Adsorption of trivalent chromium from dilute solution by conifer leaves

Chromium(III), Cr(III) adsorption capacities of the leaves of 34 conifer sp ecies were examined. Among these, Ginkgo biloba, Taxus cuspidata, Cephalota xus harringtonia var. nana, and Taxodiaceae and Cupressaceae spp. showed la rge capacities to adsorb Cr(III). The adsorption capacities of conifer leav es for Cr(III) (3.12-5.09 mg Cr g(-1) adsorbent) compared favorably with th ose of commercial activated carbons (1.23-2.75 mg g(-1)). Factors affecting Cr(III) adsorption were studied using G. biloba leaves. The factors includ ed solution pH, contact time, temperature, and the initial concentration of Cr(III). The amount of Cr(III) adsorbed on the adsorbent increased steadil y with increasing pH in a pH range from 2 to 5, with increasing contact tim e, and with increasing temperature ranging 20 to 40 degrees C. The Cr(III) adsorption was also affected by the initial concentration of Cr(III) in the solution. A linear relationship was observed between the amount of Cr(III) adsorbed and the equilibrium concentration of Cr(III) in the solution when graphed logarithmically. The maximum capacity of G. biloba leaves was 27.5 mg Cr g(-1) adsorbent by column experiments.