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Kinetic, Equilibrium and Thermodynamic Studies of Cadmium (II) Adsorption by Modified Agricultural Wastes
Department of Chemistry, Collage of Science, King Saud University, Riyadh 11451, Saudi Arabia
National Research Centre, Dokki, Cairo 12622, Egypt
* Author to whom correspondence should be addressed.
Received: 26 November 2011; in revised form: 2 December 2011 / Accepted: 8 December 2011 / Published: 15 December 2011
Abstract: Agricultural wastes have great potential for the removal of heavy metal ions from aqueous solution. The contamination of water by toxic heavy metals is a worldwide environmental problem. Unlike organic pollutants, the majority of which are susceptible to biological degradation, heavy metals do not degrade into harmless end products. Discharges containing cadmium, in particular, are strictly controlled because of the highly toxic nature of this element and its tendency to accumulate in the tissues of living organisms. This work aims to develop inexpensive, highly available, effective metal ion adsorbents from natural wastes as alternatives to existing commercial adsorbents. In particular, Tamrix articulata wastes were modified chemically by esterification with maleic acid to yield a carboxyl-rich adsorbent. The adsorption behavior of treated Tamrix articulata wastes toward cadmium ions in aqueous solutions in a batch system has been studied as a function of equilibration time, adsorbent dose, temperature and pH. Results showed that the maximum adsorption capacity was 195.5 mg/g in a pH 4 solution at 30 °C with a contact time of 120 min, an initial concentration of 400 mg/L and an adsorbent dose of 0.3 g/L. The kinetic data were analyzed using pseudo-first-order and pseudo-second-order kinetic models. It was shown that the adsorption of cadmium could be described by a pseudo-second-order equation. The experimental data were also analyzed using the Langmuir and Freundlich models of adsorption. Thermodynamic parameters such as ΔGo, ΔHo and ΔSo have been evaluated and it has been found that the sorption process was spontaneous and exothermic in nature. From all of our data, we conclude that the treated Tamrix articulata wastes investigated in this study showed good potential for cadmium removal from aqueous solutions.
Keywords: Tamrix articulata wastes; cadmium removal; adsorption; kinetic and thermodynamic study
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Al Othman, Z.A.; Hashem, A.; Habila, M.A. Kinetic, Equilibrium and Thermodynamic Studies of Cadmium (II) Adsorption by Modified Agricultural Wastes. Molecules 2011, 16, 10443-10456.
Al Othman ZA, Hashem A, Habila MA. Kinetic, Equilibrium and Thermodynamic Studies of Cadmium (II) Adsorption by Modified Agricultural Wastes. Molecules. 2011; 16(12):10443-10456.
Al Othman, Zeid A.; Hashem, Ali; Habila, Mohamed A. 2011. "Kinetic, Equilibrium and Thermodynamic Studies of Cadmium (II) Adsorption by Modified Agricultural Wastes." Molecules 16, no. 12: 10443-10456.