A novel photo-assisted electrochemically switched ion exchange technology for selective recovery of bromide ions

Effective recovery of high-value-added bromide ion (Br−) from aqueous solutions is significant because of its high application value. Electrochemically switched ion exchange (ESIX) has been proven as a valid method for the selective capture and recovery of target ions. As the photocatalysts are also used as the electroactive materials in the ESIX process, the light illumination could promote the excitation of electrons for the improvement of ion capture capacity. Herein, taking advantage of synergetic effect between photo and electric field we propose a novel photo-assisted electrochemically switched ion exchange (P-ESIX) strategy for the first time. As a try, Br−-vacancy BiOBr film is used as an ideal electrode material in P-ESIX system for the recovery of Br−, which not only possesses photo/electron bi-activity, but also exhibits high selectivity towards Br−. Compared with the traditional ESIX, this P-ESIX displays superior capture performances with a photo-assisted adsorption capacity growth rate of 23.09% with 1.23 times higher Br− adsorption capacity at 0.8 V applied potential. The capture capacity of Br− in P-ESIX reaches 106.80 mg g−1 with excellent stability. Meanwhile, P-ESIX working mechanism is deeply analyzed based on experiments and DFT calculations. This novel technology provides a new direction in separation field to achieve higher capture efficiency for the target ions.