MWCNT, activated carbon and Al2O3 supported palladium nanocatalysts synthesi̇s, characterization and investigation of the catalytic performance in the reduction of Cr+6 to Cr+3'

Hexavalent chrome (Cr(VI)) is defined as acutely toxic, mutagenic and carcinogenic, whereas trivalent chrome (Cr(III)) is thought to be an important element for living creatures in trace amounts. In this study, palladium(0) nanocatalysts (Pd(0)@MWCNT, Pd(0)@Al2O3, Pd(0)@C) supported over multi-walled carbon nanotube (MWCNT), aluminum oxide (Al2O3) and activated carbon (C) were reusably synthesized by the impregnation-reduction technique under mild conditions and characterized by HR-TEM, TEM-EDX, DR/UV-Vis, P-XRD, ICP-OES and XPS techniques. The results indicate the formation of very well dispersed metallic palladium(0) nanoparticles (2.20 ± 0.25 nm, 3.01 ± 0.19 nm, 3.98 ± 0.24 nm) onto the surface of the MWCNT, Al2O3 and C support materials. The stability and activity of catalytic perfomance of the obtained palladium(0) metal nanocatalysts were investigated in the reaction of chrome (VI) to chrome (III) in the existence of formic acid (HCOOH). Nanocatalysts were found to effectively catalyze the reduction of Cr (VI) to Cr (III) with high selectivity (~ 100 %) and high activity (TOF) (for Pd(0)@MWCNT, Pd(0)@Al2O3, Pd(0)@C respectively; 286, 138, 31 mol of Cr2O7-2/mol Pd min). To understand the natural structure of the catalytic reduction reaction of catalysts [Pd(0)@MWCNT, Pd(0)@Al2O3, Pd@C], dichromate substrate [Cr2O72−], formic acid [HCOOH], sodium formate [HCOONa] concentrations and temperature parameters, the velocity statement and activation parameters (ΔH#, ΔS# and Ea) were determined.