Adsorption of lead(II) from aqueous solution onto several types of activated carbon fibers

In this work, the adsorption of Pb(II) from aqueous solution was investigated on various types of activated carbon fibers (ACFs) manufactured from polyacrylonitrile and phenolic resin. The textural and physicochemical properties of the ACFs were determined by the N₂-BET method and acid-base titration. The experimental adsorption equilibrium data of Pb(II) on the ACFs were obtained in a batch adsorber, and the Langmuir isotherm model better fitted the experimental data. The effects of the type of ACF and precursor of ACF, solution pH and temperature upon the adsorption of Pb(II) on the ACFs were examined in detail. The adsorption capacity was highly dependent upon the precursor of ACF. The Pb(II) adsorption capacity of the ACFs augmented when the solution pH and temperature were increased from 2 to 4 and from 288 to 308 K, respectively. The effect of the pH was attributed to the interactions between the surface of the ACF and Pb²⁺ ions present in the water solution. The Pb(II) adsorption capacity of the ACFs was enhanced by oxidation with HNO₃ solution and the enhancement factor was between 1.1 and 1.4. The reversibility of the adsorption of Pb(II) was investigated by first adsorbing Pb(II) on an ACF and then desorbing the Pb(II). It was noticed that Pb(II) was substantially desorbed from ACF while reducing the solution pH to 2. It was concluded that the Pb(II) was mainly adsorbed on the ACFs by chemisorption, electrostatic interactions and ion exchange.     

Influence of anodic treatment on heavy metal ion removal by activated carbon fibers

In this work, the effect of electrochemical oxidation treatment on activated carbon fibers (ACFs) was studied in the context of Cr(VI), Cu(II), and Ni(II) adsorption behavior. Ten weight percent phosphoric acid (A-ACFs) and ammonia (B-ACFs) were used for acidic and basic electrolytes, respectively. Surface properties of ACFs were determined by X-ray photoelectron spectroscopy (XPS). The specific surface area and the pore structure were evaluated from nitrogen adsorption data at 77 K. As a result, the electrochemical oxidation treatment led to an increase in the amount of oxygen-containing functional groups. Also, the adsorption capacity of the electrochemically oxidized ACFs was improved in the order B-ACFs > A-ACFs > untreated-ACFs, in spite of a decrease in specific surface area which resulted from pore blocking by functional groups and pore destruction by acidic electrolyte. It was clearly found that the heavy metal ions were largely influenced by the functional groups on the ACF surfaces.     

活性碳纤维对银离子还原吸附能力的改进

活性碳纤维不仅对有机物有高的吸附容量,对贵金属离子也具有强的还原吸附能力,可将Pd(Ⅱ）,Ag（Ⅰ）,Au（Ⅲ）等离子还原为金属单质。因而可用于提取矿液或加收废液中的贵金属。由此,提高或改善贵金属在活性碳纤维上的还原吸附容量或分布形成,显得非常重要。本文研究了活性碳纤维制备条件、表面氧化改性、以有负载有机物等对活性碳纤维还原能力的影响。结果表明,（1）制备条件对剑麻基活性碳纤维的还原能力有很大的影响。用H3PO4或ZnCl2活化的活性碳纤维对银离子具有更高的还原吸附容量,分别可达250和700mg/g,约为水蒸汽活化剑麻基活性碳纤维对银离子还原吸附容量的2倍和5倍。（2）过氧化氢、高锰酸钾、或硝酸等无机氧化剂对活性碳纤维进行表面改性,也能提高活性碳纤维的还原能力。结果表明,虽然改性活性碳纤维的比表面积和孔体积下降10-20%左右,但基表面含氧量及含氧基团的种类发生了改变。这些改性活性碳纤维对Ag(NH3)2^ 的还原吸附量大幅度提高,可达550mg/g以上。推断表面改性在活性碳纤维表面创造了更多有利于碱性条件下发生氧化还原的活性点。（3）在活性碳纤维表面负载适当的有机物如亚甲基蓝、苯胺或对硝基苯酚,也能显著提高活性碳纤维对Ag(NH3)2^ 的还原吸附能力。     

Enhanced three-dimensional electrochemical process using magnetic recoverable of Fe3O4@GAC towards furfural degradation and mineralization

Furfural is as one of the major environmental pollutants in different industrial effluents such as refinery and petrochemical, paper, cardboard and oil refining. This toxic chemical is irritant and causes allergy for skin, eyes and mucous membranes. This study was developed to investigate the efficiency of a three-dimensional electrochemical process in the presence of granular activated carbon magnetized with Fe₃O₄ (Fe₃O₄@GAC) particle electrodes for removal of furfural from aqueous solution. The particle electrodes structural and morphological featured were determined via BET, VSM, XRD, FE-SEM and FTIR techniques. The experiments were performed based on central composite design (CCD) and the role of influencing factors including reaction time, pH, voltage and initial furfural concentrations at five levels were evaluated. The Quadratic model with high correlation coefficient = 0.9872 (R² and (R²_Adj = 0.9724)) was suggested for experimental data analysis. The performance of electrochemical oxidation towards furfural degradation was enhanced substantially after adding Fe₃O₄@GAC. The highest furfural removal efficiency (98.2%) was achieved under optimal conditions (furfural: 201 mg/L, electrolysis time: 69 min, voltage: 19 V, and pH: 5.0). Besides, over 78 and 74 % of COD and TOC were removed by Fe₃O₄@GAC-based three-dimensional process, respectively. Based on the COD/TOC ratio and average oxidation state (AOS) index, a significant increase was observed in the biodegradability of intermediates of furfural after treatment. Results showed that three-dimensional electrochemical process with particle electrodes is a promising technology for efficient removal of furfural, even at high concentrations. Results of Liquid chromatography–mass spectrometry (LC-MS) analysis and degradation pathway showed that furfural could be oxidized to compounds with smaller molecular masses, which eventually converted to carbon dioxide and water.     

Electrochemical Degradation of o-Chloronitrobenzene by Three-dimensional Electrodes

Degradation of o-chloronitrobenzene wastewater was experimentally investigated at a three-dimensional electrode(TDE) with granular activated carbon as the particle electrode, graphite as the anode, and stainless steel plate as the cathode. The kinetic model of o-chloronitrobenzene degradation was studied, and the effects of pH, electrolysis time, particle electrode, electrolyte concentration, and initial concentration of the solution on degradation efficiency were investigated to determine the optimal operating conditions. The degradation of o-chloronitrobenzene by oxidation at the TDE was monitored by chemical oxygen demand(COD) measurements, UV-Vis absorption, and high performance liquid chromatography(HPLC). COD degradation by electrochemical degradation followed pseudo-first order kinetics with respect to the concentration of o-chloronitrobenzene solutions. Optimal reaction conditions included 15 g of activated carbon as the particle electrode, 400 mg/L o-chloronitrobenzene solution containing 0.10 mol/L Na₂SO₄, pH=3, and 60 min of electrolysis. The UV-Vis absorption spectra and HPLC results illustrate that the benzene ring in o-chloronitrobenzene was rapidly broken down to form aliphatic substances through electrochemical degradation. COD degradation was approximately 98.5% at optimal conditions.     

Preparation and characterization of activated carbon fibers supported with silver metal for antibacterial behavior

In this work, the effect of immersion in silver nitrate solution on activated carbon fibers (ACFs) was investigated in relation to adsorption behavior and antibacterial activity of ACFs supported with silver (ACF/Ag). The pore and surface properties were studied in terms of BET volumetric measurement with nitrogen adsorption, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The antibacterial activities of ACF/Ag were studied in broth dilution tests against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) from a point of view of water purification. As an experimental result, the silver content of ACF/Ag increased with increasing concentration of silver nitrate. It was found that the micropore structure slightly decreased as the silver nitrate concentration increased. Otherwise, it was revealed that the ACF/Ag possessed a strong antibacterial activity and an inhibitory effect for the growing of E. coli and S. aureus, respectively. Silver content on ACF/Ag decreased rapidly because of rough morphology of silver particles in water erosion.     

Photocatalytic degradation of methylene blue by a combination of TiO2 and activated carbon fibers

Photocatalytic degradation of methylene blue (MB) in aqueous solution was investigated using TiO2 immobilized on activated carbon fibers (ACFs). The TiO2 and ACF combination (TiO2/ACF) was prepared by using epoxy as the precursor of the link between TiO2 and ACFs, followed by calcination at 460 degrees C in a N2 atmosphere. The TiO2/ACF composite prepared was easier to handle than the original TiO2 powder in suspension. More significantly, the TiO2/ACF composite can be used repeatedly without a decline in photodegradation ability. After six cycles, the amount of MB removal for the TiO2/ACF composite was still slightly higher than that for fresh P25 TiO2 in suspension. Through measurement of chemical oxygen demand in the solution and the concentration of ammonium generated during degradation of MB, it was confirmed that MB molecules are mineralized instead of adsorbed by ACFs.     

活性炭纤维电吸附重金属及磺胺甲恶唑性能研究

使用盐酸对吸附剂活性炭纤维（activated carbon fiber,ACF）进行改性,通过SEM、BET和FTIR对改性前后的ACF形貌及结构进行系统表征发现,改性后ACF较改性前表面杂质减少且沟壑更加明显,比表面积提高22%,微孔体积增加5%,含氧官能团（C-O和C=O）明显增多. 以水中重金属离子（Zn(II)及Cr(VI)）和抗生素磺胺甲恶唑（Sulfamethoxazole,SMX）为目标污染物,研究改性后ACF对目标污染物的吸附（静吸附和电吸附）性能,考察了浓度、pH、外加电压对吸附的影响. 结果表明,ACF用量为5 g,电压为1.2 V,Zn(II)、Cr(VI)及SMX浓度均为10 mg·L^-1,Zn(II)溶液pH为5时,ACF吸附水中Zn(II)的最大吸附量为9.25 mg·g^-1,是静吸附条件的2.15倍;Cr(VI)溶液pH为4时,ACF吸附Cr(VI)的最大吸附量为8.86 mg·g^-1,是静吸附条件的1.96倍;SMX溶液pH为6时,ACF吸附SMX的最大吸附量为8.32 mg·g^-1,是静吸附条件的1.84倍. ACF吸附Zn(II)、Cr(VI)及SMX的动力学曲线均符合准二级动力学模型,吸附过程为化学吸附. Freundlich等温模型能更好地描述ACF对Zn(II)、Cr(VI)及SMX的吸附特性,其吸附形式为多分子层吸附. ACF通过电极反接方式进行循环再生,脱附速率快且脱附效果明显,经4次循环再生后,ACF对Zn(II)、Cr(VI)及SMX的去除率均在90%以上.     

STUDY ON THE FACTORS AFFECTING REDUCTION CAPACITIES OF ACTIVATED CARBON FIBERS

1. INTRODUCTION The discharge of effluent containing precious metal ions, which comes from electroplating, mining, smelting, and other industries, not only contaminate the environment where people live, but also cause the waste of natural resources. From…     

乙烯渣油沥青基活性炭纤维和粘胶基活性炭纤维的表面性质与脱硫活性

研究了在O2和H2O存在下,乙烯渣油沥青基活性炭纤维(ETPACF)和粘胶基活性炭纤维(CelluloseACF)的脱硫活性.结果表明,在比表面积相近的情况下,ETPACF的脱硫活性明显低于CelluloseACF,这可归因于后者具有较强的吸附和催化氧化SO2能力及较大的吸水量,尤其是具有较强的催化氧化SO2的能力,这些能力又与其表面含有含氮官能团以及某些含氧官能团有关,因此ACF的表面官能团对其脱硫活性影响很大.     

Relation between the charge efficiency of activated carbon fiber and its desalination performance

Four types of activated carbon fibers (ACFs) with different specific surface areas (SSA) were used as electrode materials for water desalination using capacitive deionization (CDI). The carbon fibers were characterized by scanning electron microscopy and N(2) adsorption at 77 K, and the CDI process was investigated by studying the salt adsorption, charge transfer, and also the charge efficiency of the electric double layers that are formed within the micropores inside the carbon electrodes. It is found that the physical adsorption capacity of NaCl by the ACFs increases with increasing Brunauer-Emmett-Teller (BET) surface area of the fibers. However, the two ACF materials with the highest BET surface area have the lowest electrosorptive capability. Experiments indicate that the charge efficiency of the double layers is a key property of the ACF-based electrodes because the ACF material which has the maximum charge efficiency also shows the highest salt adsorption capacity for CDI.     

STUDY ON THE FACTORS AFFECTING REDUCTION CAPACITIES OF ACTIVATED CARBON FIBERS

The reduction adsorption of silver diamminonitrate on different kinds of activated carbonfibers (ACF) has been studied in this paper. The effect of different parameters, including adsorptiontemperature, concentrations of activation agents, and activation time on the silver adsorptioncapacities of activated carbon fibers has been investigated The results show that higher temperaturein which the silver complex interacts with ACF. or higher concentration of activation agent, will makehigher reduction adsorption capacities of ACFs. More over, ACFs activated with phosphoric acidhave higher reduction capacities than those activated with zinc chloride or steam.     

炭在熔融碳酸盐中的直接电化学氧化性能

研究了活性炭粉在熔融碳酸盐中的直接电化学氧化性能. 通过线性扫描伏安曲线的测试发现, 将炭粉用酸处理, 碳酸盐中的炭含量、炭粒径、反应温度和反应气氛均会对活性炭的电化学氧化性能产生影响. 研究结果表明, 用HCl处理活性炭, 升高反应温度, 适当增加炭含量及炭粒子粒径和通入N2气均会提高活性炭的电化学氧化活性. 经HCl处理的、炭含量为15 g和炭粒径<100 μm的活性炭在850 ℃下、在N2气保护下和电位扫描速率为20 mV/s时的开路电位(OCP)为-1.40 V, 在-0.4 V下的电流密度可达到200 mA/cm2.     

Electrochemical degradation of 2,4-Dinitrotoluene (DNT) from aqueous solutions using three-dimensional electrocatalytic reactor (3DER): Degradation pathway,evaluation of toxicity and optimization using RSM-CCD

2,4-Dinitrotoluene (2,4-DNT) has been found to be an important petrochemical compound, which is primarily employed for the synthesis of tolylene diisocyanate and the production of dyes, rubber, and explosives. Since this compound has high toxicity and carcinogenicity, the cautions should be considered when wastewater contaminated with DNTs and their derivatives is released into the environment. Thus, the object of the present study was the investigation of the 2,4-DNT degradation efficiency using the three-dimensional electrocatalytic reactor (3DER) with two different types of particle electrodes (granular activated carbon (GAC) and magnetized clinoptilolite zeolite (MCZ)@Fe₃O₄ nanoparticles)). Preparation of the graphite (G)/β-PbO₂ anode was done by electrochemically depositing PbO₂ layers on graphite sheets. The prepared graphite sheet and a stainless-steel 316 sheet (with the same dimensions) were employed as the anode and the cathode, respectively. Field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), and energy-dispersive X-ray spectroscopy mapping (EDS-mapping) confirmed the successful preparation of G/β-PbO₂ anode. The surface morphology, chemical composition of MCZ@Fe₃O₄ nanoparticles as a particle electrode were determined by scanning electron microscope (SEM) and XRD pattern. To determine the optimal conditions, we employed the response surface methodology-based central composite design (RSM-CCD) method. According to observed results, higher efficiency of 3DER was obtained by increasing the reaction time and current density and decreasing pH and the pollutant concentration. Studies highlighted the initial 2,4-DNT concentration of 23.5 mg/L, current density 4.8 mA/cm², pH of 4.1, electrolysis time of 50 min, particle electrodes dose = 6 g/250 cc as optimum values of parameters. The 2,4-DNT degradation efficiencies using GAC and MCZ@Fe₃O₄ nanoparticles as particle electrodes under mentioned optimal conditions were 98.6% and 96.5%, respectively. Moreover, the chemical oxygen demand (COD) and total organic carbon (TOC) removal efficiencies were 88.5% and 80.9% at the end of 50 min, respectively. Furthermore, results were indicative of an enhancement in average oxidation state (AOS) (from 1.27 to 2.36) and carbon oxidation state (COS) (from 1.27 to 3.68) in the 3DER process and a reduction in the COD/TOC ratio (from 1.81 to 1.09); these signposts the effectiveness of 3DER system for providing the biodegradability of 2,4-DNT. Considering the results, the 3DER could lead to suitable results for the degradation of wastewater containing DNT and resistant contaminants as pretreatment and has remarkable applicability for enhancing the biodegradability of wastewater.     

活性炭纤维的预处理及其SCR催化活性研究

随着中国能源工业的继续发展,氮氧化物排放相应政策法规的制定,烟气脱硝已经成为污染控制的重要组成部分.     

Determination of formal potential of NADH/NAD+ redox couple and catalytic oxidation of NADH using poly(phenosafranin)-modified carbon electrodes

The electrochemical regeneration of NADH/NAD⁺ redox couple has been studied using poly(phenosafranin) (PPS)-modified carbon electrodes to evaluate the formal potential and catalytic rate constant for the oxidation of NADH. The PPS-modified electrodes were prepared by electropolymerization of phenosafranin onto different carbon substrates (glassy carbon (GC) and basal-plane pyrolytic graphite (BPPG)) in different electrolytic solutions. The formal potential was estimated to be ? 0.365 ± 0.002 V vs. SHE at pH 7.0. As for the bare carbon electrodes, the oxidation of NADH at the BPPG electrode was found to be enhanced compared with the GC electrode. For the PPS-modified electrodes, it was found that the electrocatalysis of PPS-modified electrodes for the oxidation of NADH largely depends on the carbon substrate and electrolyte solution employed for their preparation, i.e., the PPS-modified BPPG electrode prepared in 0.2 M NaClO₄/acetonitrile solution exhibits an excellent and persistent electrocatalytic property toward NADH oxidation in phosphate buffer solution (pH 7.0) with a diminution of the overpotential of about 740 and 670 mV compared with those at the bare GC electrode and the PPS-modified GC electrode prepared in 0.2 M H₂SO₄ solution, respectively. A quantitative analysis of the electrocatalytic reaction based on rotating disk voltammetry gave the electrocatalytic reaction rate constants of the order of 10³–10⁴ M^?1 s^? 1 depending on the preparation conditions of the PPS-modified electrodes.     

Adsorption of Acid Orange II from Aqueous Solution by Plasma Modified Activated Carbon Fibers

As a main composition of dye wastewater, organic pollutant which has a negative effect on the environment can be effectively removed by active carbon adsorption. In the present work, activated carbon fiber (ACF) was modified by a novel modification technology, gilding arc discharge, while its adsorption capacity was studied with the acid orange II (AO II) solution selected as the target wastewater. Several factors, such as air flow rate, distance between samples and the discharge area, pH of the solution and plasma treating time, were investigated with respect to their effects on properties of the plasma-treated ACF, in terms of texture characteristic, surface chemical compositions and adsorption capacities. The results showed that the specific surface area and pore volume of ACF decreased after the plasma treatment, while the amounts of oxygen-containing functional groups on the surface of ACF increased compared with the raw ACF. Moreover, it was observed that the adsorption capacity of the modified ACF was improved by nearly 20.9 %, which was beneficial to the industrial application.     

Metal dispersed activated carbon fibers and their application for removal of SOx

Uniformly metal dispersed ACFs were prepared by mixing organometallic compounds with THF and pitch. The solvent was removed from this mixture and then pitch was spun, stabilized, carbonized and activated. The specific surface areas and pore size distributions of prepared ACFs and DeSO_x catalytic reactivities were determined. The mesopores of ACF were developed by the addition of Co, Ni, Mn. The DeSO_x catalytic reactivity of Ni, Pd, Co, V and Cr dispersed ACFs demonstrated much higher continuous reaction conversion than reference pitch-ACF.     

OH functionalized Multi-Walled Carbon Nanotube modified electrode as electrochemical sensor for the detection of Aceclofenac

ABSTRACT

The rapid electrochemical determination of Aceclofenac (ACF) has been employed by cyclic voltammetry (CV), differential pulse voltammetry (DPV) using developed OH-functionalised multiwalled carbon nanotube carbon paste electrode (OH-MWCNT/CPE). Modified electrode was characterised by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), X-ray diffraction spectroscopy (XRD), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The ACF exhibits two oxidation peaks at +0.4 V, +0.66 V and one reduction peak at +0.3 V. The active surface area of the bare carbon paste electrode (BCPE) and modified electrode have been characterised by using K₃[Fe(CN)₆] solution containing 0.1 M KCl. In DPV mode, variation of ACF gave the limit of detection (LOD = 3s/m) 0.246 μM over the concentration range 1.0 to 190.0 μM (R² = 0.9994). The developed electrode has good stability, reproducibility and could be successfully validated for the detection of ACF in pharmaceutical samples and biological fluids.     

Adsorption properties and photocatalytic activity of TiO2/activated carbon fiber composite

Photocatalysts of titanium dioxide (TiO₂) and TiO₂/activated carbon fiber (TiO₂/ACF) composite were prepared by sol-gel method, followed by calcining the pure TiO₂ sols and the TiO₂/ACF sols at 500°C for 2 h in a N₂ atmosphere, respectively. These photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N₂ adsorption-desorption isotherms measurement. Batch experiments were conducted to study the adsorption property of TiO₂/ACF composite using methylene blue as adsorbate. The adsorption data obtained from different batch experiments were analyzed using pseudo-second-order kinetic model, the experimental data can be adequately described by the pseudo-second-order equation. The photodecomposition behavior of TiO₂/ACF was investigated in aqueous solution using methylene blue as target pollutant. It was found that methylene blue could be removed rapidly from water by TiO₂/ACF, the photocatalytic decomposition was obviously improved when the photocatalyst was used. Kinetics analysis revealed that the photocatalytic decomposition reaction can be described well by a first-order rate equation.