Co-hydrothermal treatment of fallen leaves with iron sludge to prepare magnetic iron product and solid fuel.

The hydrothermal carbonization (HTC) was performed on Metasequoia Leaves (ML) in the presence of iron sludge, both of which were generated as solid residuals. The relations between sludge, char's properties and operating conditions were systemically investigated. Iron sludge primarily catalyzed the efficient formation of char with higher heating value (HHV) becoming 1.15-1.65 times of ML (18.21 MJ/kg) and was meanwhile reduced to magnetite. The hydrated Fe ions in octahedron crystals acted as nucleophiles facilitating the dehydration and decarboxylation reactions. The increased HHV is found strong temperature dependent while prolonging the residence time is more preferable for low organic acids generation. Thermogravimetric analysis confirmed the iron sludge enhanced conversion of volatile to fixed carbon. The as-prepared solid char showed better stability after catalytic HTC treatment, having ignition temperature increased from 253 to 426 °C as compared to the char prepared without iron sludge addition.

Persulfate oxidation assisted hydrochar production from Platanus Orientalis Leaves: Physiochemical and combustion characteristics.

Platanus Orientalis Leaves (POL), a widely planted tree in parks and along streets, was employed by sequential persulfate oxidation (Fe2+and persulfate) and hydrothermal treatment (HTC) to improve the thermal stability, energy yield and combustion behavior of hydrochars (HCs). Higher heating values (HHVs) of HCs derived from persulfate pretreated POL was increased by 30.5% at mild HTC temperature (i.e., 210°C) as compared to char without pretreatment. Elevating Fe2+/persulfate ratio to 0.2 enables HCs with high fractions of lignin, thus promoting the energy yield going up to 64.4%. The ultimate and proximate analysis, N2 adsorption-desorption isotherms, FT-IR spectroscopy and thermogravimetric analysis were conducted to probe into chars' physiochemical and combustion characteristics. Results indicated that persulfate pretreatment on POL strengthened efficient HTC conversion from volatile matter to fixed carbon, increasing the ignition temperature of HCs from 261.5 to 404.3°C as compared to the char obtained with only HTC.