Cadmium removal using clinoptilolite : influence of conditioning and regeneration

Gedik, Kadir
Clinoptilolite samples obtained from two deposits in Turkey were tested for their potential in removing cadmium from aqueous solutions. Preliminary experiments in batch mode revealed inferior cadmium uptake at low pH. Particle size was found to have no effect on cadmium removal efficiency suggesting the use of exchangeable cations found in the internal/available sites. Increasing temperature yielded positive, whereas prewashing had no effect on cadmium removal using both clinoptilolite samples. The Langmuir model fitted the equilibrium data for both samples better than the Freundlich model. The capacity reached after conditioning represents about 4 and 3 fold increase for Gördes and Bigadiç samples, respectively. The relatively poor performance of Bigadiç clinoptilolite was due to low clinoptilolite/high impurity contents. Further studies were carried out only with Gördes clinoptilolite. The performance of the Gördes samples conditioned with various chemicals were NaCl>KCl>As-received>CaCl2>HCl. 20BV of NaCl solution was found to be sufficient with no pH adjustment or water quality requirement during column conditioning. In column experiments, among the tested flowrates 5, 10 and 15 BV/hr, highest flowrate indicated inferior utilization of the removal capacity. No significant difference by decreasing particle size indicated pore diffusion resistance not to be a limiting factor. In five conditioning and regeneration cycles, clinoptilolite exhibited 36% increase in operating capacity. Cadmium removed by clinoptilolite in progressing cycles was concentrated by about 7 times. Overall, this study shows that Manisa-Gördes clinoptilolite is advantageous for the removal of cadmium ions from aqueous solutions and hold great potential to be used in practical applications.


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Citation Formats
K. Gedik, “Cadmium removal using clinoptilolite : influence of conditioning and regeneration ,” M.S. - Master of Science, Middle East Technical University, 2006.