Entrapment of AlCrFeMn based high entropy alloys in calcium alginate hydrogel balls for decolorization of azo dyes

In the past ten years, high-entropy alloys (HEAs) have attracted wide attention due to their unique structure and remarkable properties. In order to understand their functional properties in depth, the treatment of azo dyes wastewater by HEAs were studied by us. We found that ball milled (BM) AlCrFeMn (S-0), AlCrFeMnMg (S-Mg) and AlCrFeMnS (S-S) HEAs powders showed promient performance for decolorization of azo dye Direct Blue 6 (DB6). The efficiencies of the BM S-0, S-Mg, and S-S decolorizing DB6 were 3, 6.3 and 90.6 times faster than that of BM MgZn-based amorphous alloy, respectively. MgZn-based amorphous alloy is the best alloy material reported so far. However, since the HEAs powder reacts too fast with DB6, it is difficult to control, resulting in a large loss rate of HEAs powders, which is not conducive to recycling. We found that if the powders were entrapped in calcium alginate hydrogel spheres (CAHBs), these problems could be effectively solved. The BM S-0, S-Mg and S-S HEAs powder entrapped in CAHBs by a combination of electrostatic spray and microfluidic are reported in this work for the first time. To compare the S-S HEA-CAHBs with the bare S-S HEA powder, we found that the reaction of the S-S HEA-CAHBs with DB6 was easier to control and more stable for 4 cycles of the reaction. Moreover, the S-S HEA-CAHBs could be separated from the solution by simple filtering, and the loss rate of the S-S powder decreased from 45 % to 7 %, indicating that entrapment of the CAHBs could greatly reduce the powder loss. The research in this work is of great significance for wastewater treatment.