Preparation of CoS2/Fe/SA hydrogel spheres with Fe2+ slow-release effect to improve Fenton reaction efficiency

Fenton reaction is a traditional advanced oxidation process that has long been used for wastewater treatment. However, the narrow pH range of 2–4, the inefficient utilization of both H 2 O 2 and Fe 2+ , and the large amount of iron sludge formation limit its application. Here, we prepared sodium alginate composite hydrogel spheres with both Fe 2+ and CoS 2 loading (denoted as CoS 2 /Fe/SA hydrogel spheres) to construct a CoS 2 /Fe/SA + H 2 O 2 reaction system. The degradation efficiency of carbamazepine (CBZ) in the CoS 2 /Fe/SA + H 2 O 2 system was significantly enhanced with a first-order kinetic reaction constant of 0.1958 min −1 , which is 8.9 times higher than that in Fe 2+ +H 2 O 2 system. When the initial solution pH was in the range of 2–8, the removal rate of CBZ at 90 min reaction time ranged from 96.5 % to 99.9 %. The enhanced degradation efficiency even in a slightly alkaline aqueous solution was due to the sustained slow release of Fe 2+ from the CoS 2 /Fe/SA hydrogel spheres that enhances the utilization of Fe 2+ and the promotion of Fe 3+ /Fe 2+ cycling via CoS 2 . Moreover, the release amount of Fe 2+ in CoS 2 /Fe/SA hydrogel spheres could be controlled by tuning the Fe 2+ loading amount during preparation, which in turn determines its number of cycling uses.