Trivacant Keggin-type polyoxometalate/TiO2 composite for enhanced sonocatalytic degradation of AR88 from aqueous solutions

K 9 SbW 9 O 33 ·19.5H 2 O/TiO 2 Z-scheme heterojunctions were successfully constructed via a solution method. The internal electric field significantly enhanced the separation efficiency of electron and hole pairs with the assistance of the sonoelectric polarization applied by the ultrasonic vibration, so K 9 SbW 9 O 33 ·19.5H 2 O/TiO 2 exhibited excellent sonocatalytic activity. • K 9 SbW 9 O 33 ·19.5H 2 O/TiO 2 Z-scheme heterojunction was synthesized via a sol–gel method. • The K 9 SbW 9 O 33 ·19.5H 2 O/TiO 2 sonocatalyst exhibited excellent sonocatalytic activity. • The formation mechanism of K 9 SbW 9 O 33 ·19.5H 2 O/TiO 2 was systematically discussed. Polyoxometalates (POMs) have been limited in their widespread use in catalysis in previous studies due to their strong carrier complexation and limited solubility. To overcome this limitation, in this study, Z-type heterojunction composites constructed with trivacant Keggin-type POMs K 9 SbW 9 O 33 ·19.5H 2 O and TiO 2 were synthesized by the sol–gel method and used for the sonocatalytic removal of the organic pollutant AR88. The results showed that, compared with pure K 9 SbW 9 O 33 ·19.5H 2 O, the optimum K 9 SbW 9 O 33 ·19.5H 2 O/TiO 2 showed a significantly higher sonocatalytic degradation efficiency of 87.2 % for AR88, and the mineralization rate reached 51.8 %. Parameters such as dye pH and sonication power were optimized to determine the best conditions for sonocatalysis. In addition, the K 9 SbW 9 O 33 ·19.5H 2 O/TiO 2 Z-type heterojunction composites showed good stability and reusability. The excellent catalytic performance is attributed to the effective separation of charges and holes by the Z-type heterojunction, which enables them to produce active substances for AR88 decomposition. This study demonstrates the high potential of POMs for the application of sonocatalysis in the treatment of organic pollutants.