Effect of modification of environmentally friendly biosorbent wheat (Triticum aestivum) on the biosorptive removal of cadmium(II) ions from aqueous solution

The present studies investigate the use of a local environmentally friendly biosorbent material, i.e., powdered straw from Triticum aestivum (WS) for the removal of Cd(II) ions, one of three most toxic heavy metal ions (cadmium, mercury and lead). The straw has been modified with urea under the effect of microwave radiation. The FTIR spectra indicated the presence of hydroxyl, carboxyl and amino functional groups. A greater BET surface area was observed in modified wheat straw (MWS) than in WS. The biosorption of Cd(II) by WS was found to follow Freundlich model whereas that by MWS followed Langmuir model with maximum biosorption capacity (qmax) of 39.22 mg g−1. The effect of experimental parameters like pH, time of contact and temperature was optimized. The maximum sorption occurred at pH of 6 by both the materials. Biosorption by MWS was faster (equilibrium time 10 min) than by WS (equilibrium time 20 min). Elovich, pseudo first order and pseudo second order models were used to study the kinetics of the process. Biosorption of Cd(II) by both materials followed pseudo second order kinetic model. Boundary layer diffusion was found as the rate limiting step. For both materials, the sorption increased with increase in temperature. The changes in the values of standard free energy (ΔG°) and standard enthalpy (ΔH°) indicated the spontaneous, feasible and endothermic nature of sorption process. The capacities of WS and MWS have also been compared with certain other biosorbents. MWS has been found a better biosorbent for Cd(II) than simple WS.