(768c) Effect of Hydrothermal Carbonization Temperature on Acidic and Basic Groups of Hydrochars Produced from Orange Peel and Grape Skin

Hydrothermal carbonization (HTC) is a promising wet thermochemical process where biomass is treated at high-pressure high-temperature subcritical water. Hydrochar, the solid product of HTC, is a carbon-dense material which contains oxygen functional groups on the surface. Among other process parameters, HTC temperature is the most dominant for hydrochar functional properties.

The surface functional groups on the surface of hydrochars play a vital role for ntheir a adsorption properties. Recently qualitative analysis of functional groups for bio-waste (i.e., fruit peels) has been carried out to correlate the morphology of the hydrichars to their adsorption properties. In addition, analysis of surface functional groups have been carried out for hydrochars produced from model compound (i.e, cellulose) at different HTC temperature. However, studies on the surface functional group of organic waste hydrochars are lacking. Investigation and characterization of surface functional group of bio-waste hydrochars will possbly open up a new route for the production of low-cost adsorbents. The understanding of the the content of such groups on the surface of hydrochars is key to unlock significvant number of multifunctional applications.

In this study, the acidic and basic functional groups on hydrochar surface produced from the orange peel and grape skin were quantified. Hydrochars were produced in an autoclave at three different temperature (180, 220, and 250 °C). A standard titration method (Boehm method) was used to measure the both functional groups on hydrochar surface. Both, backword and forward Boehm methods were used to measure the acidic and basic groups, respectively. Results showed that total acidic group decreases with the HTC temperature while the basic group increases as evidenced by FTIR analysis.