Palladium–nickel (Pd–Ni) bimetallic nano-catalysts supported on activated carbon (Pd–Ni/AC) have been successfully prepared by impregnation method enhanced with ultrasonic. The prepared Pd–Ni/AC catalysts were used for the catalytic hydrodechlorination reaction of bleached shellac and characterized by Fourier-transform infrared spectroscopy, nitrogen adsorption, X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscope, and high-resolution transmission electron microscopy. The results show that Pd–Ni bimetallic structures in catalytic particles with the diameter of 4 and 14 nm were distributed uniformly on AC support, and the lattice fringe spacing in catalytic particles was measured as 0.213 nm which is lying in the region between monometallic Pd (111; 0.225 nm) and Ni (111; 0.203 nm), and that Pd1–Ni1/AC catalyst exhibits the best catalytic hydrodechlorination performance with the dechlorination efficiency of 92.58 wt% while it is used for the hydrodechlorination of bleached shellac, and the optimum catalytic performance is related to the synergistic electronic effect and bimetallic structure of the Pd1–Ni1/AC sample.
The aim of this paper was exploring the effective utilization of nickel converter slag by means of the methodology of pressure oxidative leaching. The central composite design of response surface methodology was employed to optimize controlling conditions for the leaching of more valuable metals such as nickel, cobalt, and copper, while dissolution of iron was curbed. XRD, SEM-EDS were performed for characterizing the structure of leach residues for analyzing the mechanism of selective leaching. Experimental results demonstrate that the effects of temperature and sulfuric acid concentration on the metals extraction and filtration rate are significant, followed by liquid/solid (L/S) ratio. The optimized conditions for the leaching of converter slag are: temperature 208 °C, sulfuric acid concentration 0.35 mol/L, and L/S ratio 5.4 mL/g. Under these conditions, 99.60% Co, 99.20% Ni, and 96.80% Cu were extracted into solution together with only 0.21% Fe, and the filtration rate of leach slurry reached 576.86 L•m-2 •h-1. The mechanism for achieving selective leaching of nickel, cobalt, and copper against iron dissolution and good filtration performance of the leach slurry was enabled by iron that dissolved in the solution, decomposed, and hydrolyzed mainly to form hematite (α-Fe 2 O 3 and γ-Fe 2 O 3), and letting silicic acid form precipitated SiO 2 in the leach residue.
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