Abstract
The objectives of the study were to find the type and species of zeolite which gives optimum adsorption of copper, provide an explanation of the mechanism involved in the adsorption process and establish the selectivity sequence among zeolites. Adsorption of Cu onto zeolites and mont-morillonite as a reference was conducted at an initial Cu concentration range of 0 - 0.60 mM in the presence of 100 mM NH4NO3 at initial pH of 5. Langmuir and Freundlich models were used in analyzing the equilibrium data and a selectivity sequence derived from the Langmuir calculation was A4 > faujasite X > modernite > Na-P1 ≈ montmorillonite ≈ faujasite Y > clinoptilolite. Zeolites A4 and faujasite X had high adsorptive capacities of 1429 mmol·kg﹣1 and 909 mmol·kg﹣1, respectively. Zeolite A4 has the highest CEC among all the samples (6150 mmol·kg﹣1), and the adsorption capacity of Cu was largely influenced by the CEC of the samples. The adsorption mechanism was based on the exchange of Cu from solution with mostly Na which was the main exchangeable cation available. These results are important in selecting the most effective and suitable adsorbent for Cu removal from polluted environments.
Highlights
Heavy metals, such as Cu, Cd, Pb and Zn, are toxic to human beings and other living organisms if their concentrations exceed certain values
The samples were analyzed before commencement of the adsorption experiments: cation exchange capacity (CEC) measurement, Si/Al ratio determination, and X-ray diffraction (XRD) analysis
From the results of this experiment, it can be concluded Cu has the highest selectivity toward synthetic zeolites, A4 to be specific, followed by artificial zeolites, natural zeolites
Summary
Heavy metals, such as Cu, Cd, Pb and Zn, are toxic to human beings and other living organisms if their concentrations exceed certain values. Copper is heavily used in industries for such uses as plating, mining and smelting, brass manufacture, electroplating, petroleum refining and Cu-based agrichemicals mining. Metals in these industries produces a lot of wastewater and sludge containing Cu in various concentrations. These have negative effects on water and the environment in general [1]. The World Health Organization recommended a maximum acceptable concentration of Cu in drinking water of 1.5 mg·L−1 [4]. The concentration of this metal must be reduced to a level that satisfies national and international environmental best practices (regulations) for various water bodies
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