Simultaneous Removal of SO2 and NOx From Flue Gas

In this paper,the recent progress of simultaneous removal of SO_2 and NO_x process at home and abroad is reviewed.We mainly introduced calcium based absorbent catalytic oxidation method,complexation absorption process,Electron beam method et al,principle of each technology are described,and the development direction was put forward in the future.

A study on simultaneous removal of NO and SO2 by using sodium persulfate aqueous scrubbing

Nitric oxide(NO) removal and sulfur dioxide(SO_2) removal by sodium persulfate(Na_2S_2O_8) were studied in a Bubble Column Reactor. The proposed reaction pathways of NO and SO_2 removal are discussed. The effects of temperatures(35–90 °C), Na_2S_2O_8(0.05–0.5 mol·L^(-1)), Fe SO4(0.5–5.0 m mol·L^(-1)) and H_2O_2(0.25 mol·L^(-1))on NO and SO_2 removal were investigated. The results indicated that increased persulfate concentration led to increase in NO removal at various temperatures. SO_2 was almost completely removed in the temperature range of 55–85 °C. Fe^(2+)accelerated persulfate activation and enhanced NO removal efficiency. At 0.2 mol·L^(-1) Na_2S_2O_8 and 0.5–1.0 mmol·L^(-1) Fe^(2+), NO removal of 93.5%–99% was obtained at 75–90 °C, SO_2 removal was higher than 99% at all temperatures. The addition of 0.25 mol·L^(-1) H_2O_2 into 0.2 mol·L^(-1) Na_2S_2O_8 solution promoted NO removal efficiency apparently until utterly decomposition of H2 O2, the SO_2 removal was as high as98.4% separately at 35 °C and 80 °C.

Highly Selective Electrocatalytic CuEDTA Reduction by MoS_(2) Nanosheets for Efficient Pollutant Removal and Simultaneous Electric Power Output

Electrocatalytic reduction of ethylenediamine tetraacetic acid copper(CuEDTA),a typical refractory heavy metal complexation pollutant,is an environmental benign method that operates at mild condition.Unfortunately,the selective reduction of CuEDTA is still a big challenge in cathodic process.In this work,we report a MoS_(2) nanosheet/graphite felt(GF)cathode,which achieves an average Faraday efficiency of 29.6%and specific removal rate(SRR)of 0.042 mol/cm^(2)/h for CuEDTA at−0.65 V vs SCE(saturated calomel electrode),both of which are much higher than those of the commonly reported electrooxidation technology-based removal systems.Moreover,a proofof-concept CuEDTA/Zn battery with Zn anode and MoS_(2)/GF cathode is demonstrated,which has bifunctions of simultaneous CuEDTA removal and energy output.This is one of the pioneer studies on the electrocatalytic reduction of heavy metal complex and CuEDTA/Zn battery,which brings new insights in developing efficient electrocatalytic reduction system for pollution control and energy output.

Controllably partial removal of thiolate ligands from unsupported Au_(25) nanoclusters by rapid thermal treatments for electrochemical CO_(2)reduction

Colloidal synthesis of metal nanoclusters will inevitably lead to the blockage of catalytically active sites by organic ligands.Here,taking[Au_(25)(PET)_(18)]-(PET=2-phenylethanethiol)nanocluster as a model catalyst,this work reports a feasible procedure to achieve the controllably partial removal of thiolate ligands from unsupported[Au_(25)(PET)_(18)]-nanoclusters with the preservation of the core structure.This procedure shortens the processing duration by rapid heating and cooling on the basis of traditional annealing treatment,avoiding the reconfiguration or agglomeration of Au_(25)nanoclusters,where the degree of dethiolation can be regulated by the control of duration.This work finds that a moderate degree of dethiolation can expose the Au active sites while maintaining the suppression of the competing hydrogen evolution reaction.Consequently,the activity and selectivity towards CO formation in electrochemical CO_(2)reduction reaction of Au_(25)nanoclusters can be promoted.This work provides a new approach for the removal of thiolate ligands from atomically precise gold nanoclusters.

Simultaneous removal of NO and SO_2 from dry gas stream using non-thermal plasma

In order to investigate the feasibility of sequential removal NO and SO2 using non-thermal plasma and adsorbent simultaneously, the removal of NO and SO2 from dry gas stream （NO/SO2/N2/O2） with very little O2 using non-thermal plasma was investigated using a coaxial dielectric barrier discharge. Comparative experiments were carried out in the dry gas stream with and without Ar respectively at O2 concentration of 0.1%. The results showed that NO could be removed remarkably and it would be enhanced in the presence of Ar in the dry gas stream. It seems that SO2 could not be removed unless there is Ar in the dry gas stream. The mechanism of removal of NO and SO2 in the dry gas stream was discussed.

Simultaneous catalytic removal of NOx and diesel PM over La_(0.9) K_(0.1) CoO_3 catalyst assisted by plasma

The simultaneous removal of NOx and particulate matter(PM) from diesel exhaust is investigated over a mixed metal oxide catalyst of La 0.9 K 0.1 CoO 3 loaded on γ-Al 2O 3 spherules with the assistant of plasma. It was found that NOx was reduced by PM in oxygen rich atmosphere, the CO 2 and N 2 were produced in the same temperature window without considering the N 2 formed by plasma decomposition. As a result, the temperature for the PM combustion decreases and the reduction efficiency of NOx to N 2 increases during the plasma process, which indicated that the activity of the catalyst can be improved by plasma. The NOx is decomposed by plasma at both low temperature and high temperature. Therefore, the whole efficiency of NOx conversion is enhanced.

Simultaneous removal of Cr(Ⅵ), Cd, and Pb from aqueous solution by iron sulfide nanoparticles: Influencing factors and interactions of metals

Cadmium(Cd),lead(Pb),and hexavalent chromium(Cr(Ⅵ)) are often found in soils and water affected by metal smelting,chemical manufacturing,and electroplating.In this study,synthetic iron sulfide nanoparticles(FeS NPs) were stabilized with carboxymethyl cellulose(CMC) and utilized to remove Cr(Ⅵ),Cd,and Pb from an aqueous solution.Batch experiments,a Visual MINTEQ model,scanning electron microscopy(SEM),X-ray diffraction(XRD),and X-ray photoelectron spectrometer(XPS) analysis were used to determine the removal efficiencies,influencing factors,and mechanisms.The FeS NP suspension simultaneously removed Cr(Ⅵ),Cd,and Pb from an aqueous solution.The concentrations of Cr(Ⅵ),Cd,and Pb decreased from 50,10,and 50 mg·L^(-1) to 2.5,0.1,and 0.1 mg·L^(-1),respectively.The removal capacities were up to 418,96,and 585 mg per gram of stabilized FeS NPs,respectively.The acidic conditions significantly favored the removal of aqueous Cr(Ⅵ) while the alkaline conditions favored the removal of Cd and Pb.Oxygen slightly inhibited the removal of Cr(Ⅵ),but it had no significant influence on the removal of Cd and Pb.A potential mechanism was proposed for the simultaneous removal of Cr(Ⅵ),Cd,and Pb using FeS NPs.The interactions of the three heavy metals involved a cationic bridging effect on Cr(Ⅵ) by Cd,an enhanced adsorption effect on Cd by [Cr,Fe](OH)_3,precipitation of PbCrO_4,and transformation of PbCrO_4 to PbS.Therefore,FeS NPs have a high potential for use in the simultaneous removal of Cr(Ⅵ),Cd,and Pb from contaminated aqueous solutions.

Simultaneous Removal of COS and H_2S at Low Temperatures over Nanoparticle a-FeOOH Based Catalysts

Catalysts using α-FeOOH nanoparticles as the active ingredient were testedby a microreactor-chromatography assessing apparatus at atmospheric pressure between 25 and 60 ℃with a gas hourly space velocity of 10,000 h^(-1), while the removal performance of H_2S withcatalysts was investigated using the thermal gravimetric method. The results show that the catalystsare highly active for COS hydrolysis at low temperatures (≤60 ℃) and high gas hourly spacevelocity, and the highest activity can reach 100%. The catalyst is particularly stable for 12 h, andno deactivation is observed. Nanoparticle α-FeOOH prepared using hydrated iron sulfate showshigher COS hydrolysis activity, and the optimum calcination temperature for the catalyst is 260 ℃.In addition, the catalysts can remove COS and H_2S simultaneously, and 60 ℃ is favorable for theremoval of H_2S. The compensation effect exists in nanoparticle-based catalysts.

Simultaneous removal of ethanol, acetaldehyde and nitrogen oxides over V-Pd/γ-Al_2O_3-TiO_2 catalyst

V-Pd/γ-Al2O3-TiO2 catalysts with different vanadium contents were prepared by a combined sol-gel and impregnation method. X-ray diffraction （XRD）, N2 adsorption-desorption （BET）, X-ray photoelectron spectroscopy （XPS） and catalytic removal of ethanol, acetaldehyde and nitrogen oxides at low temperature （〈300 ？C） were used to assess the properties of the catalysts. The results showed that the sample with 1wt% vanadium exhibited an excellent catalytic performance for simultaneous removal of ethanol, acetaldehyde and nitrogen oxides. The conversions of ethanol, acetaldehyde and nitrogen oxides at 250 ？C were 100%, 74.4% and 98.7%, respectively. V-Pd/γ-Al2O3-TiO2 catalyst with 1 wt% vanadium showed the largest surface area and higher dispersion of vanadium oxide on the catalyst surface, and possessed a larger mole fraction of V4＋ species and unique PdO species on the surface, which can be attributed to the strong synergistic effect among palladium, vanadium and the carriers. The higher activity of V-Pd/γ-Al2O3-TiO2 catalyst is related to the V4＋ and Pd2＋ species on the surface, which might be favorable for the formation of active sites.

Simultaneous Removal of Soot and NO_x over Precious Metal Catalysts O_2-Rich Atmospheres and in the Presence of H_2O and SO_2

The activities of ZrO_2-supported precious metal catalysts for simultaneous removal of soot and NO_x in the presence of rich O_2and H_2O as well as SO_2 have been studied by keeping loose contact between catalyst and soot.The results show that only Ru,Ir and Rh have catalytic activity for simultaneous removal of soot and NO_x and the order of catalytic activity is Ru > Ir > Rh.Pt has the catalytic activity only for the removal of soot,and Ag,Pd,and Au have hardly any catalytic activities for the removal of soot and NO_x.The relationships between catalytic activity of precious metal catalysts and various reaction conditions were discussed.

Application and Regeneration of a Non-Aqueous System of Cu/HCl and DMF for the Oxidation of Hydrogen Sulfide in Natural Gas

A copper-based non-aqueous-phase desulfurization agent is prepared by adding CuCl_(2) to the solvent N,Ndimethylformamide(DMF).Static desulfurization experiments show that the agent has high efficiency.However,the desulfurization reaction leads to the formation of a copper sulfide precipitate.It is found that the addition of chloride ions in the form of hydrochloric acid or potassium chloride prevents the formation of copper sulfide,and elemental sulfur is precipitated instead.The efficient absorption of H2S by the Cu/HCl–DMF agent relies on the rapid coordination of Cu^(2+)with DMF,Cl^(−),and H2S molecules to form a[Cu(DMF)_(n−p)(HS−)_(p)(Cl−)_(m)]_((2−p−m))+complex.The desulfurization agent has a sulfur capacity of up to 9.81 g/L when used in static bubble desulfurization at atmospheric pressure.The system has low viscosity and good chemical and thermal stability.It can be rapidly regenerated through continuous oxidation.After five repetitions of the regeneration procedure,the sulfur capacity reaches more than 91%of the initial capacity,indicating the potential of the system for commercial applications.

Analysis of the Effect and Influencing Factors of Rural Domestic Sewage Treatment Based on A^(2)O-MBBR Integrated Process

[Objectives] This study was conducted to solve the prominent problems in the treatment of domestic sewage in southern rural areas of China. [Methods] An integrated process treatment mode of anaerobic/anoxic/aerobic moving bed biofilm reactor (A 2O-MBBR) was proposed to analyze and study its operating effect and influencing factors. [Results] The A^(2)O-MBBR mode had good COD removal efficiency and nitrogen and phosphorus removal performance, and the water quality index of the effluent met the Class A standard of GB181918-2002. This mode is suitable for treating rural domestic sewage, and has high treatment effects in different operating periods. In spring, the average removal rates of COD, NH_(4)^(+)-N, TN, TP and SS reached (83.53 ± 2.15)%, (89.44 ± 4.97)%, (67.36±18.53)%, (88.22±11.21)% and (91.73±2.25)%, respectively;In the autumn period, the average removal rates of COD, NH_(4)^(+)-N, TN, TP and SS were (83.49±2.64)%, (89.26±9.19)%, (66.05±17.00)%, (87.48±9.68)%, and (91.13±2.35)%. [Conclusions] This study provides theoretical reference and technical support for the popularization and application of A^(2)O-MBBR integrated process.

Simultaneous nitrification and autotrophic denitrification in fluidized bed reactors using pyrite and elemental sulfur as electron donors

In this study, simultaneous nitrification and autotrophic denitrification (SNAD) with either elemental sulfur or pyrite were investigated in fluidized bed reactors in mesophilic conditions. The reactor performance was evaluated at different ammonium (12-40 mg/L of NH4+-N), nitrate (35-45 mg/L of NO3--N), and dissolved oxygen (DO) (0.1-1.5 mg/L) concentrations, with a hydraulic retention time of 12 h. The pyrite reactor supported the SNAD process with a maximum nitrogen removal efficiency of 139.5 mg/(L·d) when the DO concentration was in the range of 0.8-1.5 mg/L. This range, however, limited the denitrification efficiency of the reactor, which decreased from 90.0% ± 5.3% in phases II-V to 67.9% ± 7.2% in phases VI and VII. Sulfate precipitated as iron sulfate (FeSO4/Fe2(SO4)3) and sodium sulfate (Na2SO4) minerals during the experiment. The sulfur reactor did not respond well to nitrification with a low and unstable ammonium removal efficiency, while denitrification occurred with a nitrate removal efficiency of 97.8%. In the pyrite system, the nitrifying bacterium Nitrosomonas sp. was present, and its relative abundance increased from 0.1% to 1.1%, while the autotrophic denitrifying genera Terrimonas, Ferruginibacter, and Denitratimonas dominated the community. Thiobacillus, Sulfurovum, and Trichlorobacter were the most abundant genera in the sulfur reactor during the entire experiment.

Insight into the effect of gel drying temperature on the structure and desulfurization performance of ZnO/SiO_(2)adsorbents

A series of ZnO/SiO_(2) adsorbents were prepared by a sol-gel method using tetraethyl orthosilicate,ethylene glycol(EG)and nitrates as precursors.The effect of gel drying temperature on the structure and desulfurization performance of the adsorbents were investigated in detail.It is found that the low drying temperature led to a weak interaction among EG,Si AOH/H_(2)O and the nitrates in the gel system,which caused the oxidation of EG by NO3-and formed zinc glyoxylate complex during the gel calcination process,whereas this oxidation process also occurred at a high drying temperature during the gel drying process.The formed zinc glyoxylate complex promoted the generation of monodentate carbonate on the surface of Zn O,which resulted in the inferior desulfurization performance of adsorbents despite they have smaller Zn O nanoparticles.The gel dried at 120°C formed the hydrogen bonds between EG and Si AOH/H_(2)O and a strong interaction between zinc oxo-clusters and NO3-was also found in the gel system,which avoided the oxidation of EG by NO3-during the preparation process and the Zn O nanoparticles with sizes of 6 nm were formed by a combustion method.The adsorbent affords a highest sulfur capacity of 104.9 mg·g^(-1) in this case.In addition,the gel drying temperature has a significant influence on the textural properties of the adsorbents except their surface area.

Simultaneous adsorption of lead and cadmium on MnO_2-loaded resin

MnO2-10aded D301 weak basic anion exchange resin has been used as adsorbent to simultaneously remove lead and cadmium ions from aqueous solution. The effects of adsorbent dosage, solution pH and the coexistent ions on the adsorption were investigated. Experimental results showed that with the adsorbent dosage more than 0.6 g/L, both Pb^2＋ and Cd^2＋ were simultaneously removed at pH range 5-6. Except for HPO4^2-, the high concentration coexistent ions such as Na^＋, K^＋, Cl^-, NO3^-, SO4^2- and HCO3^-, showed no significant effect on the removal efficiency of both Pb^2＋ and Cd^2＋ under the experimental conditions. The coexistence of Mg^2＋, Ca^2＋ caused the reduction of Cd^2＋ removal, but not for Pb^2＋. The adsorption equilibrium for Pb^2＋ and Cd^2＋ could be excellently described by the Langmuir isotherm model with R^2 〉 0.99. The maximum adsorption capacity was calculated as 80.64 mg/g for Pb^2＋ and 21.45 mg/g for Cd^2＋. The adsorption processes followed the pseudo first-order kinetics model. MnO2-loaded D301 resin has been shown to have a potential to be used as an effective adsorbent for simultaneous removal of lead and cadmium ions from aqueous solution.

High-Sensitivity In-Situ Diagnosis of NO_2 Production and Removal in DBD Using Cavity Ring-Down Spectroscopy

A highly-sensitive in-situ diagnosis approach for nitrogen dioxide （NO2） has been developed in dielectric barrier discharge （DBD） based on pulsed cavity ring-down spectroscopy （CRDS）. Absorption bands of NO2 in a spectral region from 508 nm to 509 nm were used, and a detection limit of 17.5 ppb was achieved. At this level of sensitivity, the quantitative and real-time monitoring of the production and removal of NO2 are accomplished for the first time in the discharge region. By measuring the removal amount and rate at different NO2 initial number densities from 1.54 ×10^13 cm^-3 to 2.79 × 10^14 cm^-3, we determined the relationship between them and NO2 initial number densities. The removal amount linearly increases with the initial number density, while the removal rate increases logarithmically. At a lower initial number density, the removal rate is limited. By considering the chemical kinetic mechanism in plasma, a qualitative explanation for the above phenomena is proposed： the additional NO2 produced by discharge limits the removal rate, since the NO2 concentration is dominated by the competition between the forward reactions （production） and the reverse reactions （removal）.

Science Letters:Simultaneous removal of nitrate and heavy metals by iron metal

Great attention should be paid now to simultaneously removing common pollutants, especially inorganic pollutants such as nitrate and heavy metals, as individual removal has been investigated extensively. Removing common pollutants simul- taneously by iron metal is a very effective alternative method. Near neutral pH, heavy metals, such as copper and nickel, can be removed rapidly by iron metal, while nitrate removal very much slower than that of copper and nickel, and copper can accelerate nitrate removal when both are removed simultaneously. Even a little amount of copper can enhance nitrate removal efficiently. Different mechanisms of these contaminants removal by iron metal were also discussed.

Simultaneous removal of ethyl acetate, benzene and toluene with gliding arc gas discharge

The simultaneous removal of ethyl acetate, benzene and toluene with relatively low or high initial concentration is studied using a laboratory scale gliding arc gas discharge (GA) reactor. Good decomposition efficiencies are obtained which proves that the GA is effective for the treatment of volatile organic compounds (VOCs) with either low or high concentration. A theoretical decomposition mechanism is proposed based on detection of the species in the plasma region and analysis of the decomposition by-products. This preliminary investigation reveals that the GA has potential to be applied to the treatment of exhaust air during color printing and coating works, by either direct removal or combination with activated carbon adsorption/desorption process.

Mechanism of Simultaneous Nitrogen Removal and Electricity Generation by Microbial Fuel Cell

The working mechanism of MFC used for simultaneous nitrogen removal and electricity generation was studied.The results show that the electrode biofilms and suspension had different modes of electron transfer.The microorganisms growing on the electrodes and bioflocs could transfer electrons by direct contact and intermediaries respectively.The electrode biofilms and bioflocs were dominant in different functional spaces,and played a synergistic role in the process of contaminant removal,but showed a certain competitive relationship in the process of electricity generation.This study can provide a theoretical basis for the development of a new low-consumption wastewater treatment technology and promote technological innovation in wastewater treatment.

Nitrogen and phosphorus removal in pilot-scale anaerobic-anoxic oxidation ditch system

To achieve high efficiency of nitrogen and phosphorus removal and to investigate the rule of simultaneous nitrification and denitrification phosphorus removal （SNDPR）, a whole course of SNDPR damage and recovery was studied in a pilot-scale, anaerobicanoxic oxidation ditch （OD）, where the volumes of anaerobic zone, anoxic zone, and ditches zone of the OD system were 7, 21, and 280 L, respectively. The reactor was fed with municipal wastewater with a flow rate of 336 L/d. The concept of simultaneous nitrification and denitrification （SND） rate （rSND） was put forward to quantify SND. The results indicate that： （1） high nitrogen and phosphorus removal efficiencies were achieved during the stable SND phase, total nitrogen （TN） and total phosphate （TP） removal rates were 80% and 85%, respectively; （2） when the system was aerated excessively, the stability of SND was damaged, and rSND dropped from 80% to 20% or less; （3） the natural logarithm of the ratio of NOx to NH4^＋ in the effluent had a linear correlation to oxidation-reduction potential （ORP）; （4） when NO3^- was less than 6 mg/L, high phosphorus removal efficiency could be achieved; （5） denitrifying phosphorus removal （DNPR） could take place in the anaerobic-anoxic OD system. The major innovation was that the SND rate was devised and quantified.