Sorptive Removal of Per- and Polyfluoroalkyl Substances (PFAS) from Water by Biochars

Abstract

This thesis aims to employ biochar (a carbonaceous material) as a cost-effective sorbent to remove per- and polyfluoroalkyl substance (PFAS) from water by two case studies. Study 1 seeks to identify which biochars perform better for the sorption of perfluorooctane sulfonate (PFOS) from water, and which physicochemical properties of biochars control PFOS sorption. The biochars with higher sorptive capacity of PFOS are further tested in Study 2 to investigate how these biochars perform at environmentally relevant conditions (e.g., pH, salt, and natural organic matter) for the sorption of PFOS and other C4-C8 PFAS compounds. Biochars produced from Douglas fir and poplar feedstocks exhibit high PFOS sorption efficiency. Biochar properties such as specific surface area, pore diameter, pore diameter/pore volume ratio, and hydrophobicity play important roles for PFOS sorption. Salt promotes PFAS sorption, while natural organic matter decreases PFAS sorption mainly due to the competition of sorption sites of biochars.