Effects of supercritical carbon dioxide on waste banana peels for heavy metal removal

The effects of supercritical carbon dioxide (CO2) on waste banana peels for copper adsorption were evaluated. Supercritical CO2 was employed both in a solvent extraction for antioxidant compound recovery and in an emerging biomass treatment to increase the subsequent heavy metal-removal step; the latter is termed “explosion with supercritical CO2”. This lignocellulosic biomass was analyzed before and after being subjected to both processes by scanning electron microscopy and X-ray patterning. Thermal gravimetric and differential scanning calorimetry analyses were performed to understand the different effects of supercritical carbon dioxide employed in these two processes on banana peels. The explosion with supercritical CO2 process resulted in a more pronounced effect on the vegetable structure. Nevertheless, no increase in the copper-removal capacity was achieved. The adsorption studies showed similar behaviors for fresh and extracted samples, demonstrating that banana peels previously extracted with supercritical CO2 retained their adsorption capacity for subsequent heavy metal removal.

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► The effects of supercritical CO2 on banana peels for copper adsorption were evaluated.
► Banana peels previously extracted retained their heavy metal-adsorption capacity.
► The data for both samples better fitted the pseudo-second-order Lagergren model.
► The isotherms presented good adjustment to both the Langmuir and Freundlich models.