Assisted hydrothermal carbonization of agroindustrial byproducts as effective step in the production of activated carbon catalysts for wet peroxide oxidation of micro-pollutants

This work deals with the valorisation of bagasse of sugarcane - BC, bagasse of malt - BM and seed of chia - SC, through its transformation into pyrochars, hydrochars and activated carbons (ACs) by pyrolysis, hydrothermal carbonization (HTC) and sequential HTC and pyrolysis, respectively. The HTC process was carried out in the presence of H2O, FeCl3 and H2SO4 solutions. The materials resulting by HTC in the presence of FeCl3 revealed the highest burn-off, but the contents of carbon released into the liquid phase, measured as total organic carbon, and to the gaseous phase, determined by carbon balance, depend strongly on the carbon precursor. In this sense, BC generates more volatile organic compounds (up to 34% of the initial carbon content), followed by BM (< 15%) and SC (< 5%) in their HTC and pyrolysis (70%). The pyrochars, hydrochars and ACs prepared from BC also show the highest specific surface areas (S-BET < 447 m(2)center dot g(-1)) when compared to the specific surface areas of the materials prepared from BM and SC. The carbon-based materials prepared with FeCl3 show the highest catalytic activity, but iron leaching into solution is observed. On the other hand, the materials prepared with H2SO4 show high activity, enabling its application in successive cycles and the complete degradation of caffeine in concentrations ranging from 1 to 100 mg center dot L-1, after 5-60 min of reaction.

Automated summary

This study focuses on the valorization of bagasse of sugarcane, bagasse of malt, and seed of chia through their transformation into pyrochars, hydrochars, and activated carbons. The results indicate that BC generates more volatile organic compounds compared to BM and SC.