Biomass-based activated carbon by flash heating as a novel preparation route and its application in high efficiency adsorption of metronidazole

In this study, flash heating was applied for activated carbon (AC) preparation to shorten the long production period as a new heating method. Activated carbons were prepared from agricultural residues of hazelnut shell (HS), rice husk (RH), and corn stalk (CS) by KOH activation in a short time below 15 min. Surface areas were 1650, 2573, and 2304 m2/g for activated carbons prepared from hazelnut shell, rice husk, and corn stalk, respectively. Obtained products were evaluated in metronidazole removal from an aqueous solution to determine the adsorption capacities of the as-prepared ACs. The adsorption data of metronidazole (MNZ) was analyzed by the Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherm models. Adsorption data for both HS-AC and RH-AC were best fitted by Langmuir isotherm, and the maximum adsorption capacities were 526 and 588 mg/g, respectively. The best suitable correlation for CS-AC was fitted with the Freundlich isotherm with a maximum capacity of 833 mg/g. Among the related kinetic models, pseudo-second-order was the best fitted for MNZ adsorption. The thermodynamic parameters were calculated by using the Von't Hoff equation and revealed that MNZ adsorption is an exothermic character and spontaneous nature. Experimental results showed that the applied flash heating method not only shortened the activated carbon production time but also enabled to prepare activated carbons with well-developed porous structure and excellent adsorption performance.

Automated summary

Flash heating was used to prepare activated carbon in a shorter time. Agricultural residues such as hazelnut shell, rice husk, and corn stalk were activated with KOH, resulting in activated carbons with high surface areas. The flash heating method not only reduced production time but also improved the porous structure and adsorption performance of the activated carbons.