Poly- and perfluoroalkyl substances (PFAS) have received considerable attention from environmental scientists and engineers because of their stability and widespread. Sonochemical process has been widely used in the environmental field to remove pollutants due to its advantages in terms of operational simplicity, no secondary pollutant formation and safety. Currently, many studies have reported sonochemical degradation of various PFAS in laboratory settings and showed excellent removal potential. This article reviewed the effects of different power densities, ultrasonic frequencies, temperatures, atmosphere conditions, additives, and initial concentration and chemical properties of PFAS on the sonochemical degradation of PFAS. Sonochemical methods combined with conventional techniques for PFAS removal were elaborated as well. Additionally, this article discussed the challenges and prospects of using sonochemical approaches for PFAS remediation.

Coal fly ash originated from coal combustion has high concentrations of metals. If suitable leaching techniques are identified, then coal fly ash could serve as a useful source of valuable minerals including rare earth elements (REEs). In this study, three microbial strains, Candida bombicola, Phanerochaete chrysosporium and Cryptococcus curvatus were tested on their performance of leaching trace elements and REEs from fly ash. Through comparing mineral loss and leaching efficiencies resulting from indirect leaching or use of the culture supernatant, C. bombicola was identified to be the best leading to the highest mineral loss and extracting efficiencies of trace elements and REEs among the three strains. The highest mineral loss observed from using the supernatant of this yeast strain was 59.7%. Among all trace elements, As and Mo had the highest leaching efficiency of 80.9% and 79.5%, respectively. The same leaching test led to 67.7% of Yb and 64.6% of Er dissolved from the ash. This study, thus, demonstrated that bioleaching is feasible for leaching metals out of fly ash. The C. bombicola strain deserves further investigation due to its robust actions on metal leaching.