Sequestration of Hexavalent Chromium from Aqueous Medium Using Biochar Prepared from Water Hyacinth Biomass

Abstract

The global issue associated with the health of environment and human is the quality of water. A serious threat to the aquatic environment through anthropogenic activities is the heavy metal pollution. To protect our environment from the serious threats of contamination and to save many lives, it is essential to remove Cr from wastewater. This paper reports the utilization of the water hyacinth biochar, a carbonaceous material as adsorbent for removal of hexavalent chromium (Cr(VI)) from aqueous solution. The experiment was carried out in the Department of Environmental Sciences, Tamil Nadu Agricultural University, Coimbatore in a completely randomized design with 4 replications. The adsorbent was characterized by FTIR, SEM and EDX. The effect of various process parameters like solution pH, adsorbate concentration, contact time, adsorbent dosage and size has been studied. The optimum conditions for the removal of Cr(VI) were found to be  pH=2.0, adsorbent size= 0.2 mm, adsorbent dosage=2.5 g/100 ml, adsorbate concentration=100 mg/L of Cr(VI) at 25ºC at 250 rpm. The rate of adsorption was rapid and the equilibrium was attained at 36 hrs. Models of Langmuir, Freundlich and Temkin isotherms were used for mathematical description of the equilibrium adsorption data. Adsorption data was well described by the Langmuir isotherm with maximum adsorption capacity of 55.55 mg/g. On comparison with various kinetic models, our results fitted excellently with pseudo second order model (R2=0.999). It can be concluded that, carbonaceous material derived from water hyacinth biomass can be used as a low cost adsorbent for the treatment of Cr(VI) containing waste water.