with adsorptive properties is used. • Adsorbent cakes formed by precoat filtration lead to faster adsorption kinetics. • Higher volume fraction of non-adsorbing filter aid inhibits adsorption performance. • Removal of PFAS compounds shown in filtration-adsorption process.