The efficiency of activated carbon/magnetite nanoparticles composites in copper removal: Industrial waste recovery, green synthesis, characterization, and adsorption-desorption studies

Due to population growth, industrial development, and increasing environmental pollution, the treatment of water, soil, and air is crucial. Convenient and low-cost methods, including adsorption, have attracted much attention in recent years. In the present study, powdered activated carbon (PAC) and granular activated carbon (GAC) composites with magnetite nanoparticles (Fe3O4) were synthesized via a green method, using green tea extract as reducing agent. The iron required for the synthesis of adsorbents was extracted from direct reduction iron (DRI) sludge resulting from the direct reduction process of the steel industry. The adsorbents were identified using XRD, FESEM, EDX, FTIR, VSM, and BET analyses. Copper removal was examined within the initial concentration range of 0–400 mg/L from an aqueous medium. Desorption tests were performed for 100 and 300 mg/L concentrations in a 10-day cycle. The results revealed that Langmuir and Freundlich models are well fitted with the copper adsorption data. The maximum copper adsorption capacity was obtained at 23.61 and 13.37 mg/g by powdered activated carbon-magnetite nanoparticles composite (MNP-PAC) and granular activated carbon-magnetite nanoparticles composite (MNP-GAC) respectively. MNP-PAC had a higher adsorption capacity compared to MNP-GAC. The desorption results showed that the release of copper from the surface of adsorbents was very low and it diminished over time. Owing to their high efficiency in removing copper from aqueous solutions and not releasing copper over time as well as the easy separation of adsorbents after the completion of adsorption, the use of these two adsorbents, especially the MNP-PAC is recommended for the removal of copper.