Effect of Chitosan Powder Prepared from Snail Shells to Remove Lead (II) Ion and Nickel (II) Ion from Aqueous Solution and Its Adsorption Isotherm Model

Abstract

The toxic effects of heavy metals have remained a major source of concern globally because of their non-biodegradable nature which makes heavy metal pollution a serious environmental problem. The extents of removal for two heavy metals were investigated on adsorbent dose, temperature, pH, contact time and initial metals ion concentration. Maximum adsorption was obtained at pH 5 for Pb2+ ion and pH 7 for Ni2+ ion with 82.1% and 68.28%, at maximum adsorption temperature 335K and 355K for both metal ions with 87% and 80% metal removal respectively. The study shows that initial metal ion concentration and adsorbent dose on metals adsorption increases for both metal ions having a maximum adsorption dose at 99.93% and 70.58% removal at 180mins contact time for both metal ions with 99.83% and 70.37%. FTIR spectrum of raw chitosan showed the following peaks; 3263cm-1, 3109.25cm-1, 1627cm-1 and 2854cm-1 denoting –NH2/-NH asymmetric stretching,-OH stretching,-C=O stretching and –CH group showing that binding process for both metal ions onto chitosan bands at 3109.25cm-1 and 2854cm-1 in the spectrum. The spectra indicated –NH group was involved in the binding process due to substantial changes in absorption intensity of –NH stretching after adsorption and peak 1627cm-1 assigned to C=O occurred before the binding process. The two peaks in the 2800-2900 cm-1 region was observed in Pb2+ ion which disappear in the Ni2+ ion laden spectrum, the spectrum for Ni2+ ion has only one peak observed in this region while the Pb2+ ion has two and in the finger print region, 600-1000 cm-1, the spectra of Ni2+ ion and Pb2+ exhibited two and one peaks respectively. This supported the higher sorption capacity of Pb2+ ion over Ni2+ ion. The data were evaluated using Langmuir, Frieundlich and Temkin isotherms, the data complied with Frieundlich isotherm with high R2 values 0.984 and 0.971 for both metal ions while Temkin isotherm shows high R2 values 0.991 and 0.981 for both Pb2+ and Ni2+ ions respectively.