Hydroxide Ratio Research Articles

Determination of the optimal reaction conditions for the preparation of highly substituted carboxymethyl Cassia tora gum

Highly substituted carboxymethyl Cassia tora gum (CM-CTG) was prepared from CTG by treatment with monochloroacetic acid (MCA) in ethanolic aqueous solutions after alkalization under different reaction conditions. The influence of the etherification temperature, alkalization and etherification times, molar ratio of sodium hydroxide to MCA (nNaOH/nMCA), theoretical degree of substitution (DSt), and weight percentage of water (WH2O%) in the solution on the degree of substitution (DS) and reaction efficiency (RE) of the reaction were investigated. Optimum preparation conditions for a CM-CTG with DS of 1.05 are: etherification temperature, 60°C; alkalization time, 60min; etherification time, 180min; nNaOH/nMCA, 2.1; DSt, 1.4; and WH2O%, 20%. Fourier-transform infrared analysis of the products indicated that carboxymethylation was successful. Rheological studies show that all the CM-CTG pastes are pseudoplastic fluids, and the shear sensitivity varies with DS. The degree of crystallinity of CM-CTG decreases with increasing DS, as shown by X-ray diffraction measurements.

Removal of naphthenic acid from diesel by complex deacidification agents

ABSTRACTNaphthenic acid in diesel was removed by complex deacidification agents consisting of sodium hydroxide and ethanol. The effect of all parameters on removing naphthenic acid from diesel was reviewed systematically. On the basis of single factor experiments, orthogonal experiments were performed to optimize the deacidification process. The results showed that the optimum deacidification process was that the volume ratio of sodium hydroxide to ethanol was 2:1, the volume ratio of complex deacidification agents to diesel was 1.4:1, the reaction temperature was 303 K, the reaction time was 50 s, and the standing time was 30 min. The acidity of the diesel was reduced from 135.52 mg KOH/100 mL to 4.52 mg KOH/100 mL, and the deacidification rate reached 96.66% under the optimum process; thus the treated diesel met the quality requirements.

Geopolymerization behavior of fine iron-rich fraction of brown fly ash

Iron rich brown fly ash has been segregated into (a) coarse, and (b) fine size fractions using air classification. The suitability of fine iron-rich fly ash (CFA) has been evaluated for the synthesis of geopolymer. The behavior of CFA based geopolymer in relation to reactivity, NaOH concentration and sodium silicate to sodium hydroxide (S/H) ratio has been studied. The concentrations of NaOH (6, 8, 10 and 12M) and S/H ratios (0.33, 1.0 and 3.0) were the variable parameters. Calorimetric studies revealed that the total heat release increased with NaOH concentration, but decreased with the increase in S/H ratio. The geopolymer synthesis was done by thermal curing at 60°C for 24h. It was found that the compressive strength increased with an increase in the NaOH concentration. The increase in S/H ratio from 0.33 to 1.00 resulted in a significant increase in the compressive strength, but a further increase from 1.00 to 3.00 resulted in a slight decrease in compressive strength. High strength geopolymer mortar up to 70MPa at 28 days was obtained, when the mixture was formulated with 12M NaOH and S/H ratio of 1.00. From SEM-EDS studies, an increase in the degree of reaction and formation of geopolymer gel was observed with increase in NaOH concentration. Also it revealed that the geopolymer gel obtained was ferro-sialate based polymers with chemical formula close to [Ca, Na]-[-Fe-O-]x-[-Si-O-Al-O-]1−x-[-Si-O-]y, wherein “x” is less than or equal to 0.5, and “y” is a value between 0 and 25. Formation of the compact microstructure has resulted in improved strength properties of geopolymer.

Separation of high-purity syringol and acetosyringone from rice straw-derived bio-oil by combining the basification-acidification process and column chromatography.

Numerous technologies have been used to reclaim valuable chemicals from bio-oil. In this study, a combination of the basification-acidification process and column chromatography was employed for the separation of high-purity syringol and acetosyringone from rice straw-derived bio-oil. The optimal conditions for the basification-acidification process and the possible precipitation mechanism of the basification were explored. The results showed the following as the optimal conditions for the basification process: mass ratio of calcium hydroxide (Ca(OH)2 ) to bio-oil, 2.0; reaction temperature, 70°C; and reaction time, 30 min. The results also showed that 1.6 mol of hydrochloric acid (HCl) per gram of bio-oil was optimal for the acidification. The precipitation was found to proceed via a possible mechanism involving the reaction of the phenolic compounds in the bio-oil with Ca(OH)2 to produce a precipitate. After further separation by column chromatography, purities of 91.4 and 96.2% (from gas chromatography-mass spectrometry) were obtained for syringol and acetosyringone, respectively. Their recoveries for the whole process were 73.0 and 39.3%, respectively.

High Performance Humidity Sensor Based on ZnO Nanoparticles Synthesized by Co-Precipitation Method

ZnO nanoparticles were successfully synthesized by a low cost co-precipitation method using zinc nitrate and sodium hydroxide as the raw materials. It was observed that the synthesized temperatures greatly effect on the size of ZnO nanoparticles. The lower synthesized temperatures resulted in the smaller nanoparticles. By adjusting the mole ratio of sodium hydroxide, the size of ZnO nanoparticles was also changed. The smallest ZnO particles was 47 nm obtained with 0.7 mole of sodium hydroxide. The smallest ZnO nanoparticles from each synthesized temperatures were fabricated as humidity sensor, showing an impressive performance under different relative humidity (17-94% RH). It should be noticed that the ZnO nanoparticles humidity sensor synthesized at 75 °C exhibited high response for 2 times higher than that of synthesized at 95 °C. This is attributed to the higher surface area of ZnO nanoparticles for absorbed water molecule.

Improvement of the early and final compressive strength of fly ash-based geopolymer concrete at ambient conditions

Sustainable concrete has reduced CO2 emissions, is durable, and is expected to have less detrimental effect on future generations, due to the fact that it utilizes waste materials. However, the need for external heat limits construction applications. The effects of sodium hydroxide ratio, external heat amount, and partial Portland cement replacement on fly ash-based geopolymer concrete were investigated. The early compressive strength, density, absorption, and permeable voids were measured, and the microstructure of the fly ash-based geopolymer paste was observed and characterized. The activating solution was a combination of silica fume, sodium hydroxide, and water. Experimentation showed that application of external heat plays a major role in compressive strength. Results also show that early and final compressive strength gains, in case of absence of external heat, can be improved by using Portland cement as a partial replacement of fly ash. The Scanning Electron Microscopy (SEM) results showed that the addition of Portland cement utilized the free water from the geopolymerization reaction. It not only led to a reduction in the microcracks formation due to less shrinkage, but also provided extra alkalinity, such as calcium hydroxide, which helped accelerate the fly ash and the activating solution reaction. Additionally, the permeable void ratio is affected by the Portland cement replacement, showing a significant reduction when the Portland cement ratio is increased.

Performance enhancement of green concrete

Several factors, such as energy-saving methodologies and techniques and improved use of materials, need to be considered for the development of sustainable construction materials. In the present work, the feasibility of using industrial inorganic polymeric residual wastes as a total (100%) replacement for traditionally used normal concrete materials was examined in the preparation of geopolymer concrete (GPC). In this study’s GPC, the cement was replaced totally by fly ash (class F) and ground granular blast furnace slag (GGBFS), the fine aggregates were replaced totally by bottom ash, the coarse aggregates were replaced totally by water-cured fly ash aggregates (WCFAs), which were prepared by using class C fly ash by adopting the pelletisation technique. The GPC mixes were cast with WCFAs at 0, 10, 20 and 30% replacement of fly ash (class F) by GGBFS with different molar ratios of sodium hydroxide (NaOH) solutions (8, 10, 12 M). The concrete was cured at ambient temperature only to minimise the water during water curing. The physical and mechanical properties of the GPC were studied by using the combination of all the mentioned materials. It was observed that the GPC mixes at 30% GGBFS with 12 M sodium hydroxide attained a maximum compressive strength of 38·94 MPa.

Strength and microstructure evaluation of recycled glass-fly ash geopolymer as low-carbon masonry units

The objective of this research was to evaluate the strength development of industrial by-products, namely Recycled Glass (RG) and Fly Ash (FA) in the manufacture of low carbon masonry units. A low carbon concept for manufacturing masonry units using RG-FA geopolymers was explored by applying low curing temperature of 50°C and a low curing period of just 3–7days. RG, being rich in silica was used as a filler material. FA, being a silica and alumina rich industrial by-product was used as a precursor in the RG-FA geopolymers. A liquid alkaline activator (L) comprising of a sodium hydroxide-sodium silicate solution was used for the alkali activation of 30% content of FA in the RG-FA blend. Factors found to affect strength development of the RG-FA geopolymers were: (1) the ratio of sodium hydroxide and sodium silicate in the liquid activator, (2) application of a low curing temperature of only 50°C, (3) short curing periods of just 7days and (4) the L/FA ratios. A geopolymer composed of a 70% Na2SiO3:30% NaOH ratio with a L/FA ratio of 0.625 was found to be the most efficient combination to provide the required unconfined compression strengths for manufacturing masonry. The usage of RG-FA geopolymers as low carbon masonry units was found to be viable using a low curing period of just 7days and a curing temperature of just 50°C. The RG-FA geopolymers had sufficient compressive strength be used as structural masonry units and needed only a low amount of heat treatment to achieve the minimum strength requirement. Optimally, 30% of FA was found to be sufficient for geopolymerization to occur for this novel low carbon RG-FA masonry units. Furthermore, the core materials needed to produce RG-FA masonry units were industrial by-products, the sustainable usage of which would contribute significantly to efficient waste management, through the production of aesthetically pleasing masonry units.

Characterization of Fly Ash on Geopolymer Paste

The effect of loss of ignition, specific gravity, fineness, specific surface area and soluble fly ash to compressive strength of geopolymer paste were studied. Six fly ashes from two different sources and different time of collection were evaluated. Sodium hydroxide and sodium silicate were used as alkali activator. Concentration of sodium hydroxide and mass ratio of sodium hydroxide to sodium silicate were fixed 14M and one respectively. The result indicated that the improvement in compressive strength of geopolymer paste was more influenced by fineness, specific surface area and soluble content of fly ash. Soluble content of fly ash greatly affected the compressive strength of geopolymer paste compare to the compressive strength of cement paste with 20% fly ash replacement.

Factors Affecting the Setting Time of Fly Ash-Based Geopolymer

Fly ash is a waste from coal burning, that are generated with fluctuation both in its physical and chemical characteristics. This characteristics of fly ash when used in the making of geopolymer concrete will greatly affect the final products obtained. The pH value measured in fly ash, according previous research, can influence the setting time of geopolymer and fly ash with high pH values can cause flash-setting in the concrete. Understanding more clearly about the factors that affect the setting time of fly ash based geopolymer is important for further progress and development of the material. It was found that factors that influence the setting time of geopolymer was not only from the physical and chemical properties of the fly ash itself. Other factors such as composition and mix design, manufacturing process and environmental conditions can also affect its setting time. The experimental results showed that fly ash particle size, CaO and MgO content, in addition to ratio of sodium silicate and sodium hydroxide in the alkali solution, molarity of NaOH, initial temperature of the mixture, curing temperature, and mix volume could potentially influence the setting time of the geopolymer mixture.

Effects of Heating- or Caustic-Digested Starch on its Flocculation on Hematite

ABSTRACTSelective flocculation of heating or caustic-digested starch on hematite is well practical. What happens to the starch from alkali-digestion at room temperature or heating-treatment, however, may not be fully understood. An attempt to identifying possible effects of heating- or caustic-digested starch on its adsorption characteristics on fine hematite was made through a series of tests, like adsorption test, micro-flotation test, turbidities test, Fourier transform infrared spectroscopic analysis (FTIR), and Aggregation/dispersion measurement as well. All results from these tests pointed out that those traditional digestion methods have a significant influence on adsorption density of starch on mineral surfaces, as well as its adsorption mechanisms. Since a certain amount of carboxyl groups on the starch remnants resulted from heating- or caustic-digestion probably attributes to the acid/base interaction between the starch and hematite. And much more amounts of carboxyl groups seem to be harvested from the starch digested with sodium/potassium hydroxide at higher concentrations. But the homogeneous and transparent starch gel from alkali-digestion at a concentration of more than 2% at room temperature, consisting of a great many short-chain remnants, may probably weaken its flocculating capacity on hematite and lead to performing a potentially dispersing role instead. It is also worthy to notice that the starch gel from a combination of caustic-digestion at a 1.5 weight ratio of sodium hydroxide to starch and heating-treatment at the temperature of 100°C reached an adsorption density of almost 12 mg/g hematite, compared with 9.0 mg/g from caustic-digested starch at same concentration or 6.2 mg/g from heating-treated starch in boiling water only.

Synthesis of Nickel Nanoparticles using Electron Beam Irradiation

A study on the preparation of nickel oxide nanoparticles using electron beam irradiation is described. Nickel nanoparticles were synthesized with nickel chloride hexahydrate as a metal precursor and different sodium hydroxide concentrations using electron beam irradiation. The effects of sodium hydroxide concentration and electron beam absorbed doses were investigated. The samples were synthesized at different sodium hydroxide concentrations and with absorbed doses of 100 to 500 kGy at room temperature. Synthesized nanoparticles were characterized by X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM) and a vibrating sample magnetometer (VSM). The nanoparticle morphologies seemed to be non-spherical and aggregated. The 1:1 molar ratio of nickel chloride hexahydrate and sodium hydroxide showed a higher purity and saturation magnetization value of 13.0 emu/g. The electron beam absorbed dose was increased with increasing nickel nanoparticle nucleation.

Development of geopolymer with pyroclastic flow deposit called Shirasu

The study presents a preliminary investigation on the applicability of Shirasu (a pyroclastic flow deposit characterized by high percentage of volcanic glass) in geopolymer. Comparative study on compressive strength and internal pore structure has been done between geopolymers with alkali activated Shirasu and fly ash as aluminosilicates. Mortar mix proportions are selected based on variations in ratio of alkaline activators to aluminosilicate and also on silica to alkali hydroxide ratio. From the experimental study, Shirasu geopolymer exhibited fairly good compressive strength. Mix proportion based on silica to alkali hydroxide ratio is observed to have profound effect on strength development.

Effect of silica nanoparticles in mixed matrix membranes for pervaporation dehydration of acetic acid aqueous solution: plant-inspired dewatering systems

Clean technology in dehydration of acetic acid using pervaporative separations inspired by plant dewatering systems is studied in this work. The novel polyphenylsulfone-based membranes, modified with silica nanoparticles, were used to dehydrate a binary mixture of acetic acid and water. The Stöber process was applied for the synthesis of monodispersed silica colloids by hydrolysis of alkyl silicates and condensation of silicic acid in alcoholic solution. The surface free energy of the synthesized silica particles was altered through a silanization treatment with hexamethyldisilazane to convert the surface hydroxyl groups to trimethylsilyl[–Si(CH3)3] groups. The synthesized particles and the modified polyphenylsulfone based membranes were characterized using dynamic light scattering, scanning electron microscopy, atomic force microscopy, Fourier-transform infrared and macroscopic contact angle measurements. Pervaporation was used for the dehydration of 70 wt% acetic acid at 70 °C using nine different membrane variations. Inspired by the natural dewatering in plants containing silica, the performance of the synthetic silica nanoparticles filled-membranes was investigated. Similar to plants, the incorporation of silica nanoparticles in these membranes significantly affected the dewatering process. It was found that at higher concentrations of silica, an improvement of membrane properties was observed, particularly in terms of selectivity. Besides that, the hydrophilicity and surface roughness increases when sufficient amounts of silanols groups were present on the membrane surface. It was concluded that more hydrophilic silica should be first produced and incorporated into the membranes for efficient removal of water from acetic acid. This can be achieved by controlling the composition ratio of ammonium hydroxide, water and ethanol for the nanoparticle fabrication. The effect of different nanoparticle types on membrane morphology and pervaporation performance is also discussed in detail in this work.

Facile, room-temperature pre-treatment of rice husks with tetrabutylphosphonium hydroxide: Enhanced enzymatic and acid hydrolysis yields

Aqueous solutions of tetrabutylphosphonium hydroxide have been evaluated as pretreatment media for rice husks, prior to sulphuric acid hydrolysis or cellulase enzymatic hydrolysis. Varying the water:tetrabutylphosphonium hydroxide ratio varied the rate of delignification, as well as silica, lignin and cellulose solubility. Pre-treatment with 60wt% hydroxide dissolved the rice husk and the regenerated material was thus heavily disrupted. Sulphuric acid hydrolysis of 60wt%-treated samples yielded the highest amount of glucose per gram of rice husk. Solutions with good lignin and silica solubility but only moderate to negligible cellulose solubility (10–40wt% hydroxide) were equally effective as pre-treatment media for both acid and enzymatic hydrolysis. However, pre-treatment with 60wt% hydroxide solutions was incompatible with downstream enzymatic hydrolysis. This was due to significant incorporation of phosphonium species in the regenerated biomass, which significantly inhibited the activity of the cellulase enzymes.

Optimization of process parameters and its effect on particle size and morphology of ZnO nanoparticle synthesized by sol–gel method

In the present work, a systematic basic research has been performed for finding out the effect of various process parameters viz. molar ratio of zinc sulfate and sodium hydroxide, reaction time and calcination temperature on size and morphology of ZnO nanoparticles synthesized using zinc sulfate as a precursor by sol–gel method. Taguchi design method, ANOVA and regression analysis were used to find out the effect of various process parameters on the response in terms of narrow particle size distribution and crystal size. Characterization was done to find out the response such as particle size distribution and crystal size by using TEM and XRD. Results revealed molar ratio of 1:2, and calcination temperature of 700 °C could significantly form uniform-sized spherical ZnO nanoparticles (85 nm) with narrow size distribution. However, significant increase in crystal size of ZnO nanoparticles was observed with increase in calcination temperature from 300 to 700 °C. This may be primarily due to governing of higher diffusion rate at high temperature which resulted in enhanced growth rate of ZnO crystals.

Production of biodiesel with lithium glyceroxide

Alkoxide/hydroxide catalysts were synthesized by heating aqueous solutions of lithium hydroxide with glycerol under vacuum. The dehydration rates for different mole ratios of lithium hydroxide to glycerol were 3:1<2:1<1:1. Temperature showed a clear effect on dehydration rate while the effect of vacuum was less important. The resulting base catalysts were characterized by X-ray powder diffraction (XRD), Nuclear Magnetic Resonance (NMR), and Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). Catalysts prepared with 2:1 and 3:1 mole ratios comprised mono and a novel di-lithium substituted glyceroxide, as well as lithium hydroxide. Transesterification reactions of canola oil with methanol were conducted using equivalent mole amounts of sodium methoxide (0.0104mol, 0.5wt.%) and glycerol lithium base catalysts (0.0104mol, 0.2wt.%). The lithium glyceroxide/hydroxide catalyzed rapid transesterification though the reaction was slower than observed for sodium methoxide. All catalysts resulted in a high methyl ester yield (>99wt.%). The catalytic activity was 1:1<2:1<3:1 (lithium hydroxide:glycerol), and was not significantly influenced by conditions used in preparing the catalyst. The crude glycerol remaining after the lithium glyceroxide catalyzed reaction was reacted with free fatty acid to prepare glycerol insoluble lithium soap. A recovery of most of the lithium (85%) as a lithium soap was possible by filtration of the glycerol fraction producing a substantially ion free glycerol solution. This novel reaction afforded glycerol that was substantially free of catalyst and a value added lithium soap suited for use as commercial grease.

Determination of oligosaccharides and monosaccharides in Hakka rice wine by precolumn derivation high-performance liquid chromatography

This article presents a precolumn derivatization procedure with 1-phenyl-3-methyl-5-pyrazolone (PMP) reagent to detect oligosaccharides and monosaccharides in Hakka rice wine. The subsequent separation of the derivatized glucose–PMP also was performed using a mobile phase consisting of the molar ratio of acetonitrile to ammonium acetate buffer (0.1M) of 22:78 at a flow rate of 1.0 mL/min with the column temperature of 35°C, and the pH of ammonium acetate buffer at 5.5. The optimum derivation conditions were as follows: reaction temperature, 70°C; reaction time, 30 minutes; molar ratio of PMP to glucose, 10:1 (v/v); molar ratio of sodium hydroxide to glucose, 3:1 (v/v). The recovery rates were between 93.13% and 102.08% with relative standard deviation of 0.96–2.48%. The established method provides sufficient sensitivity with values of limit of detection of 0.09–0.26 mg/L and limit of quantification of 0.27–0.87 mg/L for determination of oligosaccharides and monosaccharides.

The Regeneration of Ammonia Solution by Calcium Hydroxide for Carbon Dioxide Absorption from the Flue Gas

The tests of this study were conducted by the semi-continuous flow experiments to absorb the carbon dioxide (CO2) gas in a bench-scale spraying column reactor. The absorption capacity and the regeneration efficiency of the absorbed ammonia (NH3) solution were determined. In this study, the maximum regeneration efficiency is 68.4% as the concentration of NH3 solution is 1% and the ratio of calcium hydroxide (Ca(OH)2) and CO2 is 1 as well. Furthermore, the absorption capacity of the NH3 solution decreases from 1.67 to 0.27 kg-CO2/kg-NH3 after regenerating four times due to the 30-38% loss each time. Regarding the regeneration kinetics between absorbed products and Ca(OH)2, the comparative degree of covered Ca(OH)2 during the reaction was recognized after fitting by a surface coverage model. Finally, the ammonium bicarbonate (NH4HCO3) reduced by Ca(OH)2 to calcium carbonate (CaCO3) solid and NH3 solution in the regeneration reactions was observed by scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDS) pictures and X-Ray Diffraction (XRD) analyses. Although the NH3 solution can be regenerated by Ca(OH)2 effectively in this study, the overall benefit of this process should be estimated further in the energy aspect.

Relationship between compressive strength and UPV of GGBFS based geopolymer mortars exposed to elevated temperatures

Geopolymers are innovative materials possessing properties similar to normal OPC, while having less environmental impact. The current research was conducted on GGBFS based geopolymeric mortars. The effects of sodium silicate to sodium hydroxide ratio on the compressive strength of the mortars at 1 and 7days before and after exposure to the elevated temperatures of 200°C, 400°C, 600°C, and 800°C were investigated. Additionally, the relationship between Ultrasonic Pulse Velocity (UPV) and compressive strength was investigated for before and after exposure to elevated temperatures. It was found that the sodium silicate to sodium hydroxide ratio had little or no effect on the compressive strength change between 1 and 7days. However, the compressive strength generally increased with increasing sodium silicate content. Similar trend was observed for elevated temperature exposure, in that the strength increased with increasing sodium silicate to sodium hydroxide ratio, while the overall behavior was such that the compressive strength decreased as the temperature exposure increased. UPV measurements showed similar behavior, which indicated that relationship between UPV and compressive strength was exponential and R2 was between 0.95 and 0.98.