Abstract
In this study, charred cacao shells were tested for their capability as bioadsorbent for aqueous potassium permanganate. Optimization of adsorption parameters showed that the best amount of adsorbent is 0.5% w of cacao biochar/v of 0.005 N aqueous KMnO4 with a removal efficiency of 98.79%, and the optimum particle size is 212 mm, with a corresponding removal efficiency of 99.76%. Kinetics studies showed that the adsorption fits a pseudo-first order reaction with R2 = 0.9833. Lastly, the adsorption data fits the Elovich isotherm with R2 = 0.9712, which strongly suggests a multi-layer chemisorption on a heterogenous surface. Conclusively, the charred cacao shells were found to be effective as an adsorbent of aqueous potassium permanganate. Furthermore, the resulting product of adsorption can be used to study adsorption of other substances due to its multi-layer nature.
Highlights
Cacao (Theobroma cacao L.) is one of the high value crops in the Philippines, with its annual consumption of around 50,000 metric tons
This study focused on the potential use of processed cacao shells as adsorbent in treating oxidizing wastes, potassium permanganate
The FTIR spectra of the cacao biochar (Figure 1) showed that the spectrum is similar to that of non-starchy polysaccharides such as lignin due to the O-H stretch and aromatic C=C stretch (Derkacheva and Sukhov, 2008). This suggests that the cacao biochar has not been fully charred and still contains organic plant materials that may have played a role in the adsorption of KMnO4
Summary
Cacao (Theobroma cacao L.) is one of the high value crops in the Philippines, with its annual consumption of around 50,000 metric tons. It is an important agricultural commodity marketed worldwide, whose demand is projected to reach 500,000 metric tons by 2020 (Department of Agriculture-Bureau of Plant Industry, 2017). Along with the rising demand for cacao beans and their products are the increasing amount of wastes generated through the different processes they undergo. Upon reaching maturity cacao pods are harvested, followed by the removal of the beans and adhering pulp for further processing, such as fermentation and roasting. The cacao bean contains polyphenols such as catechins, proanthocyanidins, and anthocyanins, which gives the bean a red to purple color. Upon roasting, these polyphenols are oxidized, forming high molecular weight tannins (Romero-Cortes et al, 2013).
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