Production of activated carbon from cocoa pods: Investigating benefits and environmental impacts through analytical chemistry techniques and life cycle assessment

Activated carbons currently represent a feasible adsorbent substrate for the removal of organic and inorganic compounds from solutions, due to their large specific surface area and high porosity. The chemical characterization of activated carbon and the environmental burden related to its production are a crucial point that challenges researchers all over the world for the generation of feasible absorbents at low cost, with low environmental impacts. This work aims at evaluating the preparation of activated carbons from cocoa pods using the Response Surface Methodology (RSM), and Life Cycle Assessment (LCA) to evaluate the environmental impacts of the process. Analysis of variance (ANOVA) and t-test are used to determine the major contributing factors to the production process. Results show that at a calcination time and temperature of 3 h and 600 °C respectively, coupled with an amount of 0.6 mol/L of potassium hydroxide (KOH) as activating agent are needed for the most suitable activated carbon production, in terms of maximum iodine number (995 mg/g) and yield (74.4%). The raw biomass and the produced activated carbon are characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD) and infrared spectroscopy (FTIR). The quantification of the major environmental impacts generated during the production process of activated carbon are analyzed through Life Cycle Assessment. Results show that the major contributor to environmental impact is the electricity used in the laboratory steps, with an average contribution throughout all the impact categories of almost 70%, a minimum to land use potential (≈9%), and a maximum to freshwater eco-toxicity (≈99%). Toxicity is related almost exclusively to the electric energy used (average ≈ 93% of contribution). Electricity is also the major contributor to Freshwater eutrophication potential (≈70%) together with distilled water (≈20%).