Low NaOH Concentration Research Articles

The Research of Chemical Plating of Pd/Sn on Graphite Anode Surface and its Electro-Catalytic Properties

The Pd/Sn catalytic coating on graphite electrode had been synthesized by chemical plating in this paper. Scanning electron microscope(SEM)and Electrochemical workstation(EW)were used to analyze the coating surface topography and electro-catalytic properties of modified graphite electrode with and without the coating. Results show that Pd and Sn are in the form of spherical particle and completely cover the surface of graphite electrode includes concave defects. Most Pd and Sn particles are dispersive ones of size of about 70 nm and few of which are polymerized in island forms. The peak value of current density increases with scanning speed, which goes positive potential scanning. Further more, the peak current increases with the concentration of NaOH solution, which shows nonlinear relationship between peak current and solution concentration, The peak current increases more rapidly with solution concentration increases in low NaOH concentration solution than that in high NaOH concentration solution.

알칼리 처리에 따른 아마섬유의 헤미셀룰로스 제거와 결정구조 전이

In this study, delignified flax fiber was treated with a NaOH aqueous solution. XRD diffractometry and FTIR spectroscopy were utilized to examine the structural transition of the alkali-treated flax fibers. Also, the effect of the hemicellulose removal on the structural change of flax fibers was discussed. XRD measurement revealed that the crystallinity of cellulose I increased at low NaOH concentration (3%) due to the elimination of amorphous hemicellulose. The structural transition from cellulose I to cellulose II occurred in a NaOH concentration range of 12~15%. Considering most hemicellulose in flax fiber is removed at 12% NaOH, it can be assumed that the presence of hemicellulose in flax fiber has a role in preventing the structural change of flax cellulose. IR absorbance ratios (<TEX>$A_{1370cm}{^{-1}}/A_{2900cm}{^{-1}}$</TEX> and <TEX>$A_{1430cm}{^{-1}}/A_{2900cm}{^{-1}}$</TEX>) were utilized as a barometer of cellulose I crystalline exhibiting a similar result with the cellulose I crystallinity from XRD. Another absorbance ratio (<TEX>$A_{895cm}{^{-1}}/A_{2900cm}{^{-1}}$</TEX>) reflected the cellulose II crystalline showing almost the same trend as cellulose II crystallinity. On the whole, the total crystallinity of flax fiber was increased at low NaOH concentration (3%) and decreased at 12% due to the reduction of cellulose I content and increased again at 15% attributed to the formation of cellulose II content.

MALDI-TOF, HPLC-ESI-TOF and 13C-NMR characterization of chestnut (Castanea sativa) shell tannins for wood adhesives

MALDI-TOF, HPLC-ESI-TOF and 13C-NMR techniques were used to analyse the structure of non-purified aqueous chestnut shell tannin extracts. In addition, the influence of the extraction agent (water or aqueous solutions of Na2SO3 and/or NaOH) on tannin structure was analysed by MALDI-TOF in order to select the extract with the best properties for wood adhesives. Using HPLC-ESI-TOF, catechin/epicatechin, gallocatechin/epigallocatechin, dicatechin structures, dicatechin structures without a hydroxyl group, galloyl-glucoses and ellagic acid were identified as the main monomeric components in the aqueous extract. 13C-NMR and MALDI-TOF spectra revealed that extracts are mostly composed of procyanidin and prodelphinidin structures although prorobinetidins might be also present. MALDI-TOF spectrometry was used to identify the extract oligomeric components. Extractions with Na2SO3 and/or NaOH produced changes in the predominant structures in the extracts and on the amount of sugar units linked to the flavonoid structures, which decreased in the presence of Na2SO3. Extract obtained using low Na2SO3 and NaOH concentrations (1.5 and 0.75 %, respectively) was selected as more suitable for wood adhesive preparation.

Alcohol Assisted Hydrothermal Synthesis of NaNbO3 Nanowires with Low NaOH Concentration

Alcohol Assisted Hydrothermal Synthesis of NaNbO₃ Nanowires with Low NaOH Concentration

Efficient Polyhydroxyalkanoate Recovery from RecombinantCupriavidus necatorby Using Low Concentration of NaOH

An efficient method for recovering polyhydroxyalkanoate (PHA) from bacterial cell was developed by using a low concentration of sodium hydroxide (NaOH). In this study, the effectiveness of low-concentration NaOH on PHA recovery from recombinant Cupriavidus necator was investigated by testing several NaOH concentrations, in relation to digestion time and reaction temperature. Gas chromatography (GC) analysis showed that PHA with more than 96% purity and recovery yield can be achieved after the recovery process which involved treatment of lyophilized cells with 0.05 M NaOH at 4°C for 3 h. GC analysis was supported by transmission electron microscope images and associated with considerable release of protein after NaOH addition. The recovery process developed herein was found effective in recovering PHA even from cells with low PHA content, with only 13% reduction in molecular weight (Mw). Ultimately, the present method could be an alternative to the PHA recovery by organic solvents, with added values such as being simple, nontoxic and environmental friendly.

Effects of sodium hydroxide exposure on esophageal epithelial cells in an in vitro ovine model: implications for esophagus tissue engineering

BackgroundEsophagus tissue engineering holds promises for esophageal replacement after severe caustic injuries. The aim of this study was to determine whether viable esophageal epithelial cells could be isolated from an esophagus exposed to varying concentrations of alkali with regard to number, viability, and morphology during in vitro culture. MethodsOvine esophagi were exposed to phosphate-buffered saline 2.5%, 15%, or 25% sodium hydroxide (NaOH). The effect of NaOH concentrations on epithelial damage was assessed histologically. Esophageal epithelial cells were then isolated, and cell count and viability were investigated. Finally, cell number, viability, and morphology of esophageal epithelial cells were determined for 24 days of in vitro culture. ResultsHistologic analysis showed a progressive destruction of the epithelium proportional to increasing NaOH concentrations. Esophagi treated with phosphate-buffered saline and 2.5% NaOH showed significantly higher viable cell counts after isolation and culture in comparison with those treated with 15% to 5% NaOH. ConclusionThe evidence presented in this study indicates that epithelial biopsies from an esophagus exposed to low concentrations (2.5%) of NaOH will still yield large numbers of viable cells suitable for tissue engineering applications. In cases of exposure to higher concentrations (15%-25%), alternative cell sources for epithelial regeneration, such as stem cells, will be necessary for tissue engineering applications.

Synthesis and electrochemical behaviors of nano-network NaHTi3O7 thin films on Ti/Si prepared by a hydrothermal-galvanic couple method

Nano-network NaHTi3O7 thin films have been successfully synthesized over Ti-coated Si substrates by a hydrothermal-galvanic couple method in 4M NaOH solutions at temperatures above 60°C. This is the first report to make nano-network NaHTi3O7 thin films in low concentration NaOH solutions at reaction temperatures below 100°C. The thickness and porosity of NaHTi3O7 films increased rapidly with the reaction temperature. The nano-network morphology allows sodium ions to be easily inserted into and extracted out of the NaHTi3O7 thin films. The mixed valence states of titanium (Ti+3/Ti+4) also play an important role on charge balance during the insertion and extraction processes. Charging and discharging performance reveals that the NaHTi3O7 films exhibited potentials in the applications of ionic devices.

Controllable synthesis of sodalite submicron crystals and microspheres from palygorskite clay using a two-step approach

Sodalite submicron crystals and microspheres were successfully synthesized from natural palygorskite clay through a two-step approach by varying the synthetic parameters. The effects of initial NaOH concentration, SiO2/Al2O3 molar ratio, and aluminium source on the morphology and particle size of synthetic sodalite were investigated, as well as the formation scheme of synthetic sodalite. Experimental results showed that the alkalinity of the synthesis gel controlled by initial NaOH concentration and SiO2/Al2O3 molar ratio was a critical factor for the formation of sodalite crystals and microspheres. Sodalite crystals could be synthesized at high initial NaOH concentration and SiO2/Al2O3 molar ratio, however, low initial NaOH concentration and SiO2/Al2O3 molar ratio were beneficial for the formation of sodalite microspheres via submicron crystal aggregation.

Comparative Analysis of Crystallinity Changes in Cellulose I Polymers Using ATR-FTIR, X-ray Diffraction, and Carbohydrate-Binding Module Probes

Cotton fiber cellulose is highly crystalline and oriented; when native cellulose (cellulose I) is treated with certain alkali concentrations, intermolecular hydrogen bonds are broken and Na-cellulose I is formed. At higher alkali concentrations Na-cellulose II forms, wherein intermolecular and intramolecular hydrogen bonds are broken, ultimately resulting in cellulose II polymers. Crystallinity changes in cotton fibers were observed and assigned using attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy and X-ray diffraction (XRD) subsequent to sodium hydroxide treatment and compared with an in situ protein-binding methodology using cellulose-directed carbohydrate-binding modules (CBMs). Crystallinity changes observed using CBM probes for crystalline cellulose (CBM2a, CBM3a) and amorphous cellulose (CBM4-1, CBM17) displayed close agreement with changes in crystallinity observed with ATR-FTIR techniques, but it is notable that crystallinity changes observed with CBMs are observed at lower NaOH concentrations (2.0 mol dm(-3)), indicating these probes may be more sensitive in detecting crystallinity changes than those calculated using FTIR indices. It was observed that the concentration of NaOH at which crystallinity changes occur as analyzed using the CBM labeling techniques are also lower than those observed using X-ray diffraction techniques. Analysis of crystallinity changes in cellulose using CBMs offers a new and advantageous method of qualitative and quantitative assessment of changes to the structure of cellulose that occur with sodium hydroxide treatment.

Kinetic Analysis of Alkaline Extraction on Sweet-Bamboo Leaves

This study aimed to investigate the influence of NaOH concentration and temperature used for cellulose extraction from sweet-bamboo leaves on the kinetics of the extraction reaction. The NaOH concentration and the temperature used for the extraction were varied and their effect was examined. It was found that the extraction rate was accelerated by either the increase of NaOH concentration or extraction temperature. The NaOH concentration affected the reaction rate constant, k, and the activation energy, E and the order of the reaction, n. Increase of NaOH concentration enhanced the reaction to move forwards, thus reducing the k and E values of the reaction and the order of the reaction, n, was changed. The correlation of the temperature and the NaOH concentration with the k value showed that at the lower NaOH concentration, the temperature influenced on the k value more significantly. The influence of the NaOH concentration on the k value was lessened with increase of the extraction temperature.

Influence of various parameters on reactive extraction of Jatropha curcas L. for biodiesel production

Reactive extraction ( in situ transesterification) of Jatropha curcas L. (Jatropha) seeds for biodiesel production is influenced by a variety of parameters, including seeds size, agitation speed, reaction temperature, reaction time, catalyst concentration and molar ratio of alcohol compare to the oil. In this study, these parameters were studied in the ranges of <0.5–4 mm seeds particle size, 200–300 rpm, agitation speed, 30–60 °C reaction temperature, 10–60 min reaction time, 0.1–0.2 N NaOH concentration and 100–600 molar ratio of methanol-to-oil. It was established that the smallest particle size (below 0.71 mm) resulted in the highest yield of biodiesel production. The biodiesel yield was found to be independent of intensity of the mixing once it reached 300 rpm, whereas reaction temperature did not exhibit any significant effect on the yield. It was also demonstrated that alkaline reactive extraction was complete in 20–30 min. The concentration of NaOH can affect biodiesel yield in both positive and negative way. Low concentration of NaOH (0.05 N) resulted in low yield, but at higher concentrations (0.2 N), emulsions form, due to a saponification side reaction, adversely affecting the yield. In this case, a NaOH concentration of 0.15 N produced the highest yield. It was also discovered that when the methanol-to-oil ratio reached 400, the biodiesel yield reached a constant state. The optimal conditions in this study are approximately <0.71 mm seeds particle size, 300 rpm mixing speed, 30 °C reaction temperature, 30 min reaction time, 0.15 N NaOH concentration and methanol:oil molar ratio of 400.

Oriented Nanostructured Titanates Array from Low Concentration Alkaline Solution via Hydrothermal Process

Na2Ti2O5 x H2O nanowire/nanobelt array and other nanostructures were hydrothermally prepared on Ti substrate in low concentration NaOH solution (< 5 mol/L). Then the Na2Ti2O5 x H2O nanostructures were converted to H2Ti2O5 x H2O through an ion-exchange process and finally to TiO2 anatase by calcination at 450 degrees C without changing their nanostructures. The morphology of the prepared Na2Ti2O5 x H2O nanostructures could be controlled by varying the experimental parameters such as hydrothermal temperature and alkaline solution. The formation mechanism of the nanoarray was also discussed.

Formation of titanate nanostructures under different NaOH concentration and their application in wastewater treatment

The effects of the concentration of NaOH on the formation and transformation of various titanate nanostructures were studied. With increasing NaOH concentration, three different formation mechanisms were proposed. Nanotubes can only be obtained under moderate NaOH conditions, and should transform into nanowires with prolonged hydrothermal treatment, and their formation rate is accelerated by increasing NaOH concentration. Low concentration of NaOH results in the direct formation of nanowires, while extra high concentration of NaOH leads to the formation of amorphous nanoparticles. Adsorption and photocatalysis studies show that titanate nanowires and nanotubes might be potential adsorbents for the removal of both heavy metal ions and dyes and photocatalysts for the removal of dyes from wastewater.

Stability of PVDF hollow fibre membranes in sodium hydroxide aqueous solution

The stability of PVDF hollow fibre membranes in sodium hydroxide (NaOH) aqueous solutions were investigated in this study. PVDF hollow fibre membranes were prepared from each of the three commercial raw PVDF materials (Kynar 761, Solef 1015 and Solef 6010) from two major suppliers (Atofina Chemicals Inc., USA and Solvay, Belgium) for comparison purposes. The effect of NaOH concentration, treatment time and temperature on mechanical properties, thermal properties and crystalline structure of the PVDF hollow fibre membranes were investigated through mechanical strength measurement, surface area analysis, XRD, FTIR and DSC analyses. The obtained results indicate that the reaction between PVDF and NaOH was initiated even at low concentrations of NaOH and was aggravated with the extended treatment time, resulting in the decrease in mechanical strength and crystallinity of PVDF hollow fibre membranes. The reaction was accelerated and intensified by increasing the concentration of NaOH and/or treatment temperature. At 70 °C, the mechanical integrity of the PVDF membranes was completely destroyed in 4 wt% NaOH solution within 24 h or in 10 wt% NaOH solution within 8 h. The deterioration of stability in NaOH solutions is considered universal for all PVDF employed in this study, irrespective of the raw materials or the corresponding hollow fibre membranes.

The Effect of Coal Fly Ash Crystallinity toward Methyl Violet Adsorption Capacity

Coal fly ash (CFA) generated by coal-based thermal power plants is mainly composed of some oxides having high crystallinity, like quartz and mullite. In this study, the effect of CFA crystallinity toward methyl violet (MV) adsorption capacity was investigated. To decrease crystallinity of CFA, the solution of sodium hydroxide (NaOH) of 1-7 M was used to treat CFA at various temperatures and reflux time. Then, to evaluate the effect of NaOH-treated CFA with respect to adsorption capacity, the original and NaOH-treated CFA were tested its MV adsorption capacity in batch experiments. Original or NaOH-treated CFA was contacted with 50 mL of MV solution at temperature of 26 o C. The effects of contact time, pH of solution, adsorbent dose and initial concentration of dye on the adsorption of MV were investigated. The results show that CFA treated with low NaOH concentration (1-3 M), temperature of 60 o C and 2 hours reflux time, the crystallinity of quartz and mullite decreases, but its capacity on MV adsorption increases from 34% to 97%. At higher NaOH concentration (>3M), in the range of studied reflux temperature and time, it is found that decreasing quartz and mullite crytallinity are followed by a hydroxysodalite formation which causes the decreasing of MV adsorption from 97% to 83%. The highest adsorption capacity of NaOH-treated CFA was found 1.24 x 10-5 mol g -1 . Adsorption kinetics of MV onto NaOH-treated CFA could be approximated with a pseudo second order kinetic model with the rate constant was 3.2 x 10 3 g mol -1 min -1 .

Sodium hydroxide-assisted dechlorination of a poly(vinylidene chloride)-containing wrapping film in ethylene glycol solution

Poly(vinylidene chloride) (PVDC) wrapping film was dechlorinated using solutions of NaOH in ethylene glycol (EG) at temperatures between 150 and 190 °C. The reaction was comparable to that for PVDC powder; however, it occurred at a lower NaOH concentration, which can be explained by the dissolution of additives present in the wrapping film. Therefore, the best results for the dechlorination of the wrapping film were obtained at a temperature of 190 °C and NaOH concentrations of 0.1 M and 0.5 M, resulting in dechlorination yields of almost 90% after 135 min. For the dechlorination reaction, the activation energy of the PVDC wrapping film (185 kJ mol −1) was determined to be higher than that of PVDC powder; this finding could be attributed to the presence of a stabilizer and the smaller surface area of the PVDC wrapping film.

Pretreatment of corn stover and hybrid poplar by sodium hydroxide and hydrogen peroxide

Sodium hydroxide and its derivatives are used as pulping reagents, wherein the spent NaOH is recovered in salt form and reused. In this study, use of low concentration NaOH (1-5%) in pretreatment of corn stover and hybrid poplar was investigated. It was done with the understanding that NaOH can be recovered. One of the main objectives in this study is to explore the potential of H(2)O(2) with NaOH for pretreatment of high lignin substrate such as hybrid poplar. Pretreatment time has not been optimized in this study but held constant at 24 h. Corn stover, after treatment with NaOH under moderate conditions, attains near quantitative glucan digestibility. On the other hand, hybrid poplar requires treatment at higher temperature and NaOH concentration to attain acceptable level of digestibility. Supplementation of hydrogen peroxide in the pretreatment significantly raises delignification and digestibility of hybrid poplar. It was also helpful in retaining the carbohydrates in the treated solids. Retention of hemicellulose after pretreatment provides a significant economic benefit as it eliminates the need for detoxifying hemicellulose sugars. As the residual xylan remaining after pretreatment is an impediment to enzymatic digestion of glucan, supplementation of xylanase has significantly increased the digestibility of glucan as well as xylan of the treated hybrid poplar.

Evaluation of pulp and paper making characteristics of rice stem fibers prepared by twin-screw extruder pulping

Twin-screw extrusion pulping is a new approach to the manufacture of pulp for paper production, designed for non-wood feedstocks. In this research, the production of pulp from rice stem with a newly fabricated twin-screw extruder was investigated. Extrusion pulping of rice stem was conducted following a central composite design using a two-level factorial plan involving three process variables (pretreatment NaOH concentration: 0.4, 0.8, 1.2%; extrusion temperature: 40, 60, 80 o C; and extruder rotational speed: 55, 70, 85 rpm). Responses of pulp and handsheets properties to the process variables were analyzed using statistical software (MINITAB 15). As the results show, pulping of rice stem fiber can be done at a relatively short pretreatment time about 4 hours and a low NaOH concentration about 0.8% by twin-screw extruder with limit extrusion temperature of about 80 o C and extruder rotational speed about 85 rpm. The effect of pretreatment solvent, NaOH, is greatly enhanced by increases in the extrusion temperature. Analysis of the results revealed that this process has suitable potential to be used to obtain a pulp with yields approximately equivalent to neutral sulfite semichemical pulping at fixed kappa number, which is applicable for fluting paper and linerboard production.

Electrogeneration of ferrate (VI) in low concentration NaOH solution for flow-injection–chemiluminescence detection

The possibility of direct analytical applications of ferrate (VI) solution, which was freshly electrogenerated in low-concentration NaOH electrolyte, was studied by a flow-injection–chemiluminescence (FI–CL) system. It was found that some inorganic ions, organic molecule and biomolecule could enhance the chemiluminescence emission caused by ferrate (VI)–luminol reaction. V(V), Ca(II), Mg(II), phloroglucinol, and bovine hemoglobin (Hb) chosen as samples were successfully detected by this developed method. The analytical characteristics of the system for the analytes determination including linear ranges, correlation coefficients, limits of detection combined with FI analysis were studied.

Facile Fabrication of Hierarchical Hollow Microspheres Assembled by Titanate Nanotubes

Hierarchical hollow microspheres assembled by titanate nanotubes were fabricated via a hydrothermal process. During the entire process, the hydrous titanium oxide microspheres served as a template and source of titanate ions and H(2)O(2) was used to facilitate the conversion of titanate sheets into nanotubes in low-concentration NaOH (0.1 M). Furthermore, this synthesis route is more friendly than the previous hydrothermal synthesis of TiO(2)-derived nanotubes in a highly alkaline (10-15 M) medium.