Microwave-Catalyzed Conversion of Phenolic Resin Waste to Activated Carbon and Its Applications for Removing Ammonium from Water

The influences of reactive and dielectric characteristics of activators were investigated in the microwave-catalyzed conversion of phenolic resin waste to activated carbon (AC). To compare with the dielectric interactions of the microwaves with treated samples, conventional electric heating for AC carbonization was also conducted in parallel. The porosity and chemical features of the prepared AC were examined, and the AC was used to remove ammonium from water through adsorption. The results revealed that KOH-activated wastes developed a highly porous structure, whereas H3PO4 treated wastes were functionalized with surficial phosphate groups. Both of these features were more pronounced in the cases of microwave-catalyzed carbonization than those using conventional electric heating. Because of the intense dielectric interactions of the H3PO4-activated waste with microwave, the abundant phosphate functional groups formed on the phenolic resin waste surface during microwave-catalyzed carbonization. They facilitated the resulting AC as an effective adsorbent for aqueous ammonium.