Palladium Nanoparticles Supported on Activated Carbon (C) for the Catalytic Hexavalent Chromium Reduction

İbrahim Gözeten,Mehmet Tunç

doi:10.1007/s11270-021-05479-4

İbrahim Gözeten, Mehmet Tunç

Open Access

https://doi.org/10.1007/s11270-021-05479-4

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Abstract

Hexavalent chromium is widely used in industry and causes human health and environmental problems due to its extremely toxic properties. On the contrary, trivalent chromium is necessary for living ecosystems. Therefore, reducing hexavalent chromium to trivalent chromium is the best strategy for detoxifying hexavalent chromium. Pd(0)@C nanocatalyst was prepared by a simple impregnation-reduction method in solution under mild conditions at 298 K and was identified by XPS, XRD, TEM, TEM–EDX, HR-TEM, and ICP-OES analyses. TEM results showed that very well-dispersed Pd nanoparticles were formed on the C surface (mean particle sizes 3.98 ± 0.24 nm). The catalytic performance of Pd(O)NPs impregnated on cheap and easily available commercial activated carbon were tested as heterogeneous nanocatalysts in the catalytic reduction of hexavalent chromium in the medium of formic acid, which is a good reducing agent, and sodium formate as the promoter at 298 K. It was determined that the formed Pd(0) nanoclusters could successfully reduce Cr(VI) to Cr(III) with high selectivity (~ 97%) in formic acid and sodium formate solution under mild conditions. It was also observed that the Pd(0)@C catalyst retained a significant (> 75%) initial activity even after the 5th use. In addition, the kinetic studies of the catalytic reduction reaction of Cr(VI) catalyzed by Pd(0)@C nanoparticles were investigated depending on the substrate [Cr2O72−], catalyst [Pd(0)@C], sodium formate [HCOONa], formic acid [HCOOH] concentrations, and temperature parameter. From the rich kinetic data obtained, the nature of the velocity equation was explained, and the activation parameters were calculated.

Highlights

Cr(VI) has proven to be a mutagenic, acute toxicity carcinogen in its compounds (Elliott and Zhang 2001; Stearns et al 1995)
The activated carbon supported Pd(0)@C nanoclusters were used as heterogeneous nanocatalysts in the catalytic reduction of Hexavalent chromium in formic acid medium, which is a good reducing agent under mild conditions
Pd2+ particles were supported on activated carbon in solution, followed by reduction to Pd(0) with NaBH4 under mild conditions, to synthesize the Pd(0)@C nanocatalyst in a simple and reproducible manner

Summary

Introduction

Cr(VI) has proven to be a mutagenic, acute toxicity carcinogen in its compounds (Elliott and Zhang 2001; Stearns et al 1995). Transition metal NPs have been in great demand recently due to their superior performance in the catalyzed reduction reaction of Cr(VI) (Barakat et al 2013; Zahmakiran and Ozkar 2011). Nanoclusters such as amino-functionalized palladium nanowires (Wei et al 2015), PSA-saported palladium nanoparticles (Fu et al 2014) and PVP- immobilized palladium nanotetrapods showed high activity in reducing hexavalent chromium in the presence of reducing agent HCOOH (FA) (Omole et al 2007). We developed the previously unused Pd@C catalyst for the reduction reaction of Cr(VI) in FA medium

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