Low NaOH Concentration Research Articles

EVALUATION OF THE ENGINEERING PROPERTIES OF FLY ASH-BASED GEOPOLYMER BRICKS

This paper is aimed to evaluate the engineering properties of fly ash-based geopolymer bricks. Four geopolymer brick mixtures were designed with a constant solution-to-binder ratio of 0.40 and various concentrations of sodium hydroxide solution. The engineering properties of fly ash-based geopolymer bricks consisting of compressive strength, unit weight, water absorption, water permeability, and ultrasonic pulse velocity were investigated. The microstructure of fly ash-based geopolymer bricks was also investigated by using the scanning electron microscope (SEM). Test results indicated that the compressive strength, unit weight, and ultrasonic pulse velocity (UPV) of geopolymer bricks increased, while the water absorption and water permeability of geopolymer bricks reduced with increasing NaOH concentration. Moreover, brick samples with high NaOH concentration showed a higher geopolymeric reaction of fly ash than brick samples with low NaOH concentration. All geopolymer brick samples produced in this study showed a good quality with compressive strength of above 10.1 MPa, water absorption of below 9.4%, water permeability of below 1.84 L/m2 .h, and UPV of above 2500 m/s.

13C NMR and XRD studies on the enhancement of cellulose II crystallinity with low concentration NaOH post-treatments

In this study, methods of completing the structural conversion of partly crystalline cellulose II were studied by solid-state 13C CP/MAS NMR spectroscopy and X-ray diffraction. The study incorporated post-treatments of samples that had been mercerized or regenerated to yield somewhat crystalline cellulose II. These post-treatments used different temperatures, lower concentrations of NaOH than used in, for example, the original mercerization, and different neutralization methods. The cellulose employed was originally filter paper from wood pulp that was subsequently mercerized or dissolved and regenerated to create partly crystalline cellulose II. The variations in rate of each component were monitored at different NaOH concentrations and reaction temperatures during the treatment; these components include the crystalline and accessible surface as well as the inaccessible surface/amorphous region. Subsequently, neutralization was performed for the crystallization of cellulose II and the effects of the acid employed were also evaluated. It can be thought that controlling the partial Na-cellulose construction is important for improving the assembly of cellulose II; this is achieved by optimizing the concentration of NaOH, treatment temperature, and selection of acid for neutralization. NMR spectroscopy of the intermediate state of the NaOH detected the partial generation of Na-cellulose; further, another domain exhibited the spectrum of highly crystallized cellulose II. It is believed that the selective Na-cellulose construction in the inaccessible surface cellulose is the result of an increase in the size of cellulose II crystals. During the NaOH treatment, at a concentration of 10%, the crystallinity index evaluated by both NMR and X-ray was maximized; further, at the treatment temperature of 80 °C the crystallinity of the cellulose II evaluated by NMR improved. Moreover, the neutralization, which was conducted after the alkaline treatment with H2SO4, established the most suitable conditions for the crystallization of cellulose II.

Bio-oil Production from Sweet Sorghum Bagasse Via Liquefaction Using Alkaline Solutions and Identification of Phenolic Products

The feasibility of converting biomass into bio-oil and the effect of an alkaline treatment during biomass liquefaction was studied. Sweet sorghum bagasse (SSB) was treated with NaOH concentrations of 0.5, 1.0, 3.0 and 6.0 M. The experiments were conducted in a temperature range of 260–320 °C in N2. The results showed that the alkaline treatment affected the product distribution of SSB liquefaction. The highest yield of bio-oil (53.2 wt%) and phenols extracted (≈ 40.0 wt%) were obtained at 320 °C and NaOH aqueous solution of 3.0 M. The ATR-FTIR results indicated the presence of carboxyl, ketone, ester and aromatic ring structures in the bio-oils. The absorption intensities of all the bio-oils at 1100 cm−1 (primary alcohols) substantially decreased with an increase in temperature and NaOH concentration. At given reaction temperature, the use of 3.0 and 6.0 M NaOH resulted in the extraction of more identifiable phenol derivatives than were obtained with the lower concentrations of NaOH. These results suggest that a temperature of 320 °C and a NaOH concentration of 3.0 M yields the best results among the temperatures and concentrations tested, and also that alkaline treatment is feasible for liquefaction and extraction of phenols from the bio-oil.

Extraction of a novel fungal chitin from Hericium erinaceus residue using multistep mild procedures

In this study, a novel fungal chitin was extracted from Hericium erinaceus residue using moderate chemical sequential extraction procedures. The effects of deproteinization conditions, including NaOH concentration, reaction temperature, and reaction time, on the chitin yield, purity, molecular weight (Mw), and degree of acetylation (DA) were investigated. Additionally, SEM, FTIR, XRD, NMR and TGA were applied to indicate the removal of non-chitin components from HER. Results suggested that the deproteinization processes meaningfully influence the chitin yield, purity, Mw, and DA. The chitin with most desirable parameters (yield of 16.30%, purity of 97.88%, Mw of 2.01 × 105 g/mol, and DA of 77.67%) was obtained at low NaOH concentration of 2%, reaction temperature of 85 °C, and reaction time of 3 h. In addition, non-chitin components such as minerals, proteins, and pigments were mostly removed after the extraction. The results demonstrated that the Hericium erinaceus residue can lead to a high-quality chitin, which is useful for a broad range of applications.

One-step direct fabrication of phase-pure Cu2O films via the spin-spray technique using a mixed alkaline solution

The spin-spray technique was used to fabricate phase-pure Cu2O films at 70 °C with a high deposition rate of 0.3 μm/min. The source solution, containing a mixture of CuSO4･5H2O and l-ascorbic acid, and the reaction solution, containing NH3 and NaOH, were sprayed on the rotating substrates. It was possible to control the grain size, the crystalline orientation of the films, the surface morphology, and the optical band gap by adjusting the concentrations of NH3 and NaOH in the reaction solution. The films fabricated with a low NH3 aq. concentration were composed of nanosized grains and highly [111] oriented. On the other hand, films fabricated with a high NH3 aq. concentration were composed of submicron grains and highly [100] oriented. The surface morphologies of the films varied according to the concentration of NaOH. The surface of the films fabricated with a low NaOH concentration were almost flat and had a {100} orientation on their surface. On the other hand, films fabricated with a high NaOH concentration were composed of pyramidal grains. A smaller grain size in the films corresponded with a higher optical band gap.

Enhanced modification technique for polyacrylonitrile UF membranes by direct hydrolysis in the immersion bath

ABSTRACTConventional hydrolysis modification of polyacrylonitrile (PAN) membranes is usually carried out in a post‐treatment step during which hydrophilic groups are created on the membrane surface. In this article, however, direct hydrolysis in the immersion bath is proposed as a new and simple approach for simultaneous membrane preparation and modification. The main advantages of this method include lower alkali concentrations, promptness, and the lack of need for elevating temperature compared to other studies. The cast films were immersed in the coagulation bath containing aqueous NaOH solutions of various concentrations (0.003, 0.0125, 0.025, 0.05, and 0.1 M) for 1, 3, 5, and 10 min, which were then transferred to a bath of pure water. Membranes were characterized by pure water flux, porosity, average pore diameter, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle, mechanical properties, rejection, and flux recovery ratio (FRR) measurements. At all treatment times, the pure water flux of modified membranes reached its maximum at low NaOH concentrations with a substantial increase (210%) in the membrane treated with 0.0125 M NaOH for 1 min. Furthermore, the kinetics of the hydrolysis reaction was considered to provide deeper insights into morphological changes occurring during the hydrolysis. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48583.

Simultaneous deacetylation and degradation of chitin hydrogel by electrical discharge plasma using low sodium hydroxide concentrations

Electrical discharge plasma occurring in a liquid phase, so called solution plasma, can generate highly active species, e.g. free radicals, which can involve in various chemical reactions, leading to less chemical uses. In this study, solution plasma was applied to deacetylation of chitin aiming to reduce the use of alkali. It was found that solution plasma could induce deacetylation of chitin hydrogels that were dispersed in MeOH/water solutions containing low NaOH concentrations (1–12%). Due to the action of free radicals, some extent of chain session of the polymer occurred during the plasma treatment. The degree of deacetylation and molecular weight of the obtained chitosan were 78% and 220 kDa, respectively, after the plasma treatment for five cycles (1 h/cycle) by using 90% MeOH/water solution containing 12% NaOH. The obtained chitosan could completely dissolve in 2% acetic acid solution and had antibacterial activities against S. aureus and E. coli.

A Novel Approach of Low Alkali Degumming of Ramie

ABSTRACT A novel low alkali-based chemical recipe was formulated for controlled degumming of ramie (Boehmeria Nivea L.) fiber to maintain residual gum 7–8% aiming at to improve yarn tensile performance. The method includes the application of H2SO4 at a low concentration (2%) followed by a treatment with a low concentration of NaOH (6%) on the weight of fiber. Treatment condition and chemical formulation were varied to obtain degumming to the extent of 20–22%. Degummed fiber tenacity (52.33 cN/tex), extensibility (3.85%) and modulus (2263.7 cN/tex) were found to be notably high. The gum remained in fiber surfaces produces resultant yarn of very high strength breaking load (28.7 N), tenacity (20.9 cN/tex), initial modulus (782.9 cN/tex) specific work of rupture (3.0 mJ/tex.m) with low extensibility (2.95%). COD, BOD, TDS, and pH of the generated effluent was 927 mg/L, 328 mg/L, 680 ppm, 8.7 only. Cost of chemical for the treatment was as low as USD $ 0.2/kg of fiber. Comparison of ramie and jute yarn properties suggests that ramie may be used for high-performance industrial uses where high strength, as well as high modulus, is essentially needed viz., conveyor belts, tire cords, and composites.

Cleaner production of ammonium poly-vanadate by membrane electrolysis of sodium vanadate solution: The effect of membrane materials and electrode arrangements

In this study, we put forward a clean and complete process of V2O5 production from vanadium-containing solutions. It features membrane electrolysis for V/Na separation and AMV precipitation. With the aid of membrane electrolysis, the vanadium and sodium in the leaching solution can be directly separated using membrane-electrolysis. Meanwhile, the NaOH in the cathode chamber can also be recycled for vanadium slag decomposition. The electrolysis systems and membrane types have been investigated. It was found that 3-chamber electrolysis was much more energy efficient than the traditional 2-chamber electrolysis, while F8080 membrane showed a better separation efficiency than N117, CMI7000, LF0014 membrane. The main electrolysis parameters were also investigated, and it appeared that high current density and electrolyte temperature, as well as low initial cathodic NaOH concentration were beneficial for the separation efficiency. Under the optimum electrolysis conditions the electricity consumption of producing 750 kg V2O5 and 1000 kg NaOH and was 2151 kW h, with a current efficiency of 92.9%. During the vanadium precipitation process, NH4VO3 was used as precipitant for the first time, avoiding the introduction of impurity ions, such as Cl−, SO42− or Ca2+, realizing zero waste generation by source. A low-sodium medium product of (NH4)2V6O16 was precipitated at pH between 2 and 4. The commercial quality V2O5 product could be obtained by calcination and the ammonium slat was recycled for precipitation. This method can achieve the clean production of V2O5 with no wastewater or solid waste generated through the whole process.

Rapid and efficient extraction of chitin and chitosan for scale-up production: Effect of process parameters on deacetylation degree and molecular weight

Chitin and chitosan have been successfully produced, from Moroccan shrimp shells, using the microwave technology. This efficient extraction method of chitin and chitosan was evaluated and demineralization, deproteinization and deacetylation steps were investigated. The effect of the reaction time, the HCl and the NaOH concentration, at different powers (90 W, 160 W, 350 W, 500 W and 650 W) was studied. The results shown that a chitosan with low degree of acetylation has been extracted using 50% of NaOH solution, at power range 500–650 W, and the deacetylation reaction was more than 80% completed after 10 min. Microwave assisted extraction allowed to produce chitosan with medium and high molecular weight (300–360 kDa).Chitin deacetylation by microwave heating was more efficient than the conventional heating, and high desacetylation degree was obtained using microwave heating in just a few minutes. This technology can save huge amount of energy when implemented on industrial scale, it's a highly economical extraction method. By this technology, we have successfully produced the chitosan CTS with low NaOH concentration (30%), which allows to avoid manipulating an extremely high concentration of a corrosive substance, especially at industrial scale. Chitosan CTS has a degree of acetylation of 23.4% and a molecular weight of 165 kDa.

Selenium(VI) removal from caustic solution by synthetic Ca–Al–Cl layered double hydroxides

Abstract To extract selenium(VI) from the highly caustic leachate of copper anode slime, the Ca–Al–Cl layered double hydroxides (Ca–Al–Cl–LDHs) with a formula of Ca2Al(OH)6Cl·2H2O by three co-precipitation methods were synthesized. A plate-like morphology and hexagonal crystal structure with typical mineral phases and functional groups were identified by the FESEM, XRD, FTIR, BET and XPS analysis. The forward feeding sample exhibits the best adsorption capacity of Se(VI). The factor experiments then reveal a favorable adsorption process with low temperature, low NaOH concentration and high adsorbent dosage. Furthermore, the adsorption kinetics and isotherm parameters can be well described by the Langmuir isotherm and the pseudo-second-order models, respectively. Accordingly, the maximum adsorption amount of Se(VI) onto Ca–Al–Cl–LDHs reaches 188.6 mg/g at 50 °C.

The Low Concentration of Sodium Hydroxide Influence on The Compressive Strength of Fly Ash/Natural Kaolin-Based Geopolymer

Fly ash/natural kaolin-based geopolymer with a low concentration of NaOH has been studied. The fly ash was taken from coal combustion waste of Asam-asam power plant, meanwhile the kaolin clay was taken from Tatakan, South Kalimantan, Indonesia. The kaolin powder was calcined at 750 °C for 3 hours to form pozzolanic metakaolin (Al2O3.2SiO2). The silicon content from the X-ray fluorescence (XRF) test of the fly ash and the natural kaolin was respectively 44.58% and 72.98%. The aluminium weight percentage contained in the natural kaolin was roughly three times higher than that in the fly ash. Both starting materials together with the alkali solution (NaOH/Na2SiO3) were wisely mixed to produce geopolymers with Si/Al ratio of 4. The molarities of NaOH were controlled from 2M to 5M. The mixture was then heated at a curing temperature of 60 °C for 12 hours and dried at setting time of 14 to 28 days. The finest compressive strength, i.e. 91.6 MPa, was shown by the sample with 5M NaOH and 28 days setting time. This sample had a density of 2.04 g/ml and porosity of 5.88%. To the best of our knowledge, there is a prospective feature of using fly ash/natural kaolin-based geopolymer prepared by the low NaOH molarity in infrastructural industries.

Ascorbic acid based controlled growth of various Cu and Cu2O nanostructures

Here we report a facile and fast ascorbic acid based controlled growth of various nanostructures of Cu and Cu2O by varying the concentration of NaOH. Ascorbic acid being a weak reducing agent not only slows down the reaction kinetics but also provides a better control for the self-assembly of nanostructures. Cu and Cu2O nanoparticles are synthesized by chemical reduction of copper nitrate (Cu(NO3)2 × 2.5 H2O) with different concentration of NaOH (0.01, 0.1, 0.5, 1.0, 5.0 and 10 M) solution in the presence of ascorbic acid. The low concentrations of NaOH (0.01 and 0.10 M) result the formation of almost pure phase of Cu nanoparticles. Whereas the higher concentrations (0.5, 1.0 and 5 M and 10 M) result into formation of pure nanocubes, truncated octahedron, polygon shaped and finally spherical shaped Cu2O particles respectively.

Synthesis of binderless FAU-X (13X) monoliths with hierarchical porosity

elf-standing binderless FAU-X monoliths with hierarchical trimodal porosity have been synthesized for the first time by a double pseudomorphic transformation. Parent silica monoliths obtained by the combination of spinodal decomposition and sol-gel process have first been synthesized. The silica monoliths have been then transformed into silica-alumina monoliths (0.25 < Al/Si < 0.40) in low NaOH concentration ([NaOH] = 0.24 mol/L) at 40 °C for 24 h. Silica-alumina monoliths have been then transformed into FAU-X monoliths featuring nanocrystals in the struts at high NaOH concentration ([NaOH] = 2.2 mol/L) with an aging step at 40 °C for 4 days and a crystallization step at 100 °C for 24 h. The FAU-X monoliths feature macropores with diameters adjustable from 3 to 20 μm (similar to the parent silica monolith). The skeleton of the FAU-X monoliths is formed by an aggregation of two populations of FAU-X nanocrystals (100–200 nm/400–500 nm) generating a secondary porosity between the nanocrystals of 30–1000 nm in diameter, centered at 300 nm. The FAU-X monoliths present three levels of porosity with a macropore volume of ca. 1.0 mL/g, a secondary pore volume of ca. 0.40 mL/g and a micropore volume of 0.30 mL/g. These new FAU-X monoliths with hierarchical porous structure fulfill the requirements of high performance adsorbents for continuous flow process intensification.

Low-temperature phase transitions of sodium aluminate solutions

A series of low-temperature phase transitions of sodium aluminate solutions were studied by differential scanning calorimetry (DSC) and Raman spectroscopy. The results indicate that NaOH concentration is a primary impact factor for the binary eutectic point and ice melting temperature of sodium aluminate solutions with low NaOH concentration. In addition, the phase transition process of sodium aluminate solutions with low NaOH concentration from 123.15 to 283.15 K is divided into four steps: non-crystal to crystal, ternary eutectic reaction, binary eutectic reaction and ice melt. The projection phase diagram of NaOH-Al(OH)3-H2O system at low temperature was plotted, in which the ternary eutectic temperature for sodium aluminate solutions is 183.15 K.

An enhanced regeneration strategy to improve microbial control and prolong resin lifetime for Protein A resin in large-scale monoclonal antibody (mAb) purification

Effective Protein A column regeneration is important in therapeutic monoclonal antibody (mAb) production for product quality and process economics. To design a robust and effective regeneration strategy, resin compatibility, microbial inactivation efficiency and cleaning effectiveness are three major considerations. Regenerating Protein A column using acidic (e.g. acetic acid) and/or caustic (e.g. NaOH) solutions is a common approach. However, it is challenging to balance between resin performance decline and adequate microbial control in choosing the right caustic solution concentration, even for resin with enhanced caustic tolerance such as MabSelect SuRe.This report introduces an enhanced regeneration strategy for MabSelect SuRe resin. The approach applies benzyl alcohol in low concentration acetic acid and NaOH (100 mM) solutions in sequential steps to regenerate MabSelect SuRe resin for reuse. Such solutions demonstrated good resin compatibility in resin functional test after extended solution incubation time, and demonstrated superior microbial control using eight test microorganisms. The cleaning effectiveness of the proposed strategy is demonstrated by carryover study, where product and impurity carryover was below detection limit. Finally, during a resin lifetime study, consistent step yields and product quality attributes were demonstrated, and no carryover was observed, up to 150 purification cycles. A viral clearance study further demonstrated that aged resin at the end of the resin lifetime had comparable viral clearance performance compared to new resin. No active virus was detected in the elution pool of the subsequent blank runs. These studies further verified the robustness of the proposed regeneration strategy for MabSelect SuRe resin.

Rapid and energy-saving preparation of ramie fiber in TEMPO-mediated selective oxidation system

Although oxidation systems were many and varied, alkali peroxide oxidation system was the only one used for ramie degumming in previous studies. In the work reported here, the possibility of ramie degumming in TEMPO-mediated selective oxidation system was studied. Results revealed that ramie fiber can be extracted by using TEMPO-mediated oxidation treatment (NaClO 2 mmol/g; 15 min; 20 ∼ 25 °C) followed by a low concentration NaOH scouring (2.5%, 100 °C, 60 min) and a reducing process. Fiber degummed in TEMPO-mediated selective oxidation system showed better tensile properties and lower acid group contents compared with that in alkali peroxide oxidation system. The required time for TEMPO-mediated selective oxidation degumming was about 125 min, which was 55 min shorter than hydrogen peroxide system. Moreover, the COD value of wastewater in TEMPO-mediated selective oxidation degumming was 28% lower than that in alkali peroxide oxidation degumming.

ELECTROCHEMICAL OXIDATION OF SYNTHETIC ORGANIC DYES BY FERRATE (VI), USING COMMERCIAL STEEL WOOL ELECTRODES

This paper deals with the in-situ electrochemical oxidation of Reactive Black 5 (RB-5), Reactive Blue 19 (RB-19) and Allura Red AC (AR-AC), using commercial steel wool as electrodes. At the optimal conditions (18 V and NaOH 0.33M), the decolorization of RB-19 (anthraquinone-type dye) is much more rapid than those of azo dyes RB-5 and AR-AC. The reaction rates based on a first order reaction model were 0.134 min -1 for RB-19, 0.043 min -1 for RB-5 and 0.028 min -1 for AR-AC. Color removal efficiencies were higher than 95% achieved in 120 min. The analyses of spectra of the three dyes in the visible region indicate a complete cleavage of both azo and quinoid chromophores. In the case of RB-19 no new absorption peaks occurred in the UV region, showing a partial oxidation of aromatic groups without the generation of intermediates. In case of both azo-type dyes RB-5 and AR-AC, formation/accumulation of intermediates followed by their partial oxidation may have occurred. All these observations indicate that the predominant mechanism for decolorization was the oxidation of the three dyes. We conclude that that the electrochemical oxidation by ferrate (VI), under low voltages and low NaOH concentrations, using commercial steel wool as electrodes is an efficient and cost-effective alternative for the decolorization of azo and anthraquinone type dyes. For future studies a COD analysis should be made in order to correlate the decolorization and the elimination of the organic load in the dye solutions.

Effects of Sodium Hydroxide Treatment on LLDPE/DS Composites: Tensile Properties and Morphology

In this research, the effect of different sodium hydroxide (NaOH) concentration (3, 6 and 9 wt.%) on the tensile properties of linear low density polyethylene / date seeds (LLDPE/DS) composites were investigated. The size of DS particles was measured at (125 - 250 μm) and the ratio of LLDPE over DS was fixed at 90/10 wt.%. The samples were prepared using extrusion process (screw speed at 60 rpm and barrel and die temperature at 160°C and 165°C respectively) followed by injection moulding process (from feed to exit die zone temperature at 160, 165, 170 and 175°C respectively). Results suggest that the addition of NaOH particularly 3 wt% has improved the tensile strength. Additionally, the elongation at break has improved as well. However, the high concentration of NaOH, particularly 9 wt.% effects negatively on these properties. In contrast, the Modulus shows different trend, which increased as NaOH concentration increased in the composites. The SEM section shows the improvement on DS surface as low NaOH concentration used (3 wt.%) and deterioration on the DS surface as high NaOH concentration used (9 wt.%).

Investigation of the electrochemical dissolution behavior of tungsten during electrochemical machining

With the advantageous properties of a high melting point, high strength at high temperatures, low vapor pressure, and good thermal conductivity, tungsten is widely used in several advanced industrial applications. Micro structures such as micro holes and grooves are commonly prepared on the tungsten surface to enhance its heat transfer performance. Electrochemical machining (ECM) is a promising method of generating micro structures on the metal surface. Typically, an alkaline solution is employed as an electrolyte during tungsten ECM. Unfortunately, significant stray corrosion commonly occurs on the tungsten surface when high-concentration alkaline solutions (NaOH > 1 wt.%) are used. However, the machining efficiency decreases sharply when the concentration is less than 0.5 wt.%. In order to improve machining efficiency and accuracy, this paper proposes a novel mixed electrolyte consisting of NaClO3 mixed with a low concentration of NaOH for electrochemical machining of tungsten. The NaClO3 is used to increase the conductivity as well as to improve the formation of oxide films on the tungsten surface in order to avoid stray corrosion. NaOH is used to ensure continuous machining by removing the oxide film in the region being machined. The influence of the electrolyte composition and concentration on electrochemical dissolution of tungsten is analyzed by measuring the anode polarization curve and open circuit potential, and an optimized electrolyte with of 10 wt.% NaClO3 and 0.3 wt.% NaOH is identified. This optimized electrolyte enables generation of micro-through holes with inlet and outlet diameters of 500 and 410 μm, respectively, using a tube electrode with a diameter of 250 μm. The feed rate of the tool reaches 24 μm/min, which is 4 times faster than in previous studies.