Porous carbon monoliths (PCMs) were prepared from waste corrugated cardboard box (WCCB) via slurrying in FeCl3 solution followed by molding and thermal treatment. The thermal process was analyzed by a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer. The evolution of physicochemical characteristics of PCMs was studied. The photothermal conversion and solar steam generation performances of the optimal sample (PCMFe/600) were evaluated. The adsorption properties of PCMFe/600 for methylene blue (MB) were investigated. Results showed that Fe3+ promoted the breaking of cellulose chains in WCCB, leading to the occurrence of pyrolysis of WCCB at lower temperatures and the reduction of activation energy by 76.63 kJ mol-1. Char yield raised because volatile radicals were captured by FeCl3-derived amorphous Fe(III) species, then involved in char formation. Amorphous Fe(III) continuously converted into Fe3O4 crystallites with carbonization temperature increasing from 400 to 700 °C, then α-Fe was formed at 800 °C via the carbothermal reduction of Fe3O4. FeCl3 was favorable to the formation of a developed microporous structure. Surface area significantly increased with carbonization temperature increasing from 400 to 600 °C due to the removal of volatiles. The etching of carbon by Fe3O4 above 700 °C also led to the increase of surface area. PCMFe/600 exhibited higher optical absorption than other samples due to its high graphite degree and porosity. It also had excellent photothermal performance; thus, solar steam yield was 1.46 times that of the pure water with the assistance of PCMFe/600. PCMFe/600 in floating state was effective in adsorption of MB from water. Besides, the adsorption behavior fitted Langmuir model with a monolayer adsorption capacity reached up to 70.9 mg g-1.
Keywords: Adsorption; Magnetic porous carbon monolith; Solar steam generation; TG-FTIR; Waste corrugated cardboard box.
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