Removal of Metallic Impurities from Off-Grade Copper Concentrate in Alkaline Solution

The removal of metallic impurities from off-grade copper concentrate was investigated in alkaline solution with H2O2. The analysis results of XRD and SEM-EDS revealed the oxidative mechanisms of all sulfides. The influence of various parameters of alkaline leaching were investigated including concentrations of sodium hydroxide and hydrogen peroxide, liquid to solid ratio, leaching time and temperature. The results showed that the removal rate of Mo, As and Zn were increased with increasing leaching time and H2O2 concentration, and that the removal rate of Mo, As and Zn were firstly increased and then slightly decreased with increasing liquid to solid ratio, temperature and NaOH concentration, respectively. More than 95% Mo, 94% As, and 94 % Zn are removed from the off-grade concentrate under the optimum conditions, while only 1.7% Cu is dissolved. These optimum conditions were sodium hydroxide 1.5 mol/L, hydrogen peroxide 1.0 mol/L, temperature 50°C, liquid to solid ratio 5/1 mL/g and leaching time 5 h.

Tuning photocatalytic performance of Cs_(3)Bi_(2)Br_(9)perovskite by g-C_(3)N_(4)for C(sp^(3))–H bond activation

All-inorganic halide perovskite(IHP)has been deemed promising in photocatalysis due to tunable bandgap and long lifetime of charge carriers.However,unsatisfactory photocatalytic activity and low stability prevent its practical applications.Rational construction of heterojunctions has been proved to be an efficient way to circumvent these obstacles.Herein,g-C_(3)N_(4)nanosheet was employed to construct a 2D/2D(2D:two-dimensional)heterostructure with Cs_(3)Bi_(2)Br_(9)through an electrostatic self-assembly process.Owing to the efficient transfer of photogenerated charge carriers,the activity of Cs_(3)Bi_(2)Br_(9)was boosted with enhanced generation of carbon centered radicals.The optimized 10%Cs_(3)Bi_(2)Br_(9)/g-C_(3)N_(4)composite displays the highest benzaldehyde formation rate of 4.53 mmol·h^(−1)·g^(−1)under visible light,which is 41.8 and 2.3 times that of individual g-C_(3)N_(4)and Cs_(3)Bi_(2)Br_(9),respectively.The stability of Cs_(3)Bi_(2)Br_(9)nanosheets and its selectivity for benzaldehyde(from 65%of Cs_(3)Bi_(2)Br_(9)to 90%of the composite)was enhanced by reducing its surface energy and tuning the reaction pathway,respectively.

Width-Dependent Optical Properties for Zigzag-Edge Silicene Nanoribbons

We study theoretically the optical response for perfect zigzag-edge silicene nanoribbons with N silicon atoms of the A and B sublattices（N-ZSiNRs） under the irradiation of an external electromagnetic field at low temperatures.The 8- and 16-ZSiNRs are demonstrated to exhibit a broad energy regime of absorption coefficient, refractive index, extinction coefficient, and reflectivity from infrared to ultraviolet, utilizing the dipole-transition theorem for semiconductors. The optical spectra for 8- and 16-ZSiNRs may be classified into two types of the transitions,one between valence and conduction subbands with the same parity, and the other among the edge state and bulk state subbands. With the increase of the ribbon width, the optical spectra for ZSiNRs are proved to exhibit red shift and blue shift at the lower and higher energy regimes, respectively. The obtained novel features are believed to be of significance in designs of silicene-based optoelectronic devices.