Concentration Of Reducing Agent Research Articles

Extraction of Metallic Lead from Cathode Ray Tube (CRT) Funnel Glass by Thermal Reduction with Metallic Iron

A novel and effective process of thermal reduction treatment with the addition of metallic iron (Fe(0)) to recover lead from cathode ray tube (CRT) funnel glass is introduced. The key technological breakthrough of this process is the use of a relatively lower temperature and an inexpensive reducing agent to extract the metallic lead. The influences of temperature, the reducing agent content, and the holding time for lead reduction were examined to determine the optimal extraction efficiency. The lead extraction efficiency first increased and then decreased with increasing temperature. The maximum lead extraction efficiency occurred at 700 °C. The growth of crystalline lead first increased significantly with an increase in the Fe content, reaching maximum growth at an Fe addition of 50 wt %. The most effective treatment time was determined to be 30 min, as the vitrification of lead back to the glass matrix occurred under longer treatment times. The experimentally derived results indicate that a 58 wt % lead extraction can be achieved with the optimized operational parameters (50 wt % Fe addition, heating at 700 °C for 30 min) in a single extraction operation.

Continuous ARGET ATRP of Methyl Methacrylate and Butyl Acrylate in a Stirred Tank Reactor

Activator regenerated by electron transfer atom-transfer radical polymerization of butyl acrylate and methyl methacrylate was successfully adapted from a batch process to a continuous stirred tank reactor (CSTR) with 50 ppm copper. A series of batch polymerizations were first performed to identify a solvent mixture to enhance the polymerization rate, maintain chain livingness, and eliminate unsteady-state behavior caused by the precipitation of copper(II) complexes. The batch formulations were run in a CSTR with mean residence times of 60, 90, and 120 min, with steady-state behavior reached after four residence times. The apparent rate coefficient in the CSTR experiments was higher than that in batch polymerizations, likely because of a higher steady-state reducing agent concentration in the CSTR, which shifted the copper(I)/copper(II) ratio in favor of the activating species. Polymer chain extensions showed good living characteristics, demonstrating CSTRs as a viable platform for industrial-scale control...

Robust grafting of PEG-methacrylate brushes from polymeric coatings

A study is presented of the grafting of poly(ethylene glycol)methyl ether methacrylate (PEGMA) from polymeric macroinitiator films to form well-defined polymer brushes, using activators generated/regenerated by electron transfer (AGET/ARGET) atom transfer radical polymerization (ATRP). Polymer brush coatings can potentially be obtained on surfaces of virtually any shape and composition, because of the ease of conformal casting of the anchoring macroinitiator film. Polymer brush coatings are synthesized in a robust way, as ARGET and AGET ATRP require little to no deoxygenation and make use of stable catalysts. The monomer, catalyst, ligand and reducing agent concentrations, the amount and type of initiating moiety in the anchoring films, and the choice of solvents are optimized, resulting in control over the rate of reaction, and the molecular weight of poly(PEGMA). The best conditions are determined for the formation of a poly(PEGMA) brush with high grafting density, controlled thickness and “living” ends available for post-functionalization.

AN INVESTIGATION ON KERATIN EXTRACTION FROM WOOL AND FEATHER WASTE BY ENZYMATIC HYDROLYSIS

In this study, the possibility of keratin extraction from wool and feather by an enzymatic treatment along with a reducing agent has been investigated. The effects of different parameters, that is, enzyme loading, type of substrate and surfactant, hydrolysis time, and reducing agent concentration, have been examined in order to optimize the enzymatic hydrolysis. The optimal condition for maximum keratin extraction was attained by making use of 1 g/L sodium dodecyl sulfate (an anionic surfactant) and 2.6% (v/v) protease (Savinase), along with 8.6 and 6.4 g/L sodium hydrogen sulfite (a reducing agent) for wool and feathers, respectively, at liquor to fiber ratio of 25 mL/g for 4 hr. The obtained results indicated higher degradation of wool fiber in comparison with feathers, which might be due to the higher hydrophilic nature of the former. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) patterns revealed that the molecular weights of the extracted proteins from wool and feather were lower than those for the untreated fibers. Scanning electron micrographs showed fibers fibrillation and degradation upon enzymatic treatment. Besides, Fourier-transform infrared (FTIR) spectra indicated no evident changes in the chemical structure of the hydrolyzed fibers. However, wool and feather remainders were mostly composed of α-helix and β-sheets conformations, respectively.

Radiolabeling, quality control and kit formulation of a new 99mTc-labeled antibiotic: 99mTc-doxycycline hyclate

Since radiolabeled antibiotics specifically bind to the bacterial components they are promising radiopharmaceuticals for the precise diagnosis and detection of infectious lesions. Doxycycline hyclate (DOX) was chosen to investigate as a new radiolabeled antibacterial agent since its bacteriostatic activity against a wide variety of microorganisms. The aim of the present study is to develop simple and easy formulation of DOX with 99mTc ready to use kit. 99mTc-DOX was developed and standardized under varying conditions of reducing and antioxidant agent concentration, pH, radioactivity dose and reducing agent type. Labeling studies were performed by changing the selected parameters one by one and optimum labeling conditions were determined. After observing the conditions for maximum labeling efficiency and stability, lyophilized freeze dry kits were prepared accordingly. Radiochemical purity was determined with RTLC and RHPLC which was found more than >95 %. Two different freeze dry kits were formulated with optimum labeling conditions. The improved kits were found stable up to 6 months.

ARGET ATRP of Butyl Methacrylate: Utilizing Kinetic Modeling To Understand Experimental Trends

A comprehensive kinetic Monte Carlo (kMC) model is used to interpret and better understand the results of a systematic experimental investigation of activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) of butyl methacrylate (BMA) using Sn(EH)2 as reducing agent, ethyl 2-bromoisobutyrate (EBiB) as ATRP initiator, and CuBr2/TPMA (TPMA: tris[(2-pyridyl)methyl]amine) as deactivator. The model demonstrates the importance of slow initiation, with distinct activation and deactivation rate coefficients for the initiator and polymeric species required to match the experimental data. In addition, the model incorporates a second reduction step for the reducing agent and accounts for diffusional limitations on chain-length-dependent termination. The effect of temperature on the slow ATRP initiation is limited, and a sufficiently high initial reducing agent concentration is crucial to obtain a high conversion, although achieved at the expense of decreased end-group functionality.

Influence of Electroless Ni-P Coating Bath Parameters on the Strength and Surface Finish

This experimental investigation is devoted to the analysis of the hardness and surface roughness of the electroless Ni-P coated low carbon steel substrate. Deposition of electroless nickel phosphate coating has been carried out on substrate material from bath containing Nickel chloride, Ammonium chloride, Sodium hypophosphite, and Sodium hydroxide. The coating is carried out by varying the most contributing bath parameter, like temperature, pH and the reducing agent content, within a specified range. The influence of coating bath parameters like, temperature, pH and percentage of phosphate on the hardness and surface roughness of the substrate/coating composite were investigated by microhardness and the surface roughness. The specimen preparation and experimentations were carried out according to the ASTM standards. The nature of coating, thickness and the type of indentations were analyzed with the aid of scanning electron microscopy. The result showed that the substrate material coated with pH 8, temperature 80 0 C and 20 percent of phosphate has maximum hardness and good surface finish. Also, the deposition rate at this level of bath parameters is found to be high, with the absence of the interfacial defects.

A study on the effect of reducing agent content on the thickness of electroless Ni3P deposits on B4C nanoparticles

Deposition of Ni3P nano-scale layer on B4C nanoparticles in four contents of sodium hypophosphite as reducing agent including 5, 10, 15 and 30 g/l via electroless coating were done to investigate the effect of reducing agent content on the coating thickness of deposited Ni3P. The bath pH and temperature was 5.5 and 85 °C, respectively and the coating time was 25 min. The powders were characterized by transmission electron microscopy (TEM) and the phases present were revealed by X-ray diffraction (XRD). Nickel and phosphorous contents of the coatings were measured by inductively coupled plasma analysis (ICP). The results revealed that by increasing the reducing agent content from 5 g/l to 30 g/l the average coating thickness increased from 19 nm to 28 nm. Although the increasing effect of adding sodium hypophosphite content was preserved, there is a critical amount for sodium hypophosphite content to increase the coating thickness.

Study on the Fabrication and Properties of Ni-P Composite Coating

In this paper, the method of electroless deposition of nickel-phosphorous composite coating on the sample surface is employed. The effect of the complexing agent ratio on the surface morphology and phase composition of nickel-phosphorus coating when the main salt and reducing agent concentration unchanged has been studied. The influence of heat treatment on properties and microstructure of coatings are also investigated. Experimental results show that in the case of salt and reducing agent concentration unchanged, complexing agent concentration has strong effect on the morphology of the coatings and the crystal structure of the composite coating. During heat treatment, the morphology of the composite coating changed significantly, and the hardness was improved a certain degree for all the samples, which is related to the precipitation of Ni3P.

Synthesis and characterization of semiconductor metal sulfide nanocrystals using microemulsion technique

AbstractThe semiconductor nanocrystals ZnS, PbS, CdS and CuS were synthesized via microemulsion technique involving metal acetate, reducing agent (Na2S) and Triton X‐100 as surfactant. Nanocrystals were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM) and dynamic light scattering (DLS). The average size of ZnS, PbS, CdS and CuS nanocrystals were found to be 5.6 nm, 13.3 nm, 11.4 nm and 6.2 nm, respectively. Different parameters like surfactant (Triton X‐100) concentration, water‐to‐surfactant ratio (ω), precursor concentration [zinc acetate, (Zn(AC)2], reducing agent concentration [sodium sulphide, (Na2S)] were optimized to synthesize ZnS quantum dots.

Predicting electroless Ni–Co–P coating using response surface method

Electroless Ni–Co–P coating has been studied considering pure copper (99.99 %) as a substrate material. The deposited mass per unit area of the substrate has been considered as the response variable. The individual as well as combined effects of the process parameters on the response variable has been studied. The bath temperature and the interaction of cobalt source concentration and reducing agent concentration have been found to be significant through regression analysis and Student's t test. Mathematical modelling has been carried out using a second-order response surface model with central composite design to take into account the effect of curvature in the predicted response. The equation for response surface has been determined using MATLAB software package. The response surface plots show that the rate of deposition increases significantly with the rise in temperature while the cobalt source concentration and reducing agent concentration have an interactive effect which influences the rate of deposition. The test of reliability for the predicting response surface equation shows that the equation gives an excellent fitting to the observed values.

Development of an analytical method for the determination of arsenic in gasoline samples by hydride generation–graphite furnace atomic absorption spectrometry

The purpose of the present work was to optimize the conditions for the determination of arsenic in gasoline with hydride generation–graphite furnace atomic absorption spectrometry after acid digestion using a full two-level factorial design with center point. The arsine was generated in a batch system and collected in a graphite tube coated with 150μg Ir as a permanent modifier. The sample volume, the pre-reduction conditions, the temperature program and modifier mass were kept fixed for all experiments. The estimated main effects were: reducing agent concentration (negative effect), acid concentration (negative effect) and trapping temperature (positive effect). It was observed that there were interactions between the variables. Moreover, the curvature was significant, indicating that the best conditions were at the center point. The optimized parameters for arsine generation were 2.7molL−1 hydrochloric acid and 1.6% (w/v) sodium tetrahydroborate. The optimized conditions to collect arsine in the graphite furnace were a trapping temperature of 250°C and a collection time of 30s. The limit of detection was 6.4ngL−1 and the characteristic mass was 24pg. Two different systems for acid digestion were used: a digester block with cold finger and a microwave oven. The concentration of arsenic found with the proposed method was compared with that obtained using a detergentless microemulsion and direct graphite furnace determination. The results showed that the factorial design is a simple tool that allowed establishing the appropriate conditions for sample preparation and also helped in evaluating the interaction between the factors investigated.

Automated ARGET ATRP Accelerates Catalyst Optimization for the Synthesis of Thiol-Functionalized Polymers

Conventional synthesis of polymers by ATRP is relatively low throughput, involving iterative optimization of conditions in an inert atmosphere. Automated, high-throughput controlled radical polymerization was developed to accelerate catalyst optimization and production of disulfide-functionalized polymers without the need of an inert gas. Using ARGET ATRP, polymerization conditions were rapidly identified for eight different monomers, including the first ARGET ATRP of 2-(diethylamino)ethyl methacrylate and di(ethylene glycol) methyl ether methacrylate. In addition, butyl acrylate, oligo(ethylene glycol) methacrylate 300 and 475, 2-(dimethylamino)ethyl methacrylate, styrene, and methyl methacrylate were polymerized using bis(2-hydroxyethyl) disulfide bis(2-bromo-2-methylpropionate) as the initiator, tris(2-pyridylmethyl)amine as the ligand, and tin(II) 2-ethylhexanoate as the reducing agent. The catalyst and reducing agent concentration was optimized specifically for each monomer, and then a library of polymers was synthesized systematically using the optimized conditions. The disulfide-functionalized chains could be cleaved to two thiol-terminated chains upon exposure to dithiothreitol, which may have utility for the synthesis of polymer bioconjugates. Finally, we demonstrated that these new conditions translated perfectly to conventional batch polymerization. We believe the methods developed here may prove generally useful to accelerate the systematic optimization of a variety of chemical reactions and polymerizations.

Roughness Optimization of Electroless Ni-B Coatings Using Taguchi Method

In this paper, the authors present an experimental study of roughness characteristics of electroless Ni-B coatings and optimization of the coating process parameters based on L27 Taguchi orthogonal design. Three coating process parameters are considered viz. bath temperature, reducing agent concentration, and nickel source concentration. It is observed that concentration of reducing agent together with bath temperature play a vital role in controlling the roughness characteristics of the coatings. The analysis yields the optimum coating parameter combination for minimum roughness. A reduction of about 15% is observed in roughness at the optimal condition compared to the initial condition. The microstructure, composition, and the phase content of the coating are also studied with the help of scanning electron microscopes energy dispersive X-ray analysis, and X-ray diffraction analysis, respectively.

Force optimization of ionic polymer metal composite actuators by an orthogonal array method

Ionic polymer metal composites (IPMCs), a new kind of electro-active polymer, can be used for micro robotic actuators, artificial muscles and dynamic sensors. However, IPMC actuators have the major drawbacks of a low generative blocking force and dependence on a humid environment, which limit their further application. Multiple process parameters for the fabrication of IPMCs were optimized to produce a maximum blocking force; the parameters included reducing agent concentration, platinum salt concentration in the initial compositing process, and tetraethyl orthosilicate (TEOS) content. An orthogonal array method was designed and a series of fabrication experiments were carried out to identify the optimum process parameters. The results show that the platinum salt concentration in the initial compositing process plays the most significant role in improving the blocking force of IPMCs, the TEOS content plays an important role, and the reducing agent concentration has no apparent effect on the blocking force. In the optimized conditions, the IPMC actuator exhibited maximum blocking force of 50 mN, and the corresponding displacement was 14 mm. Compared with normal conditions, the blocking force improved 2.4-fold without sacrificing the displacement, and the effective air-operating life was prolonged 5.8-fold for the blocking force and 5-fold for the displacement. This study lays a solid foundation for further applications of IPMCs.

Solventless synthesis of iridium(0) nanoparticles

In this article, we present the results of a solvent-free synthesis of iridium(0) nanoparticles, both water washed and unwashed. IrCl3 and NaBH4, as starting materials, are mixed using an agate mortar and milled for 15 min until a black powder is obtained, which is heated in a nitrogen-controlled atmosphere oven at 200 °C for 2 h. If the product of the reaction is not washed before heating, NaBH4 and IrO2 impurities are observed. On the other hand, if the reaction product is washed before the heating, the obtained powder is free of impurities. We study the effect of the variation in reducing agent concentration and the annealing temperature used after the reaction. In all cases, the calculated particle size is less than 10 nm.

천연인디고를 이용한 셀룰로오스계 직물 염색의 표준화 연구: 일단계 환원/염색에 의한 마직물 염색

One-step reduction/dyeing method was applied for ramie dyeing with natural indigo powder. The effect of reduction/dyeing conditions including the pH of bath, dye temperature and time, and concentration of indigo powder and reduction agent on dye uptake and color properties were investigated. Regardless of addition of alkali, the dyed fabrics appeared in the PB Munsell color range(<TEX>${\lambda}_{max}$</TEX>: 660 nm) and the dye uptake was much higher with no addition of sodium hydroxide. Dyeing was carried out through the use of only sodium hydrosulfite in the bath. The maximum dye uptake was obtained at 60 for 30min. Saturated dye uptake was obtained at 2 g/L of sodium hydrosulfite concentration up to 2 g/ L of indigo powder. Whereas, at higher indigo powder concentration (4 g/L), more than 3 g/L of reducing agent concentration was required for obtaining the saturated dye uptake. Color reproducibility was reliable with color difference in the range of 0.03~0.16. Regardless of color strength, fastness to rubbing was acceptable with a 3/4~4/5. Fastness to washing, dry cleaning, and light of samples with low color strength were poor. Whereas, fastness to washing, dry cleaning, and light of samples with high color strength were very good.

Synthesis and Optical Properties of Colloidal Gold Nanoparticles for Biomedical Applications

The gold nanoparticle solutions are well known as an extremely sensitive biomedical analytical tool due to the strong dependence of their absorption in the visible range on the environment. In this work, the colloidal nano golds were synthesized from metal precursor chloroauric acid (HAuCl4) using trisodium citrate dehydrate (C6H5O7Na3) as reducing and stabilizing agents. The optical characterization - absorption of colloidal gold solution have been investigated under the different synthetic conditions such as: reducing agent concentration, concentration of auric ion, pH, duration of reaction and aging time. The results show that the absorption and the stability of the colloidal gold nanoparticles depend robustly on the synthetic conditions and pH of environment.

One-step in situ synthesis of NH x-adsorbed rhodium nanocrystals at liquid–liquid interfaces for possible electrocatalytic applications

Nearly monodisperse rhodium nanoparticles with adsorbed NH x were synthesized at the CCl 4 –water interface. The presence of NH x -adsorbed species was confirmed by energy-dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS) studies. The synthesis of controlled size 2–38 nm rhodium particles was studied as a function of reducing agent concentration by transmission electron microscopy (TEM). HRTEM confirmed the formation of rhodium nanoparticles having fringe spacing consistent with reported Rh (1 1 1) planes. The continuity of these films over an area of 1 × 1 μm was revealed by atomic force microscopy (AFM) studies. The electrocatalytic application of these nanostructure Rh-NH x thin films for formaldehyde oxidation in 0.5 M NaOH was investigated by cyclic voltammetry. The Rh nanoparticles formed by the present strategy are expected to be useful for other catalytic applications also.

Fractal characterisation of electroless Ni-B coating and optimisation of coating parameters

This paper presents an experimental study of fractal characteristics of the surface profile of electroless Ni-B coating and optimisation of coating parameters based on L27 Taguchi orthogonal design. Optimum coating parameter combinations are identified to yield the optimum (maximum) fractal dimension by Taguchi analysis so that a smoother coating surface is obtained. Bath temperature is found to be the most important coating parameter in controlling the fractal characteristics of Ni-B coatings. The interaction between reducing agent concentration and the nickel source concentration also has high contribution in controlling the fractal characteristics of Ni-B coating. The coating is characterised for its microstructure and composition by scanning electron microscopy, X-ray diffraction analysis and energy dispersive X-ray analysis.