Coffee waste activated carbon impregnated with zinc chloride for efficient iron removal

Abstract The growing trend in coffee consumption has led to an increase in coffee waste, a valuable byproduct with significant potential for reuse. Repurposing this waste to produce activated carbon offers a sustainable solution to reduce environmental impact and enhance resource value. While iron (Fe) is generally non-hazardous, excessive levels in water can lead to toxicity, posing risks to human health when consumed beyond tolerable limits. This work aims to synthesize the coffee waste activated carbon (CWAC) and investigate its efficiency in removing iron solutions. The CWAC was synthesized using both physical and chemical methods. Physical activation involved carbonizing the coffee waste at 500 °C under nitrogen flow. While, for chemical activation, an impregnation ratio of 1:2 (ZnCl 2 /CWAC) was applied at 85 °C before carbonization at 500 °C under nitrogen flow. The characterization of CWAC was carried out by BET, FTIR, TGA, SEM, and AAS. The raw coffee waste and the physical and chemical activated CWAC were then used to adsorb synthetic iron to assess their performance on iron adsorption. Results from BET analysis showed that chemically activated CWAC has the highest specified surface area compared to physical activation of CWAC and raw coffee waste at 1821.38 m 2 /g, 29.53 m 2 /g, and 3.95 m 2 /g, respectively. The chemical activation of CWAC achieved higher iron removal of 94.4% compared to 66.1% of physical activation. Overall, this study highlights the potential of transforming coffee waste into a valuable resource while promoting the use of eco-friendly and cost-effective solutions for application in wastewater treatment. The CWAC impregnated with ZnCl 2 exhibits significant potential as a substitute for commercial adsorbents for the iron removal process. Future work will focus on examining its performance in treating real wastewater and assessing its potential for reuse.