Synthesis of clay-supported nanoscale zero-valent iron using green tea extract for the removal of phosphorus from aqueous solutions

This study addresses the synthesis of nanoscale zero-valent iron(n ZVI) in the presence of natural bentonite(B-n ZVI) using green tea extract. The natural bentonite and B-n ZVI were then applied for the removal of phosphorus from aqueous solutions at various concentrations, p H levels and contact time. The desorption of phosphorus(P) from adsorbents was done immediately after sorption at the maximum initial concentration using the successive dilution method. The characterization of FTIR, SEM, and XRD indicated that n ZVI was successfully loaded to the surface of natural bentonite. The sorption of phosphorus on B-n ZVI was observed to be p H-dependent, with maximum phosphorus removal occurring at the p H range of 2 to 5. The results demonstrate that the maximum sorption capacities of natural bentonite and B-n ZVI were 4.61 and 27.63 mg·g^(-1), respectively.Langmuir, Freundlich, and Redlich–Peterson models properly described the sorption isotherm data. For either adsorbent, desorption isotherms did not coincide with their corresponding sorption isotherms, suggesting the occurrence of irreversibility and hysteresis. The average percentages of retained phosphorus released from natural bentonite and B-n ZVI were 80% and 9%, respectively. The results indicated that sorption kinetics was best described by the pseudo-second-order model. The present study suggests that B-n ZVI could be used as a suitable adsorbent for the removal of phosphorus from aqueous solutions.

Eco friendly adsorbents for removal of phenol from aqueous solution employing nanoparticle zero-valent iron synthesized from modified green tea bio-waste and supported on silty clay

The present research investigated a novel route for the synthesis of nanoparticle zero-valent iron(NZVI)utilizing an aqueous extract of green tea waste as a reductant with ferric chloride.Also,the supported nanoparticle zerovalent iron was synthesized using natural silty clay as a support material(SC-NZVI).The NZVI and SC-NZVI were characterized by infrared spectroscopy(FTIR),scanning electron microscope(SEM),X-ray diffraction(XRD),Brunauer–Emmett–Teller(BET),and zeta potential(ζ).The interpretation of the results demonstrated that the polyphenol and other antioxidants in green tea waste can be used as reduction and capping agents in NZVI synthesis,with silty clay an adequate support.Additionally,the experiments were carried out to explore phenol adsorption by NZVI and SC-NZVI.To determine the optimum conditions,the impact of diverse experimental factors(i.e.,initial pH,adsorbent dose,temperature,and concentration of phenol)was studied.Langmuir,Freundlich,and Tempkin isotherms were used as representatives of adsorption equilibrium.The obtained results indicated that the adsorption processes for both NZVI and SC-NZVI well fitted by the Freundlich isotherm model.The appropriateness of pseudofirstorder and pseudosecondorder kinetics was investigated.The experimental kinetics data were good explained by the second-order model.The thermodynamic parameters(ΔH0,ΔS0,andΔG0)for NZVI and SC-NZVI were determined.The maximum removal rates of phenol at optimum conditions,when adsorbed onto NZVI and SC-NZVI,were found to be 94.8%and 90.1%,respectively.

Synthesis of nanoscale zero-valent iron supported on exfoliated graphite for removal of nitrate

Nano ZVI particles supported on micro-scale exfoliated graphite were prepared by using KBH4 as reducing agent in the H2O/ethanol system. The supported ZVI materials generally have higher activity and greater flexibility for environmental remediation applications. The exfoliated graphite as the support was treated beforehand to hydrophilic material. Nano iron particles are deposited onto the rough graphite surface while those were formed by borohydride reduction. The possible nitrate reduction pathways were proposed. The TEM image shows that iron particles are highly dispersed on the surface of graphite and several of iron particles are imbedded in the pit of support surface. In this synthesis, iron particles have a nearly spherical shape with a grain size of 50?100 nm. The surface areas of materials with different iron loadings of 3.5%, 7.0%, 10.0%, 15.0% and 20.0%(mass fraction) are 2.89, 9.55, 8.45, 23.8 and 6.18 m2·g?1 by BET surface analyzer. The chemical reduction of nitrate by supported nano ZVI in aqueous solution were tested in series batch experiments. Experiment results suggest that NO3? can be more rapidly reduced to NH4+ at neutral pH and anaerobic conditions by supported nano ZVI than unsupported nano ZVI or ZVI scraps. The 15% nano Fe/graphite shows the best reduction efficiency contrasted with other Fe loading particles.

Fischer-Tropsch synthesis by nano-structured iron catalyst

Effects of nanoscale iron oxide particles on textural structure,reduction,carburization and catalytic behavior of precipitated iron catalyst in Fischer-Tropsch synthesis（FTS） are investigated.Nanostructured iron catalysts were prepared by microemulsion method in two series.Firstly,Fe2O3 ,CuO and La2O3 nanoparticles were prepared separately and were mixed to attain Fe/Cu/La nanostructured catalyst（sep-nano catalyst）;Secondly nanostructured catalyst was prepared by co-precipitation in a water-in-oil microemulsion method（mix-nano catalyst）.Also,conventional iron catalyst was prepared with common co-precipitation method.Structural characterizations of the catalysts were performed by TEM,XRD,H2 and CO-TPR tests.Particle size of iron oxides for sep-nano and mix-nano catalysts,which were determined by XRD pattern（Scherrer equation） and TEM images was about 20 and 21.6 nm,respectively.Catalyst evaluation was conducted in a fixed-bed stainless steel reactor and compared with conventional iron catalyst.The results revealed that FTS reaction increased while WGS reaction and olefin/paraffin ratio decreased in nanostructured iron catalysts.

Nano-Phytotechnological Remediation of Endosulfan Using Zero Valent Iron Nanoparticles

Endosulfan, an organochlorine pesticide, is known for its toxicity and ability to accumulate in the environment. In India endosulfan was banned only in 2011 and hence toxic residues are still persistent in the environment. The abilities of three plant species Chittaratha (Alpinia calcarata), Tulsi (Ocimum sanctum), and Lemongrass (Cymbopogon citratus) to remove endosulfan from soil in the absence and presence of zerovalent iron nanoparticles (nZVIs) (1000 mg/Kg of soil), i.e., by phytoremediation and nano-phytoremediation, were determined. Extracted soil samples from the experimental plot were analyzed using Gas Chromatograph with Electron Capture Detector (GC-ECD) and final dehalogenated product was confirmed by Mass Spectrometer (MS). A. calcarata had the best efficiency compared to the other two plant species and the efficiency decreased in the order A. calcarata > O. sanctum> C. citrates. The initial endosulfan removal rate was high (82% was removed within 7 days) when nano phytoremediation experiments were conducted with A. calcarata but then gradually decreased, probably because the activity of nZVI decreased over time. The nZVI endosulfan degradation mechanism appears to involve hydrogenolysis and sequential dehalogenation which was confirmed by GC-MS analysis. Only small amounts of endosulfan were accumulated in the plants because the added nZVIs might have promoted the reductive dechlorination of endosulfan.

Factors Affecting the Reductive Properties of the Core-Shell SiO2-Coated Iron Nanoparticles

In this study, novel core-shell SiO2-coated iron nanoparticles (SiO2-nZVI) were synthesized using a one-step Stoeber method. The Malachite green degradation abilities of the nanoparticles were investigated. The effects of ethanol/distilled water volume ratio, presence and absence of PEG, tetraethyl orthosilicate (TEOS) dosage, and hydrolysis time used in the nanoparticles preparation process were investigated. The results indicated that the SiO2-coated iron nanoparticles had the highest reduction activity when the particles synthesized with ethanol/H2O ratio of 2:1, PEG of 0.15 ml, TEOS of 0.5 ml and the reaction time was 4 h. The SiO2-nZVI nanoparticles were characterized using Transmission Electron Microscopy (TEM), Energy Dispersive Spectrometry (EDS) and powder X-Ray Diffraction (XRD). The results showed that the average particles diameter of the SiO2-nZVI was 20 - 30 nm. The thickness of the outside SiO2 film is consistent and approximately 10 nm. The results indicated that the nanoparticles coated completely with a transparent SiO2-film. Such nanoparticles could have wide applications in dye decolorization.

Pulsed Electrochemical Deposited Nano-Iron for Water Treatment

The application of nanotechnology in drinking water treatment and pollution cleanup is promising, as demonstrated by a number of field-based (pilot and full scale) and bench scale studies. In recent years, the use of zero-valent iron (ZVI) for the treatment of toxic contaminants in groundwater and wastewater has received wide attention and encouraging treatment efficiencies have been documented. In this review, nanoscale iron was prepared by pulse electrodeposition of nano iron by chemical reduction of iron chloride and iron sulfate. Our research focuses on iron nanoparticles preparation and its use for aqueous Cr(VI) reduction. The Cr(VI) reduction by the nFe0 prepared by electrochemical and blasting method at neutral pH were carried. The results show that blasting-nFe0 show lower reaction than the electrochemical-nFe0. It is because the blasting-nFe0 surface contains more Fe2O3 than the other one.

Deactivation studies of nano-structured iron catalyst in Fischer-Tropsch synthesis

A nano-structured iron catalyst for syngas conversion to hydrocarbons in Fischer-Tropsch synthesis（FTS） was prepared by micro-emulsion method.Compositions of bulk iron phase and phase transformations of carbonaceous species during catalyst deactivation in FTS reaction were characterized by temperature-programmed surface reaction with hydrogen（TPSR-H 2 ）,and XRD techniques.Many carbonaceous species on surface and bulk of the nano-structured iron catalysts were completely identified by combined TPSR-H 2 and XRD spectra and which were compared with those recorded on conventional co-precipitated iron catalyst.The results reveal that the catalyst deactivation results from the formation of inactive carbide phases and surface carbonaceous species like graphite,and it will be increased when the particle size of iron oxides was reduced in FTS iron catalyst.

Remediation of Malathion Contaminated Soil Using Zero Valent Iron Nano-Particles

In this study, iron nano-particles were used to remediate malathion contaminated soil in the concentration range of 1 - 10 μg?g–1. The zero valent iron nano-particles were prepared by reducing ferric chloride solution with sodium boro- hydride for remediation of the soil. The optimized quantity of iron nano particles was found to be 0.1 g?kg–1 of soil con- taminated with 10 μg?g–1 of malathion. Malathion was determined in the soil after leaching to water at pH 8.2 and fol- lowed by its oxidation with slight excess of N-bromosuccinimide (NBS). The unconsumed NBS was estimated by measuring the decrease in the color intensity of rhodamine B. Degradation product formed during the oxidation of ma-lathion by zero valent iron was monitored by the Attenuated Total Reflectance Fourier Transform Infrared Spectros- copy (ATR-FTIR). The results clearly showed that quantitative oxidation of malathion was achieved within eight min- utes after the addition of zero valent iron nano particles.

Removing Iron Ions Contaminants from Groundwater Using Modified Nano-Hydroxyapatite by Nano Manganese Oxide

In this article, we study modified nano-hydroxyapatite (HAp) by nano manganese oxide (Mn3O4) as adsorbent material to remove iron ions from groundwater. Different parameters were studied to option optimum conditions of removing such as contact time, pH, initial concentration, a dosage of adsorbent, agitation speed and temperature. Kinetics studies included first order (R2 = 0.915), pseudo-first order (R2 = 0.936), second order (R2 = 0.948), pseudo-second order (R2 = 0.995), Elovich equation model (R2 = 0.977), intraparticle diffusion (R2 = 0.946), Natarajan and Khalaf (R2 = 0.915) were carried out, the obtained results revealed that the pseudo-second order is the best to describe the adsorption process because the correlation coefficient is approaching one (R2 = 0.995). Adsorption isotherm was calculated by using Freundlich, Langmuir and Temkin constants, adsorption capacity from Langmuir model was 0.606 mg/g. Thermodynamic parameters (ΔG, ΔH = ?51 KJ/mol, and ΔS = ?142 (KJ/mol)) for the adsorption process were also calculated and discussed.

铁基双金属催化剂活化过硫酸单盐(PMS)去除诺氟沙星性能研究

采用过渡金属Cu、Co和Mn对纳米零价铁(nZVI)掺杂改性,制备铁基双金属nZVI/Cu、nZVI/Co和nZVI/Mn催化剂,用于活化过氧单硫酸盐(PMS),研究了不同过渡金属、催化体系和过渡金属掺杂量对催化降解诺氟沙星(NOR)性能的影响。结果表明,当Co的掺杂量为5%时,nZVI/Co-5%/PMS活化体系在120 min内实现了84.4%的NOR去除。优异的活化降解性能主要得益于过渡金属Co的引入抑制了nZVI的钝化和团聚。

活性炭负载纳米零价铁/银复合材料对水中铅的吸附性能研究

通过液相还原法,将纳米零价铁(nZVI)和纳米银(nAg)负载到活性炭(AC)上,制备出一种新型复合材料(nAg/nZVI/AC),用于处理含铅废水。结果表明,在pH=7条件下,nAg/nZVI/AC对Pb(Ⅱ)的去除率达到99.7%,比原AC提高了74.28%。同时,银的加入提高了nZVI的反应活性,使吸附更快达到平衡。吸附过程与Langmuir模型(R2为0.972)和准二级动力学模型(R2为0.9219)更吻合。结合热力学分析结果,Pb(Ⅱ)的去除是一个以化学吸附为主的自发过程。

纳米零价铁复合材料对污染土壤修复的最新进展

土壤污染严重威胁农产品的安全和人类健康。近几年来纳米零价铁(nZVI)复合材料由于环境友好、易于制备、价格低廉、优异化学活性等特点广泛地应用于污染土壤修复,但是对土壤中不同污染类型修复的调研较少。综述主要调研nZVI复合材料修复污染土壤中重金属、有机污染物和石油有机物的最新进展。重点评述nZVI复合材料的不同性质对污染土壤中各种污染物修复效果的影响,最后对n ZVI铁复合材料修复污染土壤得出结论并对未来方向进行展望。该综述为更好地应用nZVI复合材料对污染土壤的修复提供理论依据和指导。

喷施纳米铁和纳米锌叶面肥对冬枣叶片及果实品质的影响

以七年生冬枣为试材,在果实发育期喷施不同浓度T1(2.5 mL·L^(-1))、T2(5.0 mL·L^(-1))、T3(10.0 mL·L^(-1))、T4(15.0 mL·L^(-1))的纳米铁和纳米锌混合液进行叶面施肥,以喷施清水作为对照,研究了纳米铁和纳米锌混合液对冬枣叶片及果实品质的影响,以期筛选出促进冬枣品质提升适宜的纳米铁和纳米锌混合液施用浓度。结果表明:叶面喷施10.0 mL·L^(-1)的纳米铁锌叶面肥显著改善了冬枣的果实品质,提高了单果质量、果实硬度、可溶性固形物含量、维生素C含量以及固酸比,降低了可滴定酸含量;提高了冬枣叶片的光合色素含量和光合作用;喷施浓度为15.0 mL·L^(-1)的纳米铁锌叶面肥对冬枣叶片及果实中的铁锌元素含量效果最佳。因此,叶面喷施纳米铁锌叶面肥能促进冬枣叶片铁和锌元素的积累,提高光合色素含量,促进光合作用,改善果实品质。

生物炭改性及其对除草剂污染水体和土壤修复的研究进展

除草剂已被大量使用于现代农业生产,而长期使用除草剂可能造成其在土壤中大量残留,或通过降水、淋溶和径流污染水体,因此引发环境污染问题和食品安全问题。生物炭作为一种绿色、高效的吸附剂已被广泛用于修复有机物污染水体和土壤。本文介绍了酸碱、有机物和金属盐浸渍改性,纳米零价铁和微生物负载改性等生物炭改性方法;综述了改性生物炭在除草剂污染修复中的应用情况,对比分析了生物炭改性前后的修复效果;探讨了改性生物炭自身特性、环境条件对改性生物炭修复除草剂污染的影响及机制。未来仍需对改性生物炭在除草剂污染修复过程中的稳定性、长效性和安全性等方面开展研究。

生物炭负载纳米零价铁对地下水中六价铬的修复效果和影响因素研究

纳米零价铁(nZVI)存在易团聚、钝化和迁移性差等问题,影响对六价铬[Cr(Ⅵ)]污染地下水的原位修复效果。为了开发一种低成本、绿色的nZVI改性材料,以球磨生物炭(BC)为载体负载nZVI,构建了nZVI@BC反应体系,再利用羧甲基纤维素(CMC)稳定nZVI@BC,合成了一种新型高效、抗钝化纳米级别的修复材料CMC-nZVI@BC。对改性前后的nZVI进行表征分析,探究了材料添加量、Cr(Ⅵ)初始质量浓度、初始pH值、温度及地下水化学组分对CMC-nZVI@BC去除Cr(Ⅵ)的影响,并阐明去除Cr(Ⅵ)的机理。得出如下结论:(1)铁碳质量比为2∶1时的nZVI@BC对Cr(Ⅵ)的去除效果最好,3 h内0.6 g/L CMC-nZVI@BC对50 mg/L Cr(Ⅵ)的去除率达99.9%,表现出较高的去除Cr(Ⅵ)的速率和能力;(2)去除Cr(Ⅵ)的主要机制是通过还原和沉淀反应;(3)在pH值2~10范围内,pH值对去除Cr(Ⅵ)有显著影响,温度影响较小;(4)SO_(2-)_(4)的存在促进了Cr(Ⅵ)的去除,而HCO^(-)_(3)、 NO^(-)_(3)、Ca^(2+)、Mg^(2+)和腐殖酸对Cr(Ⅵ)的去除均有不同程度的抑制作用。这些结果表明,CMC-nZVI@BC可以作为有效去除Cr(Ⅵ)的原位修复药剂,为nZVI在地下水原位修复的应用提供了依据。

融合石膏组分和微纳米结构“双基因”调控的铁尾矿粉无熟料固结体力学性能

为了探究超细铁尾矿粉颗粒表面非晶态SiO_(2)和Al_(2)O_(3)在石灰-石膏体系中的水化固化机理及调控因素,本工作考察了石膏掺量和铁尾矿粉中微纳米级颗粒含量之间的匹配对固结体强度的影响,利用XRD、TG-DSC、SEM和化学滴定法测试分析了固结体试样中水化产物的种类、形貌及含量的变化,研究了这些变化对固结体强度的影响及作用机理。结果表明,超细铁尾矿粉中小于1.096μm的微纳米颗粒含量显著影响着铁尾矿粉在碱溶液中Si和Al元素的溶出行为,固结体强度随着这些微纳米颗粒含量的增加而提高。固结体中的主要水化产物是铝掺杂的水化硅酸钙(C-(A)-S-H)和钙矾石(AFt)。石膏掺量与铁尾矿粉中微纳米颗粒含量的最佳匹配值对固结体的强度具有显著影响,并且微纳米颗粒含量越高,对应的石膏最佳掺量越大。石膏组分保证了AFt的生成和稳定,同时也加速了铁尾矿粉颗粒表面非晶态成分的水化。本工作探明了固结材料中最佳石膏掺量与微纳米铁尾矿粉颗粒含量的关联关系及其机理,证实了微纳米级颗粒是无熟料固结体结构中的基本活性单元,石膏的掺入对微纳米颗粒的水化起到调控作用,水化后的微纳米颗粒演变为固结体的基本结构单元,这种组分和结构的“双基因”调控机制影响着固结体的力学性能。

纳米铁改性生物炭载体强化厌氧氨氧化菌富集与脱氮效果研究

为实现厌氧氨氧化菌(AnAOB)在载体生物膜中快速富集,本文采用液相还原方法制备了纳米铁改性生物炭(nZVI@BC)载体,并设置两组相同的厌氧氨氧化(ANAMMOX)富集装置(R_(1)、R_(2)),通过对R_(1)、R_(2)装置添加不同载体(分别为BC和nZVI@BC),考察在富集过程中ANAMMOX装置的脱氮性能、载体表面特征和微生物群落结构差异.结果表明:①BC表面成功负载nZVI,nZVI@BC载体比BC载体具有更高的比表面积,改性后载体的比表面积从47.17 m^(2)/g增至210.82 m^(2)/g,可为微生物提供更多的附着位点.②R_(2)装置NH_(4)^(+)-N和NO_(2)^(−)-N去除率稳定达到90%所需时间均比R_(1)装置短,且稳定运行后,R_(1)、R_(2)装置的TN去除率最高分别为86.99%、89.65%.③nZVI@BC载体表面颜色由黑色变为红褐色,表明红色的ANAMMOX生物膜初步形成,且其表面生物量比BC载体表面生物量高23倍.④第20天,R_(1)、R_(2)装置中AnAOB的相对丰度分别为10.47%和29.15%;R_(1)、R_(2)装置载体表面主要的AnAOB属均为Candidatus Kuenenia,其相对丰度分别为7.49%和23.76%.研究显示,改性的nZVI@BC载体显著促进了ANAMMOX生物膜的快速形成和AnAOB的高效富集,提升了ANAMMOX过程的脱氮性能.

纳米零价铁对武威产区黑比诺葡萄新梢和叶片生长及光合特性的影响

【目的】探究叶面喷施不同浓度的纳米零价铁肥对河西走廊武威产区黑比诺葡萄植株光合特性及生长发育的影响。【方法】以甘肃武威市依诺酒庄的黑比诺酿酒葡萄为材料,设置5个不同质量浓度纳米零价铁肥喷施处理T1(5 mg·L^(-1))、T2(10 mg·L^(-1))、T3(15 mg·L^(-1))、T4(20 mg·L^(-1))、T5(25 mg·L^(-1))和1个清水喷施作为对照(CK),喷施时间6月18日开始,每隔15 d喷一次,共5次,每个处理选取长势良好、整齐一致的葡萄树植株54株,试验设3次重复,测定其叶片SPAD值、叶面积、新梢长度和粗度、叶片荧光参数等指标。【结果】喷施不同浓度的纳米零价铁对葡萄植株新梢基部粗度、节间长度、叶绿素相对含量以及叶面积均具有促进作用。此外,处理较CK相比,叶片光合作用和光能吸收与传递作用明显增加,且能不同程度地增加葡萄叶片的SPAD值,且以T5(25 mg·L^(-1))处理最佳;各处理叶片初始荧光(F0)随着纳米零价铁肥喷施呈现出先降低后升高的趋势;其次,叶面喷施不同浓度纳米零价铁肥可不同程度地提高叶片实际光化学效率(花后60~90 d)、光化学淬灭系数(花后30~45 d)、电子传递速率(花后60~90 d)、净光合速率(花后45~90 d)和气孔导度,说明叶面喷施纳米零价铁肥可增强黑比诺酿酒葡萄的光合活性,提高其叶片PSⅡ光能转化效率和光能利用率,降低通过非光化学途径的能量耗散,最终增加积累的光合产物。【结论】喷施适宜浓度的纳米零价铁肥能显著提升植株叶片光合荧光参数、叶绿素相对含量、新梢基部粗度、节间长度等,对净光合速率、蒸腾速率有促进作用,以25 mg·L(-1 T5)质量浓度处理效果最佳。

生物炭负载纳米零价铁催化降解亚甲基蓝性能研究及机理分析

为提升纳米零价铁在类芬顿反应体系中的催化能力,减少团聚现象,采用液相还原法制备了生物炭负载纳米零价铁材料(nZVI@BC)。通过表征、亚甲基蓝降解实验,探究材料性能、降解最佳条件及作用机理。结果表明,纳米零价铁(nZVI)均匀分布于生物炭表面,且材料纯度较高、稳定性较好。在降解实验中,降解100 mg·L^(-1)亚甲基蓝溶液的最佳反应条件为25℃、初始pH=3、nZVI@BC投加量30 mg·L^(-1)、H2O2投加浓度4 mmol·L^(-1),10 min内几乎完全降解。在降解过程中,·OH起主要作用,发色官能团首先断裂,随后芳环结构被破坏,最终彻底降解。且nZVI@BC循环使用性能较好,3次循环后亚甲基蓝去除率仍达85%以上。在印染废水处理实验中,nZVI@BC处理效果良好,当H2O2投加浓度为0.9 mmol·L^(-1)、nZVI@BC投加量为60 mg·L^(-1)、pH≤4.5时,出水化学需氧量(CODcr)可降至50 mg·L^(-1)以下,达到回用水标准。