Migration and transformation of Pb,Cu,and Zn during co-combustion of high-chlorine-alkaline coal and Si/Al dominated coal

Shaerhu(SEH)coal is abundant in Xinjiang,China.The utilization of SEH suffers from severe ash deposition,slagging,and fouling problems due to its high-chlorine-alkaline characteristics.The co-combustion of high-alkaline coal and other type coals containing high Si/Al oxides has been proven to be a simple and effective method that will alleviate ash-related problems,but the risk of heavy metals(HMs)contamination in this process is nonnegligible.Hence,the volatilization rates and chemical speciation of Pb,Cu,and Zn in co-combusting SEH and a high Si/Al oxides coal,i.e.,Yuanbaoshan(YBS)coal were investigated in this study.The results showed that the addition of SEH increased the volatilization rates of Pb,Cu,and Zn during the co-combustion at 800℃from 23.70%,23.97%,and 34.98%to 82.31%,30.01%,and 44.03%,respectively,and promoted the extractable state of Cu and Zn.In addition,the interaction between SEH and YBS inhibited the formation of the Pb residue state.SEM-EDS mapping results showed that compared to Zn and Cu,the signal intensity of Pb was extremely weak in regions where some of the Si and Al signal distributions overlap.The DFT results indicated that the O atoms of the metakaolin(Al_(2)O_(3)·2SiO_(2))(001)surface were better bound to the Zn and Cu than Pb atoms after adsorption of the chlorinated HMs.These results contribute to a better understanding of the effects of high-alkaline coal blending combustion on Pb,Cu,and Zn migration and transformation.

Uncovering mechanism of photocatalytic performance enhancement induced by multivariate defects on SnS_(2)

Defect engineering is recognized as an effective route to obtain highly active photocatalytic materials.However,the current understanding of defects is mainly limited to isolated atomic vacancy defects,ignoring the exploration of the functions of multivariate defects formed by the deletion of several adjacent atoms in photocatalytic system.Here,we prepared SnS2 nanostructures with the same morphology but different dominant defects,and by testing their photocatalytic performance,it was found that the multivariate defects can significantly improve the photocatalytic performance than isolated S vacancies.Combining experiments and theoretical calculations,we confirmed that the promotion of multivariate defects,especially“S-Sn-S”vacancy associates,on the photocatalytic performance is reflected in many aspects,such as the regulation of the energy band structure,the improvement of the charge separation efficiency,and the promotion of the adsorption and activation of guest molecules.SnS2 with“S-Sn-S”vacancy associates exhibits excellent photocatalytic water purification ability.Under the induction of“S-Sn-S”vacancy associates,phenol was thoroughly photocatalytically decomposed,further confirming its excellent functionality.This work not only provides new insights into identifying advantage defects in the catalyst structure,but also offers new ideas for constructing highly active photocatalysts based on defect engineering.

A comparative study of Mn/CeO_2,Mn/ZrO_2 and Mn/Ce-ZrO_2 for low temperature selective catalytic reduction of NO with NH_3 in the presence of SO_2 and H_2O

Ce-ZrO2 is a widely used three-way catalyst support. Because of the large surface area and excellent redox quality, Ce-ZrO2 may have potential application in selective catalytic reduction （SCR） systems. In the present work, Ce-ZrO2 was introduced into a low-temperature SCR system and CeO2 and ZrO2 supports were also introduced to make a contrastive study. Mn/CeO2, Mn/ZrO2 and Mn/Ce-ZrO2 were prepared by impregnating these supports with Mn（NO3）2 solution, and have been characterized by N2-BET, XRD, TPR, TPD, XPS, FT-IR and TG. The activity and resistance to SO2 and H2O of the catalysts were investigated. Mn/Ce-ZrO2 and Mn/CeO2 were proved to have better low-temperature activities than Mn/ZrO2, and yielded 98.6% and 96.8% NO conversion at 180℃, respectively. This is mainly because Mn/Ce-ZrO2 and Mn/CeO2 had higher dispersion of manganese oxides, better redox properties and more weakly adsorbed oxygen species than Mn/ZrO2. In addition, Mn/Ce-ZrO2 showed a good resistance to SO2 and H2O and presented 87.1% NO conversion, even under SO2 and H2O treatment for 6 hours, and the activity of Mn/Ce-ZrO2 was almost restored to its original level after cutting off the injection of SO2 and H2O. This was due to the weak water absorption and weak sulfation process on the surface of the catalyst.

Emission control strategies of hazardous trace elements from coal-fired power plants in China

China’s energy dependents on coal due to the abundance and low cost of coal.Coal provides a secure and stable energy source in China.Over-dependence on coal results in the emission of Hazardous Trace Elements(HTEs)including selenium(Se),mercury(Hg),lead(Pb),arsenic(As),etc.,from Coal-Fired Power Plants(CFPPs),which are the major toxic air pollutants causing widespread concern.For this reason,it is essential to provide a succinct analysis of the main HTEs emission control techniques while concurrently identifying the research prospects framework and specifying future research directions.The study herein reviews various techniques applied in China for the selected HTEs emission control,including the technical,institutional,policy,and regulatory aspects.The specific areas covered in this study include health effects,future coal production and consumption,the current situation of HTEs in Chinese coal,the chemistry of selected HTEs,control techniques,policies,and action plans safeguarding the emission control.The review emphasizes the fact that China must establish and promote efficient and clean ways to utilize coal in order to realize sustainable development.The principal conclusion is that cleaning coal technologies and fuel substitution should be great potential HTEs control technologies in China.Future research should focus on the simultaneous removal of HTEs,PM,SOx,and NOx in the complex flue gas.

Review on the NO removal from flue gas by oxidation methods

Due to the increasingly strict emission standards of NOx on various industries,many traditional flue gas treatment methods have been gradually improved.Except for selective catalytic reduction(SCR)and selective non-catalytic reduction(SNCR)methods to remove NOx from flue gas,theoxidation method is paying more attention to NOx removal now because of the potential to simultaneously remove multiple pollutants from flue gas.This paper summarizes the efficiency,reaction conditions,effect factors,and reaction mechanism of NO oxidation from the aspects of liquid-phase oxidation,gas-phase oxidation,plasma technology,and catalytic oxidation.The effects of free radicals and active components of catalysts on NO oxidation and the combination of various oxidation methods are discussed in detail.The advantages and disadvantages of different oxidation methods are summarized,and the suggestions for future research on NO oxidation are put forward at the end.The review on the NO removal by oxidation methods can provide new ideas for future studies on the NO removal from flue gas.

Suitable lithium polysulfides diffusion and adsorption on CNTs@TiO_(2)-bronze nanosheets surface for high-performance lithium-sulfur batteries

The shuttle effect of lithium polysulfides(UPSs)in lithium-sulfur batteries(LSBs)has been hampered their commercialization.Metal oxides as separator modifications can suppress the shuttle effect.Since there is no direct electron transport between metal oxides and UPSs,absorbed UPSs should be diffused from the surface of metal oxides to the carbon matrix to go through redox reactions.If diffusivity of UPSs from metal oxides surface to carbon substrate is poor,it would hinder the redox reactions of LiPSs.Nevertheless,researchers tend to focus on the adsorption and overlook the diffusion of UPSs.Herein,same morphology and different crystal phase of TiO_(2) nanosheets grown on carbon nanotubes(CNTs@TiO_(2)-bronze and CNTs@TiO_(2)-anatase)have been designed via a simple approach.Compared with CNTs and CNTs@TiO_(2)-anatase composites,the battery with CNTs@TiO_(2)-bronze modified separator delivers higher specific capacities and stronger cycling stability,especially at high current rates(~472 mAh·g^(-1) at 2.0 C after 1,000 cycles).Adsorption tests,density functional theory calculations and electrochemical performance evaluations indicate that suitable diffusion and adsorption for LiPSs on the CNTs@TiO_(2)-B surface can effectively capture LiPSs and promote the redox reaction,leading to the superior cycling performances.

Composition-dependent micro-structure and photocatalytic performance of g-C_(3)N_(4) quantum dots@SnS2 heterojunction

Semiconductor combination is one of the most common strategies to obtain high-efficiency photocatalysts;however, the effect mechanism of composition ratio on micro-structure and photocatalytic activity is remaining unclear. In this study, a case of g-C_(3)N_(4) quantum dots@SnS_(2) (CNQDn@SnS_(2)) heterojunction with different ratio of CNQD is used to uncover the origin of optimum and excess composition for photocatalysts. Research on the functional mechanism of the optimum composition shows that 0.8 wt.% CNQD are completely attached to the non-(001) facets of SnS_(2), which benefits the formation of type-II heterojunction, resulting in an optimal pollutant degradation and mineralization efficiency. For the excess composition, both experiments and theoretical calculations confirm that excess CNQD (the part exceeding of 0.8 wt.%) located on the (001) facet of SnS_(2), leading to the type-I band alignment of this heterojunction, which severely restricts the separation of photo-induced charge carriers, and thus reduces their lifetime. This work makes the functional mechanism of composition ratio on micro-structure and photocatalytic activity clearer. Related research results provide a new insight into semiconductor combination study and take an important step toward the rational design of highly active photocatalysts.

Mn-CeOx/Ti-PILCs for selective catalytic reduction of NO with NH_3 at low temperature

Titanium-pillared clays （Ti-PILCs） were obtained by different ways from TiCl4, Ti（OC3H7）4 and TiOSO4, respectively. Mn-CeOx/Ti- PILCs were then prepared and their activities of selective catalytic reduction （SCR） of NO with NH3 at low-temperature were evaluated. Mn-CeOx/Ti-PILCs were characterized by X-ray diffraction, N2 adsorption, Fourier transform infrared spectroscopy, thermal analysis, temperature-programmed desorption of ammonia and H2-temperature-programmed reduction. It was found that Ti-pillar tend to be helpful for the enlargement of surface area, pore volume, acidity and the enhancement of thermal stability for Mn-CeOx/Ti-PILCs. Mn- CeOx/Ti-PILCs catalysts were active for the SCR of NO. Among three resultant Mn-CeOx/Ti-PILCs, the catalyst from TiOSO4 showed the highest activity with 98% NO conversion at 220°C, it also exhibited good resistance to H2O and SO2 in flue gas. The catalyst from TiCl4 exhibited the lowest activity due to the unsuccessful pillaring process.

Low-temperature selective catalytic reduction of NO with NH_(3) based on MnO_(x)-CeO_(x)/ACFN

MnO_(x)-CeO_(x)/ACFN were prepared by the impregnation method and used as catalyst for selective catalytic reduction of NO with NH_(3) at 80℃-150℃.The catalyst was characterized by N_(2)-BET,scanning electron microscopy(SEM)and Fourier transform infrared spectroscopy(FT-IR).The fraction of the mesopore and the oxygen functional groups on the surface of activated carbon fiber(ACF)increased after the treatment with nitric acid,which was favorable to improve the catalytic activities of MnO_(x)-CeO_(x)/ACFN.The experimental results show that the conversion of NO is nearly 100%in the range 100℃-150℃under the optimal preparation conditions of MnO_(x)-CeO_(x)/ACFN.In addition,the effects of a series of performance parameters,including initial NH3 concentration,NO concentration and O_(2) concentration,on the conversion of NO were studied.

Removal of elemental mercury by KI-impregnated clay

This study described the use of clay impreg- nated by KI in gas phase elemental mercury （Hg°） removal in flue gas. The effects of KI loading, temperature, 02, SO2 and H20 on Hg°removal were investigated using a fixed bed reactor. The Hg° removal efficiency of KI-clay with 3% KI loading could maintain at a high level （approxi- mately 80 %） after 3 h. The KI-clay demonstrated to be a potential adsorbent for Hg° removal when compared with activated carbon based adsorbent. 02 was found to be an important factor in improving the Hg° removal. 02 was demonstrated to assist the transfer of KI to I2 on the surface of KI-clay, which could react with Hg° directly. NO and SO2 could slightly improve Hg° removal, while H20 inhibited it greatly. The results indicated that after adsorption, most of the mercury escaped from the surface again. Some of the mercury may have been oxidized as it left the surface. The results demonstrated that the chemical reaction primarily occurred between KI and mercury on the surface of the KI-clay.