Review on ultrasound assisted persulfate degradation of organic contaminants in wastewater: Influences, mechanisms and prospective.

• The synergistic influences of US and PS are reviewed. • Operational factors influencing the removal efficiency are discussed and summarized. • Reaction mechanisms of sono-activated persulfate oxidation are evaluated and outlined. • Knowledge gaps and research needs of sono-activated persulfate are proposed. Persulfate (PS) has attracted great attention as an alternative to H 2 O 2 for advanced oxidation processes in recent years. Among various activation techniques, ultrasound (US) activation acts as an emerging method and has gained increasing interest especially in recent years. The combination of US and PS is a promising alternative for organic wastewater treatment. In this review, the synergistic effects of US and PS were investigated based on wide applications. The degradation efficiency is easily influenced by the reaction factors, including ultrasonic power and frequency, pH, temperature, PS concentration, and coexisting inorganic anions etc. These factors were summarized and analyzed to give the optimal references for further in-depth studies. Moreover, the decomposing mechanisms are outlined in terms of molecular structures due to the one-sidedness of reactive radical analysis. In the end, the concluding remarks and perspectives are made for future study on US-PS technologies. This review can provide an overview for the systematic understanding of the mechanisms and synergistic effects of US and PS combination. [ABSTRACT FROM AUTHOR]