磁性Fe_3O_4/Ag_3PO_4复合光催化剂催化降解染料废水中的孔雀石绿

利用离子交换法制备了可磁性分离并具有高效可见光催化活性的Fe3O4/Ag3PO4复合光催化剂,对制备的样品进行了粉末X射线衍射(XRD)表征。同时,用孔雀石绿溶液模拟染料废水,考察了孔雀石绿溶液的初始浓度、催化剂投加量及溶液初始pH值对复合光催化剂催化降解孔雀石绿效果的影响,并探讨了Fe3O4/Ag3PO4磁性复合光催化剂的回收及循环利用特性。结果表明,该复合光催化剂在可见光照射下表现出较高的催化活性;当孔雀石绿溶液浓度为5mg/L、复合催化剂投加量为200mg/L、溶液初始pH=3.0、可见光照20min时,Fe3O4/Ag3PO4复合光催化剂对孔雀石绿的去除率可达96%;反应结束后,磁性复合光催化剂在外加磁场作用下,易于从反应体系中分离,循环使用3次后,其光催化效率仍可达到60%。实验表明,制备的复合光催化剂对染料废水中孔雀石绿有较高的降解效率,并具有优良的回收利用性。     

Activated carbon/Fe(3)O(4) nanoparticle composite: fabrication, methyl orange removal and regeneration by hydrogen peroxide

In the water treatment field, activated carbons (ACs) have wide applications in adsorptions. However, the applications are limited by difficulties encountered in separation and regeneration processes. Here, activated carbon/Fe₃O₄ nanoparticle composites, which combine the adsorption features of powdered activated carbon (PAC) with the magnetic and excellent catalytic properties of Fe₃O₄ nanoparticles, were fabricated by a modified impregnation method using HNO₃ as the carbon modifying agent. The obtained composites were characterized by X-ray diffraction, scanning and transmission electron microscopy, nitrogen adsorption isotherms and vibrating sample magnetometer. Their performance for methyl orange (MO) removal by adsorption was evaluated. The regeneration of the composite and PAC-HNO₃ (powdered activated carbon modified by HNO₃) adsorbed MO by hydrogen peroxide was investigated. The composites had a high specific surface area and porosity and a superparamagnetic property that shows they can be manipulated by an external magnetic field. Adsorption experiments showed that the MO sorption process on the composites followed pseudo-second order kinetic model and the adsorption isotherm date could be simulated with both the Freundlich and Langmuir models. The regeneration indicated that the presence of the Fe₃O₄ nanoparticles is important for a achieving high regeneration efficiency by hydrogen peroxide.     

Heterogeneous Fenton degradation of bisphenol A catalyzed by efficient adsorptive Fe3O4/GO nanocomposites

A new method for the degradation of bisphenol A (BPA) in aqueous solution was developed. The oxidative degradation characteristics of BPA in a heterogeneous Fenton reaction catalyzed by Fe₃O₄/graphite oxide (GO) were studied. Transmission electron microscopic images showed that the Fe₃O₄ nanoparticles were evenly distributed and were ～6 nm in diameter. Experimental results suggested that BPA conversion was affected by several factors, such as the loading amount of Fe₃O₄/GO, pH, and initial H₂O₂ concentration. In the system with 1.0 g L^?1 of Fe₃O₄/GO and 20 mmol L^?1 of H₂O₂, almost 90 % of BPA (20 mg L^?1) was degraded within 6 h at pH 6.0. Based on the degradation products identified by GC–MS, the degradation pathways of BPA were proposed. In addition, the reused catalyst Fe₃O₄/GO still retained its catalytic activity after three cycles, indicating that Fe₃O₄/GO had good stability and reusability. These results demonstrated that the heterogeneous Fenton reaction catalyzed by Fe₃O₄/GO is a promising advanced oxidation technology for the treatment of wastewater containing BPA.     

Fe0/Fe3O4复合材料同时去除水中多种重金属的效果

零价铁(Fe0)具有中等还原性,可通过还原反应或通过铁腐蚀产物的吸附和共沉淀过程去除水中重金属.但由于铁表面易钝化,导致铁腐蚀反应难以持续,这是限制Fe0应用的关键.因此,本研究通过原位制备零价铁复合体系(Fe0/Fe3O4),并采用批处理和连续流的流化床反应器考察了该复合体系同时去除水中Zn2+、Ni2+和Cr(Ⅵ)...     

Sustainable adsorptive removal of antibiotics from aqueous streams using Fe3O4-functionalized MIL101(Fe) chitosan composite beads

Environmental Science and Pollution Research - In this study, we synthesized recyclable Fe3O4-functionalized MIL101(Fe) chitosan composite beads for the removal of tetracycline (TC), doxycycline...     

Photooxidation of naphthalenesulfonic acids: comparison between processes based on O(3), O(3)/activated carbon and UV/H(2)O(2)

The aim of the present study was to analyze and compare the efficacy of UV photodegradation with that of different advanced oxidation processes (O(3), UV/H(2)O(2), O(3)/activated carbon) in the degradation of naphthalenesulfonic acids from aqueous solution and to investigate the kinetics and the mechanism involved in these processes. Results obtained showed that photodegradation with UV radiation (254 nm) of 1-naphthalenesulfonic, 1,5-naphthalendisulfonic and 1,3,6-naphthalentrisulfonic acids is not effective. Presence of duroquinone and 4-carboxybenzophenone during UV irradiation (308-410 nm) of the naphthalenesulfonic acids increased the photodegradation rate. Addition of H(2)O(2) during irradiation of naphthalenesulfonic acids accelerated their elimination, due to the generation of ()OH radicals in the medium. Comparison between UV photodegradation 254 m and the advanced oxidation processes (O(3), O(3)/activated carbon and UV/H(2)O(2)) showed the low-efficacy of the former in the degradation of these compounds from aqueous medium. Thus, among the systems studied, those based on the use of UV/H(2)O(2) and O(3)/activated carbon were the most effective in the oxidation of these contaminants from the medium. This is because of the high-reactivity of naphthalenesulfonic acids with the *OH radicals generated by these two systems. This was confirmed by the values of the reaction rate constant of *OH radicals with these compounds k(OH), obtained by competitive kinetics (5.7 x 10(9) M(-1) s(-1), 5.2 x 10(9) M(-1) s(-1) and 3.7 x 10(9) M(-1) s(-1) for NS, NDS and NTS, respectively).     

Potential application of highly reactive Fe(0)/Fe3O4 composites for the reduction of Cr(VI) environmental contaminants

We describe the use of highly reactive Fe(0)/Fe3O4 composites for the reduction of Cr(VI) species in aqueous medium. The composites were prepared by simple mechanical alloying of metallic iron and magnetite in different proportions, i.e. Fe(0) 25, 50, 75 and 90wt%. While after 3h of reaction pure Fe(0) and pure Fe3O4 showed only a low reduction efficiency of 15% and 25% Cr(VI) conversion, respectively, the composites, in particular Fe(0)(25wt%)/Fe3O4, showed a remarkable activity with ca. 65% Cr(VI) conversion. Kinetic experiments showed a high reaction rate during the first 3h, which subsequently decreased strongly, probably due to a pH increase from 6 to 8. Experiments with composites based on Fe(0)/alpha-Fe2O3, Fe(0)/gamma-Fe2O3 and Fe(0)/FeOOH showed very low activities, suggesting that Fe(oct)2+ in the magnetite structure plays an important role in the reaction. Scanning and high resolution electron microscopies and M?ssbauer spectra (transmission and conversion electron M?ssbauer spectroscopy) indicated that the mechanical alloying process promotes a strong interaction and interface between the metallic and oxide phases, with the Fe(0) particles completely covered by Fe3O4 particles. The high efficiency of the composite Fe(0)/Fe3O4 for Cr(VI) reduction is discussed in terms of a special mechanism where an electron is transferred from Fe(0) to magnetite to reduce Fe(oct)3+ to Fe(oct)2+, which is active for Cr(VI) reduction.     

Abiotic reduction of antimony(V) by green rust (Fe(4)(II)Fe(2)(III)(OH)(12)SO(4).3H(2)O)

Green rust (Fe(4)(II)Fe(2)(III)(OH)(12)SO(4).3H(2)O) is an intermediate phase in the formation of iron (oxyhydr)oxides such as goethite, lepidocrocite, and magnetite. It is widely considered that green rust occurs in many soil and sediment systems. Green rust has been shown to reduce sorbed Se(VI), Cr(VI), and U(VI). In addition, it is also reported that green rust does not reduce As(V) to As(III). In this study, we have investigated for the first time the interaction between Sb(V) and green rust using XAFS and HPLC-ICP-MS. Most of the added Sb(V) was adsorbed on green rust, and Sb(III), a reduced form, was observed in both solid and liquid phases. Thus, it was shown that green rust has high affinity for Sb(V), and that Sb(V) was reduced to more toxic Sb(III) by green rust despite the high stability of the Sb(V) species even under reducing condition as reported in previous studies. Therefore, green rust can be one of the most important reducing agents for Sb(V), which can influence the Sb mobility in suboxic environments where green rust is formed.     

Functionalized porous nanoscale Fe3O4 particles supported biochar from peanut shell for Pb(II) ions removal from landscape wastewater

Environmental Science and Pollution Research - The large amounts ofheavy metal from landscape wastewater have become serious problems of environmental pollution and risks for human health. The...     

The Cl-initiated oxidation of CH3C(O)OCH=CH2, CH3C(O)OCH2CH=CH2, and CH2=CHC(O)O(CH2)3CH3 in the troposphere

Background, aim, and scope  

Unsaturated esters are emitted to the atmosphere from biogenic and anthropogenic sources, including those from the polymer industry. Little information exists concerning the atmospheric degradation of unsaturated esters, which are mainly initiated by OH radicals. Limited information is available on the degradation of alkenes by Cl atoms and almost no data exists for the reactions of unsaturated esters with Cl atoms. This data is necessary to assess the impact of such reactions in maritime environments where, under circumstances, OH radical- and Cl atom-initiated oxidation of the compounds can be important. Rate coefficients for the reactions of chlorine atoms with vinyl acetate, allyl acetate, and n-butyl acrylate have been determined at 298 ± 3 K and atmospheric pressure. The kinetic data have been used in combination with that for structurally similar compounds to infer the kinetic contributions from the possible reaction channels to the overall reaction rate.     

改性炭化谷壳负载纳米Fe3O4对含As(V)废水的吸附性能

以谷壳为原料,通过600℃缺氧高温热解制备一种炭化谷壳（CRH-I）,并利用CRH-I通过改性负载方法获得另一种新型的负载纳米Fe3O4的碱改性炭化谷壳（CRH-II）。经过对比表面积进行表征分析发现,CRH-II相较CRH-I的BET比表面积增大约30%,达到182 m2·g-1,微比表面积和微孔体积都扩大了6倍左右。FTIR分析结果表明,相比CRH-I,CRH-II分子间的羧基和酚羟基官能团有所增加,产生了芳构化反应和脂肪醚类物质。吸附实验表明,相对CRH-I而言,CRH-II对As（V）的吸附率明显提高。pH=2时,CRH-II对溶液中As（V）的吸附率达到98.3%;但是As的吸附率随着溶液pH值升高而逐渐降低,pH=11时下降最为明显,吸附率只有63.4%。CRH-II吸附反应满足准动力学二级方程,其相关系数为R2=0.999;在不同温度下,将CRH-II对As（V）的吸附验数据进行Langmuir方程和Freundlich等温方程拟合,结果更符合Langmuir方程;在25℃时,相关系数R2=0.985。解吸吸附实验证明,CRH-II依然具备良好的吸附性能,且再生吸附性能稳定。     

3-Chlorophenol elimination upon excitation of dilute iron(III) solution: evidence for the only involvement of Fe(OH)2+

The transformation of 3-chlorophenol (3CP) photoinduced by iron(II) in aqueous solution has been investigated under monochromatic irradiation (lambda(exc) = 365 nm) representative of atmospheric solar emission. Hydroxyl radicals are formed via an intramolecular photoredox process in iron(III) excited hydroxy-complexes. Fe(OH)2+ is the most active complex in terms of HO* formation and according to our experiments and calculations, it appears that Fe(OH)2+ is the only iron(III) species involved in 3CP oxidation process. Hydroxyl radicals react very rapidly with 3CP, which is eliminated from the solution. The primary intermediates do not accumulate in the medium but rapidly degraded to non-absorbing compounds by a subsequent action of hydroxyl radicals.     

Fe3O4负载非晶态(碳酸)氧化锆复合材料对磷的吸附性能及机理

有效控制富营养化和磷酸盐回收是近年来日益受到重视的问题.为此,采用溶剂热法合成了一种去除水中磷酸盐的Fe3O4负载非晶态(碳酸)氧化锆复合材料(MZCO),通过X射线衍射仪(XRD)、场发射扫描电镜(SEM)、高分辨率透射电镜(TEM)、傅里叶变换红外光谱仪(ATR-IR)、X光电子能谱仪(XPS)等对其进行了结构表征...     

NiFe2O4/ZnAl-LDH吸附去除水中Cr(VI)

采用共沉淀法合成磁性复合材料NiFe2O4/ZnAl-LDH,通过静态吸附试验考察复合材料去除水中Cr（VI）的性能,系统地研究了溶液初始pH值、吸附剂投加量、吸附时间和温度等因素对Cr（VI）去除效果的影响。结果表明,当溶液初始pH值为2、初始Cr（VI）浓度为50 mg·L-1、吸附剂投加量为4 g·L-1时,吸附过程在240 min内达到平衡,此时Cr（VI）的去除率为89.5%。动力学和吸附等温式的研究表明：NiFe2O4/ZnAl-LDH吸附Cr（VI）的过程符合准二级动力学和Langmuir等温吸附模型。热力学参数表明该吸附过程为自发、放热的反应过程,低温有利于吸附剂对Cr（VI）的吸附。吸附剂经4次再生后对Cr（VI）仍有83.1%的去除率,且其在外加磁场的作用下能快速与水溶液分离,因此NiFe2O4/ZnAl-LDH可作为去除水中Cr（VI）的良好吸附剂。     

Hydroxyl (OH) radical production rates in snowpacks from photolysis of hydrogen peroxide (H2O2) and nitrate (NO3−)

Atmospheric chemistry directly above snowpacks is strongly influenced by ultraviolet (UV) radiation initiated emissions of chemicals from the snowpack. The emission of gases from the snowpack to the atmosphere is in part due to chemical reactions between hydroxyl radical, OH (produced from photolysis of hydrogen peroxide (H₂O₂) or nitrate (NO₃⁻)) and impurities in the snowpack. The work presented here is a radiative-transfer modelling study to calculate the depth-integrated production rates of hydroxyl radical from the photolysis of hydrogen peroxide and nitrate anion in snow for four different snowpacks and for solar zenith angles 30°–90°. This work also demonstrates the importance of hydrogen peroxide photolysis to produce hydroxyl radical relative to nitrate photolysis with (a) different snowpacks, (b) different ozone column depths, and (c) snowpack depths. The importance of hydrogen peroxide photolysis over nitrate photolysis for hydroxyl radical production increases with increasing depth in snowpack, column ozone depth, and solar zenith angle. With a solar zenith angle of 60° the production of hydroxyl radical from hydrogen peroxide photolysis accounts for 91–99% of all hydroxyl radical production from hydrogen peroxide and nitrate photolysis.     

Removal of SO2 from O2-containing flue gas by activated carbon fiber (ACF) impregnated with NH3

Adsorption of SO(2) from the O(2)-containing flue gas by granular activated carbons (GACs) and activated carbon fibers (ACFs) impregnated with NH(3) was studied in this technical note. Experimental results showed that the ACFs were high-quality adsorbents due to their unique textural properties. In the presence of moisture, the desulphurization efficiency for the ACFs was improved significantly due to the formation of sulfuric acid. After NH(3) impregnation of ACF samples, nitrogen-containing functional groups (pyridyl C(5)H(4)N- and pyrrolyl C(4)H(4)N-) were detected on the sample surface by using an X-ray photoelectron spectrometer. These functional groups accounted for the enhanced SO(2) adsorption via chemisorption and/or catalytic oxidization.     

The Greenhouse effect: impacts of ultraviolet-B (UV-B) radiation, carbon dioxide (CO2), and ozone (O3) on vegetation

There is a fast growing and an extremely serious international scientific, public and political concern regarding man's influence on the global climate. The decrease in stratospheric ozone (O3) and the consequent possible increase in ultraviolet-B (UV-B) is a critical issue. In addition, tropospheric concentrations of 'greenhouse gases' such as carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4) are increasing. These phenomena, coupled with man's use of chlorofluorocarbons (CFCs), chlorocarbons (CCs), and organo-bromines (OBs) are considered to result in the modification of the earth's O3 column and altered interactions between the stratosphere and the troposphere. A result of such interactions could be the global warming. As opposed to these processes, tropospheric O3 concentrations appear to be increasing in some parts of the world (e.g. North America). Such tropospheric increases in O3 and particulate matter may offset any predicted increases in UV-B at those locations. Presently most general circulation models (GCMs) used to predict climate change are one- or two-dimensional models. Application of satisfactory three-dimensional models is limited by the available computer power. Recent studies on radiative cloud forcing show that clouds may have an excess cooling effect to compensate for a doubling of global CO2 concentrations. There is a great deal of geographic patchiness or variability in climate. Use of global level average values fails to account for this variability. For example, in North America: 1. there may be a decrease in the stratospheric O3 column (1-3%); however, there appears to be an increase in tropospheric O3 concentrations (1-2%/year) to compensate up to 20-30% loss in the total O3 column; 2. there appears to be an increase in tropospheric CO2, N2O and CH4 at the rate of roughly 0.8%, 0.3% and 1-2%, respectively, per year; 3. there is a decrease in erythemal UV-B; and 4. there is a cooling of tropospheric air temperature due to radiative cloud forcing. The effects of UV-B, CO2 and O3 on plants have been studied under growth chamber, greenhouse and field conditions. Few studies, if any, have examined the joint effects of more than one variable on plant response. There are methodological problems associated with many of these experiments. Thus, while results obtained from these studies can assist in our understanding, they must be viewed with caution in the context of the real world and predictions into the future. Biomass responses of plants to enhanced UV-B can be negative (adverse effect); positive (stimulatory effect) or no effect (tolerant). Sensitivity rankings have been developed for both crop and tree species. However, such rankings for UV-B do not consider dose-response curves. There are inconsistencies between the results obtained under controlled conditions versus field observations. Some of these inconsistencies appear due to the differences in responses between cultivars and varieties of a given plant species; and differences in the experimental methodology and protocol used. Nevertheless, based on the available literature, listings of sensitive crop and native plant species to UV-B are provided. Historically, plant biologists have studied the effects of CO2 on plants for many decades. Experiments have been performed under growth chamber, greenhouse and field conditions. Evidence is presented for various plant species in the form of relative yield increases due to CO2 enrichment. Sensitivity rankings (biomass response) are agein provided for crops and native plant species. However, most publications on the numerical analysis of cause-effect relationships do not consider sensitivity analysis of the mode used. Ozone is considered to be the most phytotoxic regional scale air pollutant. In the pre-occupation of loss in the O3 column, any increases in tropospheric O3 concentrations may be undermined relative to vegetation effects. As with the other stress factors, the effects of O3 have been studied both under controlled and field conditions. Thboth under controlled and field conditions. The numerical explanation of cause-effect relationships of O3 is a much debated subject at the present time. Much of the controversy is directed toward the definition of the highly stochastic, O3 exposure dynamics in time and space. Nevertheless, sensitivity rankings (biomass response) are provided for crops and native vegetation. The joint effects of UV-B, CO2 and O3 are poorly understood. Based on the literature of plant response to individual stress factors and chemical and physical climatology of North America, we conclude that nine different crops may be sensitive to the joint effects: three grain and six vegetable crops (sorghum, oat, rice, pea, bean, potato, lettuce, cucumber and tomato). In North America, we consider Ponderosa and loblolly pines as vulnerable among tree species. This conclusion should be moderated by the fact that there are few, if any, data on hardwood species. In conclusion there is much concern for global climate change and its possible effects on vegetation. While this is necessary, such a concern and any predictions must be tempered by the lack of sufficient knowledge. Experiments must be designed on an integrated and realistic basis to answer the question more definitively. This would require very close co-operation and communication among scientists from multiple disciplines. Decision makers must realize this need.     

EDTAD-modified cassava stalks loaded with Fe3O4: highly efficient removal of Pb2+ and Zn2+ from aqueous solution

Environmental Science and Pollution Research - In this study, a novel magnetic cassava stalk composite (M-EMCS) was prepared through modification with ethylenediamine tetraacetic anhydride (EDTAD)...     

Mechanism of OH-initiated atmospheric photooxidation of the organophosphorus insecticide (C2H5O)3PS

O,O,O-triethyl phosphorothioate ((C₂H₅O)₃PS, TEPT) is a widely used organophosphorus insecticide. TEPT may be released into the atmosphere where it can undergo transport and chemical transformations, which include reactions with OH radicals, NO₃ radicals and O₃. The mechanism of the atmospheric reactions of TEPT has not been fully understood due to the short-lifetime of its oxidized radical intermediates, and the extreme difficulty in detection of these species experimentally. In this work, we carried out molecular orbital theory calculations for the OH radical-initiated atmospheric photooxidation of TEPT. The profile of the potential energy surface was constructed, and the possible channels involved in the reaction are discussed. The theoretical study shows that OH addition to the PS bond and H abstractions from the CH₃CH₂O moiety are energetically favorable reaction pathways. The dominant products TEP and SO₂ arise from the secondary reactions, the reactions of OH-TEPT adducts with O₂. The experimentally uncertain dominant product with molecular weight 170 is mostly due to (C₂H₅O)₂P(S)OH and not (C₂H₅O)₂P(O)SH.