Carbon based solid sorbent for perfluorooctanoic acid removal

Perfluorooctanoic acid (PFOA) is one of the per- and polyfluorinated substances (PFAS). PFOA has been considered an environmental pollutant that affects human health through water and food contamination, characterized by strong chemical bonds and high inertness. Many approaches have been used to remove PFOA and adsorption methods are the most effective techniques for treating PFOA. This study aims to compare the efficiency of PFOA removal using commercial activated carbons (bituminous activated carbon and coconut shell activated carbon) and activated carbon synthesized from dried hemp stem. The porous textures of activated carbon were examined by N2-sorption measurements. The functional groups of the samples were investigated using a Fourier-transform infrared spectrometer (FTIR) in transmission mode. Batch adsorption tests were used to determine the adsorption isotherms and adsorption kinetics, in which the adsorptions were investigated using high performance liquid chromatography (HPLC). The results showed that the commercial activated carbons derived from bituminous have higher PFOA removal (87.95% and 90.26%) than that synthesized from hemp stem activated at 450 °C (HEMP450, 60.27%) and coconut shell activated carbon (15.30%). The adsorption isotherms of HEMP450 and the commercial activated carbon derived from bituminous fit well with the Redlich-Peterson model and reduced to the Langmuir model, suggesting homogenous monolayer adsorption. However, the activated carbon derived from coconut shell fits with Temkin model assuming the indirect interaction of adsorbent and adsorbate. The kinetic adsorption followed the pseudo second order model for the chemisorption kinetic process.