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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.

ZnO materials with a range of different morphologies have been synthesized via a simple solvothermal method in dimethylacetamide (DMAc) media. DMAc was used as the base source and solvent in such solvothermal syntheses for the first time. The effect of the DMAc content in the solvothermal process on nucleation, growth, and the final morphology of the ZnO nanostructures was investigated. XRD results revealed that single-phase ZnO with the wurtzite crystal structure was obtained for different DMAc contents in solution. X-ray photoelectron spectroscopy confirmed high purity of the as-prepared ZnO crystals. SEM imaging showed that ZnO with spherical shapes, dumbbell, and rod-like were synthesized by controlling DMAc content. In addition, vibrational properties of ZnO crystals with different morphologies were investigated by Raman spectroscopy. The optical properties of the as-prepared ZnO materials were investigated by UV–vis absorption and room temperature photoluminescence. The possible mechanism was also proposed to account for the growth of the ZnO crystals in the DMAc solvent.

In this work, carbon-doped TiO2 nanocoating (TiO2–C) was prepared by a sol–gel process and employed as the support of Pt nanoparticles for methanol oxidation reaction (MOR). The obtained Pt/TiO2–C catalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. XRD characterization shows that the average crystallite sizes of Pt particles and TiO2–C support are 2.7 and 6.5 nm, respectively. TEM characterizations show that Pt particles are highly dispersed on TiO2 nanocoating, which preserves its nanoscale structure without no apparent sintering after carbon doping. XPS characterization shows that the Pt particles anchored on TiO2–C exhibit positively shifted binding energies of Pt 4f. Cyclic voltammetry (CV) and chronoamperometry (CA) characterizations show that TiO2–C has a greatly enhanced electrical conductivity and Pt/TiO2–C catalyst has better electrocatalytic activity and stability than Pt/C catalyst for MOR, which could be attributed to the high dispersion of Pt particles on TiO2–C support, the strong metal-support interactions between Pt particles and TiO2–C support, and the rich active –OH species on TiO2–C support.

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.

Recently, biodiesel has received much more attention. Soybean oil, rapeseed oil, palm oil and corn oil are primary feedstock for biodiesel production. However, biodiesel production from these traditional oil-rich crops is limited by land availability, climate, and environmental and social issues regarding the use of feed and food crops for fuel. Oleaginous microorganisms, including micro-algae, bacteria, yeast and fungi can be cultivated with high lipid contents and used as promising feedstock for biodiesel production. However, the high cost of biodiesel production using oil microorganisms has been the biggest obstacle for its industrialization. The process of biodiesel production from microorganisms involves many steps, of which the lipids extraction is the most important and costly. Therefore, searching for an effective and economical extraction system is critical. Various approaches of lipids extraction are discussed in this review, including traditional extraction procedures such as solvent extraction, pressing and solvent integrated extraction, as well as some new procedures.