Characterization of Water Hyacinth Powder Using FTIR Spectroscopy and the Adsorption Behaviour of Pb2+, Cd2+, Zn2+, Ni2+ and Cr2+ in Aqueous Solution

Abstract

The adsorption behavior of selected metal ions on water hyacinth powder was investigated by Fourier Transform Infrared (FTIR) spectroscopy. Water hyacinth powder was used as an adsorbent due to its popularity, low cost and ease of availability. Water hyacinth stems were dried and ground to a powder. Batch adsorption experiments were conducted at room temperature by adding known concentrations of Pb2+, Cd2+, Cr3+, Zn2+ and Ni2+ to 5 g of water hyacinth powder in different test tubes and allowed to stand for the same time respectively. Adsorption is one of the methods used to remove heavy metals from aqueous solutions and wastewaters. FTIR analysis was performed to identify the functional groups in the water hyacinth powder using the KBr disc method. The study showed a strong broad absorption band in the region of 3300-3200cm-1 which is characteristic of O-H stretching vibrations of the adsorbed water molecules at the surface of raw water hyacinth powder particles. Other peaks appeared at 1732cm-1 which corresponded to C=O stretching vibrations while the band at 1396cm-1 could be attributed to C-H bonds. The functional groups identified were: C-H; O-H; C=O or C-O. After adsorption there was a disappearance, reduction or a shift in the adsorption bands depending on the type of metal ion. Lead for example showed a strong absorption band in the region of 1732cm-1 which is characteristic of C=O stretching bond structure which is found in esters and carboxylic acids. The disappearance of the peaks indicated that the H atom present in the functional groups of the raw water hyacinth powder could have been substituted with lead ion. The intensity of the adsorption bands reduced for all the metals confirming that functional groups were responsible for adsorption of the heavy metal ions on to the material.