Abstract
Conventional separation methods are not suitable for recovering palladium present in low concentrations in ore leaching solutions. In this study, a novel isopentyl sulfide (S201)-impregnated α-MnO2 nanorod adsorbent (BISIN) was prepared, characterized, and applied for the selective adsorption and separation of palladium from the leaching liquor of ores. Batch studies were carried out, and the main adsorption parameters were systematically investigated, in addition to the relevant thermodynamic parameters, isotherms, and kinetic models. The thermodynamic parameters reflected the endothermic and spontaneous nature of the adsorption. Moreover, the experimental results indicated that the Langmuir isotherm model fits the palladium adsorption data well and the adsorption was well described by the pseudo-second-order kinetic model. The main adsorption mechanisms of palladium were elucidated at the molecular level by X-ray crystal structure analysis. Thiourea was found to be an excellent desorption agent, and the palladium-thiourea complex was also confirmed by X-ray crystal structure analysis. The results indicated that almost all of the Pd(II) (>99.0%) is adsorbed on BISIN, whereas less than 2% of the adsorbed Pt(IV), Fe3+, Cu2+, Ni2+, and Co2+ is observed under the optimum conditions. The proposed method can be used for the efficient adsorption and separation of palladium from the leaching liquor of ores.
Highlights
Chemical precipitation and solution extraction have been employed in industry for the separation and recovery of palladium from the leaching liquors of ore or spent automotive catalysts [1,2,3,4]
The prerequisite for employing solvent extraction is that the concentration of palladium in the solution must be greater than several hundreds of milligrams per liter [7]
The results indicated that the sorbent amount remarkably affects the adsorption of
Summary
Chemical precipitation and solution extraction have been employed in industry for the separation and recovery of palladium from the leaching liquors of ore or spent automotive catalysts [1,2,3,4]. The concentration of Pd(II) in the leaching solutions of ores in the industry is extremely low, only 10 mg·L−1 to 45 mg·L−1. Owing to these low Pd(II) concentrations, solvent extraction must be performed at a high phase ratio. The enrichment factor depends on the ore grade and leaching process parameters All these factors make extraction of Molecules 2017, 22, 1117; doi:10.3390/molecules22071117 www.mdpi.com/journal/molecules
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