article · Applied Sciences
Used coffee grounds can be converted into powdered activated carbon through chemical activation with potassium hydroxide. When examined alongside commercial activated carbon using structural, spectroscopic, and chemical characterisation techniques, the material demonstrated viable adsorption capabilities. Performance evaluations using batch adsorption tests assessed the removal of the cationic dye crystal violet and hexavalent chromium from aqueous solutions. The adsorption processes followed pseudo-second order kinetics and conformed to the Langmuir isotherm model for both contaminants. Furthermore, thermodynamic analyses indicated that the uptake of both the dye and the heavy metal is spontaneous and exothermic, leading to decreased disorder at the solid-liquid boundary. The findings demonstrate that chemically treated spent coffee grounds serve as an effective alternative adsorbent for remediating water contaminated with heavy metals and synthetic dyes.
Industrial effluents frequently introduce hazardous synthetic dyes and toxic heavy metals into aquatic ecosystems. Reusing spent coffee grounds to manufacture activated carbon supports circular economy models by valorising organic waste into functional filtration media. This approach demonstrates a practical method for water remediation that reduces dependence on standard commercial adsorbents while addressing pollution challenges.
This research represents early-stage laboratory work demonstrating water treatment potential. The activated carbon could serve industrial wastewater treatment operators and municipal filtration facilities seeking lower-cost adsorbents for heavy metals and dyes. However, moving toward commercial application requires scaling production beyond laboratory batch tests, evaluating continuous flow performance, and establishing processing costs compared to existing commercial carbons.
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In the context of the circular economy, used coffee grounds were transformed into powdered activated carbon by chemical activation using potassium hydroxide. Its characterisation was conducted in comparison with that of a commercial activated carbon by scanning electron microscopy (SEM) coupled with energy dispersive X-ray microanalysis (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Boehm titration, and point zero charge (pHPZC) and by determination of the methylene blue number (MBN) and the iodine number (IN). Performance of the prepared activated carbon was tested in the adsorption of the cationic dye crystal violet (CV) and hexavalent chromium. Batch adsorption tests were carried out and the effects of operating parameters were studied. The results collected on the adsorption kinetics show that the adsorption followed pseudo-second order kinetics and that the Langmuir isotherm best fits the equilibrium data for crystal violet and hexavalent chromium. The thermodynamic study showed that the adsorption of both adsorbates is spontaneous and exothermic and leads to a decrease in disorder at the solid–liquid interfaces. These results indicate that this activated carbon can be used as an alternative adsorbent to remove cationic dyes and heavy metals from aqueous solutions.
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DOI: 10.3390/app13020985
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