Adsorption of chromium(VI) from aqueous solutions by chemically treated water hyacinth Eichhornia crassipes

Abstract

The adsorption potential of water hyacinth Eichhornia crassipes for the removal of Cr(VI) from aqueous solutions has been stidied. The influence of various parameters including contact time, temperature, solution pH, initial adsorbate and adsorbent concentrations and effect of competing anions were studied. Results obtained indicate that the treated weed Eichhornia crassipes has remarkable adsorption capacity for Cr(VI) at pH below 4. The rate of adsorption was rapid and equilibrium attained within 2 h. The method followed first order kinetics. The adsorption process does exhibit a Langmuir type behaviour which is affected by the temperature. The maximum Cr(VI) removal was found to be 7.5 mg/g of dry weight weed at pH of 3.0 in 120 min at 25ºC. The calculated activation energy for the method studied was around 54.6 kJ/mol. About 500 mg weed could remove Cr(VI) successfully from 100 mL of chromite mine water containing 2.8 mg/L Cr(VI) at normal conditions.