Activated carbon blended with grape stalks powder: Properties modification and its application in a dye adsorption

In this study, activated carbon was blended with grape stalks powder to adsorb methylene blue (MB) dye with various concentrations from a wastewater. For this purpose, five independent variables involving pH (2–13), contact time (5–270 min), grape stalks powder dosage (0.1–10 g/l), methylene blue initial concentration (20–300 mg/l), and activated carbon dosage (0.1–10 g/l) for methylene blue adsorption were studied. The Central Composite Design (CCD) under Response Surface Methodology (RSM) was applied to estimate the independent variables effects on the methylene blue adsorption. The pseudo- first order, pseudo-second order, Elovich and intraparticle diffusion models were employed to study the adsorption kinetics and isotherm. The Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherm models were applied to investigate the adsorption isotherm. It was concluded that the intraparticle diffusion isotherm and pseudo-second order kinetic models could show the best results. Furthermore, some data such as physical adsorption (by analyzing FTR and applying some standard equations) and mean free energy (E) were discovered in this research. Finally, activated carbon blended with grape stalks powder as an effective bio-adsorbent for the methylene blue reduction from a wastewater was introduced.     

碳纳米管吸附水溶液中双酚A的热力学

以甲醇和去离子水组成的体系（体积比90∶10）为流动相,建立了以香烟过滤嘴作吸附剂,固相萃取（SPE）与高效液相色谱（HPLC）联用测定水中双酚A(Bisphenol A,BPA)的新方法。研究了水溶液中碳纳米管(CNTs)吸附双酚A的热力学特性,测定了不同温度下的吸附等温线,并探讨了其可能的吸附机理。结果表明,CNTs对BPA 的吸附主要以快速吸附为主,常温下,碳纳米管对于70 mg·L-1的双酚A水溶液的吸附量可达到 24.65 mg g-1,吸附量随初始浓度的增加而增加,随温度的降低而增大,采用Freundlich和Langmuir方程拟合,相关系数均大于0.99,热力学函数ΔG、ΔH及ΔS分别为-39.48 ~ -43.51 KJ·mol-1、-18.06 KJ·mol-1、71.73 J·mol-1·K-1,吸附为放热、熵增的自发过程,降低温度有利于吸附,并且具有物理吸附特征。     

Sulfur fixation on bagasse activated carbon by chemical treatment and its effect on acid dye adsorption

Heteroatoms are known to introduce specific surface functionalities that can enhance the adsorption properties of carbons. Sulfur fixation on bagasse-activated carbon was conducted by a low temperature chemical treatment with sulfuric acid followed by physical activation with CO₂ at 900?°C. The effect of sulfur fixation on the surface chemical properties of bagasse-activated carbons were investigated and on their subsequent acid dye removal (CIBA AB80) behavior. Surface chemical development were examined and followed using Fourier transform infrared spectroscopy (FTIR), heteroatom analysis and carbon surface acidity. Functional group stability with thermal treatment was also investigated. The textural properties of the activated carbons were characterized by nitrogen adsorption. Chemical pre-treatment and gasification was able to fix up to 0.2 wt% of sulfur on the activated carbon. Although the sulfur fixed by chemical treatment is low, this method introduced several advantages in comparison to fixation by thermal methods. The chemical method did not interfere with the textural development of the carbon, as found in thermal methods. In addition, the surface chemistry generated by these levels of sulfur groups was sufficient to increase the uptake of acid blue dyes by more than 700% based on adsorption capacities normalized by the surface area of the carbon.     

Quantitative determination of acetylsalicylic acid and acetaminophen in tablets by FT-Raman spectroscopy

A procedure for quantitative determination of acetylsalicylic acid and acetaminophen in pharmaceuticals by PLS (partial least squares) and PCR (principal component regression) treatment of FT (Fourier transform)-Raman spectroscopic data is proposed. The proposed method was tested on powdered samples. Three chemometric models were built: the first, for samples consisting of an active substance diluted by lactose, starch and talc; the second, in which a simple inorganic salt was applied as an internal standard and additions were not taken into account; and the third, in which a model was constructed for a commercial pharmaceutical, where all constituents of the tablet were known. By utilising selected spectral ranges and by changing the chemometric conditions it is possible to carry out fast and precise analysis of the active component content in medicines on the basis of the simplified chemometric models. The proposed method was tested on five commercial tablets. The results were compared with data obtained by intensity ratio and pharmacopoeial methods. To appraise the quality of the models, the relative standard error of predictions (RSEPs) were calculated for calibration and prediction data sets. These were 0.7-2.0% and 0.8-2.3%, respectively, for the different PLS models. Application of these models to the Raman spectra of commercial tablets containing acetylsalicylic acid gave RSEP values of 1.3-2.0% and a mean accuracy of 1.2-1.7% with a standard deviation of 0.6-1.2%.     

Oxygen adsorption characteristics on hybrid carbon and boron‐nitride nanotubes

In this work, first‐principles density functional theory (DFT) is used to predict oxygen adsorption on two types of hybrid carbon and boron‐nitride nanotubes (CBNNTs), zigzag (8,0), and armchair (6,6). Although the chemisorption of O₂ on CBNNT(6,6) is calculated to be a thermodynamically unfavorable process, the binding of O₂ on CBNNT(8,0) is found to be an exothermic process and can form both chemisorbed and physisorbed complexes. The CBNNT(8,0) has very different O₂ adsorption properties compared with pristine carbon nanotubes (CNTs) and boron‐nitride nanotube (BNNTs). For example, O₂ chemisorption is significantly enhanced on CBNNTs, and O₂ physisorption complexes also show stronger binding, as compared to pristine CNTs or BNNTs. Furthermore, it is found that the O₂ adsorption is able to increase the conductivity of CBNNTs. Overall, these properties suggest that the CBNNT hybrid nanotubes may be useful as a gas sensor or as a catalyst for the oxygen reduction reaction. © 2014 Wiley Periodicals, Inc.     

Humic acid adsorption on fly ash and its derived unburned carbon

Fly ash is solid waste from combustion process, containing oxide minerals and unburned carbon. In this investigation, fly ash has been separated into metal oxide mineral section and unburned carbon. The fly ash with different contents of unburned carbon was employed for humic acid adsorption to investigate the influence of unburned carbon on adsorption. It is found that metal oxides and unburned carbon in fly ash exhibit significant difference in humic acid adsorption. The unburned carbon plays the major role in adsorption. Higher content of unburned carbon in fly ash results in higher surface area and thus higher humic acid adsorption. Fly ash and unburned carbon exhibit adsorption capacity of humic acid of 11 and 72 mg/g, respectively, at 30 degrees C, pH 7. Humic acid adsorption is also affected by ion strength, pH, and temperature. The thermodynamic calculations indicate that the adsorption is endothermic nature with DeltaH(0) and DeltaS(0) as 5.79 kJ/mol and 16.0 J/K mol, respectively.     

Characterization and sensing properties of a carbon nanotube paste electrode for acetaminophen

New separation and preconcentration procedures based on the coprecipitation of Fe(III) and Pb(II) ions with Cu(II) salicylaldoxime coprecipitant and of Cu(II) with Ni(II) salicylaldoxime coprecipitant were studied comparatively. The coprecipitation conditions for each method, such as the effect of the pH, the amounts of carrier elements and reagent, sample volume and matrix effects were examined in detail. The determinations of analyte ions were performed by flame AAS. Under optimised conditions the detection limits of the methods (3s/b) were 1.58, 3.56 and 1.32 μg L^?1 for iron(III), lead(II) an copper(II), respectively. The precision (as RSD %) of the methods was ≤3.2%. Each method was validated by both spiked tap water, dam water samples and by the analysis of certified reference material (TMDA-54.4 fortified lake water). It was found that the recovery of Fe(III), Pb(II) and Cu(II) from the water samples was ≥90%.     

Anodic oxidation of hydrazine at carbon nanotube powder microelectrode and its detection

Carbon nanotube powder microelectrodes (CNTPMEs) were used to study the anodic oxidation of hydrazine at Carbon nanotube (CNT)-the novel carbon material. It was found that the electrochemical behaviours were greatly improved at CNTs, indicating that the anodic oxidation could be catalyzed at CNTs. The kinetics parameters of this process were calculated, the heterogeneous electron transfer rate constant k was 0.0019 cm s(-1), (1-alpha)n(alpha) was 0.22. The CNTPMEs were also found with high sensitivity for hydrazine detection, could be used as hydrazine sensors.     

Wax-impregnated carbon paste electrode modified with mercuric oxalate for the simultaneous determination of heavy metal ions in medicinal plants and Ayurvedic tablets.

A wax-impregnated carbon paste electrode with mercury oxalate as the bulk modifier is found to be suitable for the determination of heavy metal ions by differential pulse anodic stripping voltammetry. The contents of binder and modifier have been optimized, until they showed low background current and easy renewability. The bulk-modified electrode is applied for the simultaneous determination of Zn, Cd, Pb and Cu in medicinal plants and Ayurvedic tablets (Liv 52). The results obtained have been validated with HMDE and AAS and are found to be comparable.     

甲烷在活性炭上吸附平衡模型的研究

比较吸附模型分析甲烷在活性炭上吸附平衡的适用性,为吸附式天然气(ANG)的工程应用提供准确的预测模型。基于在温度268.15～338.15 K、压力0～12.5 MPa测试的甲烷在Ajax活性炭上的吸附平衡数据,选择Langmuir、Langmuir-Freundlich和Toth方程,应用非线性回归拟合方程参数后,确定绝对吸附量和甲烷吸附相态,并比较方程在不同压力区域内的预测精度。结果表明,甲烷吸附相密度随平衡温度和压力变化;由绝对吸附量确定的甲烷在Ajax活性炭上的平均等量吸附热为15.72 kJ/mol,小于由过剩吸附量的标绘结果;Langmuir、Langmuir-Freundlich和Toth方程预测结果在0～0.025 MPa的累积相对误差为6.449 8%、7.918 4%和0.910 0%,在1～10 MPa为0.491 1%、0.161 3%和0.369 4%。Toth方程在整个压力范围内的预测结果最为准确,但Langmuir-Freundlich方程在较高压力区域内具有较高的预测精度。     

The determination of acetaminophen using a carbon nanotube:graphite-based electrode

The oxidation of acetaminophen was studied at a glassy carbon electrode modified with multi-walled carbon nanotubes and a graphite paste. Cyclic voltammety, differential pulse voltammetry and square wave voltammetry at various pH values, scan rates, and the effect of the ratio of nanotubes to graphite were investigated in order to optimize the parameters for the determination of acetaminophen. Square wave voltammetry is the most appropriate technique in giving a characteristic peak at 0.52 V at pH 5. The porous nanostructure of the electrode improves the surface area which results in an increase in the peak current. The voltammetric response is linear in the range between 75 and 2000 ng.mL^?1, with standard deviations between 0.25 and 7.8%, and a limit of detection of 25 ng.mL^?1. The method has been successfully applied to the analysis of acetaminophen in tablets and biological fluids.     

Possibilities of powder X-ray diffraction methods in determining structural characteristics of carbon materials

The possibilities of using powder X-ray diffraction methods in the study of carbon materials are discussed. To determine the phase composition of the crystalline materials the X-ray phase analysis is employed; the real structure is established by the harmonic analysis of diffraction profiles; the structural features and phase composition of the nanomaterials are found by the radial electron density distribution function.     

新铜试剂分光光度法测定片剂中的对乙酰氨基酚含量及其反应机理的研究

使用分光光度法测定扑热息痛中主要化学成分对乙酰氨基酚的含量。结果表明:在0.04~8.00 mg·L-1范围内对乙酰氨基酚含量与吸光度(A)呈良好的线性关系,其线性方程:A=0.1210c+0.0261,相关系数r=0.9968。表观摩尔吸光系数为1.8×104 L·mol-1·cm-1,平均回收率为100.2%,相对标准偏差RSD为1.51%。该实验所用仪器简单,且操作方便、快速。用该方法测定扑热息痛片剂对乙酰氨基酚的含量,取得了较好的效果。     

活性炭的表面化学改性及其对有机硫化物的吸附性能的研究

活性炭; 表面化学改性; 有机硫化物; 吸附性     

Thermodynamic parameters of adsorption of adamantane and its derivatives on graphitized thermal carbon black

The adsorption equilibrium constants for adamantane, 1-fluoro-, 1-chloro-, 1,3-difluoro-, 1,3-dichloro-, 1,3-dibromo-, and 1-hydroxyadamantane, and methyl 1-adamantyl ketone were determined by gas chromatography. The results were compared with molecular statistical calculations based on the known atomic-atomic potentials of the interaction of atoms of the sorbate molecule with the C atom of graphitized thermal carbon black (GTCB). The experimental adsorption heats exceed the calculated values by 3-10 kJ mol^-1. The reasons for this divergence are discussed. The changes in the adsorption entropy show that the molecules of the studied compounds form a layer of the ideal dimeric gas on the GTCB surface upon adsorption.     

Nitrogen-doped carbon nanotubes modified with gold nanoparticles for simultaneous analysis of N-acetylcysteine and acetaminophen

A novel film consisting of nitrogen-doped multi-walled carbon nanotubes modified with gold nanoparticles (further denoted as N-MWCNTs/AuNPs) was fabricated and applied for the simultaneous electrochemical analysis of N-acetylcysteine (NAC) and acetaminophen (AC) in phosphate buffer solution (PBS, pH 7.0). The fabricated film exhibits powerful response towards simultaneous analysis of NAC and AC followed by well-separated cyclic voltammetric waves (～440 mV). The oxidation peak currents of NAC and AC increase linearly with their concentrations in the ranges of 0.100–1.510 mM and 0.063–0.190 mM, respectively. The detection limits of N-MWCNTs/AuNPs towards NAC and AC were estimated to be 3.0 and 0.35 μM, respectively. The good catalytic activity, the high detection ability, and the great stability of N-MWCNTs/AuNPs verify that such composite materials are extremely promising for the construction of biosensors.     

Synthesis of carbon nanotube‐based nanocomposite and application for wastewater treatment by ultrasonicated adsorption process

The sorption of methylene blue (MB) and basic yellow 28 (BY28) dyes in water on Ag@ZnO/MWCNT (Ag‐doped ZnO loaded on multiwall carbon nanotubes) nanocomposite is investigated in a batch process, optimizing starting initial dye concentration, sonication time and adsorbent mass. Isotherms and kinetic behaviours of MB and BY28 adsorption onto Ag@ZnO/MWCNT were explained by extended Freundlich and pseudo‐second‐order kinetic models. Ag@ZnO/MWCNT was synthesized and characterized using X‐ray diffraction, energy‐dispersive X‐ray spectroscopy, field emission scanning electron microscopy and Brunauer–Emmett–Teller analysis. According to the experimental data, adaptive neuro‐fuzzy inference system (ANFIS), generalized regression neural network (GRNN), backpropagation neural network (BPNN), radial basic function neural network (RBFNN) and response surface methodology (RSM) were developed, and applied to forecast the removal performance of the sorbent. The influence of process variables (i.e. sonication time, initial dye concentration, adsorbent mass) on the removal of MB and BY28 was considered by central composite rotatable design of RSM, GRNN, ANFIS, BPNN and RBFNN. The performances of the developed ANFIS, GRNN, BPNN and RBFNN models were compared with RSM mathematical models in terms of the root mean square error, coefficient of determination, absolute average deviation and mean absolute error. The coefficients of determination calculated from the validation data for ANFIS, GRNN, BPNN, RBFNN and RSM models were 0.9999, 0.9997, 0.9883, 0.9898 and 0.9608 for MB and 0.9997, 0.9990, 0.9859, 0.9895 and 0.9593 for BY28 dye, respectively. The ANFIS model was found to be more precise compared to the other models. However, the GRNN method is much easier than the ANFIS method and needs less time for analysis. So, it has potential in chemometrics and it is feasible that the GRNN algorithm could be applied to model real systems. The monolayer adsorption capacity of MB and BY28 was 292.20 and 287.02 mg g^?1, respectively.