Emulsion hydrogel microbeads encapsulating extractants prepared by O/W/O double Pickering emulsions for the recovery of Cu(II) from water

Abstract

In a double emulsion, the cross contamination between internal and external phase is an unavoidable problem, which limits its widely application. This work focused on the preparation of the cross contamination-free O/W/O Pickering emulsions for the fabrication of Pickering emulsion hydrogel (PEHG) microbeads encapsulating copper extractants. KH-570 was used to hydrophobically modify silica for the stabilization of O/W Pickering emulsions. Batch and fixed-bed experiments were conducted for the recovery of Cu(Ⅱ) from water using PEHG microbeads. The results showed that the formed particle-polymer networks in oil-water interface strengthen the stability of O/W Pickering emulsions. The cross contamination ratio of O/W/O Pickering emulsions was reduced to less than 3% under preset conditions. The size of PEHG microbeads was controlled by adjusting the dosage of hydrophobic silica and the optimal diameter used in extraction was 1.8–2.2 mm. The extraction capacity of copper extractants in PEHG microbeads was 86.43 mg/g, with the operation time of 80 min (D = 1.8 mm). The fixed-bed extraction experiment was completed in 250 min and the stripping rate was 97.1%. Compared to previous work, the extractants in PEHG microbeads possessed a better utilization.