Biosorption of lead(II) and chromium(VI) on groundnut hull: equilibrium, kinetics and thermodynamics study / Biosorción de plomo (II) y cromo (VI) en cáscaras de maní: estudio de equilibrio, cinética y termodinámica

The biosorption of lead(II) and chromium(VI) on groundnut hull was investigated. Batch biosorption experiments were conducted to find the equilibrium time and biosorption capacity. Effect of parameters like pH, temperature and initial metal concentration was studied. The maximum biosorption capacity of lead(II) and chromium(VI) was found to be 31.54 +/- 0.63 and 30.21 +/- 0.74 mg g-1, respectively. The optimum pH for lead(II) and chromium(VI) removal was 5 ± 0.1 and 2 +/- 0.1, respectively. The temperature change, in the range of 20 - 45ºC affected the biosorption capacity. The maximum removal of lead(II) was achieved at 20 +/- 2ºC, where as maximum uptake of chromium(VI) was observed at 40 +/- 2ºC. The biosorption data was fitted to the Langmuir and the Freundlich isotherm models. The Langmuir model showed better representation of data, with correlation coefficient greater than 0.98. The kinetics of biosorption followed the pseudo second order kinetics model. The thermodynamics parameters were evaluated from the experimental data.

Heavy metal uptake by agro based waste materials

Presence of heavy metals in the aquatic systems has become a serious problem. As a result, there has been a great deal of attention given to new technologies for removal of heavy metal ions from contaminated waters. Biosorption is one such emerging technology which utilized naturally occurring waste materials to sequester heavy metals from industrial wastewater. The aim of the present study was to utilize the locally available agricultural waste materials for heavy metal removal from industrial wastewater. The wastewater containing lead and hexavalent chromium was treated with biomass prepared from ficus religiosa leaves. It was fund that a time of one hr was sufficient for sorption to attain equilibrium. The equilibrium sorption capacity after one hr was 16.95 ± 0.75 mg g-1 and 5.66 ± 0.43 mg g-1 for lead and chromium respectively. The optimum pH was 4 for lead and 1 for chromium. Temperature has strong influence on biosorption process. The removal of lead decreased with increase in temperature. On the other hand chromium removal increased with increase in temperature up to 40ºC and then started decreasing. Ion exchange was the major removal mechanism along with physical sorption and precipitation. The biosorption data was well fitted to Langmuir adsorption model. The kinetics of biosorption process was well described by the pseudo 2nd order kinetics model. It was concluded that adsorbent prepared from ficus religiosa leaves can be utilized for the treatment of heavy metals in wastewater.