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.

Simultaneous removing SO_2 and NO by a new system containing cobalt complex

Absorption and catalytic oxidation of nitric oxide can be achieved by using cobalt（Ⅲ） ethylenediamine （Co（en）3^3＋. When simultaneous absorbing SO2 and NO, the precipitation of Co2（SO3）3 will be yielded and the NO removal will be decreased. A new catalyst system using Co（en）3^3＋ coupled with urea has been developed to simultaneous remove NO and SO2 in the flue gas. NO is absorbed and catalytically oxidized to nitrite and nitrate by Co（en）3^3＋. The dissolved oxygen in scrubbing solution from the feed stream acts as oxidant. Urea restrains the precipitation of Co2（SO3）3 by oxidizing SO3^2-to SO4^2- as COSO4 is more soluble in water. The experimental results proved that nearly all SO3^2- can be oxidized to SO4^2- and the high NO and SO2 removal could be obtained with the new system. The NO removal is influenced by gas flow rate, the concentration of Co（en）3^3＋ and urea in the absorption solution, the temperature of the scrubbing solution and the content of oxygen in the flue gas. The low gas flow rate is favorable to increase the NO removal. The experiments proved that the NO removal could be maintained at more than 95% by the system of 0.02 mol/L Co（en）3^3＋ and 1% urea at 50℃ with 10% O2 in the flue gas.

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 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 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.

Continuous treatment of azo acid dyes by photo-dependent denitrifying sludge

Simultaneous removals of dye and nitrate by photo dependent denitrifying sludge(PDDS) have been demonstrated in a continuous flow bench scale reactor. The best C/N for the degradation of azo dyes by PDDS was 1.5. The specific removal rate of azo dye AB92 decreased with a decrease in hydraulic retention time and increased with a decrease in solids retention time. The degradation rate of TOC decreased with a decrease in hydraulic retention time. AB92, which has nitro and hydroxyl substitutions in non para positions, was uniquely degraded. During continuous flow treatment experiments using PDDS, complete degradation of azo dyes AB92 and AO20 at influent concentrations of 40 mg/L and 30 mg/L, respectively, was achieved with an HRT of 16.

Effect of substrate COD/N ratio on performance and microbial community structure of a membrane aerated biofilm reactor

Two parallel carbon-membrane aerated biofilm reactors were operated at well-defined conditions to investigate the effect of substrate COD/N ratios on the performance and microbial community structure of the bioreactor. Results showed that at substrate COD/N of 5, organic and nitrogen could be eliminated simultaneously, and COD removal degree, nitrification and denitrification efficiency reached 85%, 93% and 92%, respectively. With increasing substrate COD/N ratios, the specific oxygen utilization rates of nitrifying bacteria in biofilm were found to decrease, indicating that nitrifying population became less dominant. At substrate COD/N ratio of 6, excessive heterotrophs inhibited the activity of nitrifying bacteria greatly and thus led to poor nitrification process. With the help of fluorescence in situ hybridization （FISH）, Nitrosomonas and Nitrosospira were identified as dominant ammonia-oxidizing bacteria in the biofilm at substrate COD/N of 0, whereas only Nitrosospira were detected in the biofilm at COD/N ratio of 5. Nitrospira were present as dominant nitrite-oxidizing bacteria in our study. Confocal laser scanning microscopy images revealed that at substrate COD/N ratio of 0 nitrifying bacteria existed throughout the biofilm and that at COD/N ratio of 5 they were mainly distributed in the inner layer of biofilm.

Using NH_(2)-MIL-125(Ti)for efficient removal of Cr(Ⅵ)and Rh B from aqueous solutions:Competitive and cooperative behavior in the binary system

The coexistence of inorganic and organic contaminants is a challenge for real-life water treatment applications.Therefore,in this research,we used NH_2-MIL-125(Ti)to evaluate the single adsorption of hexavalent chromium(Cr(Ⅵ))or Rhodamine B(RhB)in an aqueous solution and further investigate simultaneous adsorption experiments to compare the adsorption behavior changes.The main influencing factors,for example,reaction time,initial concentration,reaction temperature,and pH were studied in detail.In all reaction systems,the pseudo-second-order kinetic and Langmuir isotherm models were well illuminated the adsorption progress of Cr(Ⅵ)and RhB.Thermodynamic studies showed that the adsorption process was spontaneous and endothermic.As compared to the single system,the adsorption capacity of Cr(Ⅵ)in the binary system gradually decreased as the additive amount of RhB increased,whereas the adsorption capacity of RhB in the binary system was expanded brilliantly.When the binary reaction system contained 100 mg/L Cr(Ⅵ),the removal rate of RhB increased to 97.58%.The formation of Cr(Ⅵ)-RhB and Cr(Ⅲ)-RhB complexes was the cause that provided facilitation for the adsorption of RhB.These findings prove that the interactions during the water treatment process between contaminants may obtain additional benefits,contributing to a better adsorption capacity of co-existing contaminant.

Simultaneous removal of selected oxidized contaminants in groundwater using a continuously stirred hydrogen-based membrane biofilm reactor

A laboratory trial was conducted for evaluating the capability of a continuously stirred hydrogen-based membrane biofllm reactor to simultaneously reduce nitrate （NO3--N）, sulfate （SO42-）, bromate （BrO3-）, hexavalent chromium （Cr（VI）） and para- chloronitrobenzene （p-CNB）. The reactor contained two bundles of hollow fiber membranes functioning as an autotrophic biofiim carder and hydrogen pipe as well. On the condition that hydrogen was supplied as electron donor and diffused into water through membrane pores, autohydrogenotrophic bacteria were capable of reducing contaminants to forms with lower toxicity. Reduction occurred within 1 day and removal fluxes for NO3--N, SO42-, BrO3-, Cr（VI）, and p-CNB reached 0.641, 2.396, 0.008, 0.016 and 0.031 g/（day.m2）, respectively after 112 days of continuous operation. Except for the fact that sulfate was 37% removed under high surface loading, the other four contaminants were reduced by over 95 %. The removal flux comparison between phases varying in surface loading and 1-12 pressure showed that decreasing surface loading or increasing 1-12 pressure would promote removal flux. Competition for electrons occurred among the five contaminants. Electron-equivalent flux analysis showed that the amount of utilized hydrogen was mainly controlled by NO3--N and SO42- reduction, which accounted for over 99% of the electron flux altogether. It also indicated the electron acceptor order, showing that nitrate was the most prior electron acceptor while sulfate was the second of the five contaminants.

Simultaneous removal of NO_(x)and chlorobenzene on V_(2)O_(5)/TiO_(2)granular catalyst:Kinetic study and performance prediction

The synergetic abatement of multi-pollutants is one of the development trends of flue gas pollution control technology,which is still in the initial stage and facing many challenges.We developed a V_(2)O_(5)/TiO_(2)granular catalyst and established the kinetic model for the simultaneous removal of NO and chlorobenzene(i.e.,an important precursor of dioxins).The granular catalyst synthesized using vanadyl acetylacetonate precursor showed good synergistic catalytic performance and stability.Although the SCR reaction of NO and the oxidation reaction of chlorobenzene mutually inhibited,the reaction order of each reaction was not considerably affected,and the pseudo-first-order reaction kinetics was still followed.The performance prediction of this work is of much value to the understanding and reasonable design of a catalytic system for multi-pollutants(i.e.,NO and dioxins)emission control.

Simultaneous denitrification and denitrifying phosphorus removal in a full-scale anoxic–oxic process without internal recycle treating low strength wastewater

Performance of a full-scale anoxic-oxic activated sludge treatment plant（4.0×10-5 m-3/day for the first-stage project） was followed during a year.The plant performed well for the removal of carbon,nitrogen and phosphorus in the process of treating domestic wastewater within a temperature range of 10.8℃ to 30.5℃.Mass balance calculations indicated that COD utilization mainly occurred in the anoxic phase,accounting for 88.2% of total COD removal.Ammonia nitrogen removal occurred 13.71% in the anoxic zones and 78.77% in the aerobic zones.The contribution of anoxic zones to total nitrogen（TN） removal was 57.41%.Results indicated that nitrogen elimination in the oxic tanks was mainly contributed by simultaneous nitrification and denitrification（SND）.The reduction of phosphorus mainly took place in the oxic zones,51.45% of the total removal.Denitrifying phosphorus removal was achieved biologically by 11.29%.Practical experience proved that adaptability to gradually changing temperature of the microbial populations was important to maintain the plant overall stability.Sudden changes in temperature did not cause paralysis of the system just lower removal efficiency,which could be explained by functional redundancy of microorganisms that may compensate the adverse effects of temperature changes to a certain degree.Anoxic-oxic process without internal recycling has great potential to treat low strength wastewater（i.e.,TN 〈 35 mg/L） as well as reducing operation costs.

Simultaneous removal of NO and dichloromethane(CH_(2)Cl_(2)) over Nb-loaded cerium nanotubes catalyst

Herein,a series of niobium oxide supported cerium nanotubes(Ce NTs)catalysts with different loading amount of Nb_(2)O_(5)(0–10 wt.%)were prepared and used for selective catalytic reduction of NOxwith NH_(3)(NH_(3)-SCR)in the presence of CH_(2)Cl_(2).Commercial V_(2)O_(5)-WO_(3)-TiO_(2) catalyst was also prepared for comparison.The physcial properties and chemical properties of the Nb_(2)O_(5) loaded cerium nanotubes catalysts were investigated by X-ray diffractometer,Transmission electron microscope,Brunauer-Emmett-Teller specific surface area,H_(2)-temperature programmed reduction,NH_(3)-temperature programmed desorption and Xray photoelectron spectroscopy.The experiment results showed that the loading amount of Nb_(2)O_(5) had a significant effect on the catalytic performance of the catalysts.10 wt.%Nb-Ce NTs catalyst presented the best NH_(3)-SCR performance and degradation efficiency of CH_(2)Cl_(2) among the prepared catalysts,due to its superior redox capability,abundant surface oxygen species and acid sites,the interaction between Nb and Ce,higher ratio of Nb^(4+)/(Nb^(5+)+Nb^(4+))and Ce^(3+)/(Ce^(3+)+Ce^(4+)),as well as the special tubular structure of cerium nanotube.This study may provide a practical approach for the design and synthesis of SCR catalysts for the simultaneously removal NOxand chlorinated volatile organic compounds(CVOCs)emitted from the stationary industrial sources.

Performance and recent improvement in microbial fuel cells for simultaneous carbon and nitrogen removal: A review

Microbial fuel cells（MFCs） have become a promising technology for wastewater treatment accompanying electricity generation. Carbon and nitrogen removal can be achieved by utilizing the electron transfer between the anode and cathode in an MFC. However,large-scale power production and high removal efficiency must be achieved at a low cost to make MFCs practical and economically competitive in the future. This article reviews the principles, feasibility and bottlenecks of MFCs for simultaneous carbon and nitrogen removal, the recent advances and prospective strategies for performance improvement, as well as the involved microbes and electron transfer mechanisms.

Tailoring the simultaneous abatement of methanol and NO_(x) on Sb-Ce-Zr catalysts via copper modification

Simultaneously removal of NO_(x)and VOCs over NH3-SCR catalysts have attracted lots of attention recently.However,the presence of VOCs would have negative effect on deNOx efficiency especially at low temperature.In this study,copper modification onto Sb_(0.5)CeZr_(2)O_(x)(SCZ)catalyst were performed to enhance the catalytic performance for simultaneous control of NNO_(x)and methanol.It was obtained that copper addition could improve the low-temperature activity of both NOx conversion and methanol oxidation,where the optimal catalyst(Cu_(0.05)SCZ)exhibited a deNOx activity of 96%and a mineralization rate of 97%at 250℃,which are around 10%higher than that of Cu free sample.The characterization results showed that copper addition could obviously enhance the redox capacity of the catalysts.As such,the inhibition effect of methanol incomplete oxidation on NO adsorption and NH3 activation were then lessened and the conversion of surface formamide species were also accelerated,resulting in the rising of NOx conversion at low temperature.However,excessive copper addition would damage the Sb-Ce-Zr oxides solid solution structure owing to Cu-Ce strong interactions,decreasing the surface area and acidity.Meanwhile,due to easier over-oxidation of NH3 with more Cu addition,the temperature window for NOx conversion would become quite narrow.These findings could provide useful guidelines for the synergistic removal of VOCs over SCR catalyst in real application.

Supported catalysts for simultaneous removal of SO_(2),NO_(x),and Hg^(0)from industrial exhaust gases:A review

The simultaneous removal of SO_(2),NO_(x)and Hg^(0)from industrial exhaust flue gas has drawn worldwide attention in recent years.A particularly attractive technique is selective catalytic reduction,which effectively removes SO_(2),NO_(x)and Hg^(0)at low temperatures.This paper first reviews the simultaneous removal of SO_(2),NO_(x)and Hg^(0)by unsupported and supported catalysts.It then describes and compares the research progress of various carriers,eg.,carbon-based materials,metal oxides,silica,molecular sieves,metal-organic frameworks,and pillared interlayered clays,in the simultaneous removal of SO_(2),NO_(x)and Hg^(0).The effects of flue-gas components(such as O_(2),NH3,HCl,H2 O,SO_(2),NO and Hg^(0))on the removal of SO_(2),NOx,and Hg^(0)are discussed comprehensively and systematically.After summarizing the pollutantremoval mechanism,the review discusses future developments in the simultaneous removal of SO_(2),NOx and Hg^(0)by catalysts.

Enhanced catalytic activity for simultaneous removal of PCDD/Fs and NO over carbon nanotubes modified MnO_(x)-CeO_(2)/TiO_(2)catalyst at low temperatu

Simultaneous catalytic removal of polychlorinated dibenzo-p-dioxins and dibenzofurans(PCDD/Fs)and nitrogen oxides(NO_(x))emission at low temperature is of great significance to solve the multiple air pollution problem caused during waste incineration.A novel catalyst with excellent low-temperature activity towards PCDD/Fs catalytic decomposition,as well as selective catalytic reduction(SCR)of NO with NH_(3)is urgently needed to simultaneously control PCDD/Fs and NO emis-sions.Manganese-cerium composite oxides supported on titanium dioxide(MnO_(x)-CeO_(2)/TiO_(2))or TiO_(2)and carbon nano-tubes(CNTs)composite carrier(MnO_(x)-CeO_(2)/TiO_(2)-CNTs)were prepared using sol-gel method,and their catalytic activity towards simultaneous abatement of ortho-dichlorobenzene(o-DCBz,model molecular to simulate PCDD/Fs)and NO was investigated.In comparison with their removal,the simultaneous removal efficiencies of o-DCBz and NO over MnO_(x)-CeO_(2)/TiO_(2)catalyst are lowered to 27.9%and 51.3%at 150℃under the gas hourly space velocity(GHSV)of 15,000 h−1,due to the competition between the reactants for the limited surface acid sites and surface reactive oxygen species.CNTs addition improves the catalytic activity for their simultaneous removal.The optimum condition occurs on MnO_(x)-CeO_(2)/TiO_(2)combined with 20 wt.%CNTs that above 70%of o-DCBz and NO are removed simultaneously.Characterization results reveal that MnO_(x)-CeO_(2)/TiO_(2)-CNTs catalyst with proper CNTs content has larger Brunauer-Emmet-Teller surface area and greatly improved surface acidity property,which are beneficial to both o-DCBz and NO adsorption.Moreover,the relatively higher surface atomic concentration of Mn^(4+)as well as the existence of abundant surface Ce^(3+)atom accelerates the redox cycle of the catalyst and enriches the surface reactive oxygen species.All the above factors alleviate the competition effect between o-DCBz catalytic oxidation and NH_(3)-SCR reaction and are conducive to the simultaneous abatement of o-DCBz and NO.However,excess CNTs make less contribution on enhancing the interaction between Mn atom and Ce atom,thereby result-ing in less improvement in the catalytic activity.

A Cu-modified active carbon fiber significantly promoted H_(2)S and PH_(3) simultaneous removal at a low reaction temperature

Poisonous gases,such as H_(2)S and PH3,produced by industrial production harm humans and damage the environment.In this study,H_(2)S and PH3 were simultaneously removed at low temperature by modified activated carbon fiber(ACF)catalysts.We have considered the active metal type,content,precursor,calcination,and reaction temperature.Experimental results exhibited that ACF could best perform by loading 15%Cu from nitrate.The optimized calcination temperature and reaction temperature separately were 550℃ and 90℃.Under these conditions,the most removal capacity could reach 69.7 mg/g and 132.1 mg/g,respectively.Characterization results showed that moderate calcination temperature(550℃)is suitable for the formation of the copper element on the surface of ACF,lower or higher temperature will generate more cuprous oxide.Although both can exhibit catalytic activity,the role of the copper element is significantly greater.Due to the exceptional dispersibility of copper(oxide),the ACF can still maintain the advantages of larger specific surface area and pore volume after loading copper,which is the main reason for better performance of related catalysts.Finally,increasing the copper loading amount can significantly increase the crystallinity and particle size of copper(oxide)on the ACF,thereby improving its catalytic performance.In situ IR found that the reason for the deactivation of the catalyst should be the accumulation of generated H_(2)PO_(4)^(-) and S0_(4)^(2-)(H_(2)0)^(6) which could poison the catalyst.

Influence of Limestone Addition on Combustion and Emission Characteristics of Coal Slime in the 75 t/h CFB Boiler with Post-Combustion Chamber

Coal slime can be disposed in quantity and fully utilized in a well-designed circulating fluidized bed(CFB)boiler,but the nitrogen oxides(NO_(x))and sulphur dioxide(SO_(2))emissions generated in the combustion of coal slime have contributed to serious atmospheric pollution.High Temperature&Post-combustion Technology,a novel and high-efficient way to reduce the NO_(x)emission in the process of combustion,is applied to a 75 t/h CFB boiler burning exclusively coal slime,which will succeed to meet the ultra-low NO_(x)emission standard.To further explore an appropriate method to reduce the SO_(2)emission under the condition of new technology,the experiments were conducted on a 75 t/h CFB boiler with post-combustion chamber to study the influence of limestone addition on the combustion and emission characteristics of coal slime.The experimental results showed that High Temperature&Post-combustion Technology combined with the sorbent injection in the furnace is a very promising technology to control the NO_(x)and SO_(2)emissions simultaneously.Limestone addition can cause the slight decrease in combustion temperature.Limestone addition will lead to the increase in NO_(x)emission in the combustion of coal slime.In 75 t/h coal slime CFB boiler,the desulfurization efficiency of limestone injection in furnace is close to 98%,achieving the ultra-low SO_(2)emission.To meet the standard of ultra-low NO_(x)and SO_(2)emission,the two technologies for simultaneous removal of NO_(x)and SO_(2)emissions are economical and feasible currently:Removal of SO_(2)under ultra-low NO_(x)emission and Removal of NO_(x)under ultra-low SO_(2)emission.

Crosslinking acrylamide with EDTA-intercalated layered double hydroxide for enhanced recovery of Cr(Ⅵ)and Congo red:Adsorptive and mechanistic study

We prepared ethylenediaminetetraacetic acid(EDTA)-intercalated MgAl-layered double hydroxide(LDH-EDTA),then grafted acrylamide(AM)to the LDH-EDTA by a cross-linking method to yield a LDH-EDTA-AM composite;we then evaluated its adsorptive ability for Congo red(CR)and hexavalent chromium(Cr(Ⅵ))in single and binaiy adsorption systems.The adsorption process on LDH-EDTA-AM for CR and Cr(Ⅵ)achieved equilibrium quickly,and the removal efficiencies were minimally affected by initial pH.The maximum uptake quantities of CR and Cr(Ⅵ)on LDH-EDTAAM were 632.9 and 48.47 mg/g,respectively.In mixed systems,chromate removal was stimulated by the presence of CR,while the adsorption efficiency of C R was almost not influenced by coexisting Cr(Ⅵ).The mechanisms involved electrostatic attraction,surface complexation,and anion exchange for the adsorption of both hazardous pollutants.In the Cr(Ⅵ)adsorption process,reduction also took place.The removal efficiencies in real contaminated water were all higher than those in the laboratory solutions.