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The leaching kinetics of potassium from phosphorus-potassium associated ore in hydrochloric acid/fluorite (CaF2) system was studied. HCl concentration, liquor/solid ratio, CaF2 dosage, and temperature were found to be the main factors. The leaching rate of potassium can be reached more than 92% under the optimum operation conditions. A classic shrinking core model with the mixed chemically diffusion as the rate-controlling step was successfully modeled the leaching kinetics of potassium, and the activation energy was found to be 30.7 kJ·mol−1. The leaching mechanism of potassium was also elucidated based on the experimental results.

Carbon-doped TiO2 nanocoating (TiO2-C) on carbon black (CB) was prepared and employed as the support of Pd catalyst for ethanol oxidation reaction (EOR) in alkaline media. The obtained catalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. TEM characterization shows that TiO2 nanocoating is formed uniformly on CB and still preserves its structure with no apparent sintering after carbon doping, and Pd particles are well dispersed on the conductive TiO2-C support. XRD characterization shows that TiO2-C presents an anatase structure. XPS characterization shows that oxygen vacancy defects resulting from carbon doping present in TiO2-C. Cyclic voltammetry (CV) and chronoamperometry (CA) results demonstrate that the as-prepared Pd/TiO2-C catalyst exhibits much enhanced catalytic activity and stability for EOR in alkaline media than Pd/C catalyst. The enhanced activity presented by the Pd/TiO2-C catalyst may result from the strong interactions between TiO2 and Pd, the facilitated oxidation removal of CH3COads intermediate, and the facilitated transportation of ethanol to Pd active sites.

High alloyed Pd-Au/C catalyst is prepared through a rate-limiting strategy in water/ethylene glycol solution. Pd/C and low alloyed Pd-Au/C catalysts are prepared with trisodium citrate and sodium borohydride as stabilizing and reducing agents, respectively. Transmission electron microscopy (TEM) shows that the synthesized Pd(Au) particles are well dispersed on the catalysts. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) show that the high alloyed Pd-Au/C catalyst presents a relatively homogenous structure while the low alloyed Pd-Au/C catalyst presents a Pd-rich shell/Au-rich core structure. Electrochemical characterization shows that the low alloyed Pd-Au/C catalyst exhibits the best catalytic activity for ethanol oxidation reaction (EOR) in alkaline media, which could be attributed to its relatively large exposed Pd surface area as compared with the high alloyed Pd-Au/C catalyst due to its Pd-rich shell structure and its enhanced adsorption of OHads as compared with Pd/C catalyst due to its core-shell structure.

Vertically oriented TiO2 nanotube (TNT) arrays (TNTs/Ti) of different tube lengths are prepared by anodization process and Pd particles are well dispersed on the TNTs/Ti substrates by pulse electrodeposition technique. Electrochemical measurements show that the conductivity of TNTs/Ti substrate can be largely improved after the deposition of Pd particles and the Pd–TNTs/Ti electrodes show good electrocatalytic activity for ethanol oxidation in alkaline media, which may be ascribed to the well dispersion of Pd particles on the TNTs/Ti substrate, the reduced poisoning on the Pd surface, the high utilization of Pd catalyst and the enhanced direct electron transfer. The Pd particles supported on the TNTs/Ti substrate with the smallest tube length exhibit the best electrocatalytic activity and stability for ethanol oxidation, which may result from the smallest transport resistance of reactants and products and the highest conductivity for TNTs/Ti substrate with the smallest tube length.