Higher NaOH Concentrations Research Articles

Role of a Surfactant in Caustic Alkali Cleaning of Polyethylene Terephthalate Surfaces Fouled with Organic Substances

The role of polyoxyethylene lauryl ether (POELE), a nonionic surfactant, in removing bovine serum albumin (BSA) and catechin from polyethylene terephthalate (PET) particles was quantitatively studied. Relatively large fractions of adsorbed BSA and catechin were removed from PET particles under weak alkaline conditions below pH 9, whereas cleaning with high concentrations of NaOH was not so effective, especially on the removal of BSA. This was attributed to the lower susceptibility of PET particles to water-based alkali (OH-) cleaning because of the lower degree of the polarity of PET surfaces. The combined use of NaOH solutions of moderate pHs and POELE could successfully improve the efficiency of cleaning of PET particles without a significant dissolution of PET materials. There was a good correlation between the lowered surface tension (7) of the NaOH solution with POELE and the removal efficiency of BSA or catechin. No effect of POELE was observed on the NaOH cleaning of hydrophilic alumina (A12O3) particles fouled with BSA. It could be concluded that the role of POELE in NaOH cleaning of PET particles was to lower the gamma of the NaOH solution and hence to facilitate penetration of OH- ions into the PET-BSA and PET-catechin interfaces.

PREPARATION AND CHARACTERIZATION OF HYDROXYAPATITE BY A REACTION OF CALCIUM TUNGSTATE WITH PHOSPHATE

Hydroxyapatite was prepared by a reaction of CaWO4 with phosphate at temperatures from 90 °C to 210 °C. High concentration of NaOH was appropriate for the formation processes of hydroxyapatite. The temperature dependence of reaction rate was related to the mass transport through a reaction layer. Very small activation energy of reaction, 25.5 kJ/mol, was attributed to the diffusion of Ca2+ ions in liquid among reaction products.

The Mathematical Model of Mechanical Pulp Bleaching Process.

The control task of the bleaching process is complicated by long retention time and strong process nonlinearity. The classical control tools are ineffective because of long retention time and new neuronal control systems have serious difficulties with process nonlinearity. After process change, they have to learn again to find parameters for the new working point. To support learning process of the multivariable controllers, the mathematical model of the bleaching process has been designed.The basic kinetic model is the reaction of dissociated HOO– molecules with chromophore groups. Ongoing reaction decreases HOO– concentration and changes bleaching conditions for following reactions. The NaOH creates conditions for peroxide dissociation and also attacks the lignin molecules, decreasing yield of bleaching process. The yellowing reaction due to high concentration of NaOH is included, as well. The peroxide decomposition process caused by high temperature or heavy metals is also part of the bleaching model. To simplify solution of complicated system of partial differential equations, the whole volume of the bleaching tower has been vertically divided to thin slices. The bleaching conditions in one slice are considered to be homogenous an constant during time t and t+? t. The chromophore are divided into the light, difficult bleachable and non bleachable groups with corresponding consumption of HOO– molecules. The supporting chemical reactions are also calculated in each slice separately creating conditions for next calculation step.The parameters of the chemical reactions have to be found using laboratory results. The model of peroxide bleaching process forecasts the bleaching results with an accuracy of ±1% taking into consideration, of course, that the main process variables are measured. Bigger deviation between calculated and measured results means significant changes in not measured process variables. This fact can be used as alarm. The model of the bleaching process integrated into multivariable model predictive controller enables setting of controller parameters in short time instead to learn controller from process.The model of bleaching process was tuned according to the results of laboratory bleaching trials. After setting of model parameters the model reached laboratory values for final brightness, pH, residual peroxide and COD. Model has been tuned to several different bleaching trials of mechanical pulps and also to results of laboratory bleaching of waste paper has been used to prove model universality. In all cases it was possible to tune model to meet bleaching results according to the used bleaching recipe.The model was also tested on-line in field-side reference HC Bleach Plant. Model parameters were tuned according to the laboratory results. Measured process values like pulp flow, consistency, charging of bleaching chemical and incoming brightness have been used as model variables. The Model calculated bleaching reactions and the out coming calculated brightness was over 90% of tested period very closed to the measured one (±1%).

Histochemical Study of the Chemical Composition of Vestured Pits in two Species of Eucalyptus

We analyzed the chemical composition of vestures of vessel elements and wood fibres of Eucalyptus camaldulensis and Eucalyptus globulus by ultraviolet (UV) microscopy, transmission electron microscopy (TEM) after staining with potassium permanganate (KMnO4) or the PATAg reaction, and field-emission scanning electron microscopy (FE-SEM). Samples were treated with dilute solutions of NaOH at various concentrations. Before treatment with alkali, the vestures on the secondary walls of vessel elements and wood fibres were visible on UV micrographs taken at 280 nm and were strongly stained by KMnO4. Vestures were strongly stained by the PATAg reaction in samples that had been treated with 0.1% NaOH. However, treatment with higher concentrations of NaOH dissolved the vestures. FE-SEM observations showed that the process of dissolution of vestures during alkali extraction differed between the two species. It appears that vestures in Eucalyptus woods consist mainly of alkali-soluble polyphenols and polysaccharides. In addition, the chemical composition of vestures may differ between the two species of Eucalyptus that we examined.

Synthesis of Multiwalled Carbon Nanotubes through a Modified Wolff−Kishner Reduction Process

We report the synthesis of highly crystallized multiwalled carbon nanotubes through a modified Wolff-Kishner reduction process at a low temperature of 180 degrees C without adding the conventional catalysts of Fe/Co/Ni into the reaction vessel. The as-synthesized carbon nanotubes are about 10-40 nm in diameter and several tens of micrometers in length. The experimental results indicate that a high concentration of NaOH is essential to the formation of carbon nanotubes. This technique opens a new route for the synthesis of CNTs and other carbon nanostructured materials.

Co-doped titanate nanotubes

Co-doped titanate nanotubes were synthesized through 130 °C treatment of Co-doped TiO2 powders in high concentration NaOH aqueous solutions in a hydrothermal autoclave. The obtained nanotubes were identified to be of a monoclinic layered trititanate structure, the same as H2Ti3O7, their un-doped counterpart. The incorporation of Co ions was identified by energy dispersive spectroscopy. The Ti:Co atomic ratio in the obtained nanotubes was found significantly less than the value in the powder precursor. This indicates that the precursor powders were deformed in NaOH solution before the formation of nanotubes. Magnetic measurement showed a hysteresis loop at room temperature.

Synthesis of Nanotubular Mg3Si2O5(OH)4-Ni3Si2O5(OH)4 Silicates at Elevated Temperatures and Pressures

Mg3Si2O5(OH)4-Ni3Si2O5(OH)4 nanotubes with the chrysotile structure and MgO : NiO molar ratios of 1 : 2 and 2 : 1 are synthesized by hydrothermal reactions at temperatures from 250 to 450°C and pressures from 30 to 100 MPa. The reaction path and kinetics, as well as the dimensions and morphology of the resulting nanotubes, are shown to depend on the nature of the starting reagents, chemical composition of the reaction system, and hydrothermal synthesis conditions. At higher nickel concentrations in the hydrous silicates, nanotube formation requires higher temperatures, longer hydrothermal treatment times, and higher NaOH concentrations in the reaction system.

Controllable Synthesis of ZnO Nanorod and Prism Arrays in a Large Area

ZnO nanorod and nanoprism arrays have been directly synthesized on a large-area zinc substrate via a convenient solution method. The products were characterized with XRD, SEM, HRTEM, and photoluminescence (PL) spectroscopy. The influence of the solvent and the concentration of NaOH on the size and shapes of the as-prepared ZnO samples have been studied. It was found that ZnO nanorod or nanowire arrays were fabricated in alcohol, whereas ZnO nanoprisms with pyramid tips were produced in an alcohol-water mixture. The diameters of the nanorods or nanoprisms became thicker when a higher concentration of NaOH was used. Room-temperature PL spectra of the ZnO products showed a UV emission and a broad green band. The mechanism of the nanorods and nanoprisms in two systems is briefly discussed.

The coexistence of geopolymeric gel and calcium silicate hydrate at the early stage of alkaline activation

Scanning electron microscopy was used to study the effects of the addition of ground granulated blast furnace slag (GGBFS) on the microstructure and mechanical properties of metakaolin (MK) based geopolymers. It was found that it is possible to have geopolymeric gel and calcium silicate hydrate (CSH) gel forming simultaneously within a single binder. The coexistence of these two phases is dependent on the alkalinity of the alkali activator and the MK / GGBFS mass ratio. It has been found that the formation of CSH gel together with the geopolymeric gel occurs only in a system at low alkalinity. In the presence of high concentrations of NaOH (> 7.5 M), the geopolymeric gel is the predominant phase formed with small calcium precipitates scattered within the binder. The coexistence of the two phases is not observed unless a substantial amount of a reactive calcium source is present initially. It is thought that voids and pores within the geopolymeric binder become filled with the CSH gel. This helps to bridge the gaps between the different hydrated phases and unreacted particles; thereby resulting in the observed increase in mechanical strength for these binders.

Low-temperature hydrothermal synthesis of multiwall carbon nanotubes

Since the discovery of carbon nanotubes (CNTs) by Iijima [1], an endless list of potential applications of CNTs have been proposed. Consequently, a worldwide research interest has been focused on the growth of CNTs to realize their potential applications [2]. Numerous methods for the synthesis of CNTs have been developed [3–11]. Among the variety of methods, chemical vapor deposition (CVD) is the most widely used to synthesize CNTs. Although CVD offers the benefit of significantly lower synthesis temperatures than arc-discharge and laser ablation techniques, it still requires a growth temperature of 600–950 C. Recently, it has been reported that high-temperature hydrothermal process is an alternative route for the synthesis of CNTs [12,13]. Yoshimura and co-workers synthesized CNTs using polyethylene (PE), ethylene glycol (EG) and other sources with and without catalysts Fe/Co/Ni under hydrothermal conditions at 700– 800 C and 60–100 MPa [12,13]. However, the temperature is comparable with the CVD technique. Hence, it is still a challenge to develop a new approach for the synthesis of CNTs at a low temperature. To date, the lowest-reported temperature for the synthesis of multiwall carbon nanotubes (MWCNTs) is 175 C, from decomposition of CCl4 using iron-encapsulated polypropyleneimine dendrimers as a catalyst in supercritical carbon dioxide medium [14]. In this letter, we report the synthesis of MWCNTs by the decomposition of polyethylene glycol (PEG; MW 20,000) in a basic aqueous solution with high concentration of NaOH under hydrothermal conditions at a temperature as low as 160 C, which is the lowest to our knowledge, without the addition of catalyst Fe/Co/Ni. The morphologies and microstructures of the as-prepared MWCNTs were studied with transmission electron microscopy (TEM, JEOL 2010F). In a typical synthesis, 80 mL ethyl alcohol, 10 mL distilled water, 7 g NaOH and 2 g PEG were added to a 250 mL flask. The mixtures were stirred in a magnetic stirrer for 30 min, and then transferred to a Parr reactor (model 4750, Parr Company, Moline, IL) with a capacity of 125 mL. The Parr reactor was sealed and then kept at 160 C for 20 h in a furnace, and then cooled down to room temperature. The products were washed with alcohol and distilled water for several times, and then dried in a vacuum oven at 60 C for 10 h. Fig. 1 shows the TEM images of the as-synthesized MWCNTs at different magnifications. It can be seen that the MWCNTs have outer diameters ranging from 9 to 19 nm and inner diameters ranging from 4 to 8 nm. It is worth pointing out that the diameters of the as-prepared MWCNTs by the current low-temperature hydrothermal route are much smaller than those [14] Vesselenyi I, Niesz K, Siska A, Konya Z, Hernadi K, Nagy JB, et al. React Kinet Catal Lett 2001;74:329–36. [15] Willems I, Konya Z, Fonseca A, Nagy JB. Appl Catal A: Gen 2002;229:229–33. [16] Yuan L, Li T, Saito K. Carbon 2003;41:1889–96. [17] Emmenegger C, Bonard JM, Mauron P, Sudan P, Lepora A, Grobety B, et al. Carbon 2003;41:539–47. [18] Zhang M, Yudasaka M, Bandow S, Lijima S. Chem Phys Lett 2003;369:680–3. [19] Motiei M, Hacohen YR, Moreno JC, Gedanken A. J Am Chem Soc 2001;123:8624–5. [20] Dresselhaus MS, Dresselhaus G, Pimenta MA, Eklund PC. In: Pelletier MJ, editor. Analytical applications of Raman spectroscopy. Oxford: Blackwell Science; 1999 [Chapter 9].

焼却灰から合成されるフィリップサイトの純度および収率の多段階合成法による向上

This paper proposes a new multi-stage synthesis method of phillipsite at a high purity and an improved yield from coal fly ash and rice husk ash. Fly ashes are treated hydrothermally with NaOH solution to form aluminate ion and silicate ion and they are separated from insoluble residues of fly ash for the preparation of phillipsite. The products of phillipsite obtained from coal fly ash and rice husk ash are over 90% in purity and the adsorption performance is comparable to the artificial zeolite available on the market. Total yield of phillipsite is also improved to 35.0% from 25.0% which was attained in our previous work (Fukui, et al., J. Society of Powder Technology, Japan, 40, 497-504, 2003). It is also found that the aluminate ion concentration is higher at a higher NaOH concentration and that the generated amount of phillipsite increases with the aluminate ion concentration.

Morphological and grafting modification of natural cellulose fibers

AbstractCrystal structure and mechanical properties of cellulose fibers were studied to investigate the effect of chemical treatment on the fiber. Pretreatment by acetone extraction, mercerization with 3–20% wt/v sodium hydroxide (NaOH), and acrylonitrile (AN) grafting initiated by azo‐bis‐isobutylonitrile were performed. From Fourier transform infrared spectroscopy and wide‐angle X‐ray diffraction quantitative measurements, the pretreated fibers showed an induced slight decrease of crystallinity index. The structural transformation of the fibers from cellulose I to cellulose II was observed at high NaOH concentration of 10–20% wt/v. The amount of grafting, 1.56, 2.94, 6.04, 8.34, or 10.46%, was dependent upon the initiator concentration and the volume of monomer in the reactor. The AN grafted fibers had no transformation of crystalline structure as observed after mercerization. Only a variation of X‐ray crystallinity index with grafting amount was observed. Moisture regain of pretreated and modified fibers depended on the structure of the fiber and the amount of grafting. The mechanical properties performed by a single fiber test method were strongly influenced by the cellulose structure, lateral index of crystallinity, and fraction of grafting. Scanning electron microscopy was used for analysis of surface morphologies of treated fibers. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2456–2465, 2004

Synthesis of zeolite from coal fly ashes with different silica–alumina composition

Coal fly ashes can be converted into zeolites by hydrothermal alkaline treatment. This study focuses on the effect of Si/Al molar ratio of the fly ash source on the type of formed zeolite, which also is affected by the alkaline condition. The fly ashes were mixed with an aqueous NaOH solution and hydrothermally treated at about 100 °C. Zeolite Na–P1 and/or hydroxy-sodalite appeared after the treatment. Zeolite Na–P1 predominantly formed from silica-rich fly ash at a low-NaOH concentration. The cation exchange capacity of the product with a large content of zeolite Na–P1 reached a value of 300 meq/100 g. The type of the product was controlled by addition of aerosil silica or alumina. It was found that silica addition effectively enhances the formation of zeolite Na–P1, even at a high-NaOH concentration. These results were discussed on the basis of a formation mechanism of zeolite from coal fly ash through dissolution–precipitation process.

Synthesis of Cu(OH)2 Nanowires at Aqueous−Organic Interfaces

Cu(OH)2 nanowires have been successfully synthesized at the organic−aqueous interface by the interaction of the copper−bis(2-ethylhexyl) phosphate complex in the organic layer with NaOH in aqueous layer. The nanowires have an average length of 4 μm and are several nanometers in width. CuO nanowires and short wiskers are conveniently prepared through dehydration of Cu(OH)2 at high concentrations of NaOH under ambient conditions. Transmission electron microscopy and X-ray diffraction techniques have been used to characterize the microstructures and morphologies of the nanowire materials.

Enhancing the Durability of Linen-Like Properties of Low Temperature Mercerized Cotton

In order to develop durable linen-like cotton yam with low temperature mercerization, pretreatment methods ensuring efficient and uniform penetration of the low temperature alkali solution into cotton yarn are studied. Pretreatments consisting of an alkaline scouring at higher NaOH concentrations and of a cellulase treatment and subsequent alkaline scouring are evaluated for their efficiency in removing wax and enhancing absorptive properties. The cellulase treatment/alkaline scouring is more efficient at re moving wax than alkaline scouring at higher NaOH concentrations. The cellulase treat ment and subsequent alkaline scouring result in wax contents lower than 0.1%. The cellulase treatment appears to degrade the cellulose on the surface of the cotton fibers, making it more accessible to the scouring agent and making wax removal easier. Swelling and wetting times are compared to identify a pretreatment sufficient for developing linen-like cotton. In low temperature mercerization, the pretreatment consisting of cellu lase treatment and alkaline scouring yields a linen-like cotton yarn whose stiffness is durable to knitting, wet processing, and even ten laundering cycles. The durability appears to be sufficient for practical applications of the process for producing linen-like cotton.

Enhanced enzymatic hydrolysis of steam-exploded Douglas fir wood by alkali-oxygen post-treatment.

Good enzymatic hydrolysis of steam-exploded Douglas fir wood (SEDW) cannot be achieved owing to the very high lignin content ( >40%) that remains associated with this substrate. Thus, in this study, we investigated the use of alkali-oxygen treatment as a posttreatment to delignify SEDW and also considered the enzymatic hydrolyzability of the delignified SEDW. The results showed that under optimized conditions of 15% NaOH, 5% consistency, 110 degrees C, and 3 h, approx 84% of the lignin in SEDW could be removed. The resulting delignified SEDW had good hydrolyzability, and cellulose-to-glucose conversion yields of over 90 and 100% could be achieved within 48 h with 20 and 40 filter paper units/g of cellulose enzyme loadings, respectively. It was also indicated that severe conditions, such as high NaOH concentration and high temperature, should not be utilized in oxygen delignification of SEDW in order to avoid extensive condensation of lignin and significant degradation of cellulose.

Electrochemical formation and characterization of Ag2O

The process of Ag2O formation has been investigated in 0.1M, 0.3 M, 1.0Mand 2.0 M NaOH solutions on polycrystalline Ag electrodes by cyclic voltammetry potentiostatic pulse and SEM techniques. The SEM micrographs of the chemically polished Ag surface and the surface after oxide formation revealed considerable roughening of the Ag surface after Ag2O formation and reduction. The roughening was more pronounced at higher NaOH concentrations, indicating that only the first cycle or pulse applied on a freshly polished Ag electrode should be considered in mechanistic studies of Ag2O formation. In the given range of NaOH concentrations, it was shown that the process is not controlled simply by the diffusion of the reacting species.Anucleation phenomenon was clearly detected in all the examined solutions. The SEM micrographs confirm that the two anodic peaks, present on the voltammograms of Ag2O formation correspond to two types of oxide film, i.e., non-homogeneously and homogeneously distributed ones. Potentiostatic formation of the oxide at potentials corresponding to the first and second anodic peak yielded simple cubic Ag2O but of very different grain size.

Modeling Alkaline Silicate Solutions at 25 °C

A thermodynamic model is developed to describe silicate behavior in solutions containing high concentrations of both NaOH and NaNO3. Experimental solubility data in such solutions are also presented. The model itself applies Pitzer's ion-interaction approach and involves several aqueous polymeric species. Model predictions compare well with a variety of experimental datasolubilities, NMR results, and pH measurements.

Evaluation of alkaline borohydride solutions as the fuel for fuel cell

A fuel cell was assembled using alkaline borohydride solutions as the fuel. The specific gravity, specific viscosity, and melting points of the borohydride solutions were evaluated. With increasing the NaBH4 concentration, the specific gravity was decreased but the viscosity was increased consistently. The effects of NaBH4 and NaOH concentrations on the cell and electrode polarizations were investigated. The increase of NaBH4 concentration improved the anode performance a little but obviously increased the cathode polarization due to the BH4− crossover. As a result, the cell polarization increased when using high concentrated borohydride solutions. According to the Nernst’s equation, the increase of NaOH concentration is favorable to the anode, but negative to the cathode polarization. In principle, the cell polarization has nothing to do with the NaOH concentration according to the cell reaction NaBH4+O2=NaBO2+2H2O. However, the experimental results showed that the high concentration of NaOH aggravated the cell polarization at higher current densities.

Polymerization by phase transfer catalysis. 27. Synthesis of polyesters containing silicon or germanium. Influence of the base concentration

Polyesters derived from diphenols containing Si or Ge and isophthalic and terephthalic acids dichlorides have been synthesized using phase transfer conditions, and characterized by spectroscopic methods. Two phase transfer catalysts and three molar ratios NaOH/diphenol were used, and the results evaluated by the yields and the inherent viscosity values; these are compared with those obtained without catalyst. When the catalysts were used there was an increase of the yields and the η inh values, due to the effectivity of the phase transfer process. Also, when the base concentration was increased, there was an increase of the yields due to a salting out effect which permits a higher transference of the diphenolate to the organic phase in which the reaction takes place, and an increase in the amount of the polyesters and, to a lesser extent, the molecular weight. There was no influence of the higher NaOH concentration on the stability of either the acid dichloride or the polyesters.