Ultrasound and microwave-assisted preparation of Fe-activated carbon as an effective low-cost adsorbent for dyes wastewater treatment

Abstract

A composite adsorbent (Fe-activated carbon) was synthesized by impregnating Fe(NO₃)₃ onto activated carbon, and heated via microwave heating to remove methylene blue (MB), utilizing ultrasound-microwave combined preparation methods. The optimal MB removal capacity and yield of Fe-activated carbon is 257 mg g⁻¹ and 83.31%, respectively, under optimal conditions such as 700 W of microwave power, 700 °C of temperature and 25 min of heating time. The ultrasound was used for assisted-impregnation of Fe(NO₃)₃ onto the activated carbon via its acoustic cavitation. The removal capacity on MB of Fe-activated carbon increases by 17.12%, as compared to that of it without ultrasound assisted-impregnation. The physico-chemical properties of Fe-activated carbon were examined by XRD, XPS, SEM, EDX, FTIR, Raman and N₂ adsorption. Moreover, the existence of Fe₃O₄ leads to Fe-activated carbon having magnetic properties, which makes it easily separable from dyes wastewater in an external magnetic field. The equilibrium adsorption data showed that the adsorption behavior followed the Langmuir isotherm, and a pseudo-second order model matched well the kinetic data. Compared with raw activated carbon, the maximum monolayer adsorption capacity of Fe-activated carbon increases by 25.96%. According to these results, Fe-activated carbon is a promising adsorbent for the removal of dye from wastewater.