Adsorption Behavior of Perfluorooctanesulfonate (PFOS) onto Activated Spent Coffee Grounds Biochar in Synthetic Wastewater Effluent

By Jessica M. Steigerwald and Jessica R. Ray
J Haz. Mat. L
May 4, 2021
DOI: 10.1016/j.hazl.2021.100025

Improved understanding of human health risks, environmental persistence, and widespread dispersion of per- and polyfluoroalkyl substances (PFAS) has driven ongoing development of stringent regulations for these compounds in water. Char materials produced from agricultural food waste have recently been explored as alternatives to granular activated carbon for PFAS removal in water. Herein, spent coffee grounds (SCG) were pyrolyzed, activated with alkaline hydroxide, and evaluated for perfluorooctanesulfonate (PFOS) adsorption. At environmentally-relevant PFOS concentrations, pyrolyzed SCG showed minimal PFOS removal while activated SCG removed 9.9% to 99.6% of PFOS depending on activation conditions. SCGKOH (produced from a 1:1 mass ratio of pyrolyzed SCG and potassium hydroxide) had a maximum adsorption capacity of 43.4 mg/g compared to Filtrasorb® F300 activated carbon (55.7 mg/g) and a wood-based fly ash char (79.5 mg/g). All adsorbents display non-linear pseudo first-order adsorption behavior with rate constants of 0.414 h^-1, 0.062 h^-1, 0.090 h^-1 for fly-ash biochar, SCGKOH and F300, respectively. Additionally, PFOS removal by all adsorbents decreased in the presence of simulated effluent organic matter. SCGKOH presents an exciting alternative to existing commercial char adsorbents. The widely available feedstock and low-input production process could make this material a viable water treatment option for resource-constrained communities.

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