Influence Of NaOH Concentration Research Articles

Study on the interfacial bonding properties between alkali-treated bamboo fibers and high-performance seawater sea-sand concrete

In this paper, the interfacial bonding properties between alkali-treated bamboo fibers and the matrix in fiber-reinforced high-performance seawater sea-sand concrete (HPSSC) materials were investigated. The natural bamboo fibers were modified with NaOH solution, and the cellulose crystallinity, chemical composition, and microstructure of the bamboo fibers before and after modification were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The impact of alkali treatment on the water absorption and mechanical properties of bamboo fibers were evaluated by water absorption test and single fiber tensile test. In addition, the influences of NaOH concentration, treatment time, and embedded length on the interfacial bonding properties were analyzed by pull-out test. Subsequently, the bonding mechanism between the fibers and the matrix was revealed based on the SEM scans of the extracted fiber surfaces. The experimental results indicate that appropriate alkali treatment could significantly eliminate the non-structural substances on the surface of bamboo fibers, reduce the water absorption, and increase the cellulose crystallinity. This process made the bamboo fibers exhibit better stability and bonding performance while ensuring the initial mechanical properties. Moreover, various fiber embedded lengths have a significant impact on the pull-out behavior of bamboo fibers. The maximum pull-out force of bamboo fibers increased with the increase of embedded length, while the fiber-matrix interfacial shear strength decreased. Based on the experimental results, a theoretical model for the pull-out behavior of bamboo fibers was proposed, and the predicted results showed a strong correlation with the experimental results.

Influence of NaOH Concentration on Structural, Morphological, Optical, and Electrical Characterization of Perovskite Sodium Bismuth Titanate Prepared by Hydrothermal Method

The hydrothermal method successfully prepares a lead-free sodium bismuth titanate (NBT) perovskite film. The prepared films were studied structurally, and morphologically using X-ray diffraction, and field-emission scanning electron microscopy (FESEM), respectively. Varying the concentration of NaOH showed a noticeable effect on the properties studied. Good crystallization of NBT perovskite films without impurities was obtained at 18 and 20 M concentrations, where the crystalline size was 14 nm according to the Scherer equation. Also, when varying the concentration of NaOH, a similar film thickness was obtained through a cross-section of the FESEM images. It was observed that there was a difference in the intensity of the peaks of the photoluminescence spectra of the prepared films with a change in the concentration of NaOH, which confirms a change in the concentration of oxygen vacancies. The activation energy of the prepared films was deduced from the Arrhenius plot, as it showed small values in the films prepared with a low concentration of NaOH. The results showed that the maximum value of mobility of NBT films was at 20 M of NaOH concentration through the Hall Effect.

The influence of NaOH concentration on the strength and microstructure of ceramic binders prepared from coal gangue through geopolymerization

The efficient utilization of coal gangue plays an indispensable role in reducing environmental pressure, improving resource utilization efficiency and promoting green development. As a kind of solid waste rich in silicon and aluminium, coal gangue can be used to prepare ceramic materials. Therefore, a new ceramic preparation process was proposed in this study to prepare ceramic binders for grinding wheels by geopolymerization. The SiO2-B2O3-Al2O3-RO-R2O ceramic binder, a green and low-cost material, was successfully prepared using this method. The effect of the concentration of NaOH on the mechanical properties and microstructure of the ceramic binder was also studied. The strength and microstructure of different ceramic binders were characterized by XRD, TG-DTG, SEM-EDS and FT-IR. The results show that the bending strength of the geopolymer ceramic binder increases proportionately with the increase of NaOH concentration. When the concentration of sodium hydroxide is 15 M, the bending strength reaches 19 MPa. N-A-S-H gel and zeolite formed in the geopolymerization reaction and the pores formed in the sintering process have a significant effect on the bending strength of the ceramic binder. This technology can significantly stimulate the chemical activity of coal gangue and provide innovative ideas for efficient utilization of coal gangue.

Random forest and Shapley additive explanation for compressive strength prediction of NaOH-pretreated crumb rubber concrete

The compressive strength (CS) of crumb rubber concrete (CRC) can be improved through a chemical pretreatment involving immersion of the crumb rubber particles in a NaOH solution. Despite the potential benefits of this treatment, accurately estimating the CS value of NaOH-pretreated CRC remains challenging. To address this issue, a comprehensive database encompassing 118 entries on the fundamental mixtures of CRC along with NaOH concentration and pretreatment duration has been meticulously compiled for machine learning analysis. The random forest (RF) algorithm is employed to predict the 28-day CS value of NaOH-pretreated CRC. The model hyperparameters are optimized using a random search technique with 10-fold cross-validation. The findings reveal that the optimized RF attains acceptable predictive performance, yielding RMSE, MAE, and R2 values of 3.83 MPa, 2.84 MPa, and 0.85, respectively, on the testing dataset. Additionally, the model is interpreted using multiple techniques, including permutation importance, RF model-based feature importance, and Shapley additive explanation from global or local perspectives. The feature importance analyses consistently highlight the crucial role of crumb rubber content in determining the 28-day CS value of NaOH-pretreated CRC, and the influence of NaOH concentration and pretreatment time appear relatively inconsequential compared to features associated with the CRC mixture. This research contributes to a deeper understanding and better mixture design of CS for NaOH-pretreated CRC.

Investigating the strength and durability properties of alkali activated red mud for tailings pond embankment material

This article investigates the applicability of alkali-activated red mud (RM) as a geo-material for the construction of tailings pond (TP) embankments. A series of unconfined compressive strength (UCS) and direct shear tests (DST) are carried out to examine the mechanical performance of RM activated with sodium hydroxide (NaOH). While doing so, the influence of NaOH concentrations, curing conditions and curing period are also investigated. Furthermore, durability tests are performed to examine the weathering resistance of stabilized RM specimens against extreme environmental conditions. Finally, the effectiveness of alkali activated RM (as an embankment material) is demonstrated with the help of numerical analysis performed on a model TP. Based on the experimental results, the compressive strength of bare RM is improved from 0.34 MPa to 5.6 MPa, 0.57 MPa to 10.55 MPa and 0.97 MPa to 29.34 MPa under controlled ambient curing (CAC, 25±2 °C), open air curing (OAC, 25±7 °C) and dry curing (DC, 60 °C) conditions respectively. On the other hand, effective friction angle and cohesion of bare RM is found to increase from 16.76° to 52.85° and 6.58 kPa to 391.11 kPa respectively, after alkali activation. Furthermore, alkali activated RM specimens exhibit a significantly high weathering resistance than bare RM against 12 cycles of alternate wetting and drying. The numerical analysis reveals a notable increase in the factor of safety values when alkali activated RM is utilized for the construction of TP, indicating its potential as an embankment material.

Effect of calcium carbide residue on the sulphate resistance of metakaolin-based geopolymer mortars

Sulphate resistance is an essential indicator for assessing the durability of geopolymer mortars. This study investigates the effects of calcium carbide residue (CCR) addition on the sulphate resistance of metakaolin-based geopolymer mortar via strength tests. The influence of NaOH concentration and NaOH/Na2SiO3 mass ratios on the compressive strengths was investigated. The prepared geopolymer mortars, with and without CCR, were cured at room temperature, and their durability was evaluated in a 5 % magnesium sulphate solution. The durability of the optimum geopolymer mix was compared with Ordinary Portland Cement mortar. The results indicated that the optimum 7-day compressive strength for geopolymers with and without CCR was achieved at 10 M NaOH with a NaOH/Na2SiO3 mass ratio of 1:2. The addition of CCR resulted in an increase in compressive strength by 26.12 % compared to the geopolymer without CCR. The sulphate resistance of geopolymer material with CCR was lower than those without CCR but higher than OPC-based mortar, which recorded a reduction in strength of about 3.2 % after sulphate exposure. The findings indicate that CCR addition to metakaolin-based geopolymer can produce high compressive strength with enhanced sulphate resistance compared to the OPC.

Synthesis and study of adsorption for ion Cu(II) from aqueous solution by chitosan beads

Chitosan beads were synthesized by sodium lauryl ether sulfate (SLES) gelation process and alkaline treatment. The characterization and morphology of chitosan beads were investigated by Fourier-transform infrared spectroscopy technique (FT-IR), optical microscope and scanning electron microscope technique (SEM). The influence of NaOH concentration, pH, reaction time and adsorption isotherm was studied. Langmuir and Freundlich adsorption models were applied to describe isothermal lines. The alkalization process enhanced significantly Cu(II) adsorption capacity of CS/SLES/NaOH to 4489,6 mg/g. The results showed that chitosan beads would be a promising material to remove heavy metals in wastewater.

Alkali treatment to transform natural clinoptilolite into zeolite Na–P: Influence of NaOH concentration

In this study, natural clinoptilolite was treated with NaOH solutions of different concentrations under mild ambient conditions. The composition and structure of the as-prepared samples were characterized, and their performance was assessed in terms of the removal of the heavy metal ions Cd2+, Cu2+, and Cr3+ from the aqueous solution. The results showed that the composition, structure, and capability of removal of heavy metal ions of the samples were significantly influenced by the NaOH concentrations. The crystal structure of clinoptilolite remained invariant under a relatively low NaOH concentration (≤0.5 M), began transforming into zeolite Na–P under a medium NaOH concentration (∼1.0 M), and then completely transformed into it under a high NaOH concentration (2.0–4.0 M). The samples treated with NaOH had lower SiO2/Al2O3 ratios, and were superior to unmodified natural zeolite in removing the heavy metal ions. This method of treatment with relatively high concentrations of NaOH is a simple and effective way to transform natural clinoptilolite into the zeolite Na-P rich ion exchanger, which is suitable for removing heavy metal ions.

Influence of NaOH concentration on the decolorization of crystal violet dyed cotton fabric

Synthetic dye removal is a topic of increasing interest as textile recycling has become more popular in industries. While methods involving dye removal from wastewater effluent have been widely studied and reported on, research on decolorization of fabric itself remains quite unknown. In regard to the lack of research, this study presents cotton fabric samples dyed with crystal violet (CV) that were treated with varying concentrations of sodium hydroxide (NaOH). Fabric decolorization was studied using several characterization methods. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy data showed that the cellulose structure remained unchanged after CV and NaOH treatment. Characteristic CV peaks in the FTIR and Raman spectra were apparent only in the control sample, while the spectra of NaOH-treated samples were very similar to that of the cotton fabric. X-ray diffractometry (XRD) data also confirmed that the crystallite size of cellulose was not affected by CV and NaOH treatment. A visible violet hue remained in all NaOH-treated samples, though CV intensity was inversely proportional to NaOH concentration. The L*a*b* values were utilized to complement characterization results. As the concentration of NaOH was increased, the CIELAB parameters aligned more with those of the plain untreated fabric.

Effects of petroleum sludge ash in fly ash-based geopolymer mortar

Due to its encapsulation capacity and low carbon emission, geopolymer mortar is recognized as a possible substitute for Portland cement. This paper reports an experimental procedure of producing geopolymer mortar using petroleum sludge ash (PSA) and fly ash. Replacement levels of PSA were 0 – 20% by the weight of fly ash, 8 – 16 molarity of NaOH, 1.5 – 2.5 ratio of Na2SiO3 to NaOH were used. The 28 days compressive strength of geopolymer mortar made with 10% PSA was found to be the highest (31 MPa). Using variance analysis, the influence of NaOH concentration, the ratio of Na2SiO3 to NaOH, and PSA on the behavior of geopolymer mortars was acquired. The defined models were found to be significant for p-values < 5%. The concentrations of the targeted heavy metals were found to be within the permissible level of USEPA.

PENGARUH KONSENTRASI NaOH TERHADAP KUALITAS TEPUNG TULANG IKAN BANDENG (Chanos chanos)

Fishbone is one form of waste from fish processing. Milkfish bone flour has high calcium and phosphorus content and can be an alternative source for the fulfillment of calcium and phosphorus in the body. The aimed of this research to find out the effect of NaOH concentration on the quality of milkfish bone meal (Chanos chanos). The research was conducted at the Animal Products Technology Laboratory, Tadulako University. Simultaneously, the analysis of calcium and water content was located at the Soil Science Laboratory of the Faculty of Agriculture, University of Tadulako. The length of time for the study is one month from March -April 2019. The research method that will be used is an experiment with a Completely Randomized Design (CRD) with the effect of NaOH concentration as follows: P1: 1% NaOH with a boiling temperature of 70 oC; P2: 2% NaOH with a boiling temperature of 70 oC; P3: 3% NaOH with a boiling temperature of 70 oC; and P4: 4% NaOH with a boiling temperature of 70 oC. The results of variance showed that it could be stated that the results of the analysis of calcium levels with the influence of NaOH concentration on the quality of milkfish bone meal do not have a significant effect on the value of calcium levels in fishbone meal flour.

Efficient Hydrolysis of Sodium Borohydride by Co‐B Supported on Nitrogen‐doped Carbon

AbstractIn this work, dehydrogenation of NaBH4 in alkaline solutions was catalyzed by amorphous Co‐B catalysts supported on nitrogen doped carbon (N‐C) that is rarely utilized in this field. The physicochemical properties of the as‐prepared catalysts were characterized by X‐ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), High Resolution Transmission Electron Microscopy (HRTEM), X‐ray Photoelectron Spectroscopy (XPS), Raman Spectroscopy and BET (Brunner−Emmet−Teller) measurements. Among all the catalysts made in this paper, Co‐B/N‐C‐700 exhibited best activity, which is likely to be attributed to the possession of more metal Co as active sites. The hydrogen generation rate (HGR) reached 2649 ml H2 min−1 g−1cat in 10 wt. % NaOH + 10 wt. % NaBH4 solution at 30 °C. The value of activation energy is 37.57 kJ mol−1 and compares favorably with values of some previous reports. Besides, influences of NaOH concentration, NaBH4 concentration, temperature, recycle times and amount of catalyst for the catalytic performance of Co‐B/N‐C‐700 were also investigated to reflect more on hydrolysis of sodium borohydride.

Extraction of alumina from alumina rich coal gangue by a hydro-chemical process.

Vast quantities of gangue from coal mining and processing have accumulated over the years and caused significant economic and environmental problems in China. For high added-value utilization of alumina rich coal gangue (ARCG), a mild hydro-chemical process was investigated to extract alumina. The influences of NaOH concentration, mass ratio of alkali to gangue, reaction temperature and reaction time were systematically studied. An alumina extraction rate of 94.68% was achieved at the condition of NaOH concentration 47.5%, alkali to gangue ratio of 6, reaction temperature of 260°C and reaction time of 120 min. The obtained leaching residues were characterized through X-ray diffraction, scanning electron microscopy and energy-dispersive spectrometer. Research confirmed that kaolinite the main alumina-bearing phase of ARCG can be decomposed and transformed to Na8Al6Si6O24(OH)2(H2O)2 and Ca2Al2SiO6(OH)2 at relatively low temperature and short reaction time. Additionally, Na8Al6Si6O24(OH)2(H2O)2 and Ca2Al2SiO6(OH)2 are unstable and will transform to alumina-free phase NaCaHSiO4 under the optimal conditions, which is the major reason for high alumina extraction rates.

Selective removal of As from arsenic-bearing dust rich in Pb and Sb

Abstract The selective removal of arsenic from arsenic-bearing dust containing Pb and Sb in alkaline solution was studied. The influence of NaOH concentration, temperature, leaching time, liquid to solid ratio, and the presence of elemental sulfur on the dissolution of As, Sb and Pb in NaOH solution was investigated. The results indicate that the presence of elemental sulfur can effectively prevent leaching of lead and antimony from arsenic. The Sb2O3, As2O3 and Pb5(AsO4)3OH in the raw material convert to NaSb(OH)6 and PbS in the leaching residue, while arsenic is leached out as As(III) or As(V) ions in the leaching solution. Arsenic leaching efficiency of 99.84% can be achieved under the optimized conditions, while 97.82% of Sb and 99.97% of Pb remain in the leach residue with the arsenic concentration of less than 0.1%. A novel route is presented for the selective removal of arsenic and potential recycle of lead and antimony from the arsenic-bearing dust leached by NaOH solutions with the addition of elemental sulfur.

Free-Standing Copper Oxide Films with In Situ Tailorable Nanostructures toward Detection of Hydrogen Peroxide

In this study, in-situ synthesized Cu(OH)2 nanostructures on copper foil substrates were realized via anodization method. With the precise manipulation of deposition conditions, qualitative modulation of the dimensionality of Cu(OH)2 nanostructures were achieved. The influences of NaOH concentration, current density, reaction temperature and time on the morphologies of Cu(OH)2 nanostructures were investigated using complementary techniques. Furthermore, the as-prepared Cu(OH)2 nanostructures can be successfully transformed to CuO with unnoticeable changes in morphology after thermal treatment in nitrogen atmosphere; therefore, leading to a freestanding electrode for integrated-sensors. The resultant morphology and crystallographic identification of the as-prepared samples were studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the pine-needle-like CuO modified electrode exhibited excellent electrochemical catalytic performance toward H2O2 reduction. Highly sensitive and fast-and-linear responses were achieved with its large specific surface area and efficient charge transfer properties. Hence, we report the freestanding CuO films with facile tailorable nanostructures as a promising candidate for efficient, stable and highly sensitive non-enzymatic amperometric detection of H2O2.

One-pot hydrothermal synthesis of micaceous iron oxide pigment from jarosite waste

In this study, jarosite waste was adopted as feed material for micaceous iron oxide (MIO) pigment preparation by a one-pot hydrothermal reaction. The formation of MIO started from jarosite decomposition into akaganeite (β-FeOOH) nanoparticles in alkali solution, which then recrystallized and transformed into MIO crystals under high temperature and OH− concentration. The influences of NaOH concentration and reaction temperature on MIO formation were investigated. It was found that MIO formed when NaOH concentration and reaction temperature were equal to or higher than 2 M and 180°C, respectively. With an increase of NaOH concentration or reaction temperature, the particle size of MIO increased, leading to darkened color of the product. Moreover, quality evaluation indicated that the synthesized MIO fulfilled the required characteristics of micaceous iron oxide pigments for paints and the international standard of ISO 10601-2007 MIO-A1.

ผลของความเข้มข้นของโซเดียมไฮดรอกไซด์ต่อกำลังอัดของคอนกรีตที่ผสมเถ้าถ่านหิน

ผลของความเข้มข้นของโซเดียมไฮดรอกไซด์ต่อกำลังอัดของคอนกรีตที่ผสมเถ้าถ่านหิน

Generation of parallelepiped-shaped mesopores and structure transformation in highly stable ferrierite zeolite crystals by framework desilication in NaOH solution

Desilication and recrystallization of a low-silica NaK-form ferrierite (NaKFER) were conducted by one-step hydrothermal method in sodium hydroxide solution containing cetyltrimethylammonium bromide (CTAB). The attack by NaOH induced unprecedented mesopore formation in highly stable ferrierite crystals through framework desilication. Interestingly, the generated mesopores are parallelepiped-shaped and oriented along the [001] directions (10 MR) of the FER structure. The CTAB surfactant could be inserted between the layers of ferrierite crystals under the assistance of NaOH. This process was associated with the formation of occluded mesopores and led to partial delamination of layered crystals. Under severe treatment conditions, NaKFER transformed to GIS and SOD phases, successively. The samples were characterized by XRD, N2 sorption, SEM, TEM, EDS, TG, etc. The influence of NaOH concentration, temperature, reaction time, CTAB and cation form of the parent zeolite was investigated in order to study the mechanism of mesopores formation, delamination process and phase transformation of ferrierite. Phase diagrams were established to show the transformation process of NaKFER as a function of NaOH concentration, reaction time and temperature.

SINTESIS O-KARBOKSIMETIL KITOSAN PADA BERBAGAI KONSENTRASI NaOH DAN SUHU REAKSI SERTA APLIKASINYA SEBAGAI ANTIBAKTERI

The research about the influence of NaOH concentrations and reaction temperature to O-Carboxymethyl Chitosan (O-CMC) synthesis and it is antibacterial application was done. This research intent on detect NaOH concentration and reaction temperature that resulting of O-CMC with highest of yield, solubility, and substitution degrees, and also to find out FTIR spectrum and antibacterial activity of O-CMC. The produce of O-CMC was done by using a Completely Randomized Design (CRD) with the variation of NaOH concentration of 20%, 30%, 40%, 50%, and 60%, and also reaction temperature of 20, 30, and 40oC. The result was showed that on the NaOH concentration of 60% (w/v) and temperature of 30oC was resulted highest of yield, solubility, and substitution degrees of 41.5%, 31 g/L, and 0.67, respectively. FTIR spectrum was showed that bending vibration of primary amine (-NH2) give two bands for O-CMC. The broadest inhibition area of O-CMC (1.43 cm) was showed on Salmonella sp.Keywords: chitosan, O-CMC, substitution degree, antibacterial

Influence of NaOH concentration on microstructure and properties of cured alkali-activated calcined clay

Microstructure of cured mixes composed of kaolinitic-illitic raw clay calcined at 700°C and sodium hydroxide (4–14M) was investigated using X-ray diffraction, Fourier-transform infrared spectroscopy, Scanning electron microscopy and Thermal analysis. The change of the properties (flexural strength, density, water absorption, open porosity and electrical conductivity) versus NaOH concentration was evaluated and the possible formation of zeolite ZK-14 within the geopolymer matrix from the amorphous clay phases (mainly metakaolinite) was examined. Sodium carbonate was detected as a carbonation product. Due to heating, geopolymers were characterized by dehydration and subsequent recrystallization into nepheline. The development of the fibrous-zeolitic phase was favored by the increase of NaOH concentration and its impact on the studied properties was somewhat advantageous. The rise of alkali concentration within 4–11.5M enhanced the extent of geopolymerization. The water absorption kinetic obeyed a pseudo-first order equation and the constant was in the range (18.38–51.01)×10−2min−1.