Enhanced dechlorination of 2,4-dichlorophenol by recoverable Ni/Fe–Fe3O4 nanocomposites

Ni/Fe-Fe_3O_4 nanocomposites were synthesized for dechlorination of 2,4-dichlorophenol(2,4-DCP). The effects of the Ni content in Ni/Fe-Fe_3O_4 nanocomposites, solution pH, and common dissolved ions on the dechlorination efficiency were investigated, in addition to the reusability of the nanocomposites. The results showed that increasing content of Ni in Ni/Fe–Fe_3O_4 nanocomposites, from 1 to 5 wt.%, greatly increased the dechlorination efficiency; the Ni/Fe–Fe_3O_4 nanocomposites had much higher dechlorination efficiency than bare Ni/Fe nanoparticles. Ni content of 5 wt.% and initial p H below 6.0 was found to be the optimal conditions for the catalytic dechlorination of 2,4-DCP. Both 2,4-DCP and the intermediate product 2-chlorophenol(2-CP) were completely removed, and the concentration of the final product phenol was close to the theoretical phenol production from complete dechlorination of 20 mg/L of 2,4-DCP, after 3 hr reaction at initial p H value of 6.0,3 g/L Ni/Fe-Fe_3O_4 , 5 wt.% Ni content in the composite, and temperature of 22℃. 2,4-DCP dechlorination was enhanced by Cl-and inhibited by NO3-and SO_4~(2-). The nanocomposites were easily separated from the solution by an applied magnetic field. When the catalyst was reused, the removal efficiency of 2,4-DCP was almost 100% for the first seven uses, and gradually decreased to 75% in cycles 8–10. Therefore, the Ni/Fe–Fe_3O_4 nanocomposites can be considered as a potentially effective tool for remediation of pollution by 2,4-DCP.     

Effect of competing solutes on arsenic（Ⅴ） adsorption using iron and aluminum oxides

The study focused on the effect of several typical competing solutes on removal of arsenic with Fe_2O_3 and AL_2O_3.The test results indicate that chloride,nitrate and sulfate did not have detectable effects,and that selenium(Ⅳ)(Se(Ⅳ))and vanadium(Ⅴ)(V(Ⅴ)) showed slight effects on the adsorption of As(Ⅴ)with Fe_2O_3.The results also showed that adsorption of As(Ⅴ)on AL_2O_3 was not affected by chloride and nitrate anions,but slightly by Se(Ⅳ)and V(Ⅴ)ions.Unlike the adsorption of As(Ⅴ)with Fe_2O_3,that with Fe_2O_3 was affected by the presence of sulfate in water solutions.Both phosphate and silica have significant adverse effects on the adsorption of As(Ⅴ)adsorption with Fe_2O_3 and Al_2O_3.Compared to the other tested anions,phosphate anion was found to be the most prominent solute affecting the As(Ⅴ)adsorption with Fe_2O_3 and Al_2O_3.In general,Fe_2O_3 has a better performance than Al_2O_3 in removal of As(Ⅴ)within a water environment where multi competing solutes are present.     

Preparation, characterization and performance of an electrospun carbon nanofiber mat applied in hexavalent chromium removal from aqueous solution

Hexavalent chromium, Cr(VI), a highly toxic oxyanion known as a carcinogen and mutagen,is an issue of concern due to its adverse impact on human health. Therefore, development of effective technologies and/or materials for Cr(VI) removal from water has been of great interest for researchers. In this study, an electrospun carbon nanofiber(CNF) mat was prepared via electrospinning polyacrylonitrile(PAN), followed by thermal pre-oxidation and carbonization. Scanning electron microscopy(SEM) observation showed that the fiber diameter of the CNF with carbonization temperature of 950°C(CNF_(950)) was about 266 nm.Potentiometric titration analysis demonstrated that the point of zero charge p H(pHpzc) of CNF_(950) was around 7.93. CNF_(950) demonstrated high adsorption capacity and fast adsorption kinetics for Cr(VI) at pH 3. Langmuir isotherm calculations showed that the maximum adsorption capacity of Cr(VI) on CNF_(950) was 118.8 mg/g at pH 2. The adsorption isotherm of Cr(VI) on CNF_(950) was well described by the Redlich–Peterson model, revealing that Cr(VI)adsorption was the result of a combination of monolayer and multilayer adsorption,depending on the initial Cr(VI) concentration. Solution pH greatly affected Cr(VI) adsorption onto CNF_(950) due to the electrostatic interaction, and the adsorption capacity was relatively high when pH was below 3. X-ray photoelectron spectroscopy(XPS) analysis revealed that the removal of Cr(VI) might be the result of a combination of redox reaction and electrostatic adsorption. The adsorption-saturated CNF_(950) could be regenerated by NaOH solution. This study extends the potential applicability of electrospun CNF mats for Cr(VI)-contaminated water purification.     

Simultaneous removal of Cu(Ⅱ) and Cr(Ⅵ) by Mg–Al–Cl layered double hydroxide and mechanism insight

Mg–Al–Cl layered double hydroxide(Cl-LDH) was prepared to simultaneously remove Cu(Ⅱ)and Cr(VI) from aqueous solution. The coexisting Cu(Ⅱ)(20 mg/L) and Cr(VI)(40 mg/L) were completely removed within 30 min by Cl-LDH in a dosage of 2.0 g/L; the removal rate of Cu(Ⅱ) was accelerated in the presence of Cr(VI). Moreover, compared with the adsorption of single Cu(Ⅱ) or Cr(VI), the adsorption capacities of Cl-LDH for Cu(Ⅱ) and Cr(VI) can be improved by 81.05% and 49.56%, respectively, in the case of coexisting Cu(Ⅱ)(200 mg/L) and Cr(VI)(400 mg/L). The affecting factors(such as solution initial p H, adsorbent dosage, and contact time) have been systematically investigated. Besides, the changes of p H values and the concentrations of Mg~(2+) and Al~(2+)in relevant solutions were monitored. To get the underlying mechanism, the Cl-LDH samples before and after adsorption were thoroughly characterized by X-ray powder diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. On the basis of these analyses, a possible mechanism was proposed. The coadsorption process involves anion exchange of Cr(VI) with Cl-in Cl-LDH interlayer, isomorphic substitution of Mg~(2+) with Cu~(2+), formation of Cu_2Cl(OH)_3precipitation, and the adsorption of Cr(VI) by Cu_2Cl(OH)_3. This work provides a new insight into simultaneous removal of heavy metal cations and anions from wastewater by Cl-LDH.     

Investigation of adsorption/desorption behavior of Cr(VI) at the presence of inorganic and organic substance in membrane capacitive deionization (MCDI)

The adsorption and desorption behavior of Cr(VI) in membrane capacitive deionization (MCDI) was investigated systematically in the presence of bovine serum albumin (BSA) and KCl with different concentrations, respectively. Results revealed that Cr(VI) absorption was enhanced and the adsorption amount for Cr(VI) increased from 155.7 to 190.8?mg/g when KCl concentration increased from 100 to 200?mg/L in the adsorption process, which was attributed to the stronger driving force. However, the adsorption amount sharply decreased to 90.2?mg/g when KCl concentration reached up to 1000?mg/L suggesting the negative effect for Cr(VI) removal that high KCl concentration had. As for the effect of BSA on ion adsorption, the amount for Cr (VI) significantly declined to 78.3?mg/g and pH was found to be an important factor contributing to this significant reduction. Then, the desorption performance was also conducted and it was obtained that the presence of KCl had negligible effect on Cr(VI) desorption, while promoted by the addition of BSA. The incomplete desorption was obtained and the residual chromium ions onto the electrode after desorption was detected via energy-dispersive X-ray spectroscopy (EDS). Based on above analysis, the enhanced removal mechanism for Cr(VI) in MCDI was found to be consisted of ion adsorption onto electrode surface, the redox reaction of Cr(VI) into Cr(III) and precipitation, which was demonstrated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM).     

Newly developed Fe3O4–Cr2O3 magnetic nanocomposite for photocatalytic decomposition of 4-chlorophenol in water

Chlorophenols, typically 4-chlorophenols are highly toxic and non-biodegradable organic contaminants which pose serious threat to the environment, particularly when released into aqueous medium. The removal of these pollutants by efficient method has received worldwide concern in recent past. A new Fe_3O_4–Cr_2O_3 magnetic nanocomposite was synthesized by wet chemical method under ultrasonic irradiation. Microstructure and morphology of the nanocomposite were characterized by powder X-ray diffraction(XRD),Fourier transform infrared(FT-IR), and a transmission electron microscope(TEM). Magnetic and optical properties were studied by a vibrating sample magnetometer(VSM) and an ultraviolet–visible(UV–Vis) spectrophotometer respectively. The magnetic nanocomposite(MNC) was used as photocatalyst for effective decomposition of 4-chlorophenol in water under ultraviolet(UV) irradiation.     

Cr(VI) removal from aqueous solution with bamboo charcoal chemically modified by iron and cobalt with the assistance of microwave

Bamboo charcoal (BC) was used as starting material to prepare Co-Fe binary oxideloaded adsorbent (Co-Fe-MBC) through its impregnation in Co(NO3)2 , FeCl3 and HNO3 solutions simultaneously, followed by microwave heating. The low-cost composite was characterized and used as an adsorbent for Cr(VI) removal from water. The results showed that a cobalt and iron binary oxide (CoFe2O4 ) was uniformly formed on the BC through redox reactions. The composite exhibited higher surface area (331 m2/g) than that of BC or BC loaded with Fe alone (Fe-MBC). The adsorption of Cr(VI) strongly depended on solution pH, temperature and ionic strength. The adsorption isotherms followed the Langmuir isotherm model well, and the maximum adsorption capacities for Cr(VI) at 288 K and pH 5.0 were 35.7 and 51.7 mg/g for Fe-MBC and Co-Fe-MBC, respectively. The adsorption processes were well fitted by the pseudo second-order kinetic model. Thermodynamic parameters showed that the adsorption of Cr(VI) onto both adsorbents was feasible, spontaneous, and exothermic under the studied conditions. The spent Co-Fe-MBC could be readily regenerated for reuse.     

Effects of coal-fired power plants on soil microbial diversity and community structures

Long-term deposition of atmospheric pollutants emitted from coal combustion and their effects on the eco-environment have been extensively studied around coal-fired power plants.However,the effects of coal-fired power plants on soil microbial communities have received little attention through atmospheric pollutant deposition and coal-stacking.Here,we collected the samples of power plant soils (PS),coal-stacking soils (CSS) and agricultural soils(AS) around three coal-fired power plants and backg...     

Impact of microbial communities from tropical soils on the mobilization of trace metals during dissolution of cinnabar ore

Biodissolution experiments on cinnabar ore(mercury sulphide and other sulphide minerals,such as pyrite) were performed with microorganisms extracted directly from soil. These experiments were carried out in closed systems under aerobic and anaerobic conditions with 2 different soils sampled in French Guyana. The two main objectives of this study were(1) to quantify the ability of microorganisms to mobilize metals(Fe, Al, Hg) during the dissolution of cinnabar ore, and(2) to identify the links between the type and chemical properties of soils, environmental parameters such as season and the strategies developed by indigenous microorganisms extracted from tropical natural soils to mobilize metals.Results indicate that microbial communities extracted directly from various soils are able to(1) survive in the presence of cinnabar ore, as indicated by consumption of carbon sources and,(2) leach Hg from cinnabar in oxic and anoxic dissolution experiments via the acidification of the medium and the production of low molecular mass organic acids(LMMOAs). The dissolution rate of cinnabar in aerobic conditions with microbial communities ranged from 4.8 × 10~(-4) to 2.6 × 10~(-3) μmol/m~2/day and was independent of the metabolites released by the microorganisms. In addition, these results suggest an indirect action by the microorganisms in the cinnabar dissolution. Additionally, because iron is a key element in the dynamics of Hg, microbes were stimulated by the presence of this metal,and microbes released LMMOAs that leached iron from iron-bearing minerals, such as pyrite and oxy-hydroxide of iron, in the mixed cinnabar ore.     

Substrate-induced changes in microbial community-level physiological profiles and their application to discriminate soil microbial communities

The addition of simple substrates could affect the microbial respiration in soils. This substrate-induced respiration is widely used to estimate the soil microbial biomass, but little attention has been paid to its influence on the changes of community-level physiological profiles. In this study, the process of microbial communities responding to the added substrate using sole-carbon-source utilization （BIOLOG） was investigated. BIOLOG is biased toward fast-growing bacteria; this advantage was taken to detect the prompt response of the active microbial communities to the added substrate. Four soil samples from agricultural fields adjacent to heavy metal mines were amended with L-arginine, citric acid, or D-glucose. Substrate amendments could, generally, not only increase the metabolic activity of the microbial communities, but also change the metabolic diverse patterns compared with no-substrate control. By tracking the process, it was found that the variance between substrate-induced treatment and control fluctuated greatly during the incubation course, and the influences of these three substrates were different. In addition, the application of these induced changes to discriminate soil microbial communities was tested. The distance among all samples was greatly increased, which further showed the functional variance among microbial communities in soils. This can be very useful in the discrimination of microbial communities even with high similarity.     

Nb_2O_5 nanowires in-situ grown on carbon fiber: A high-efficiency material for the photocatalytic reduction of Cr(Ⅵ)

Niobium oxide nanowire-deposited carbon fiber(CF) samples were prepared using a hydrothermal method with amorphous Nb_2O_5·nH_2O as precursor. The physical properties of the samples were characterized by means of numerous techniques, including X-ray diffraction(XRD), energy-dispersive spectroscopy(EDS), scanning electron microscopy(SEM), transmission electron microscopy(TEM), selected-area electron diffraction(SAED), UV–visible spectroscopy(UV–vis), N_2 adsorption–desorption, Fourier transform infrared spectroscopy(FT-IR), and X-ray photoelectron spectroscopy. The efficiency for the removal of Cr(VI) was determined.Parameters such as pH value and initial Cr(VI) concentration could influence the Cr(VI) removal efficiency or adsorption capacity of the Nb_2O_5/carbon fiber sample obtained after hydrothermal treatment at 160°C for 14 hr. The maximal Cr(VI) adsorption capacity of the Nb_2O_5 nanowire/CF sample was 115 mg/g. This Nb_2O_5/CF sample also showed excellent photocatalytic activity and stability for the reduction of Cr(VI) under UV-light irradiation: the Cr(VI) removal efficiency reached 99.9% after UV-light irradiation for 1 hr and there was no significant decrease in photocatalytic performance after the use of the sample for 10 repeated cycles. Such excellent Cr(VI) adsorption capacity and photocatalytic performance was related to its high surface area,abundant surface hydroxyl groups, and good UV-light absorption ability.     

Effects of biochars on the bioaccessibility of phenanthrene/pyrene/zinc/lead and microbial community structure in a soil under aerobic and anaerobic conditions

The immobilization of co-contaminants of organic and inorganic pollutants by biochar is an efficient remediation strategy. However, the effect of biochar amendments on the bioaccessibility of the co-contaminants in dry versus flooded soils has rarely been compared. In batch experiments, bamboo-derived biochar(BB) had a higher sorption capacity for phenanthrene(Phe)/pyrene(Pyr)/zinc(Zn) than corn straw-derived biochar(CB), while CB had a higher sorption capacity for lead(Pb) than BB. After 150 days of incubation, the amendments of 2% CB, 0.5% BB and 2% BB effectively suppressed the dissipation and reduced the bioaccessibility of Phe/Pyr by 15.65%/18.02%, 17.07%/18.31%and 25.43%/27.11%, respectively, in the aerobic soils. This effectiveness was more significant than that in the anaerobic soils. The accessible Zn/Pb concentrations were also significantly lower in the aerobic soils than in the anaerobic soils, regardless of treatments.The Gram-negative bacterial biomass and the Shannon–Weaver index in the aerobic soil amended with 2% CB were the highest. The soil microbial community structure was jointly affected by changes in the bioaccessibility of the co-contaminants and the soil physiochemical properties caused by biochar amendments under the two conditions. Therefore, dry land farming may be more reliable than paddy soil cultivation at reducing the bioaccessibility of Phe/Pyr/Zn/Pb and enhancing the soil microbial diversity in the short term.     

Kinetics and mechanism of hexavalent chromium removal by basic oxygen furnace slag

Basic oxygen furnace slag(BOFS) has the potential to remove hexavalent chromium(Cr(VI))from wastewater by a redox process due to the presence of minerals containing Fe2+. The effects of the solution p H, initial Cr(VI) concentration, BOFS dosage, BOFS particle size, and temperature on the removal of Cr(VI) was investigated in detail through batch tests. The chemical and mineral compositions of fresh and reacted BOFS were characterized using scanning electron microscope(SEM) equipped with an energy dispersive spectrometer(EDS)system and X-ray diffractometer(XRD). The results show that Cr(VI) in wastewater can be efficiently removed by Fe2+released from BOFS under appropriate acidic conditions. The removal of Cr(VI) by BOFS significantly depended on the parameters mentioned above. The reaction of Cr(VI) with BOFS followed the pseudo-second-order kinetic model. Fe2+responsible for Cr(VI) removal was primarily derived from the dissolution of Fe O and Fe3O4 in BOFS. When H2SO4 was used to adjust the solution acidity, gypsum(Ca SO4·2H2O)could be formed and become an armoring precipitate layer on the BOFS surface, hindering the release of Fe2+and the removal of Cr(VI). Finally, the main mechanism of Cr(VI) removal by BOFS was described using several consecutive reaction steps.     

Removal of Cd2+ from water by Friedel’s salt (FS: 3CaO.Al2O3·CaCl2·10H2O): Sorption characteristics and mechanisms

The development of low-cost and efficient new mineral adsorbents has been a hot topic in recent years. In this study, Friedel’s salt (FS:3CaO·A12O3 ·CaCl2 ·10H2O), a hexagonal layered inorganic absorbent, was synthesized to remove Cd2+ from water. The adsorption process was simulated by Langmuir and Freundlich models. The adsorption mechanism was further analyzed with TEM, XRD, FT-IR analysis and monitoring of metal cations released and solution pH variation. The results indicated the adsorbent FS had an outstanding ability for Cd(Ⅱ) adsorption. The maximum adsorption capacity of the FS for Cd(Ⅱ) removal can reach up to 671.14 mg/g. The nearly equal numbers of Cd2+ adsorbed and Ca2+ released demonstrated that ion-exchange (both surface and inner) of the FS for Cd(Ⅱ) played an important role during the adsorption process. Furthermore, the surface of the FS after adsorption was microscopically disintegrated while the inner lamellar structure was almost unchanged. The behavior of Cd(Ⅱ) adsorption by FS was significantly affected by surface reactions. The mechanisms of Cd2+ adsorption by the FS mainly included surface complexation and surface precipitation. In the present study, the adsorption process was fitted better by the Langmuir isotherm model (R2 = 0.9999) than the Freundlich isotherm model (R2 = 0.8122). Finally, due to the high capacity for ion-exchange on the FS surface, FS is a promising layered inorganic adsorbent for the removal of Cd(Ⅱ) from water.     

Novel functional fiber loaded with carbon dots for the deep removal of Cr(VI) by adsorption and photocatalytic reduction

A novel functional fiber (PAN-CDs) loaded with carbon dots (CDs) with excellent photoreduction and adsorption properties for Cr(VI) was prepared via an amidization reaction between the CDs' carboxyl groups and amine groups on polyacrylonitrile (PAN)-based ion exchange fibers, which could completely preserve the fluorescence properties of the CDs. The photoluminescence (PL), photocatalysis and adsorption properties of PAN-CDs were characterized and analyzed. The PAN-CDs possess high adsorption capacity (297.6?mg/g) and excellent kinetic behavior (attaining adsorption equilibrium in 30?min) for Cr(VI) adsorption. Furthermore, the residual Cr(VI) (approximately 3?mg/L) after adsorption could be removed completely by subsequent photoreduction by the PAN-CDs. The Cr-saturated PAN-CDs could be easily separated by filtering and regenerated, with no observable decay of removal efficiency after five regeneration cycles. In addition, due to the PL quenching action of Cr(VI), the PAN-CDs can also be used as sensor for quantitative detection of trace Cr(VI) in aqueous solution.     

Copper pollution decreases the resistance of soil microbial community to subsequent dry–rewetting disturbance

Dry–rewetting(DW) disturbance frequently occurs in soils due to rainfall and irrigation, and the frequency of DW cycles might exert significant influences on soil microbial communities and their mediated functions. However, how microorganisms respond to DW alternations in soils with a history of heavy metal pollution remains largely unknown.Here, soil laboratory microcosms were constructed to explore the impacts of ten DW cycles on the soil microbial communities in two contrasting soils(fluvo-aquic soil and red soil)under three copper concentrations(zero, medium and high). Results showed that the fluctuations of substrate induced respiration(SIR) decreased with repeated cycles of DW alternation. Furthermore, the resistance values of substrate induced respiration(RS-SIR)were highest in non-copper-stressed(zero) soils. Structural equation model(SEM) analysis ascertained that the shifts of bacterial communities determined the changes of RS-SIR in both soils. The rate of bacterial community variance was significantly lower in noncopper-stressed soil compared to the other two copper-stressed(medium and high) soils,which might lead to the higher RS-SIR in the fluvo-aquic soil. As for the red soil, the substantial increase of the dominant group WPS-2 after DW disturbance might result in the low RS-SIR in the high copper-stressed soil. Moreover, in both soils, the bacterial diversity was highest in non-copper-stressed soils. Our results revealed that initial copper stress could decrease the resistance of soil microbial community structure and function to subsequent DW disturbance.     

A nanocomposite consisting of silica-coated magnetite and phenyl-functionalized graphene oxide for extraction of polycyclic aromatic hydrocarbon from aqueous matrices

In this study,graphene oxide was covalently immobilized on silica-coated magnetite and then modified with 2-phenylethylamine to give a nanocomposite of type Fe_3O_4@SiO_2@GO-PEA that can be applied to the magnetic solid-phase extraction of polycyclic aromatic hydrocarbons(PAHs) from water samples.The resulting microspheres(Fe_3O_4@SiO_2@GO-PEA) were characterized by Fourier transform-infrared spectroscopy(FT-IR),scanning electron microscopy(SEM),CHNS elemental analysis,and vibrating sample magnetometry(VSM) techniques.The adsorbent possesses the magnetic properties of Fe_3O_4 nanoparticles that allow them easily to be separated by an external magnetic field.They also have the high specific surface area of graphene oxide which improves adsorption capacity.Desorption conditions,extraction time,amount of adsorbent,salt concentration,and pH were investigated and optimized.Following desorption,the PAHs were quantified by gas chromatography with flame ionization detection(GC-FID).The limits of detection(at an S/N ratio of 3) were achieved from 0.005 to0.1 μg/L with regression coefficients(R~2) higher than 0.9954.The relative standard deviations(RSDs) were below 5.8%(intraday) and 6.2%(inter-day),respectively.The method was successfully applied to the analysis of PAHs in environmental water samples where it showed recoveries in the range between 71.7%and 106.7%(with RSDs of 1.6%to 8.4%,for n = 3).The results indicated that the Fe_3O_4@SiO_2@GO-PEA microspheres had a great promise to extraction of PAHs from different water samples.     

Structure and function of rhizosphere and non-rhizosphere soil microbial community respond differently to elevated ozone in field-planted wheat

To assess the responses of the soil microbial community to chronic ozone(O_3), wheat seedlings(Triticum aestivum Linn.) were planted in the field and exposed to elevated O_3(e O_3)concentration. Three treatments were employed:(1) Control treatment(CK), AOT40 = 0;(2) O_3-1, AOT40 = 1.59 ppm·h;(3) O_3-2, AOT40 = 9.17 ppm·h. Soil samples were collected for the assessment of microbial biomass C, community-level physiological profiles(CLPPs), and phospholipid fatty acids(PLFAs). EO_3 concentration significantly reduced soil microbial carbon and changed microbial CLPPs in rhizosphere soil, but not in non-rhizosphere soil.The results of the PLFAs showed that e O_3 concentrations had significant effects on soil community structure in both rhizosphere and non-rhizosphere soils. The relative abundances of fungal and actinomycetous indicator PLFAs decreased in both rhizosphere and non-rhizosphere soils, while those of bacterial PLFAs increased. Thus the results proved that e O_3 concentration significantly changed the soil microbial community function and composition, which would influence the soil nutrient supply and carbon dynamics under O_3 exposure.     

Preparation of cross-linked magnetic chitosan with quaternary ammonium and its application for Cr(VI) and P(V) removal

Pollutants that exist in anionic species are issues of concern in water treatment. Compared to cationic pollutants, the removal of anionic pollutants by adsorption is more difficult because most adsorbents carry predominantly negative charges in neutral and alkaline environments. In this study, a cross-linked chitosan derivative with quaternary ammonium and magnetic properties（QM-chitosan） was prepared and employed to remove chromium（VI） and phosphorus（V）（Cr（VI） and P（V）） from aqueous environments. The QM-chitosan was characterized by Fourier transform infrared spectrometry（FT-IR）,thermogravimetric analysis（TGA）, energy dispersive X-ray（SEM-EDX） and zeta potential.Batch experiments show that QM-chitosan can effectively remove Cr（VI） and P（V）, and the main mechanism was believed to be electrostatic interaction. A pseudosecond-order model was fitted to describe the kinetic processes of Cr（VI） and P（V） removal. The adsorption isotherms of both Cr（VI） and P（V） on the QM-chitosan were well fitted by the Langmuir isotherm equation. The saturated adsorption capacity of P（V）（2.783 mmol/g） was found to be higher than that of Cr（VI）（2.323 mmol/g）, resulting from the size of the H2PO-4ions being smaller than that of the HCr O-4ions. However, the theoretical calculation and experimental results showed that QM-chitosan had a stronger affinity for Cr（VI） than P（V）. The adsorption–desorption of the QM-chitosan was evaluated, and high regeneration rates were demonstrated.     

Flower-, wire-, and sheet-like MnO_2-deposited diatomites:Highly efficient absorbents for the removal of Cr(Ⅵ)

Flower-, wire-, and sheet-like MnO2-deposited diatomites have been prepared using a hydrothermal method with Mn(Ac)2, KMnO4and/or MnSO4 as Mn source and diatomite as support. Physical properties of the materials were characterized by means of numerous analytical techniques, and their behaviors in the adsorption of chromium(VI) were evaluated.It is shown that the MnO2-deposited diatomite samples with different morphologies possessed high surface areas and abundant surface hydroxyl groups(especially the wire-like MnO2/diatomite sample). The wire-like MnO2/diatomite sample showed the best performance in the removal of Cr(VI), giving the maximum Cr(VI) adsorption capacity of 101 mg/g.