Enhanced simultaneous absorption of NO_(x) and SO_(2) in oxidation-reduction-absorption process with a compounded system based on Na_(2)SO_(3)

Oxidation of sulfite and competitive absorption existed in Na_(2)SO_(3) solution for simultaneous removal of NO_(x) and SO_(2),inhibited the long-term high-efficiency when used for practical applications.A matching strategy was developed to solve these problems.Antioxidants combination was used to retard the oxidation of antioxidant and enhance inhibition of S(IV)(tetravalent sulfur)oxidation.Hydroquinone(HQ)and sodium thiosulfate(ST)showed a positive synergistic effect on inhibition of S(IV)oxidation.When SO_(2) concentration was 500 and 2000 ppmV,the addition of 0.1 wt.%HQ and 1 wt.%ST decreased the percentage of S(IV)oxidized by oxygen by over 30%and 40%,respectively.Alkali(Na_(2)CO_(3))alleviated the competitive absorption between NO_(x) and SO_(2).Moreover,Na_(2)CO_(3) exhibited an enhancement effect on the absorption of NO_(x) and SO_(2) when coupled with anti-oxidants.While the increase of oxygen pressure accelerated the oxidation of S(IV),the anti-oxidants can retard the oxidation.The measurement of pH suggested the removal efficiency of NO_(x) highly depended on SO_(3)^(2-) concentration rather than pH.The further investigation of the mechanism suggested the match effect was related to the interaction between ST and the intermediate product of HQ.The match strategy holds a potential for application of SO_(3)^(2-) to denitration.

Synthesis,characterization and experimental investigation of Cu-BTC as CO_2 adsorbent from flue gas

Porous Cu-BTC material was synthesized by the solvothermal method. Powder X-ray diffraction （PXRD） was used to test the phase purity of the synthesized material and investigate its structural stability under the influence of flue gas components. The thermal stability of the material was determined through thermal gravimetric （TG） analysis. Scanning electron microscopy （SEM） was employed to study the microstructure of the material. Cu-BTC was demonstrated not only to have high CO2 adsorption capacity but also good selectivity of CO2 over N2 by means of packed bed tests. The adsorption capacity of Cu-BTC for CO2 was about 69 mL/g at 22℃. The influence of the main flue gas components on the CO2 capacity of the material were discussed as well.

Absorption characteristics of elemental mercury in mercury chloride solutions

Elemental mercury （Hg^0） in flue gases can be efficiently captured by mercury chloride （HgCl2） solution. However, the absorption behaviors and the influencing effects are still poorly understood. The mechanism of Hg^0 absorption by HgCl2 and the factors that control the removal were studied in this paper. It was found that when the mole ratio of Cl^- to HgCl2 is 10：1, the Hg^0 removal efficiency is the highest. Among the main mercury chloride species, HgCl3^- is the most efficient ion for Hg^0 removal in the HgCl2 absorption system when moderate concentrations of chloride ions exist. The Hg^0 absorption reactions in the aqueous phase were investigated computationaIIy using Moller-Plesset perturbation theory. The calculated Gibbs free energies and energy barriers are in excellent agreement with the results obtained from experiments. In the presence of SO3^2- and SO2, Hg^2＋ reduction occurred and Hg^0 removal efficiency decreased. The reduced Hg^0 removal can be controlled through increased chloride concentration to some degree. Low pH value in HgCla solution enhanced the Hg^0 removal efficiency, and the effect was more significant in dilute HgCl2 solutions. The presence of SO4^2- and NO3^- did not affect Hg^0 removal by HgCl2.

Removal of elemental mercury with Mn/Mo/Ru/Al2O3 membrane catalytic system

In this work, a catalytic membrane using Mn/ Mo/Ru/A12O3 as the catalyst was employed to remove elemental mercury （Hg^0） from flue gas at low temperature. Compared with traditional catalytic oxidation （TCO） mode, Mn/A12O3 membrane catalytic system had much higher removal efficiency of Hg^0. After the incorporation of Mo and Ru, the production of C12 from the Deacon reaction and the retainability for oxidants over Mn/A12O3 membrane were greatly enhanced. As a result, the oxidization of Hg^0 over Mn/A12O3 membrane was obviously promoted due to incorporation of Mo and Ru. In the presence of 8 ppmv HC1, the removal efficiency of Hg^0 by Mn/Mo/Ru/A12O3 membrane reached 95% at 423 K. The influence of NO and SO2 on Hg^0 removal were insignificant even if 200 ppmv NO and 1000 ppmv SO2 were used. Moreover, compared with the TCO mode, the Mn/Mo/Ru/A12O3 membrane catalytic system could remarkably reduce the demanded amount of oxidants for Hg^0 removal. Therefore, the Mn/Mo/Ru/A12O3 membrane catalytic system may be a promising technology for the control of Hg~ emission.

Chemical characteristics of fine particulate matter emitted from commercial cooking

The chemical characteristics of fine particulate matter （PM2.5） emitted from commercial cooking were explored in this study. Three typical commercial restau- rants in Shanghai, i.e., a Shanghai-style one （SHS）, a Sichuan-style one （SCS） and an Italian-style one （ITS）, were selected to conduct PM2.5 sampling. Particulate organic matter （POM） was found to be the predominant contributor to cooking-related PM2.5 mass in all the tested restaurants, with a proportion of 69.1% to 77.1%. Specifically, 80 trace organic compounds were identified and quantified by gas chromatography/mass spectrometry （GC/MS）, which accounted for 3.8%-6.5% of the total PM2.5 mass. Among the quantified organic compounds, unsaturated fatty acids had the highest concentration, followed by saturated fatty acids. Comparatively, the impacts of other kinds of organic compounds were much smaller. Oleic acid was the most abundant single species in both SCS and ITS. However, in the case of SHS, linoleic acid was the richest one. ITS produced a much larger mass fraction of most organic species in POM than the two Chinese cooking styles except for monosaccharide anhy-drides and sterols. The results of this study could be utilized to explore the contribution of cooking emissions to PM2.5 pollution and to develop the emission inventory of PM2.5 from cooking, which could then help the policymakers design efficient treatment measures and control strategies on cooking emissions in the future.

Surface protection method for the magnetic core using covalent organic framework shells and its application in As(Ⅲ)depth removal from acid wastewater

Fe_(3)O_(4)-based materials are widely used for magnetic separation from wastewater.However,they often suffer from Fe-leaching behavior under acidic conditions,decreasing their ac-tivity and limiting sustainable practical applications.In this study,covalent organic frame-works(COFs)were used as the shell to protect the Fe_(3)O_(4) core,and the Fe_(3)O_(4)@COF core-shell composites were synthesized for As(Ⅲ)removal from acid wastewater.The imine-linked COFs can in situ grow on the surface of the Fe_(3)O_(4) core layer by layer with[COFs/Fe_(3)O_(4)]mol ratio of up to 2∶1.The Fe-leaching behavior was weakened over a wide pH range of 1-13.Moreover,such composites keep their magnetic characteristic,making them favorable for nanomaterial separation.As(Ⅲ)batch adsorption experiments results indicated that,when COFs are used as the shell for the Fe_(3)O_(4) core,a balance between As(Ⅲ)removal efficiencies and the thickness of the COF shell exists.Higher As(Ⅲ)removal efficiencies are obtained when the[COFs/Fe_(3)O_(4)]mol ratios were<1.5∶1,but thicker COF shells were not beneficial for As(Ⅲ)removal.Such composites also exhibited better As(Ⅲ)removal performances in the pH range of 1-7.Over a wide pH range,the zeta potential of Fe_(3)O_(4)@COF core-shell compos-ites becomes more positive,which benefits the capture of negative arsenic ions.In addition,thinner surface COFs were favorable for mass transfer and facilitating the reaction of Fe and As elements.Our study highlights the promise of using COFs in nanomaterial surface protection and achieving As(Ⅲ)depth removal under acidic conditions.

Regulated adsorption sites using atomically single cluster over biochar for efficient elemental mercury uptake

Carbon-based materials have been widely used in gaseous pollutant removal because of their sufficient surface functional groups;however,its removal efficiency for elemental mercury(Hg^(0))is low.In this study,we fabricated biomass using a chelated coupled pyrolysis strategy and further constructed the regulated adsorption sites for gaseous Hg^(0) uptake.A series of Mnδ-N_(2)O_(2)/BC with different manganese cluster sizes demonstrated that manganese clusters anchored on biochar acted as highly active and durable adsorbents for Hg^(0) immobilization,which increased the adsorption efficiency of Hg^(0) by up to 50%.Shrimp-and crab-based biochar adsorbents exhibited excellent Hg^(0) removal because of their chitosan-like structure.In particular,small Mn clusters and oxygen species around the defect led to a boost in the Hg^(0) adsorption by carbon.The results of density functional theory calculation revealed that the presence of oxygen in the carbon skeleton can tune the electrons of small-sized Mn clusters,thereby promoting the affinity of mercury atoms.The newly developed Mnδ-N_(2)O_(2)/BCshrimp had an adsorption capacity of 7.98-11.52 mg g^(−1) over a broad temperature range(50-200°C)and showed a high tolerance to different industrial flue gases(H2O,NO,HCl,and SO2).These results provide novel green and low-carbon disposal methods for biomass resource utilization and industrial Hg^(0) emission control.