Zinc Adsorption as Affected by Concentration, Temperature, and Time of Contact in the Presence of Electrolytic and Aqueous Medium in Benchmark Soils of Punjab in Northwest India
2012
Guraprīta Kaura, | Sharma, B. D. | Sharma, P.
Adsorption of zinc (Zn) ions by soil colloids is significant because of its greater adsorbing surface, thus making it an important process in controlling Zn availability to plants. The adsorption processes depend upon a number of factors including temperature, pH, time of contact, clay content, and calcium carbonate content. Therefore, adsorption behavior of Zn was studied for eight benchmark soils of Punjab in northwestern India, varying widely in physical and chemical characteristics. The adsorption of Zn was studied at varying Zn concentrations, temperatures, and time of contact in the presence of 0.01 M sodium sulfate (Na₂SO₄) electrolyte and in aqueous medium. The greatest amount of Zn adsorbed in the presence of electrolyte and in aqueous medium (deionized water) was in arid series (Gahri Bhagi, Jassipauwali), followed by semi-arid series (Fatehpur, Kanjli) and subhumid series (Dhar, Chamror). The results revealed that irrespective of the soils, Zn adsorption increased with an increase in Zn concentration and decreased with an increase in temperature from 25 ᵒC to 35 ᵒC. Zinc adsorption was found to be greater in 0.01 M Na₂SO₄ solution as compared to aqueous medium. Further adsorption of Zn increased with increase in time of contact. The Zn adsorption data was well fitted to the Langmuir and Freundlich adsorption equations. The values of distribution coefficient Kd and partial molar free energy change () were greater in the presence of 0.01 M Na₂SO₄ as compared to aqueous medium, suggesting that greater driving force is involved in adsorption of Zn in the presence of 0.01 M Na₂SO₄ as compared to aqueous medium.
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