Preparation of highly porous carbon from fir wood by KOH etching and CO 2 gasification for adsorption of dyes and phenols from water

Abstract

Fir wood was first carbonized for 1.5 h at 450 °C, then soaked in a KOH solution KOH/char ratio of 1, and last activated for 1 h at 780 °C. During the last hour CO 2 was poured in for further activation for 0, 15, 30, and 60 min, respectively. Carbonaceous adsorbents with controllable surface area and pore structure were chemically activated from carbonized fir wood (i.e., char) by KOH etching and CO 2 gasification. The pore properties, including the BET surface area, pore volume, pore size distribution, and pore diameter, of these activated carbons were first characterized by the t-plot method based on N 2 adsorption isotherms. Fir-wood carbon activated with CO 2 gasification from 0 to 60 min exhibited a BET surface area ranging from 1371 to 2821 m 2 g −1, with a pore volume significantly increased from 0.81 to 1.73 m 2 g −1. Scanning electron microscopic (SEM) results showed that the surfaces of honeycombed holes in these carbons were significantly different from those of carbons without CO 2 gasification. The adsorption of methylene blue, basic brown 1, acid blue 74, p-nitrophenol, p-chlorophenol, p-cresol, and phenol from water on all the carbons studied was examined to check their chemical characteristics. Adsorption kinetics was in agreement with the Elovich equation, and all equilibrium isotherms were in agreement with the Langmuir equation. These results were used to compare the Elovich parameter ( 1 / b ) and the adsorption quantity of the unit area ( q mon / S p ) of activated carbons with different CO 2 gasification durations. This work facilitated the preparation of activated carbon by effectively controlling pore structures and the adsorption performance of the activated carbon on adsorbates of different molecular forms.