Preparation and Characterization of Activated Carbon from the Pyrolysis of Physic Nut (Jatropha curcas L.) Waste

Abstract

Use of waste as raw material for producing porous carbon was investigated in this work. Physic nut (Jatropha curcas L.) residue from oil extraction for biodiesel production was pyrolyzed at 400–800 °C with hold times of 15, 120, and 240 min to obtain char precursors. Activated carbon, with favorable Brunauer–Emmett–Teller surface area in a narrow range, was prepared by soaking these chars in concentrated KOH, H3PO4, as well as a pure CO2 gas flash activator. The maximum specific surface area of 532.30 m2 g−1 was developed for the alkaline-treated sample. The carbon fraction of activated materials was as much as 90 wt %, significantly higher than the char precursor. Mesopore of 2–50 nm and total pore volumes of the materials were also significantly enhanced by these activations. Nitrogen adsorption isotherms of physic-nut-waste-activated carbons indicated that they were mainly mesopores. Pores of char activated by KOH and H3PO4 are irregular, of different shapes and sizes, and the macropores seemed to be connected to mesopores, especially for the KOH-activated case. Surface analysis of pyrolyzed and activated char using Fourier transform infrared spectroscopy indicated main functional groups that are considerably different to those of activated materials, which may lead to greater adsorption potential of activated samples. However, functional groups on each activated carbon are quite similar even with different activation processes. According to the data obtained, physic nut residue pyrolyzed at 800 °C and followed by KOH activation could be used as a low-cost adsorbent with favorable surface properties.