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 degrees 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, N-2 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 degrees C as compared to the char obtained with only HTC.