Adsorptive Removal of PFAS from Aqueous Solutions Using GAC, PAC and Ball-Milled Colloidal Activated Carbon: Characterizing Efficiency, Kinetics, and Mechanisms
Mahlet M. Kebede, Md Abdullah Al Masud, Sarah Ortbal, Won Sik Shin, Mesfin M. Mekonnen, T. Prabhakar Clement, Leigh G. Terry
Abstract
High Resolution Image Download MS PowerPoint Slide Per-and polyfluoroalkyl substances (PFAS) present significant challenges for remediation due to their persistence in nature. Activated carbon is a widely used adsorbent for removing PFAS. In this study, three forms of activated carbon, granular activated carbon (GAC), powdered activated carbon (PAC), and ball-milled colloidal activated carbon (CAC BM ), are compared for their effectiveness in removing short and long-chain PFAS. Physical modification through ball-milling process enhanced the adsorptive properties of activated carbon, resulting in smaller particle size ( d 50 = 0.318 μm), increased surface area (968.59 m 2 g –1 ), and improved suspension stability compared to conventional GAC and PAC. Kinetic experiments showed that CAC BM demonstrated superior removal efficiencies of long-chain PFAS (up to 89% for perfluorooctanesulfonic acid (PFOS) and 73% for perfluorooctanoic acid (PFOA)), and moderate removal of short-chain PFAS (55% for perfluorobutanesulfonic acid (PFBS) and 30% for perfluorobutanoic acid (PFBA)). The pseudo-first-order model adequately described adsorption trends; however, the pseudo-second-order model provided a better fit, with intraparticle diffusion identified as the rate-limiting step. Isotherm studies indicated that PFAS adsorption aligned well with the Freundlich model. Competitive adsorption experiments revealed a hierarchical pattern. Overall, the study demonstrates CAC BM as a promising adsorbent for remediation of PFAS-contaminated water systems.