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.

Study of diclofenac removal by the application of combined zero-valent iron and calcium peroxide nanoparticles in groundwater

Diclofenac(DCF)is one of the most frequently detected pharmaceuticals in groundwater,posing a great threat to the environment and human health due to its toxicity.To mitigate the DCF contamination,experiments on DCF degradation by the combined process of zero-valent iron nanoparticles(nZVI)and nano calcium peroxide(nCaO_(2))were performed.A batch experiment was conducted to examine the influence of the adding dosages of both nZVI and nCaO_(2)nanoparticles and pH value on the DCF removal.In the meantime,the continuous-flow experiment was done to explore the sustainability of the DCF degradation by jointly adding nZVI/nCaO_(2)nanoparticles in the reaction system.The results show that the nZVI/nCaO_(2)can effectively remove the DCF in the batch test with only 0.05 g/L nZVI and 0.2 g/L nCaO_(2)added,resulting in a removal rate of greater than 90%in a 2-hour reaction with an initial pH of 5.The degradation rate of DCF was positively correlated with the dosage of nCaO_(2),and negatively correlated with both nZVI dosage and the initial pH value.The order of significance of the three factors is identified as pH value>nZVI dosage>nCaO_(2)dosage.In the continuous-flow reaction system,the DCF removal rates remained above 75%within 150 minutes at the pH of 5,with the applied dosages of 0.5 g/L for nZVI and 1.0 g/L for nCaO_(2).These results provide a theoretical basis for the nZVI/nCaO_(2)application to remove DCF in groundwater.

Carbon dioxide catalytic conversion to nano carbon material on the iron–nickel catalysts using CVD-IP method

The over-consumption of fossil fuels resulted in the large quantity emission of carbon dioxide （CO2）, which was the main reason for the climate change and more extreme weathers. Hence, it is extremely pressing to ex- plore efficient and sustainable approaches for the carbon-neutral pathway of CO2 utilization and recycling. In our recent works with this context, we developed successfully a novel ＂chemical vapor deposition integrated process （CVD-IP）＂ technology to converting robustly CO2 into the value-added solid-form carbon materials, The monometallic FeNi0-Al2O3 （FNi0） and bimetallic FeNix-Al2O3 （FNi2, FNi4, FNi8 and FNi20） samples were synthesized and effective for this new approach. The catalyst labeled FNi8 gave the better performance, exhibited the single pass solid carbon yield of 30%. These results illustrated alternative promising cases for the CO2 capture utilization storage （CCUS）, by means of the CO2 catalytic conversion into the solid-form nano carbon materials.

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.

Effects of different types of biochar on the properties and reactivity of nano zero-valent iron in soil remediation

The addition of nano zero-valent iron(nZVI)is a promising technology for the in situ remediation of soil.Unfortunately,the mobility and,consequently,the reactivity of nZVI particles in contaminated areas decrease due to their rapid aggregation.In this study,we determined how nZVI particles can be stabilized using different types of biochar(BC)as a support(BC@nZVI).In addition,we investigated the transport behavior of the synthesized BC@nZVI particles in a column filled with porous media and their effectiveness in the removal of BDE209(decabromodiphenyl ether)from soil.The characterization results of N2 Brunauer-Emmett-Teller(BET)surface area analyses,scanning electron microscopy(SEM),X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FTIR)indicated that nZVI was successfully loaded into the BC.The sedimentation test results and the experimental breakthrough curves indicated that all of the BC@nZVI composites manifested better stability and mobility than did the bare-nZVI particles,and the transport capacity of the particles increased with increasing flow velocity and porous medium size.Furthermore,the maximum concentrations of the column effluent for bagasse-BC@nZVI(B-BC@nZVI)were 19%,37%and 48%higher than those for rice straw-BC@nZVI(R-BC@nZVI),wood chips-BC@nZVI(W-BC@nZVI)and corn stalks-BC@nZVI(C-BC@nZVI),respectively.A similar order was found for the removal and debromination efficiency of decabromodiphenyl ether(BDE209)by the aforementioned particles.Overall,the attachment of nZVI particles to BC significantly increased the reactivity,stability and mobility of B-BC@nZVI yielded,and nZVI the best performance.

Immobilization and transformation of co-existing arsenic and antimony in highly contaminated sediment by nano zero-valent iron

Arsenic(As)and antimony(Sb)are usually coexistent in mine wastes and pose a great threat to human health.The As immobilization by nano zero-valent iron(n ZVI)is promising,however,the stabilization for co-occurring As and Sb is not known.Herein,the immobilization and transformation of As and Sb in n ZVI-treated sediments were evaluated using complementary leaching experiments and characterization techniques.Raw sediment samples from a gold-antimony deposit revealed the co-existence of ultrahigh As and Sb at 50.3 and 14.9 g/kg,respectively.Leaching results show that As was more efficiently stabilized by n ZVI than Sb,which was primarily due to the soluble fraction that was readily absorbed by n ZVI of As was higher.As the n ZVI treatment proceeds,the oxidation and reduction of As and Sb occur simultaneously as evidenced by XPS analysis.The primary oxidant,hydroxyl radicals,was detected by EPR studies,proving the occurrence of n ZVI induced Fenton reaction.This study sheds light on differences in the interaction and immobilization of n ZVI with Sb and As in co-contaminated sediments.

Zero-valent manganese nanoparticles coupled with different strong oxidants for thallium removal from wastewater

Nano zero-valent manganese(nZVMn,Mn^0)was prepared through a borohydride reduction method and coupled with different oxidants(persulfate(S2O8^2-),hypochlorite(CIO^-),or hydrogen peroxide(H2O2))to remove thallium(TI)from wastewater.The surface of Mn°was readily oxidized to form a core-shell composite(MnOx@Mn°),which consists of Mn°as the inner core and MnOr(MnO,M112O3,and Mn3O4)as the outer layer.When Mn^0 was added alone,effective T1(I)removal was achieved at high pH levels(>12).The Mn-H2O2 system was only effective in T1(I)removal at high pH(>12),while the Mn^0-S2O8^0or Mn0-ClO^-system had excellent T1(I)removal(>96%)over a broad pH range(4-12).The Mn-S2O8 oxidation system provided the best resistance to interference from an external organic matrix.The isotherm of T1(I)removal through the Mn°-S2O8^2-system followed the Freundlich model.The Mn°nanomaterials can activate persulfate to produce sulfate radicals and hydroxyl radicals.Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy suggested that oxidation-induced precipitation,surface adsorption,and electrostatic attraction are the main mechanisms for T1(I)removal resulting from the combination of Mn^0 and oxidants.Mn^0coupled with S2O8^2-/ClO^-is a novel and effective technique for T1(I)removal,and its application in other fields is worthy of further investigation.

降雨条件下纳米零价铁镍对污染土壤中六价铬迁移的影响

通过模拟降雨进行土柱淋溶实验来研究降雨条件下纳米零价铁镍(nZVI/Ni)对污染土壤六价铬迁移的影响,并测定淋溶液的Cr(Ⅵ)浓度、pH、电导率和累积释放量.使用改进BCR连续提取法测定淋溶后各层土壤的铬形态分布,分析施加nZVI/Ni对土壤中铬形态的影响.结果表明,降雨条件下六价铬的释放过程主要分为快速和慢速释放两个阶段.随着淋溶体积的增加,土壤淋溶液的pH逐渐升高后最后趋于平稳,电导率和Cr(Ⅵ)浓度迅速下降后趋于平稳.模拟降雨条件下,土壤中投加nZVI/Ni显著降低了淋溶液中Cr(Ⅵ)的累积释放量.投加0.10%nZVI/Ni土壤淋溶液的Cr(VI)累积释放量低于空白对照57.53%.在nZVI/Ni投加量相同时,模拟降雨的pH值越低nZVI/Ni的修复效果越好;降雨的淋溶次数对修复效果基本无影响;采用均匀混合的方式投加nZVI/Ni有着更好的修复效果.在土壤中nZVI/Ni对Cr(Ⅵ)修复过程中,纳米铁材料起主要作用,Fe(Ⅱ)的贡献很小.土壤经nZVI/Ni修复后,可还原态铬含量减少,可氧化态铬含量增加,表明纳米零价铁镍可以降低土壤中铬的迁移性,降雨条件下对六价铬污染土壤具有一定的修复效果.

改性纳米铁镍去除水中2,4-DCP的研究

采用Pluronic F-127改性纳米零价铁后负载镍,形成改性纳米铁镍(F-NZVI/Ni)。探讨了Ni的负载量、F-NZVI/Ni的投加量、2,4-DCP初始浓度、pH及反应温度对2,4-DCP去除率的影响。同时探究了F-NZVI/Ni去除2,4-DCP的最佳条件下F-NZVI/Ni去除2,4-DCP的反应过程。结果表明,F-NZVI/Ni去除2,4-DCP的能力优于NZVI,当F-NZVI/Ni投加量为3 g/L,镍负载率为5%,2,4-DCP初始浓度为20 mg/L,反应温度为35℃,初始pH值为7时,2,4-DCP的去除率为97%。F-NZVI/Ni去除2,4-DCP主要是先吸附,然后在镍催化剂作用下将2,4-DCP降解为苯酚。

nZVI-Ni/MCM-41活化过硫酸盐降解左氧氟沙星

采用液相还原法将纳米零价铁镍(nZVI-Ni)双金属材料负载于介孔材料MCM-41上,制备成复合催化剂nZVI-Ni/MCM-41,采用TEM、XRD和XPS等方法对所制备的样品进行了表征。以左氧氟沙星(LOF)为目标污染物,考察了nZVI-Ni/MCM-41活化过硫酸盐(PS)降解LOF的效果。结果表明,在LOF质量浓度为50 mg/L、nZVI-Ni/MCM-41投加量为1.0 g/L、PS投加量为0.10 g/L、铁镍摩尔比为10∶1、pH=7.3的条件下,LOF去除率达93.14%。自由基猝灭实验表明,反应过程中同时存在SO_(4)^(-)·和·OH,·OH是主要活性物种,且同时存在自由基路径和非自由基路径。

Production of metallic iron nanoparticles in a baffled stirred tank reactor: Optimization via computational fluid dynamics simulation

The aim of this work is to optimize iron nanoparticle production in stirred tank reactors equipped with two classical impellers:Rushton and four-pitched blade turbines,which are largely used in batch industrial synthesis and efficient scale-up.The main operative parameters of nanoparticle synthesis are the precursor initial concentration,reducing agent/precursor molar ratio,impeller-tank clearance,and impeller rotational velocity.These parameters were varied during the synthesis to find the optimal operating values based on the Fe(0)(%)production,zeta potential,particle size distribution,and powder X-ray diffraction pattern obtained.We found that the optimal operating conditions for nanoparticle production were an impeller velocity of 1500 rpm,initial iron precursor concentration of 20 mM,molar ratio of reducing agent to iron precursor of 3 mol/mol,and impeller clearance of 0.25 and 0.4 times the vessel diameter for Rushton and four-pitched blade impellers,respectively.Setting these conditions achieved a total conversion of 0.94-0.98 and yielded a product with a unimodal size distribution and average diameters in the range 30-50 nm.The computational fluid dynamics results agreed with the expectations,and the obtained mixing Damkohler numbers show that the process is mixed controlled.

A highly porous animal bone-derived char with a superiority of promoting nZVI for Cr(Ⅵ)sequestration in agricultural soils

Paddy soil and irrigation water are commonly contaminated with hexavalent chromium[Cr(Ⅵ)]near urban industrial areas,thereby threatening the safety of agricultural products and human health.In this study,we develop a porous and high specific area bone char(BC)to support nanoscale zero-valent iron(n ZVI)and apply it to remediate Cr(Ⅵ)pollution in water and paddy soil under anaerobic conditions.The batch experiments reveal that BC/n ZVI exhibits a higher removal capacity of 516.7 mg/(g·n ZVI)for Cr(Ⅵ)than n ZVI when normalized to the actual n ZVI content,which is 2.8 times that of n ZVI;moreover,the highest n ZVI utilization is the n ZVI loading of 15%(BC/n ZVI15).The Cr(Ⅵ)removal efficiency of BC/n ZVI15 decreases with increasing p H(4–10).Coexisting ions(phosphate and carbonate)and humic acid can inhibit the removal of Cr(Ⅵ)with BC/n ZVI15.Additionally,BC exhibits a strong advantage in promoting Cr(Ⅵ)removal by n ZVI compared to the widely used biochar and activated carbon.Our results demonstrate that reduction and coprecipitation are the dominant Cr(Ⅵ)removal mechanisms.Furthermore,BC/n ZVI15 shows a significantly higher reduction and removal efficiency as well as a strong anti-interference ability for Cr(Ⅵ)in paddy soil,as compared to n ZVI.These findings provide a new effective material for remediating Cr(Ⅵ)pollution from water and soil.