Chromium (VI) removal from water using starch coated nanoscale zerovalent iron particles supported on activated carbon

Starch coated nanoscale zerovalent iron (S-nZVI) was immobilized in activated carbon (AC) and its Cr (VI) removal characteristics were studied. Macroscopic evidence and mechanism analysis proved that S-nZVI and AC were closely linked and mutual complementary. Different factors including pH of the original solution, reaction time, and mass ratio (S-nZVI@AC/Cr =10:1, 20:1, 30:1, 50:1, 60:1, 70:1) were studied to analyze the removal rate. Results showed that the removal rate of Cr (Ⅵ) could reach 99.96% under the condition of pH of 5, and temperature =25?°C, when the mass ratio of S-nZVI@AC/Cr was 60:1. The removal of Cr(Ⅵ) by S-nZVI@AC followed pseudo-second-order kinetics. X-ray diffraction (XRD) resulted demonstrate that S-nZVI@AC existed in a Fe₃C state before reaction and in a Fe(III) state after reaction. XPS (X-ray photoelectrons spectroscopy) analysis suggested that the mechanism of Cr (VI) removal by S-nZVI@AC is adsorption and reduction. S-nZVI@AC might be a potential composite material for the purification and detoxification of Cr (VI) in water because of its efficiency and stability.     

电镀废水中铬(VI)分析的研究进展

综述了近5年来电镀废水中铬(VI)的分析测定方法,主要包括分光光度法、催化光度法、荧光光度法、原子吸收法、电化学法、化学传感器法、化学发光法及共振光散射法等。     

Electrospinning of polyacrylonitrile nanofibers embedded with zerovalent iron and cerium oxide nanoparticles,as Cr(VI) adsorbents for water treatment

Zerovalent iron (ZVI) and cerium oxide (CeO₂) nanoparticles (NPs) embedded in polyacrylonitrile nanofibers (NFs) were obtained via electrospinning. Each NF was characterized using Fourier transform infrared spectroscopy and X-ray diffraction. The scaffold morphology and average diameter of the NFs were determined using scanning electron microscopy (SEM). Energy dispersive X-ray spectroscopy (EDS) mapping and Raman spectroscopy were used to characterize the NPs dispersion in the NFs. The Cr(VI) removal efficiency (%E) of ZVI and CeO₂ NPs was compared with the efficiency of their corresponding NFs. CeO₂ NPs showed 79% Cr(VI) removal; the efficiency was better for their NFs (96%). Regeneration of ZVI NFs was 98 %E. ZVI NPs were the best adsorbent with 99.9% efficiency. An adsorption mechanism was proposed using Langmuir, Freundlich, and Temkin isotherm models. SEM–EDS analyses revealed that Cr adsorbed on the NP and NF surfaces. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48663.     

Removal of Cr(VI) from wastewater by adsorption on iron nanoparticles

Due to rapid industrialisation, the presence of heavy metals in water and wastewater is a matter of environmental concern. Though some of the metals are essential for our system but if present beyond their threshold limit value (TLV), they are harmful and their treatment prior to disposal becomes inevitable. The present communication has been addressed to the removal of Cr(VI) from aqueous solutions by nanoparticles of iron. Nanoparticles of iron were prepared by sol–gel method. The characterisation of the nanoparticles was carried out by XRD and TEM analysis. Batch experiments were adopted for the adsorption of Cr(VI) from its solutions. The effect of different important parameters such as contact time and initial concentration, pH, adsorbent dose, and temperature on removal of chromium was studied. The removal of chromium increased from 88. 5% to 99.05% by decreasing its initial concentration from 15 to 5 mg L^?1 at optimum conditions. Removal of Cr(VI) was found to be highly pH dependent and a maximum removal (100%) was obtained at pH 2.0. The process of removal was governed by first and pseudo‐second‐order kinetic equations and their rate constants were determined. The process of removal was also governed by intraparticle diffusion. Values of the thermodynamic parameters viz. ΔG°, ΔH°, and ΔS° at different temperatures were determined. The data generated in this study can be used to design treatment plants for chromium rich industrial effluents. Adsorption results indicate that nanoiron particles can be effective for the removal of chromium from aqueous solutions.     

Multiwalled CNTs for Cr(VI) removal from industrial wastewater: An advanced study on adsorption,kinetics, thermodynamics for the comparison between the embedded and non‐embedded carboxyl group

The adsorption capabilities of multiwalled carbon nanotubes (MWCNTs) with and without the embedded carboxyl group for the removal of parts per million levels of hexavalent chromium were examined as a function of several parameters, namely contact time, pH of initial solution, initial concentration of Cr(VI), adsorbent dosage as well as temperature of solution. Adsorption isotherms have been utilized to explain the adsorption mechanism. Ion exchange, intra‐particle diffusion, and electrostatic interactions are found to be the fundamental mechanisms describing the adsorption of Cr(VI). The maximum adsorption capacities of Cr(VI) ion by raw MWCNTs and functionalized MWCNTs were found to be 84.75 and 78.13 mg · g^?1, respectively, as calculated by the Langmuir adsorption isotherm model. This is with regard to the electron‐rich atoms inside the functional group which repels the negatively charged dichromate ions. Kinetic studies were performed, and the data was found in good agreement with the pseudo‐second‐order.     

大块液膜技术处理含六价铬废水

以磷酸三丁酯(TBP)为载体,煤油为稀释剂,NaOH为反萃剂,采用大块液膜技术处理含95~100mg/LCr(VI)的模拟废水。考察了液膜相用量、载体体积分数及反萃剂浓度对大块液膜过程中Cr(VI)传质过程的影响。结果表明,大块液膜技术对废水中Cr(VI)的去除效果较好。Cr(VI)迁移速率随TBP体积分数的提高而加快。当反萃剂NaOH浓度大于0.5mol/L时,反萃剂浓度对Cr(VI)传质过程的影响较小。处理后废水中Cr(VI)含量降至0.5mg/L以下,达到国家排放标准。     

零价铁在污水脱氮除磷方面的研究进展

对零价铁的脱氮除磷机理、影响因素,以及与生物法、现有污水处理工艺结合等方面的研究进行了综述。零价铁脱氮的主要作用机理是表面吸附和氧化还原反应,除磷的主要机理是零价铁的表面吸附作用、Fe2+对磷酸根的化学沉淀作用及铁氢氧化物与磷酸根的共沉淀作用。影响脱氮除磷的主要因素有混合强度、酸度、零价铁浓度、初始硝氮(磷)浓度等。零价铁对微生物的除氮除磷过程有协同促进作用,不仅能提高去除速率和效率,并且能够促进产物转化为无害物质。零价铁与现有传统污水处理方式结合在污水处理领域具有广阔前景,这也是未来零价铁应用在污水处理领域的发展方向。     

Facile fabrication of graphene oxide-polyethylenimine composite and its application for the Cr(VI) removal

A binary composite consisting of graphene oxide (GO) and polyethylenimine (PEI) was fabricated by a facile physical mixing. Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscope (FE-SEM), thermo-gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and Zeta potential were used to characterize the prepared graphene oxide-polyethylenimine composite (GOPC). A series of experiments were carried out to investigate the effects of some important parameters, such as molecular weight of PEI, pH, time and temperature, on the adsorption efficiency of GOPC. Due to the high amine density of GOPC, its adsorption for Cr(VI) occurred more easily at lower pH mainly via electrostatic interaction. The adsorption process matched well with the Langmuir isotherm model and the pseudo-second-order kinetic model. The maximum adsorption capacity from the Langmuir model was 370.37 mg/g at pH 2.0 and 45°C for GOPC. Thermodynamic parameters revealed spontaneous and endothermic nature of the Cr(VI) adsorption onto GOPC. The main adsorption mechanism of GOPC toward Cr(VI) was electrostatic interaction. The adsorption-desorption experiments suggested GOPC was easily recycled and its stable adsorption capacity endowed it great potential as an adsorbent of Cr(VI) from wastewater.     

生物质吸附材料对Cr(VI)的吸附还原研究进展

重金属污染是当今工业发展所面临的一个重要环境问题,传统处理含铬废水的方法具有工艺简单、操作方便等优点,但存在二次污染、处理成本高等问题。寻找成本低、去除效率高的重金属废水处理方法是当下研究的一个重要方向。本工作介绍了生物质吸附法对含铬废水的处理研究,简述了生物质材料在金属吸附回收领域的优势,分析了当前生物质吸附材料的研究内容和发展现状,归纳了目前常用的物理、化学改性方法,并详细介绍了改性生物质材料对Cr(VI)的吸附效果,然后根据吸附剂表面活性基团与吸附质之间相互作用的类型,分析总结了生物质吸附材料对Cr(VI)的四种吸附机理以及在吸附过程中氨基、羟基、硫醇等活性基团作为电子供体对Cr(VI)的还原机理。最后,从研究与应用的角度,对生物质吸附材料吸附还原Cr(VI)的未来研究方向做出展望。     

Dynamical modeling of the electrochemical process to remove Cr (VI) from wastewaters in a tubular reactor

This work is aimed at obtaining and calibrating a dynamical model of the electrochemical reduction of Cr(VI) in a tubular continuous reactor with a spiral wire shaped anode at different conditions of pH (1.0 to 2.0) and residence times. An industrial wastewater sampled from a Mexican electroplating industry with about 1000 mg dm^?3 of Cr(VI) was used for the experiments. It was found that pH exerts a strong influence on the performance of electrochemical reduction of Cr(VI). Thus at a wastewater influent pH = 1.0 and a residence time in the reactor of 38.5 min it is possible to reduce the Cr(VI) concentration from 1000 to 0.37 mg dm^?3. However at an influent pH higher than 1.5, an effluent Cr(VI) concentration lower than 0.5 mg dm^?3 cannot be obtained. A more complete dynamic model was applied incorporating pH and the dispersion effects that affect the electrochemical Cr(VI) removal. The model, which adequately describes the performance of the electrochemical process, can be used to optimize the performance of this kind of reactor with more reliability. Copyright © 2007 Society of Chemical Industry     

Rapid removal of Cr(VI) ions from aqueous solutions by the macroporous poly(N,N′‐dimethylamino ethyl methacrylate) hydrogels

To improve the adsorption ability of hexavalent chromium [Cr(VI)], the macroporous poly(N, N′‐dimethylamino ethyl methacrylate) [poly(DMAEMA)] hydrogels were successfully fabricated by free‐radical copolymerization in ethanol/water mixture using N, N′‐dimethylamino ethyl methacrylate (DMAEMA) as the monomer, N, N′‐methylenebisacrylamide (MBAA) as the cross‐linker, and Na₂SO₄ solution as the porogen. The effects of various parameters, such as the concentration of Na₂SO₄ solutions, the dosage of MBAA, pH values, adsorption kinetic, and isotherm curves, were all investigated through systematic experiments. Scanning electron microscope (SEM) was employed to characterize the various pore structures. The experimental results showed that the influence of Na₂SO₄ solution to the pore morphology in the matrix was significant. The poly(DMAEMA) hydrogels can effectively adsorb Cr(VI) ions in aqueous media, and the macroporous structures could obvious improve the response rate and adsorption capacity. These results prove that the macroporous poly(DMAEMA) gels can be treated as a potential material for environmental pollution control. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Comparing the efficacy of a novel waste-based adsorbent with PAC for the simultaneous removal of chromium (VI) and cyanide from electroplating wastewater

The potential of powdered pistachio hull (PHP) for the co-adsorption of Cr(VI) and cyanide from electroplating wastewater was compared to that of powdered activated carbon (PAC). The results of dynamic adsorption experiments indicated that the complete and simultaneous removal of Cr(VI) and cyanide from wastewater was achieved with 2 g/L of PHP after 60 min of contact. Alternatively, with PAC, 69.2 and 77.8% of Cr(VI) and cyanide, respectively, were removed under the same conditions. Adsorption of Cr(VI) and cyanide by PHP and PAC followed pseudo-second order kinetics, and the equilibrium adsorption data best fit the Langmuir isotherm. The maximum capacity of PHP for the co-adsorption of Cr(VI) and cyanide was 117.6 and 151.5 mg/g, respectively, and the maximum capacity of PAC for the adsorption of Cr(VI) and cyanide was 47.6 and 39.4 mg/g, respectively. It was found that which intraparticle diffusion controlled the adsorption of Cr(VI) and cyanide onto PHP and PAC under the selected conditions. Overall, PHP efficiently adsorbed Cr(VI) and cyanide from industrial effluents; thus, PHP is an affordable and cost-effective system for the treatment of wastewater.     

Arsenic (V) removal with nanoparticulate zerovalent iron: Effect of UV light and humic acids

Results on As(V) removal in the presence of oxygen using the zerovalent iron technology with commercial iron nanoparticles (NanoFe^®) are presented, showing the effect of (NanoFe^®) mass, UV light and addition of humic acids. The nanosized iron particles (NZVI) were characterized in their particle size, surface area and constituent phases. As(V) removal was rapid and increased with NZVI mass (0.005–0.1 g L⁻¹) attaining more than 90% after 150 min of time contact with the optimal NanoFe^® concentration. The removal followed a biexponential kinetic decay, with rate constants increasing with NZVI mass. (NanoFe^®) presented an outstanding ability to remove As due to not only a high surface area and low particle size but also to a high intrinsic activity. Humic acids (HA) decreased around 50% the removal efficiency in the dark, indicating competition with As(V) for active surface sites. In contrast, UV light doubled removal rates, the process being even more enhanced in the presence of HA, with an almost total arsenic removal within 4 h. In all cases, adsorption on iron corrosion phases was found the main mechanism of As(V) removal, promoted by formation of Reactive Oxygen Species and enhanced under UV irradiation by the formation of multiple active species. Preliminary results with As-polluted groundwater of the Chacopampean Plain of Argentina (Tucumán Province) are also reported. Addition of NanoFe^® under UV irradiation for 3 h resulted in As contents well in agreement with the regulations (<10 μg L⁻¹).     

Preparation and characterization of iron(III) complex of an amino‐functionalized polyacrylamide‐grafted lignocellulosics and its application as adsorbent for chromium(VI) removal from aqueous media

The growth and decay processes of optically induced birefringence in two novel azobenzene compounds [one was a hyperbranched poly(aryl ether) containing azobenzene groups, and the other was a hydrogen‐bonded complex] were studied. The temperature dependence of the birefringence signal was investigated. The curves for the buildup and decay of birefringence fit well to biexponential functions. The dependence of the fitting parameters on the temperature is also discussed. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Kinetic,equilibrium and thermodynamic studies on removal of Cr(VI) by activated carbon prepared from Ricinus communis seed shell

A study on the removal of hexavalent chromium ions from aqueous solution by using activated carbon prepared from Ricinus communis has been done. In this process, it was carbonised and activated by treating with concentrated sulphuric acid followed by heating for 5 h at 500°C. Batch adsorption experiments are also carried out as a function of pH, contact time, initial concentration of the adsorbate, adsorbent dosage and temperature. The experimental data are fitted well to the Freundlich adsorption isotherm. Thermodynamic parameters such as ΔH°, ΔS° and ΔG° are calculated, which indicated that the adsorption is spontaneous and endothermic in nature. Adsorbent used in this study is characterised by FT‐IR and SEM before and after the adsorption of Cr(VI). © 2011 Canadian Society for Chemical Engineering     

藻类去除煤气化废水氨氮及总氮的实验研究

采用柱式光合反应器对藻类去除煤气化废水的氨氮及总氮开展了探索性实验研究。实验结果表明:优化条件下,四尾栅藻、斜生栅藻、混合藻(黄丝藻和席藻)都在3 d内完全去除氨氮,同时总氮去除率都在第5天达到最大,分别是四尾栅藻86.02%,斜生栅藻83.33%,混合藻71.81%。说明选用合适的藻类去除煤气化废水的氨氮及总氮可行,同时相比生物硝化/反硝化脱氮工艺该方法具有一定的新颖性。     

生物除铁除锰在钢铁废水回用处理中的应用

研究了锰砂过滤工艺在钢铁废水回用处理中除铁除锰的应用.在滤速5.0 m/h、工作周期4 d、反冲洗强度21 L/(m2·h)和反冲洗时间6 min的操作条件下,经过自然生物培养成熟的锰砂滤层对钢铁回用废水中的总铁、锰的去除率达80%以上,出水总铁和锰都达到再生水用作循环冷却用水的水质要求.同时成熟的锰砂滤料还具有一定的COD和氨氮去除能力.