Comparative Study on Pollutants (Dyes and Heavy Metals) Removal onto Nano Limestone/Chitosan Composite as Natural Sorbent
Powdered Nano Limestone modified by Chitosan (NLS/Cs) have been investigated as an adsorbent for the removal of Methylene Blue (MB), brilliant Green (BG), Congo Red (CR), cadmium (Cd) and Lead (Pb) from aqueous solutions. The surface area increased in case of NLS upto 6.2 m2/g, while it equal to 0.5 m2/g in case of LS. Batch experiments were carried out to investigate the effect of pH, the favorable pH for maximum dye adsorption was at 7 for MB and BG but for CR it was 5.5. The adsorption capacity calculated by Langmuir equation was 38.5 mg/g for MB, 33.6 mg/g for BG at pH 7 and 30.7 mg/g for CR at pH 5.5 and was 75.1 mg/g for Cd (II) and 68.4 for Pb (II) at pH 7. The adsorption capacity increased with temperature and the kinetics followed a pseudo second-order rate equation. The enthalpy change (ΔH0) was 20.8 J/mol-1 for MB, 14.9 Jmol-1 for BG and 12.5 for CR while it was 25.4 Jmol-1 for Cd (II) and 20.8 Jmol-1 for Pb(II). The entropy change (ΔS0) was 94.6 JK-1mol-1 for MB, 90.4 JK-1 mol-1 for BG and 86.5 for CR, while it was 41.6 JK-1 mol-1 for Cd(II) and 38.7 JK-1 mol-1 for Pb(II), which substantiates the endothermic and spontaneous nature of the dyes and heavy metals adsorption process. All of the results suggested that the NLS is very strong and could be excellent Nano-adsorbents for cobalt contaminated water treatment more than Limestone.
Keywords: pollutant dye, heavy metals, kinetics, thermodynamic, adsorption and Nano limestone.