Activating And Utilization Of Hydrochar Derived From Hydrothermal Liquefaction Of Biomass

In recent years, increasing attention has been paid to hydrothermal liquefaction of waste biomass for the production of high value-added chemicals and bio-oil, with few studies focusing on the application of hydrochar, a solid residue from HTL process. Due to low level of aromcticity and high degree of oxygen-containing functional groups, hydrochar has the potential to be an efficient adsorbent for pollutants removal. However, one shortcoming of hydrochar is its limited porosity and surface area (< 10 m2·g-1), which hinders its wide application in the field of environmental remediation. Therefore, it is necessary to activate hydrochar for the sustainable application of hydrochar.This study firstly investigates the variation of characteristics of waste hydrochar via pyrolysis under inert atmosphere at different temperatures (300-700℃), as well as tetracycline (TC) adsorption behavior on hydrochar and its derived porous carbon (PC). The changes of characteristics suggest that PC samples produced at high activated temperature (500-700 ℃) are well carbonized and exhibit a high surface area (> 270 m2·g-1). The hydrochar and PC samples exhibit a remarkable range of surface properties, as characterized by Boehm titration, the FTIR and NMR spectra. The XRD spectra confirm the evolution of whewellite and calcite. Positive correlation are obtained between Freundlich adsorption affinity coefficient (KF) and elemental atomic ratio, while negative correlation between KF and surface area and pore volume are observed. Futhermore, the high adsorption capacity of PC samples is attributed to its high aromaticity, surface area, pore volume and low polarity.Taking the difficult separation and recovery of used PC samples, and still lower surface area into account, a novel approach of simultaneous activation and magnetization is then proposed for the fabrication of magnetic carbon composites via the thermal pyrolysis of hydrochar that has been pretreated with mixtures of ferric chloride (FeCl3) and zinc chloride (ZnCl2). The main objective of this part is the investigation of the variation of characteristics of magnetic carbon composites produced at various conditions, as well as triclosan (TCS) adsorption behavior on such composites. This presented simple one-step synthesis method has the following advantages:(a) the hydrochar is activated with high surface area and pore volume (up to 1351 m2·g-1 and 0.549 cm3·g-1, respectively), (b) activation and magnetization are simultaneously achieved without further modification, (c) the magnetic particles are stable under an acidic medium (pH of 3.0 and 4.0), and (d) the products have the potential to remove TCS from aqueous solutions with a maximum adsorption capacity of 892.2 mg·g-1. The results indicate the effectiveness of this facile synthesis strategy in converting low-value biowaste into a functional material with high performance for pollutant removal from aqueous solutions.