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The mineralogy of saprolitic laterites has been characterised using X-ray diffraction, Fourier transform infrared spectroscopy, thermal analysis and X-ray fluorescence. The results showed that the ore consists mainly of nickel- and iron-substituted lizardite and minor quantities of magnetite. Several experiments were conducted to investigate the extraction of nickel and cobalt from lizardite at atmospheric pressure in acidic media as a function of particle size, sulphuric acid concentration, reaction time, temperature and liquid to solid ratio. Generally, as much as 69·6%Ni and 30·8%Co were extracted under the experimental condition of 10% (v/v) H2SO4, reaction temperature 90°C, reaction time 2 h, particle size 59·9% passing through 74 μm, stirring at 500 rev min–1 and liquid to solid ratio 3 mL g–1. Increased extraction of Ni and Co from lizardite with sulphuric acid could be obtained by introducing leaching additives such as ferric chloride (Ni leaching rate 74·8%, Co leaching rate 45·4%), organic acid (Ni leaching rate 76·3%, Co leaching rate 48·7%) and fluoride (Ni leaching rate 81·7%, Co leaching rate 52·3%). [ABSTRACT FROM AUTHOR]

This paper makes research on solving the problem in China concerning the suitable particle size for flotation and the optimum particle size of the concentrate required by the subsequent Bayer process. Grinding experiments under different conditions and flotation tests had been used to investigate the comminution property of bauxite and aluminosilicate as well as their separation by flotation. The results showed that different kinds of grinding medium led to different grinding effects, the following being the order of the selective grinding effect: (column+ball)>ball>rod, and the separation between Al and Si in bauxite has been improved after selective grinding. It is indicated that the crystal structural difference between diaspore and aluminosilicate leads to their difference of comminution property. A demo plant built by the novel process of ‘selective grinding–flotation’ had been successfully commissioned in China since 2003. [ABSTRACT FROM AUTHOR]

Objective: To explore the psychological status of medical staff during COVID-19 epidemic, so as to provide reference and scientific basis for carrying out further psychological intervention and ensuring the mental health of medical staff. Methods: By using convenient sampling method and the Stresss-Anxiety ubscale of Depression Anxiety Stress (DASS-21) , the mental health status of 615 medical staff was investigated by the way of questionnaire star from February 4 to 16, 2020. A total of 615 questionnaires were distributed and collected, and 615 were valid, with an effective recovery rate of 100%. Results: The detection rates of psychological stress and anxiety of medical staff were 13.82% (85/615) and 25.37% (156/615) , respectively. 31-40 years old and working in key departments were risk factors for psychological stress of medical staff ( OR =1.779, 2.127) ; Women, frequently washing hands with soap/hand sanitizer/disinfectant were protective factors for psychological stress ( OR =0.520, 0.528) . Medical staff working in designated hospitals and key departments were more likely to have anxiety ( OR =2.042, 2.702) ; The high fit of the mask to the face and bridge of the nose was a protective factor for the psychological anxiety of medical staff ( OR =0.500) . Conclusion: Medical staff show higher stress and anxiety during the epidemic of COVID-19. Psychological intervention should be carried out early, focusing on men, age 31 to 40, medical staff working in designated hospitals and key departments.