Investigation of Metal Ion Binding by Agricultural By-products

Oat and wheat straw are abundant yet at the same time are not widely used. For this reason they were tested as metal ion removers from water solutions. Batch experiments were done to determine the affinity of both biomasses for Cu(II), Pb(II), Cr(III), Cr(VI), Ni(II), Zn(II), and Cd(II) metal ions at several pHs; times of reaction and the adsorption capacity for each metal were determined under optimum conditions. The metal ion removal from the biomass was also measured. The batch experiments show that pH 5 was the best pH for adsorption of most of the metal ions, the exception being Cr(VI) (pH 2) in both biomasses. The best adsorp-tion capacities were observed for Pb(II), Cu(II), and Cd(II) for both biomasses. The biomasses were also tested after modification with NaOH to improve their adsorption capacities. The NaOH modification conditions were established by experiments carried out on each biomass. Surprisingly, it was noticed that the drying process during modification affects the adsorption capacity of oat biomass but not wheat biomass. Simultaneous experiments for adsorption capacities of each metal ion were performed by exposing both the unmodified and NaOH modified biomasses to the same environmental conditions. It seems that both biomasses can be employed in heavy metal ion removal processes. INTRODUCTION One of the methods employed for removing contaminants, like heavy metals, from waste