Valorisation of Cocoa (Theobroma cacao) pod husk as precursors for the production of adsorbents for water treatment

ABSTRACT

Cocoa pod husk (CPH) has been valorised as adsorbents for the removal of a variety of chemical species from aqueous media. This review was conducted to catalogue the empirical findings, discuss the current state of knowledge, observe the research trend, identify research gaps and predict future perspectives in the research area. CPH has been processed into unmodified biosorbent, chemically modified biosorbent and bio-based-activated carbon. Much of the research interest in CPH adsorption has been majorly focused on heavy metals and dyes. The removal efficiency of the CPH adsorbent for most of the pollutants was above 90% but for a few exceptions. The effect of temperature, solution pH, adsorbent dosage, agitation time and initial concentration of the pollutants were considered in the review. Furthermore, the equilibrium data were always best fit to either Langmuir or Freundlich isotherm models. It was also observed that the pseudo-second order kinetic model was the best fit for the adsorption of pollutants onto CPH adsorbents. Thermodynamic calculations revealed that CPH adsorption was mainly spontaneous and exothermic. Future perspectives were suggested in the domain of desorption studies, reusability studies, continuous flow experiments and adsorbent immobilisation, pilot and semi-pilot scale-up systems and financial and techno-economic investigations.

GRAPHICAL ABSTRACT

KEYWORDS:

• Cocoa pod husk
• adsorbent
• pollutants
• environment
• wastewater

Acknowledgement

The members of the Environmental Engineering Laboratory, Department of Chemical Engineering at the University of Ilorin are hereby acknowledged.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes on contributors

        Omodele A. A. Eletta is an associate professor at the Department of Chemical Engineering at the University of Ilorin. She obtained her Bachelor Degree in Chemical Engineering (1986) from the University of Lagos, Nigeria. She also obtained her Masters’ Degree in Chemical Engineering (1996) from the University of Lagos, Nigeria. She completed her PhD in Chemistry (Environmental/Analytical Chemistry) (2005) from the University of Ilorin, Nigeria. Her research interests include environmental engineering with a special focus on the remediation of water pollution by adsorption.

        Adewale George Adeniyi is a senior lecturer in the Department of Chemical Engineering, University of Ilorin, Nigeria. He holds a PhD in Chemical Engineering from Ladoke Akintola University of Technology, Ogbomoso, Nigeria. He is interested in process and product development with a focus on computer-aided modelling and the optimisation of chemical process systems, biofuel production and solid waste recycling.

        Joshua O. Ighalo obtained his Bachelor's Degree in Chemical Engineering in 2015 from the University of Benin, Nigeria. He also obtained a Masters’ Degree in Chemical Engineering in 2019 from the University of Ilorin, Nigeria. His research interests include computer-aided modelling and optimisation of chemical process systems, biofuel production, solid waste management and environmental pollution control.

        Damilola Victoria Onifade has a Bachelor’s Degree in Chemical Engineering from Ladoke Akintola University of Technology, Ogbomoso, Nigeria. She also holds a Master’s Degree in Chemical Engineering, which she gained in 2019 from the University of Ilorin, Nigeria. Her research interests include solid waste management, chemical process optimisation, computer-aided modelling and design, biofuels and product development.

        Fisayo Oyepeju Ayandele obtained a Bachelor's Degree in Chemical Engineering from Ladoke Akintola University of Technology, Ogbomoso, Nigeria. She also obtained a Masters’ Degree in Chemical Engineering (2019) from the University of Ilorin, Nigeria. Her research interest includes environmental pollution control with a special focus on the adsorption process.

ORCID

Omodele A. A. Eletta http://orcid.org/0000-0002-5079-5548

Adewale George Adeniyi http://orcid.org/0000-0001-6615-5361

Joshua O. Ighalo http://orcid.org/0000-0002-8709-100X

Damilola Victoria Onifade http://orcid.org/0000-0002-2608-1860

Fisayo Oyepeju Ayandele http://orcid.org/0000-0003-0760-3843