Enhancement of hydrothermal carbonization of chitin by combined pretreatment of mechanical activation and FeCl3

Abstract

In this work, a combined mechanical activation and FeCl₃ (MA + FeCl₃) method was applied to pretreat chitin to enhance the degree of hydrothermal carbonization. MA + FeCl₃ pretreatment significantly disrupt the crystalline region of chitin and Fe³⁺ entered into the molecular chain, resulting in the destruction of the stable structure of chitin. The chemical and structural properties of hydrochars were characterized by EA, SEM, FTIR, XRD, XPS, ¹³C solid state NMR, and N₂ adsorption-desorption analyses. The results showed that the H/C and O/C atomic ratios of HC-MAFCT/230 (the hydrochar derived from MA + FeCl₃ pretreated chitin with hydrothermal reaction temperature of 230 °C) were 0.96 and 0.34, respectively. Van Krevelen diagram indicated that the hydrothermal carbonization of chitin underwent a series of reactions such as dehydration, decarboxylation, and aromatization. HC-MAFCT/230 had abundant oxygen- and nitrogen-containing functional groups. HC-MAFCT/230 exhibited a porous structure, with the specific surface area of 128 m² g^-1, which was a promising carbon material.

Keywords: Chitin; Hydrothermal carbonization; Mechanical activation.