Abstract
Batch adsorption studies were conducted to determine the extent and nature of adsorption of Ni(ll), Cu(ll) and Cd(ll) ions from aqueous solutions onto JatrophacurcasSeed pod. The effects of pH, initial metal ion concentration and presence of co-ions were studied. Results showed that the adsorption process was dependent on pH, having optimum pH for adsorption of Ni(ll) at 7.0 and with maximum amount adsorbed as 9.23 mg/g. That of Cu(ll) occurred at pH 8.0 with maximum amount adsorbed as 9.65 mg/g while for Cd(ll), the pH for optimum adsorption occurred at pH 6.0 with maximum amount of 9.99 mg/g adsorbed. Evaluation of percentage removal shows that the percentage of Ni(ll), Cu(ll) and Cd(ll) adsorbed at their optimum pH corresponded to 92.30%, 96.50% and 99.90% respectively. Increasing the initial concentration of the metal ions was also found to increase the adsorption capacity for the metal ions by the adsorbent. The experimental data were interpreted using three isotherm models viz; the Langmuir, Freundlich and Dubinin-RadushKevich isotherms. Results showed that the Freundlich isotherm provided the best fit to the experimental adsorption data. The mean free energy values, E (which ranged from 1.343 to 2.275 kJ mol-1) calculated from the Dubinin-RadushKevich (D-R) isotherm equation suggests weak interaction between the metal ions and the adsorbent, thus revealing that the mode of the adsorption process follows physisorption. Assessment of competitive adsorption of the metal ions from mixed metal ions solutions shows that the presence of foreign ions in the solution diminished the adsorption density of the metal ion under consideration. The results generally showed that the order of adsorption of the metal ions onto the biosorbent follows the trend Cd(ll) > Cu(ll) > Ni(ll).
Highlights
Heavy metals have been excessively released into the environment due to rapid industrialization and have created a global concern
Lead, zinc, cadmium, nickel, mercury and chromium are often detected in industrial wastewaters which originate from metal plating, mining activities, smelting, battery manufacturing, tanneries, petroleum refining, paint manufacturing, pesticides, pigment manufacturing, printing and photographic industries [1,2,3,4]
That of Cu(ll) has its maximum amount adsorbed as 9.65 mg/g at a pH 8.0 while optimum pH for adsorption of Ni(ll) occurred at pH 7 and with maximum amount adsorbed as 9.23 mg/g corresponding to 92.30% removal
Summary
Heavy metals have been excessively released into the environment due to rapid industrialization and have created a global concern. It is imperative to treat heavy metal contents in wastewaters before discharge into water bodies because of the numerous adverse effects their presence cause. Some of the heavy metals have great affinity for Sulphur and attacks Sulphur bonds in enzymes making them immobilized. They bind to cell membranes and affect the transport process through the cell wall. Mercury in the form of methyl mercury is the most toxic species It causes energy deficiency in the brain cells and disorders in the transmission of nerve impulse [5]. In view of the above facts, it is important to prevent water pollution due to heavy metals. Research is currently been focused on development of suitable technologies to either prevent heavy metals pollution or reduce their
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