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Abstract
This paper describes the application of hollow fiber supported liquid membranes for the simultaneous extraction and recovery of low-concentration palladium from waste aqua regia solutions. A mathematical model to predict the palladium transport was also developed and verified. We found that the optimum conditions for transport of palladium were pH 2 in the feed with 0.005 M thioridazine and 0.05 M oleic acid in liquid membrane, 0.03 M NaNO2 in the stripping solution, and an operating flowrate of 100 mL/min. With thioridazine and oleic acid as the extractant carrier, a synergistic enhanced extraction was observed. By employing a 3-cycle operation in repeated operating cycle mode, the cumulative palladium extraction and recovery was 82% and 78% respectively.
Our mathematical model was developed based on reaction flux. The reaction order and the rate constant were determined. It revealed that the first order rate law governed the reaction system for both the extraction and the recovery. The extraction rate constant (k f ) and the stripping rate constant (k s ) were calculated to 0.0140 s−1 and 0.0248 s−1, respectively.
The model was set up for a scenario based on a varying flowrate and a repeated operating cycle mode. The results showed good agreement with theoretical data (curve fittings gave R2 > 0.9).
ACKNOWLEDGEMENTS
The authors highly appreciate the support from the 90th anniversary of Chulalongkorn University Fund (Ratchadaphiseksomphot Endowent Fund), the Graduate School of Engineering, Chulalongkorn University and the ASAHI Glass Foundation.
Notes
Abbreviations: SE: Solvent Extraction, LSM: Liquid Surfactant Membrane, BLM: Bulk Liquid Membrane, FSSLM: Flat Sheet Supported Liquid Membrane, HFSLM: Hollow Fiber Supported Liquid Membrane.
NB*Pancharoen U. et al. (Citation17).
NB*Pancharoen U. et al. (Citation17).