Efficient Electrochemical Oxidation of Charged Cryogel Adsorbed Reactive Dyes in Non-aqueous Media

Reactive Red 141 (RR 141) was efficiently adsorbed and enriched from an aqueous solution by oppositely charged cryogels. The cryogels were prepared with acryl amide (AAm) and dimethyl diallyl ammonium chloride (DDAC) as the monomers, along with N,N′-methylene-bis acrylamide (MBA) as the cross-linker. In the presence of DDAC, the prepared macroporous cryogels hold a strong affinity to the reactive dye. The elasticity and mechanical properties of the cryogels were improved when the mass ratio of the monomer and the cross-linker was 2:1. A maximum adsorption capacity was achieved with 21 wt% of DDAC in reactants. The impacts of conditions of non-aqueous electrolysis such as solvent types, electrolytic voltages, and electrolyte concentrations were investigated. When subjected to non-aqueous electrolysis in organic media of N-methyl pyrrolidone (NMP), propylene carbonate (PC), and ethylene carbonate (EC), the cryogel-adsorbed dye underwent a quick and efficient degradation. Higher Faradaic efficiencies were obtained compared with that from the same operations in aqueous media. The specific degradation rate of RR 141 in a non-aqueous electrolysis is substantially larger than that reported. In addition, both the cryogel and the organic solvents can be repeatedly used, making it a sustainable method to deal with related pollution problems of reactive dyes.