Comparing the metal sorption capacity of biochar and flax fibers.

Abstract

Metal contaminated water can lead to severe health consequences for humans as well as other organisms. Biochar and flax fibers have been shown to be effective adsorbents for several such toxic metals. The ability of Douglas fir-derived biochar and flax fibers for removing metals (Pb and Cr) from solutions were compared in this study. Batch reactors were set with varying amounts of adsorbents, starting metal concentrations and reaction time. The concentration of the metals before and after the experiments were analyzed using an inductively coupled plasma-optical emission spectrometer (ICP-OES). About 65% of Pb was removed by flax fibers, twice as much as biochar. Cr removal rate was less than 5% with both adsorbents. The larger surface area offered by flax fiber is likely the reason for the better removal of Pb. Further analysis indicated that the data fit well with pseudo-second-order kinetic models, revealing that the sorption processes in all cases were chemically driven, i.e., chemisorption. The sorption increased with increasing concentration of the adsorbents and the data fitted well with a Langmuir-Freundlich model. The results help compare the efficacy of two common, cheaply available, bio-based products that can serve as metal adsorbents in water.