Zhijun Sun

Synthesis of Superhard and Elastic Carbon Nitride Films by Filtered Cathodic Vacuum arc Combined with Radio Frequency Ion Beam Source

Superhard and elastic carbon nitride films with hardness and elastic recovery of 47 GPa and 87.5%, respectively, were synthesized by using a double-bend filtered cathodic vacuum arc combined with radio-frequency nitrogen ion beam source. The bombardment of energetic nitrogen atom onto the growing film surface results in the high atomic ratio of N/C (0.4), which contributes to the high sp 2 content and the formation of a five-membered ring structure in the carbon nitride film at room temperature. The buckling of the five-membered ring basal planes may facilitate cross-linking between the planes through sp 3 coordinated carbon atoms. A rigid three-dimensional network is formed, which contributes to the high hardness and elastic recovery of the deposited films.

Magnetically separable AgI–BiOI/CoFe2O4 hybrid composites for Hg0 removal: characterization, activity and mechanism

A series of magnetically separable AgI–BiOI/CoFe2O4 hybrid composites were successfully synthesized via a solvothermal and subsequent coprecipitation method. The microstructure and magnetism of the materials were characterized by X-ray diffraction (XRD), N2 adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), photocurrent test, electron spin resonance (ESR) and vibrating sample magnetometer (VSM). The photocatalytic performance of AgI–BiOI/CoFe2O4 composites on Hg0 removal from simulated flue gas was carefully designed and evaluated under fluorescent light (FSL) irradiation. The results showed that AgI–BiOI/CoFe2O4 composites displayed superior photocatalytic activities because of the synergistic effects between AgI, BiOI, and CoFe2O4 under FSL irradiation. The optimal weight ratio between AgI and the total weight of AgI–BiOI/CoFe2O4 photocatalyst was 0.3. The presence of a small amount of SO2 had a dramatic inhibition on Hg0 removal, while the inhibitory effect of NO on Hg0 removal could only be observed at a higher NO concentration. The trapping experiments indicated that photoinduced holes (h+) and superoxide radicals (˙O2−) were the primary active substances in the AgI–BiOI/CoFe2O4 photocatalytic oxidation system. According to the experimental and characterization results, one plausible mechanism for enhanced Hg0 removal performance over AgI–BiOI/CoFe2O4 composites was proposed.

Speciation analysis and leaching behaviors of selected trace elements in spent SCR catalyst

This study investigated heavy metal chemical speciation and leaching behavior from a board-type spent selective catalytic reduction (SCR) catalyst containing high concentrations of vanadium, chromium, nickel, copper, zinc, and lead. A three-step sequential extraction method, standard toxicity characteristic leaching procedure (TCLP), and leaching characteristic tests have been performed. It was found that the mobility of six heavy metals in the spent SCR catalyst was significantly different. The mobility of the six heavy metals exhibited the following order: Ni > Zn > V > Cr > As > Cu. Meanwhile, TCLP test results revealed relatively high Zn and Cr leaching rate of 83.20% and 10.35%, respectively. It was found that leaching rate was positively correlated with available contents (sum of acid soluble, reducible and oxidizable fractions). Leaching characteristics tests indicated that pH substantially affected the leaching of these heavy metals. In particular, the leaching of Cr, Ni, Cu, and Zn was positively influenced by strong acid, while V and As were easily released in the presence of strong acid and strong alkali (pH < 3 or pH > 11). In terms of kinetics, the leaching of Cr, Ni, Cu, Zn, and As within the spent catalyst was dominated by erosion and dissolution processes, which were rapid reaction processes. V was released in large amounts within 1 h, but its leaching amount sharply decreased with time due to readsorption.