Kinetic Study of Garlic and Ginger Particles in Adsorption of Heavy Metals in Aqueous Solution

Abstract

This study involved investigation and comparison of the capacity of garlic and ginger particles in adsorption of lead, cadmium and chromium ions from contaminated water. This was motivated by the perennial contamination of well water by crude oil, which carried alongside heavy metals from earth surface and other sources in contact with it while discharging from oil facilities to the subsurface region. Heavy metal analysis on the well water and crude oil from the polluted site showed high level of heavy contamination. Effect of initial concentration of heavy metals, adsorbents dosage and contact time on adsorption of the lead, cadmium and chromium ions in aqueous solution by garlic and ginger particles were studied. Garlic and ginger particles adsorption process was studied using Langmuir and Temkin isotherms. Also, to describe the kinetics of the adsorption process, the Pseudo first and second order kinetics as well as the intra-particle diffusion kinetics were used to study the experimental data. The analysis showed that the percentage of lead, cadmium and chromium ions adsorbed by garlic and ginger particles decreased as the initial concentration of metals in solution and contact time were increased. Similarly, the percentage of lead, cadmium or chromium ions adsorbed by the garlic and ginger particles at equilibrium increased as adsorbent dosages was increased due to increased effective surface area of the adsorbent. Equilibrium was attained at about 60 minutes with either garlic or ginger particles. However, garlic particles adsorbed the heavy metals more than the particles of ginger at all conditions. Also, it was observed that lead ion has more affinity to both garlic and ginger particles followed by cadmium ion. The adsorption of lead, cadmium and chromium ions were better explained by the Langmuir isotherm model than the Temkin’s isotherm model. The maximum adsorption capacity for lead, cadmium and chromium ions with garlic particles were 3.9308 mg/g, 3.3223 mg/g and 1.992 mg/g while that of ginger particles were 2.9011 mg/g, 2.3121 mg/g and 1.9543 mg/g respectively. The adsorption of lead, cadmium and chromium ions in the solution of both adsorbents revealed that diffusion and chemisorptions occurred in the adsorption process, which was best fitted in the Pseudo second order kinetics. Indicating that the Pseudo second order kinetics was the rate controlling step, and thus, will predict accurately the concentration of metal ions adsorbed. Conclusively, the garlic and ginger particles showed capacity for the removal of lead, cadmium and chromium in aqueous solution, and therefore are recommended for use in adsorption of heavy metals in wastewater. Keywords : Garlic, Ginger, Heavy metals, Adsorption Isotherm, Kinetics DOI : 10.7176/CPER/60-04 Publication date :March 31 st 2019