The development and utilization of high‑sulfur iron ore in China has provided abundant raw materials for the iron and steel industry, but it has also created severe environmental challenges, particularly in controlling sulfur dioxide emissions. Although the current sulfur-fixation technology has made some progress, it still has limitations such as low efficiency and less stability. This study will in-depth explore the mechanism of in-situ sulfur fixation with the aim of solving aforementioned issues and realizing the transition from terminal desulphurization to process control. Firstly, the effects of oxidation roasting temperature, oxygen concentration, gas flow rate and sulfur-fixation agent concentration on the sulfur-fixation efficiency were investigated to determine the regulation mechanism of sulfur fixation technology. Moreover, the sulfur-fixation activities of CaO and MgO were also compared in depth by Density Functional Theory (DFT) calculation in terms of surface adsorption energy, transition state and partitioned density of states (PDOS). Finally, the sulfur-fixation mechanism was analyzed in depth by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) tests in terms of phase composition, crystal structure and surface morphology. Therefore, the work will present basic theory and systematic guidance for in-site sulfur-fixation of high‑sulfur iron ore under oxidation roasting process.

In China, most of the high-sulfur iron ores have not been fully developed and utilized due to the lack of breakthrough progress in the research on the sulfur migration and the desulfurization mechanism during the roasting process. This study will focus on revealing the release and fixation mechanisms of sulfur during the roasting process to achieve the transformation of desulfurization from terminal treatment to process control. Experimental results show that as the roasting temperature increases, the release rate of SO2 also increases, reaching the maximum release rate at 900 °C. Simultaneously, it is found that at the same roasting temperature, the release rate and amount of SO2 under the O2/N2 atmosphere is significantly greater than that under the pure N2 and air atmospheres. Meanwhile, X-ray diffraction (XRD) is utilized to explore the phase composition of the roasted product and the sulfur release mechanism. In addition, the adsorption energy, stability and electron transfer of SO2 on the CaO surface are calculated through density functional theory (DFT), and the optimal adsorption active site perpendicular to the O atom (O-top) is also determined. Finally, the sulfur fixing agent CaO is used to study the SO2 fixation mechanism. When the concentration reaches 10%, the sulfur fixation efficiency reaches more than 80%. Therefore, this work will present basic knowledge and systematic guidance for the sulfur migration and release of high-sulfur iron ore under the oxidizing roasting process.

In order to overcome the complexity and high cost of preparation of iron-based modified catalyst, a novel process of natural pyrite (FeS2) superimposed pulsed electro-assisted activation peroxymonosulfate (PMS) for contamination treatment was developed. Tetracycline hydrochloride (TCH) was selected as the target pollutant because of its persistence and high drug-resistance toxicity. Firstly, the optimum parameters (pulse current intensity, duty cycle, pH, PMS concentration) were determined by different conditional experiments. Then, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize pyrite before and after the reaction. And electron spin resonance (ESR) and quenching experiment were used to discern the active species in the reaction processes. The results showed that pyrite could effectively activate PMS to degrade into hydroxyl radicals (.OH) and sulfate radicals (SO4.- ) to treatment contamination. In addition, the pulsed electro-assisted addition could weaken concentration polarization, improve TCH removal efficiency to 93%, and reduce energy consumption. More importantly, pulsed current was better than the direct current for converting SO2-4 to SO.-4 . And Fe(III) can be converted to Fe(II) through the action of electrons and S22- in the pulse electro-assisted pyrite activation of PMS process. These findings provide new insights into PMS activation by iron-based catalyst and electrochemistry.

弓长岭一选厂及二三选厂铁尾矿全铁品位在10％以上,主要杂质成分为SiO2,有害成分S、P含量均较低,-200目含量接近60％.现场预富集粗精矿返回主流程的二段磨矿系统,导致系统运行状况不理想,磨矿系统循环量大、球磨机利用系数和磨矿效率低,最终导致精矿TFe品位不高.为解决该问题进行了选矿试验,结果表明,中强磁选(358.28 kA/m)预富集粗精矿单独再磨至-500目40％情况下,采用1次弱磁粗选(71.66 kA/m)、1次磁选柱精选(63.70 kA/m、上升水流12 L/min)流程处理,最终获得铁品位65.40％、回收率14.47％的精矿.研究表明,中强磁选预富集—陶瓷介质搅拌磨机磨矿—弱磁粗选—磁选柱精选流程是处理弓长岭磁铁矿尾矿的高效流程.

In recent years, sulfur-doped modified iron-based catalysts have been widely used to activate peroxymonosulfate (PMS) or peroxydisulfate (PDS) for the contamination elimination, however, the manufacturing complicated and costly limit further industrial application. Therefore, a new water purification technology using pyrite activation PMS with electro-assisted is developed, and the parameters are adjusted and underlying mechanism is clarified. It has been found PMS is effectively activated by FeS2, achieving similar to 90% tetracycline hydrochloride (TCH) removal. Sulfide is the main electron donor for activation PMS and mediates the regeneration of Fe(II) on the pyrite surface, and different sulfur conversion intermediates such as short-chain polysulfides S-n(2-) , elemental sulfur S-0, and sulfate form from the oxidation of sulfides (S-2(2-) ). Moreover, the iron ions in-situ generation from pyrite activation PMS involve in TCH degradation, and concurrently is greatly affected by current, PMS and pH. The production of hydroxyl radicals ((OH)-O-center dot) and sulfate radicals (SO4 center dot- ) by pyrite-activated PMS is confirmed by electron paramagnetic resonance (ESR) and quenching tests. Finally, the mechanism is proved electro-oxidation, non-radical-oxidation and radical-oxidation synergistically eliminate TCH in EC/PMS/pyrite system. Overall, this study provides a new horizons for heterogeneous activation PMS and unveils the advantages and potential applications of sulfur-containing iron-based activators.

Simultaneous treatment NO and SO2 from industrial flue gas by wet processes, a large number of sulfate (SO42-) ions will be generated in the system, and SO42- ion is corrosive to concrete buildings used for subsequent sewage treatment. If the generated SO42- ions can be in-situ reutilization to be converted to sulfate radicals (SO4 center dot-) with strong oxidizing, then they can continue to oxidize removal NO and SO2 in the flue gas, which will further promote the effect of flue gas treatment. Therefore, a novel strategy with C/C electrodes electro-activated peroxymonosulfate (PMS) is developed, utilizing electrons to activate PMS to generate radicals while carbon electrodes converting SO42- ions to SO4 center dot- radicals via direct electron transfer, and then use the radicals and other active substance generated to remove NO. The effects of current intensity, temperature on NO removal and the types of oxides produced in the electro-activated system are investigated. In addition, the relationships of current intensity and conversion time with the SO4 center dot- radical signal intensity detected are discussed respectively. Accordingly, a catalytic mechanism is proposed involving SO4 center dot- (OH)-O-center dot and O-1(2) radicals oxidation and C-PMS* non-radical oxidation.

Nitric oxide (NO) emissions seriously threaten the atmospheric ecology and cause air quality degradation, and the acid rain type has gradually changed from sulfuric acid to nitric acid in some areas of China. To this end, an efficient, facile, innovative strategy of NO removal from simulated flue gas using Fe/Gr periodically reversing electro-activated peroxymonosulfate (PMS) system is proposed for the first time. Encouragingly, we find that the graphite (Gr) electrode has the similar electrochemical property to those of the boron-doped diamond (BDD) and platinum (Pt) electrodes, converting SO42- to sulfate radicals (SO4 center dot-), and provide direct spectroscopy evidence for the theory that the electron e(-) can activate PMS to generate SO4 center dot- and hydroxyl radicals ((OH)-O-center dot) via the electron paramagnetic resonance (ESR) tests. In addition to the two free radicals mentioned above the singlet oxygen (O-1(2)) is detected synchronously in the electrical-activated PMS system. And the signal intensity of the radicals detected increases with increasing current intensity correspondingly. Addition of excess methanol has a greater effect on the NO removal than tert-butanol and sodium azide, demonstrating that SO4 center dot- dominates the NO removal. Furthermore, the results show PMS concentration, current intensity, pH, in-situ generated Fe2+ and O-2 concentration have the distinct effect on the NO removal. Compared with different electro-activation systems of Fe/Fe and Gr/Gr and BDD/Gr, Fe/Gr achieves the optimum NO removal effect. Finally, the reaction mechanism is proposed: direct electrode oxidation, non-radical oxidation, and radical oxidation are combined to remove NO in the electro-activated PMS reaction system.

In this study, the kinetics of on nitric oxide (NO) removal from simulated flue gas using peroxymonosulfate (PMS) with synergic activation of Fe(II) ions and high temperature in a multi-stage stirred bubble reactor were investigated. The new reactor was designed with multiple stages and equipped with multiple agitators, which can increase the gas content in liquid and promote the gas-liquid mass transfer process. In this research we discussed the kinetics of NO removal reaction comprehensively and deeply. To confirm the kinetic model, the effects of initial PMS concentration and reaction temperature of the NO removal process were investigated. The results, with good reliability (0.979, 0.98, 0.963 and 0.963), showed that the removal process of NO in simulated flue gas was considered a pseudo first-order reaction. It worth noting that we have not only investigated the elementary kinetic parameters such as the diffusion coefficient, mass transfer coefficient, reaction rate constant, and enhancement factor of chemical absorption reaction, but also examined other indispensable kinetic parameters such as liquid-phase reaction utilization efficiency, critical concentration equation of liquid solvent and the increase of interface temperature for the first time. The result of liquid-phase reaction utilization efficiency was close to 0 and critical concentration equation of liquid solvent was 8.291-8.732 mmol/L. And the interface temperature slight increase was not enough to affect the entire reaction process. The indispensable kinetic parameters results provide systematic and comprehensive technical parameters to enable the application of NO removal techniques to industrial scale experiments.

An advanced oxidation process involving combined activation of peroxymonosulfate (PMS) by Fe(II) ions and heating for NO and SO2 removal from coal-fired flue gas was conducted for the first time in a rotating packed bed (RPB) pilot reactor. The major influencing factors, radical species, reaction mechanisms and products, the mass transfer process, and the kinetics of simultaneous removal of NOx and SO2 were investigated. The results indicated that the NO removal efficiency reached above 70%, while SO2 and NO2 were almost completely removed. As the temperature increased, the (NO)-N-center dot removal efficiency increased. Moreover, the intensity of SO4 center dot-, center dot OH, and O-1(2) radicals generated by the activated PMS and (NO)-N-center dot radical converted by the radical-radical reaction enhanced with the increasing temperature, assessed by the electron spin resonance spectroscopy test. The increased liquid flow led to a higher NO removal efficiency, and the increased gas flow played the opposite role. The increased rotational speed first resulted in an increase in the NO removal efficiency and then its decrease. Furthermore, the mass transfer coefficient obtained in this RPB was significantly higher than that in the conventional bubbling reactor. Finally, the NO removal process in the PMS/Fe(II)/RPB system was proved to be a pseudo-first-order reaction and was considered to be a fast reaction as the reaction process completed in the liquid film based on the investigation of the Hatta number, strengthening factors, and the liquid-phase reaction utilization efficiency. The pilot experiment is conducted to further study the main parameters affecting the chemical reaction on a certain scale device and to solve the problems that the laboratory cannot solve or discover, and it is the necessary link for the transformation of scientific and technological achievements.

A strategy for removing nitric oxide (NO) from simulated flue gas by transition metal ion (Fe2+, Co2+, and Fe3+)-induced production of sulfate (SO4 center dot-), hydroxyl ((OH)-O-center dot), and singlet oxygen radicals (O-1(2)) from peroxymonosulfate (PMS) at high temperature was investigated, and the catalytic performances of the three metal ions were compared. The nitric oxide radical ((NO)-N-center dot) was detected in solution using electron spin-resonance (ESR) spectroscopy, and a pathway for reaction between NO and the radicals was further explored and refined. The metal ion-catalyzed decomposition of PMS could be considered a pseudo-first order reaction with good reliability (R-2 > 0.97), and the rate constant, k(0), for metal ion-catalyzed PMS degradation followed the sequence: Fe2+ > Co2+ > Fe3+. Specific experiments were optimized to select the optimal experimental parameters (PMS/metal molar ratio and solution pH) for maximizing the NO removal efficiency. ESR was employed to monitor the progress of PMS activation, and it was found that: 1) SO4 center dot-, (OH)-O-center dot, and O-1(2) radicals were mainly produced during the activation of PMS by the three metal ions; 2) the three radicals synergistically removed NO; 3) the generation of O-1(2) was more sensitive to temperature than the generation of the SO4 center dot- and (OH)-O-center dot radicals; 4) the capacity of the metals to catalyze the oxidation reaction followed the order: Fe2+ > Co2+ > Fe3+. These findings provide new insight into PMS activation by transition metal catalysts at high temperature.

In this article, a novel control strategy on nitric oxide (NO) removal from simulated flue gas by high temperature and transition metal Fe(II) to activate peroxymonosulfate (PMS) to generate sulfate radicals (SO4-) and hydroxyl radicals ((OH)-O-center dot) was investigated for the first. The high oxidation capacity of PMS, in combination with the high activation performance of Fe(II) ions, made the processes significantly effective for NO removal, and a removal efficiency of more than 86% was observed after 25 min treatment. Some experiments were optimized to select optimal experimental parameters: the molar ratio of PMS/Fe(II), solution pH value and activation temperature in terms of NO removal efficiency. The effect of free radical quenching, combined with electron spin-resonance (ESR) analysis confirmed that the presence of SO4 center dot- and (OH)-O-center dot radicals, and verified that SO4 center dot- was the dominated radical during NO removal process and the strategy of heating and Fe(II) had stronger function to activate PMS. The classical steady-state approximation technique was adopted to obtain the kinetic model of the whole reaction, and the result satisfactorily interpreted the experimental data and had the good reliability (0.978) and (0.988). The removal process of NO from simulated flue gas by the PMS-Fe(II) systems was a pseudo-first-order reaction.