Keywords: Clinoptilolite, Ion exchange, Pretreatment, Lead, Ammonium, Removal, Column, Multicomponent.
Abstract: Wastewaters resulted from anthropogenic influence can encompass a wide range of potential contaminants and concentrations. There are numerous procedures that can be used to clear out wastewaters depending on the type and extent of contamination, however; disposal of pollutants from wastewaters in industrial scale is a difficult and costly problem.
In this study, the use of ion exchange theory utilizing natural Turkish clinoptilolite zeolite from Gördes-Manisa as ion exchange resins in down-flow column mode is investigated. The clinoptilolite with particle size range of 0.25-0.50 mm is used in the removal of lead Pb2+ and ammonium NH4 + ions from aqueous solutions.
The aim of the study is to set up the conditions under which clinoptilolite may be used in an economical and efficient approach in the removal process. Experiments were divided into two sets: binary studies, and ternary studies, and the effects of conditioning clinoptilolite with NaCl solution, flow rate, and initial concentration of the solutions on the removal behavior were investigated.
In binary studies, results showed that increasing the loading volumetric flow rate resulted in decreasing the breakthrough capacity and the column efficiency, while the total capacity remained constant. The maximum total capacity was determined as 1.16 meq/g of zeolite for NH4 +, and 1.1 meq/g of zeolite for Pb2+ and these values were close to each other and to the sodium content of Na-form of pretreated clinoptilolite (1.16 meq/g of zeolite). In addition, by decreasing the initial contaminant concentration, an increase in breakthrough capacity and column efficiency was observed.
In ternary studies, the results showed that the removal of Pb2+ and NH4 + ions are dependent on the flow rate, in which at moderately low flow rate, a higher ion exchange capacity is yielded. That was explained as at higher flow rates, the retention time was insufficient for the ion exchange process to take place completely between clinoptilolite and lead and ammonium ions. Thus, a competition between Pb2+ and NH4 + ions for the exchange sites on clinoptilolite was observed and this competition was in favor of lead ions.
Consequently, it was observed that the clinoptilolite zeolite has affinity for both Pb2+ and NH4 + ions. However, the affinity of clinoptilolite for lead ions is higher than that for ammonium ions. Therefore, the cations selectivity for clinoptilolite according to their affinity is determined as the following sequence: NH4 + > Pb2+ > Na+.
Author: Bahaalddin, Ahmad Dh.
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