For many decades, Costa Rica main crop has been coffee. However, its industrialization brings many environmental concerns as nearly 600 million kilograms of coffee waste are generated. One of the coffee wastes is known as coffee outer parchment which is found to have between 75 and 78 weight percentage of cellulose. It might be possible then to obtain nanocellulose from this type of lignocellulosic material.  In this work, coffee parchment was milled, and meshed. Relative humidity, ashes, water solubility, and lignin, hemicellulose, a-cellulose contents were assessed. Therefore, parchment was treated with a NaOH(aq) 2 wt.%, 80 �C, 4 hours (or 24 hours at room temperature), followed by a bleaching with a NaOCl(aq) 2.5 wt.% during 4 hours at room temperature. Bleached cellulose was hydrolized with HCl (aq) 2 M in a reflux system using several temperatures (80, 90, 95, 97 and 100 �C) and corresponding timings (20, 30, 15, 10 and 20 minutes) in order to obtain microcellulose (MC). Microcellulose was then washed with NH4OH (aq) 0.25 wt.% and water until neutrality was reached. Then it was dried in a oven at 60 �C. The MC was then subjected to a further hydrolisis with H2SO4(aq) 60 wt.%, at 45�C, with a cellulose to acid ratio of 1:10 (wt/vol %) during 30 minutes. Several acid concentrations, temperatures and timings were tested in order to find out the optimal experimental conditions. Then the reaction mix was diluted with distilled water, folllowed by washings, and membrane dialisis until reaching neutrality. This solution was then sonicated, filtered and storaged in a refrigerator.  Characterization of the nanocellulose was carried out by means of a dynamic light scattering (DLS), transmission electron microscopy (TEM), themogravimetry analysis (TGA), and X-ray diffraction (XRD) to find out size, shape and properties of the nanocellulose produced.

Coffee wastes as potential source of nanocellulose

247th National Meeting (2014)

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