Comparison of a homemade cocoa shell activated carbon with commercial activated carbon for the removal of reactive violet 5 dye from aqueous solutions

• Acidified cocoa activated carbon (ACC-1.0) was prepared and characterised.
• Adsorption of RV-5 dye was studied using ACC-1.0 and CAC.
• Adsorption maximum values were 603.3 mg g−1 (ACC-1.0) and 517.1 mg g−1 (CAC).
• General order kinetic model suitably described the adsorption processes.
• ACC-1.0 effectively decolourised simulated industrial effluents.

A novel homemade furnace setup for preparation of chemically activated carbon was proposed in a quest for industrial wastewater treatment. Cocoa shell was initially mixed with inorganic components (red mud + lime + KOH + Al(NO3)3 + Na2SO4) and water to form a paste. The paste was placed in a mould cylinder, dried at a room temperature, and then the material was placed in a stainless steel reactor and heated up to 1073 K under inert atmosphere. Three carbon adsorbents with inorganic: organic ratio of 1.0 (CC-1.0), 1.5 (CC-1.5) and 2.0 (CC-2.0) were prepared. The adsorbents were acidified with a 6 mol L−1 HCl under reflux (24 h) to obtain corresponding ACC-1.0, ACC-1.5 and ACC-2.0. The chemical activation process was completed by leaching the inorganic components from the carbonaceous matrix through acidification. ACC-1.0 exhibited highest sorption capacity compared with the other two adsorbents. CC-1.0 and ACC-1.0 were characterised using FTIR, SEM, N2 adsorption/desorption curves and X-ray diffraction. A well-known commercially activated carbon (CAC) was used to compare the sorption capacity of ACC-1.0. The ACC-1.0 and CAC adsorbents were used for adsorption of reactive violet 5 (RV-5) textile dye from aqueous solutions. The equilibrium times of 45 and 150 min were observed for ACC-1.0 and CAC, respectively, at optimum pH 2.0. General order kinetic model best described the adsorption process than pseudo first-order and pseudo-second order kinetic models. Liu isotherm model gave the best fit of the equilibrium data at all experimental temperatures. The maximum amounts of RV-5 dye adsorbed at 298 K were 603.3 (ACC-1.0) and 517.1 mg g−1 (CAC). The adsorbents were tested on two simulated dyehouse effluents. ACC-1.0 is effectively capable of decolourising industrial textile effluents.

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