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Abstract
In this study, a clay sample recovered from an archaeological excavation from the Krobo Mountains in Ghana was examined for its potential to decolorize and adsorb cationic methylene blue. The raw and calcined clay samples were characterized with XRD, SEM, FTIR and EDX. The supernatant obtained by washing the raw clay with 70% ethanol solution decolorized methylene blue. The decolorization of methylene blue was independent of calcination temperature up to 300°C. The clay material subjected to calcination temperature at 600°C showed strong adsorption towards cationic methylene blue. The equilibrium adsorption data fitted well with the Freundlich isotherm indicating adsorption unto heterogeneous surface with the interaction between the adsorbed molecules which is not restricted to the formation of a monolayer. The data also fitted well with the Weber and Morris model which described the rate-controlling steps. The intra-particle diffusion was controlled by pore and surface diffusion. In addition, the adsorption data followed a pseudo-second-order kinetic model, indicating a chemisorption process. The results highlight a unique property of the clay material as an effective decolorizing and adsorption agent for the removal of water-soluble dyes from contaminated water bodies.
Public Interest Statement
Water is the most basic need in life. However, water pollution through environmental pollutants such as dyes, pesticides, pharmaceutical water and heavy metals has rendered most water sources unsafe for human consumption. Water pollution by dyes has serious effect on human health and aquatic species. To reduce the impact of water pollution, different water purification strategies have been developed. However, some of the water treatment technologies developed are expensive, and hence, the need to look into developing water treatment technologies that are less costly. In this study, a clay sample recovered from an archaeological excavation from the Krobo Mountains in Ghana was examined for its potential to decolorize and adsorb cationic methylene blue. The results are very promising and showed the potential application of the clay deposit at Krobo Mountains in Ghana in developing water treatment technologies.
Competing Interests
The authors declare no competing interests.
Acknowledgements
The researchers acknowledge the Department of Materials Science and Metallurgy, the University of Cambridge for running the TGA, SEM and XRD experiments. We thank West Africa Center for Cell Biology of Infectious Pathogens (WACCBIP) for supporting this work. We also thank Mr. Solomon Kingsley Katu for assisting in data collection. The work received support from Wellcome Trust (WACCBIP DELTAS grant #; 107755/Z/15/Z) and the World Bank Africa Centre of Excellence project (ACE02-WACCBIP).
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Elvis K. Tiburu
Dr Emmanuel Nyankson holds a BSc in Chemical Engineering from the Kwame Nkrumah University of Science and Technology, Ghana, MSc in Materials Science and Engineering from the Norwegian University of Science and Technology, Norway, and PhD in Chemical Engineering from Auburn University, USA. He is a Commonwealth Early Academic Fellow. He is also a fellow of the Cambridge-Africa Alborada Trust and CAPREx Fellowship. His research is focused on the development of novel materials for water purification, biomedical, environmental remediation and oil and gas applications. The material presented in this paper has a wider application in water treatment technologies and in biomedical applications.