Separation of Dissolved Organic Matter (DOM) and Per- and Polyfluoro-Alkyl Substances (PFAS) from Landfill Leachate Using Modified Coal Fly-Ash (CFA)

Abstract

Per and Poly-fluoroalkyl Substances (PFAS) has been a major subject of research in environmental sector ever since it was found in the environment and blood serums at toxic levels. As landfills are the final disposal method for majority of the waste, PFAS concentration in landfill leachate have been found in the range of few µg/L to mg/L. Only few conventional treatments such as Activated Carbon, Reverse Osmosis, and Ion-Exchange has been proven effective in removing PFAS. However, these treatment methods are proving to be very expensive and generate secondary contamination that needs to be disposed-off or treated. Since the phase out of C8-PFAS compounds, more short chain PFAS compounds are detected in landfill leachate. Hence, an effective treatment strategy is needed to keep up with the rising concentration levels and variety of PFAS compounds. The purpose of this study was to develop a sustainable and cost-effective process using modified Coal Fly-Ash (CFA) that can treat both short chain and long chain PFAS compounds. Previous studies have shown application of CFA in removal of dye and metals from different types of wastewaters. In previous studies CFA was modified to enhance its surface properties, that can improve the adsorption of organic and anionic contaminants. In this study, thermo-chemical modification was used on CFA to remove organic matter and PFAS compounds. Preliminary results showed that, CFA can remove more than 90% UV absorbance, more than 80% TOC and approximately 40% of total PFAS compounds. The maximum adsorption capacity for total PFAS was found to be 84 ng PFAS per g CFA, out of which 70 ng was for short chain PFAS and 14 ng for long chain PFAS compounds. An effective removal of organic matter and PFAS compounds, show a promising application of CFA in leachate treatment. However, further research is needed to analyze the adsorption dynamics, kinetics, post-treatment disposal method, and any possible contamination when mixing CFA with landfill leachate.

An Overview of Treatments for Ultraviolet Quenching Substances (UVQS) and Per- and Polyfluoroalkyl Substances (PFAS) Removal from Landfill Leachate

“…Biochar produced from biomass pyrolysis at 500-600°C can adsorb 80% of longchain PFAS and is highly stable [110]; if biochar is created using a pyrolytic combustion integrated process, it may adsorb 90%, while short-chain PFAS performs poorly [111]. The adsorption of shortchain PFAS can be improved by using a modified coal fly ash as an adsorbent [112]. Coal-based magnetic activated carbon removed 72.8-89.6% PFCA with 8 g/150 mL adsorption dosage and 120 min contact time [113].…”