Trace-Level PFAS Adsorption from Real Drinking Water by Mineral- and Coconut-Shell-Derived Activated Carbons

Granular activated carbon is widely applied for per- and polyfluoroalkyl substance (PFAS) removal, yet adsorption data are frequently generated in simplified laboratory waters and at concentrations well above those encountered in drinking-water treatment. This study compared a mineral-based and a coconut-shell-derived activated carbon using an actual drinking-water matrix characterized by high mineralization (conductivity 1300 µS cm⁻¹, hardness 66 °f, and fixed residue 988 mg L⁻¹). The water was fortified with a multicomponent PFAS mixture at 500 ng L⁻¹ per compound, and unreplicated screening tests were conducted at carbon doses of 10–200 mg L⁻¹ for 96 h. Short-chain PFAS governed the residual dissolved fraction, whereas longer-chain compounds were removed rapidly and, for the mineral carbon, were frequently below effective quantification limits. The mineral carbon showed nonlinear, favorable adsorption for PFBA, PFPeA, PFBS, and PFHxA, while the coconut-shell carbon exhibited a broader near-linear response and stronger low-dose removal of PFBA and PFPeA under the tested conditions. PFBA progressively dominated the residual mixture as carbon dose increased, identifying it as the conservative compound for treatment screening. The study provides a direct evaluation in a chemically complex real drinking-water matrix and a basis for replicated batch tests and subsequent column validation.