Abstract
Contamination of river sources in various rural areas of Colombia with mercury ions (Hg2+) has become an increasingly frequent problem, primarily associated with mining activities. This represents a significant environmental and public health issue, as these water bodies serve as drinking water sources. In this context, activated carbons (AC) synthesized from agricultural waste are emerging as promising alternatives for the valorization of vegetable residual biomass and the treatment of wastewater effluents containing mercury. This research aims to synthesize AC from cocoa husks in a tubular reactor and test it to remove Hg2+ ions in contaminated water. A 23 factorial design was used for obtain the synthesize better conditions: temperature (600 and 800 °C), activation time (0.5 and 1 h), and KOH impregnation ratio of the activated carbons (3:1 and 4:1) as factors. Surface area and ash content were selected as response variables for results analysis. ACs were characterized using analytical techniques, including nitrogen adsorption-desorption isotherms, Fourier transform infrared spectroscopy (FTIR-ATR), Raman spectroscopy, ICP-OES, and adsorption isotherms to evaluate Hg2+ adsorption capacity. The results indicated that AC with a high surface area of 815 m²/g was produced, mainly influenced by activation temperature, impregnation ratio, and reaction time, with optimal conditions of 600 °C, 4:1, and 60 min, respectively. FTIR-ATR analysis confirmed the presence of aromatic, alkoxy, and carbonyl functional groups. Furthermore, for effluents with initial Hg2+ ion concentrations of 100 and 120 ppm, removal efficiencies of 84.1% and 83.6%, respectively, were achieved. Finally, the Freundlich model provides the best fit for the multilayer adsorption behavior of activated carbons on heterogeneous surfaces.
