Water and Desalination Research Journal (WDRJ)

Research Article

Role of surface chemistry and textural characteristics of ACs from coffee and cocoa seed husks biomass in the adsorption of Ni and Co ions

Mónica Hernández Rodríguez^1,3, Jan Yperman2, Robert Carleer², José Falcón Hernández³, Alexis Otero Calvis¹, Grazyna Gryglewicz⁴ and Katarzyna Chomiak⁴

¹Mineral and Metallurgic Institute (ISMM), Moa, Holguín, Cuba.

²Research group of Applied and Analytical Chemistry, Hasselt University, Agoralaan building D, 3590-Diepenbeek, Belgium.

³Faculty of Chemical Engineering, Universidad de Oriente, Santiago de Cuba, Cuba.

⁴Department of Polymer and Carbonaceous Material, Faculty of Chemistry, Wroclaw University of Technology, Gdanska 7/9, 50-344 Wroclaw, Poland.

Submitted: September 2, 2019; Accepted: October 13, 2019

Abstract

The aim of this research is to relate surface chemistry and textural characteristics of activated carbons (ACs) in the adsorption of Ni and Co ions present in single, bi and multi-element solutions, which simulates the wastewater from an acid leaching mineral processing technology. The chars were treated with Na₂S solution before activation process for pore development. Batch adsorption test were done as a function of heavy metal concentration, adsorbent doses, temperature and adsorption time. The adsorption behaviour was evaluated through isotherm models, thermodynamics and kinetics parameters. At 25oC Langmuir maximum adsorption capacity (q_m) for Ni and Co ions is higher for the ACs without chemical pre-treatment. The adsorption of the metallic species is endothermic and spontaneous in nature, with the combination of physical and chemical forces. Both surface functionalities and contribution of mesopores affect the kinetics. However, the rate-controlling step is chemisorption and their behaviour is explained by a “surface enhancement” associated with highly energetic and heterogeneous surface. In multi-element solutions containing Ni(II), Co(II), Mn(II) and Mg(II) ions, the adsorption is enhanced for ACs with better developed mesoporosity.

Keywords

Adsorption; Ni(II); Co(II); coffee husks; cocoa seed husks.

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