Abstract
Effective recovery of palladium ions from acidic waste solutions is important due to palladium’s intensive usage as a catalyst for different industrial processes and to the high price paid for its production from natural resources. In this paper, we test the ability of a new adsorbent, MgSiO3 functionalized by impregnation with DL-cysteine (cys), for palladium ion recovery from waste solutions. The Brunauer–Emmett–Teller (BET) surface area analysis, Barrett–Joyner–Halenda (BJH) pore size and volume analysis, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and Fourier-Transformed Infrared (FTIR) spectroscopy have been performed to characterize this material. Firstly, the maximum adsorption capacity of the new obtained material, MgSiO3-cys, in batch, was studied. To establish the adsorption mechanism, the obtained experimental data were fitted using the Langmuir, Freundlich and Sips adsorption isotherms. Studies on the adsorption of palladium ions on the synthesized material were performed in a dynamic regime, in a fixed-bed column. The Pd(II) recovery mechanism in the dynamic column regime was established based on Bohart–Adams, Yoon–Nelson, Thomas, and Clark models. The obtained equilibrium adsorption capacity was 9.3 (mg g−1) in static regime (batch) and 3 (mg g−1) in dynamic regime (column). The models that best describe the Pd(II) recovery process for batch and column adsorption are Sips and Clark, respectively.
Highlights
The noble metals platinum, palladium and rhodium have a wide application range based on their distinct physical and chemical properties [1,2,3,4,5]
The current paper presents a new adsorbent, MgSiO3 functionalized with DL-cysteine, designed for palladium ion recovery from waste solutions
The modeling of the experimental data obtained in the batch system showed that the Sips isotherm best describes the adsorption process, because the correlation coefficient R2 approaches 1 and the maximum calculated adsorption capacity (9.62 mg g−1 ) is close to the experimentally determined value (9.23 mg g−1 )
Summary
The noble metals platinum, palladium and rhodium have a wide application range based on their distinct physical and chemical properties [1,2,3,4,5]. Palladium and its alloys are currently used by the telecommunication and automotive industries (as catalytic converters), the metallurgy and chemical industries, for jewelry manufacturing and in the medical field (dental alloy production) [5,6,7,8,9]. In 2010, to official recognition as the fourth most precious metal, after gold, silver and platinum, a statute that requires the marking of each jewel. White gold contains variable amounts of palladium (up to 20%); dental alloys can contain up to 10%. Public Health 2020, 17, 9500; doi:10.3390/ijerph17249500 www.mdpi.com/journal/ijerph
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