Effect Of Alkali Research Articles

Halloysite nanotubes in analytical sciences and in drug delivery: A review

Halloysite (HNT) is a natural inorganic mineral that has many applications in manufacturing. This review (with 192 references) covers (a)the chemical properties of halloysites, (b)the effects of alkali and acid etching on the loading capacity and the release behavior of halloysites, (c)the use of halloysite nanotubes in analytical sciences and drug delivery, and (d)recent trends in the preparation of magnetic HNTs. Synthetic methods such as co-precipitation, thermal decomposition, and solvothermal method are discussed, with emphasis on optimal magnetization. In the analytical field, recent advancements are summarized in terms of applications of HNT-nanocomposites for extraction and detection of heavy metal ions, dyes, organic pollutants, and biomolecules. The review also covers methods for synthesizing molecularly imprinted polymer-modified HNTs and magnetic HNTs. With respect to drug delivery, the toxicity, techniques for drug loading and the various classes of drug-halloysite nanocomposites are discussed. This review gives a general insight on the utilization of HNT in analytical determination and drug delivery systems which may be useful for researchers to generate new ideas. Graphical abstract Schematic presentation of the structure of halloysite nanotubes, selected examples of modifications and functionalization, and represetative field of applications.

An experimental study on the coalescence behavior of oil droplet in ASP solution

Abstract The alkali-surfactant-polymer (ASP) flooding as one of efficient enhanced oil recovery technology has attracted great interest in the recent years. Nevertheless, the high stability of the oily water has become a threat to the environmental security. And most of the separation methods have been gained through trial-and-error approaches at present. However, there is a lack of clear microscopic scale study with respect to the mechanisms that govern the separation efficiency. In this paper, the effects of alkali (A), surfactant (S) and polymer (P) on the coalescence behavior of oil droplets are experimentally investigated with high-speed photography. The results indicate that the composition of the ASP flooding solution substantially influences the coalescence patterns of oil droplets. The optimum solute concentration of each component in ASP for oil droplet coalescence is obtained based on the microscopic experimental results. Statistical investigation on contact angles of the coalesced oil droplets is concluded that effective contact angles are distributed asymmetrically within the ranges of conditions studied. And most of the oil droplets are found to coalesce at small contact angles (5–25°) or large contact angles (50–80°). The research findings are of great significance for developing high-efficient processing technology for ASP flooding produced water.

CO2 gasification performance and alkali/alkaline earth metals catalytic mechanism of Zhundong coal char

Gasification is generally considered as the most effective for low rank coal exploitation, and CO2 gasification offers the advantage of upgrading a greenhouse gas. Herein, the effects of alkali and alkaline earth metals on gasification of char derived from Zhundong low rank coal (R-char) were investigated using a thermo-gravimetric analyzer (TGA). Additionally, the characteristics of chars were analyzed by X-ray fluorescence (XRF) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The results show that the carbon conversion increases as the temperature and CO2 concentration increases. The R-char possesses a higher gasification rate and carbon conversion than the acid washing R-char (AR-char). It can be explained that the alkali and alkaline earth metals presence in coal char can remarkably facilitate the compound’s decomposition and make more char surface exposure to react during the gasification process. For the kinetic analysis, the volumetric reaction model reveals a proper description among the three models (VRM, RPM, SCM), and the R-char and AR-char presents a compensation effect in VRM. Besides, the detailed correlation of two chars is ln (k0)=0.10 E A −1.77 (R-char) and ln (k0)=0.10 E A −2.85 (AR-char), respectively.

Preparation and Characterization of Modified Porous Wood Flour/Lauric-Myristic Acid Eutectic Mixture as a Form-Stable Phase Change Material

In this research, porous wood flour (WF) and a eutectic mixture of lauric acid (LA) and myristic acid (MA) were prepared as a form-stable phase change material (FSPCM) using a vacuum impregnation method. The effects of alkali (NaOH), cetyltrimethylammonium bromide, and complex salts (CS) on the pore size of the WF were investigated. The results showed that the CS-treated WF (CS-WF) achieved the maximum pore size and impregnation ratio. The characterization by Fourier-transform infrared spectrometer, X-ray photoelectron spectrometer, and X-ray diffractometer illustrated that the combination of the LA-MA eutectic mixture and the CS-WF was a physical combination. The differential scanning calorimetry results suggested that the optimum melting temperature and the latent heat of the CS-WF/LA-MA FSPCM were 33.1 °C and 98.2 kJ kg–1, respectively. The maximum impregnation ratio of the LA-MA eutectic mixture into the CS-WF was 60.3%. In addition, the thermogravimetric analysis indicated that the CS-WF/LA-MA FSPCM ...

Experimental investigation on effect of alkali, salts on the rheological properties of polyacrylamide and mixed assembly of polymer-surfactant

Abstract An experimental study was conducted to evaluate the effect of addition of alkali, salts and surfactants on the rheological properties of polyacrylamide (PAM) solution by rheometry. The results show the addition of inorganic salts (NaCl, Na2SO4, MgCl2), alkali (NaOH) and surfactants (CTAB, Gemini-5 and Gemini-6) strongly influence the rheological behavior of polyacrylamide solution. The shear thinning behavior of the solution at low shear rate was observed. The scope of this experimental work also includes the measurements of viscoelastic behavior, transient shear stress response and yield stress. The results are quite interesting and the mixed systems can be used as ASP flooding in Enhance oil recovery.

Effect of alkali and alkaline earth metal dopants on catalytic activity of mesoporous cobalt oxide evaluated using a model reaction

Herein we report the synthesis of mesoporous cobalt oxides in pure (Co3O4) and alkali and alkaline earth metal doped form (Li-, Ca-, Cs-, and Na-, K-, and Mg/Co3O4) via the inverse micelle method. The as-prepared materials were characterized by powder X-ray diffraction (pXRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), nitrogen sorption (BET), hydrogen-temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS). Characterization results suggested that the as-synthesized materials are of amorphous and mesoporous nature. Their catalytic activity was investigated using a model reaction, namely the liquid-phase morin oxidation. Results revealed pure cobalt oxide to be the better catalyst compared to its doped counterparts. The stability of Li/Co3O4 material was investigated exemplarily by recycling and reusing the catalysts for as many as four catalytic cycles. Conversion of morin was complete in all runs and no significant metal leaching could be detected by the use of inductively coupled plasma mass spectrometry (ICP-MS).

Effects of Alkali and Alkaline Earth Metallic Species and Chemical Structure on Nascent Char–O2 Reactivity

Factors influencing the nascent char–O2 reactivity was investigated in this study from the aspects of alkali and alkaline earth metallic species and char chemical structure. Char samples were prepared from the fast pyrolysis of two low-rank coals (Loy Yang brown coal and Collie sub-bituminous coal) in a wire-mesh reactor at temperature ranging from 600 to 1200 °C with holding time up to 5 s. The concentrations of alkali and alkaline earth metallic species in char were determined by inductively coupled plasma-optical emission spectroscopy. The char chemical structure was characterized by Fourier transform-Raman spectroscopy. Our results show that the char–O2 reactivity is greatly related to the Raman sensitive O-containing functional groups at the initial stage of char formation (short residence time at 600 °C during pyrolysis). As char pyrolysis proceeded to higher temperature, the loss of O-containing functional groups and the condensation of aromatic ring systems play a key role in the decreasing magnitude of char–O2 reactivity. The chemical structure of 1200 °C pyrolysis char is relatively stable, thereby posing limited effect on the changes in char–O2 reactivity. For Loy Yang brown coal, the volatilization of alkali and alkaline earth metallic species during pyrolysis at 1200 °C became the dominant reason for the observed decreases in char–O2 reactivity.

Effect of alkali and alkaline earth metal on Co/CeO2 catalyst for the water-gas shift reaction of waste derived synthesis gas

We prepared a series of alkali (Na and K) and alkaline earth metal (Ca and Ba) promoted Co/CeO2 catalysts to investigate the effect of the promoter on the catalytic performance of the catalyst in the high-temperature water-gas shift (WGS) reaction of waste derived synthesis gas. Interestingly, alkali metal promoted catalysts deactivated rapidly compared to alkaline earth metal promoted catalysts. Alkaline earth metal promoted catalysts showed relatively higher stability (> 50 h) even at a very high gas hourly space velocity of 143,000 h−1. X − ray diffraction (XRD) and transmission electron microscopy (TEM) results reveal that the higher stability of the alkaline earth metal promoted catalysts was due to the strong resistance to sintering, showing a relatively small crystallite size of metallic cobalt compared to the alkali metal promoted catalysts after WGS reaction.

The Effects of Alkali and Temperature on the Hydrolysis Rate of N-methylpyrrolidone

By studying the hydrolysis of N-methylpyrrolidone, it was found that the effects of NaOH concentration and temperature on N-methylpyrrolidone's hydrolysis were remarkable. Fourier transform infrared (FTIR) and Gel Permeation Chromatography (GPC) detected that the mainly hydrolyzate was 4-(methylamino)butyric acid, and the hydrolyzate can generate polymers, which of molecular weight increases with temperature rising. The results of Gas Chromatography (GC) and moisture meter test showed that adding alkaline and raising temperature can aggravate hydrolysis of NMP. This study provide theoretical basis for recycling solvent (NMP) in the production of polyphenylene sulfide (PPS).

Effect of Alkali and Transition Metal ions on the Crystal Growth of on Ammonium Dihydrogenate Phosphate (ADP)

Effect of Alkali and Transition Metal ions on the Crystal Growth of on Ammonium Dihydrogenate Phosphate (ADP)

Effect of crude oil fractions on the interfacial tensions of alkali-betaine mixed solutions

The effects of alkalis on the dynamic interfacial tensions (IFTs) of two betaine solutions with different hydrophilic parts, erucyl dimethyl amidopropyl carboxybetaine (EDAC) and erucyl dimethyl amidopropyl sulfobetaine (EDAS), against crude oil and model oils containing crude oil fractions (such as saturate, aromatic, resin, asphaltene and acidic fractions) have been investigated by spinning drop tensiometer. The experimental results show that the IFTs of EDAC solutions against decane are slightly lower than those of EDAS solutions because the hydrophilic part of EDAS is larger than that of EDAC. The crude oil fractions can directly adsorb at the interface to form mixed film with betaine molecules and drastically reduce IFT values. This synergistic effect becomes better with the enhancement of surface activity of fractions. The adding of alkali will improve the synergistic effects between betaines and fractions in general by enhancing the adsorption of fractions and producing soaps. EDAS molecules have synergistic effects with both fractions and soaps, while EDAC molecules show synergistic effect mainly with fractions, because of the difference of hydrophilic parts. Therefore, after adding different alkalis, the IFTs of EDAS solutions are obviously lower than those of EDAC solutions for almost all model oils. The dependence of size-compatibility becomes unimportant for the synergistic effect between betaines and crude oil in reducing IFT and pH value plays the most crucial role in controlling synergistic effect. Ultralow IFT values can be reached for both two betaines during a wide range of alkali concentrations.

The influence of alkali and alkaline earth metals on char and volatile aromatics from fast pyrolysis of lignin

The effect of alkali and alkaline earth metals (AAEM) on fast pyrolysis of polysaccharides has been well documented. This paper examines the effect of AAEM on fast pyrolysis of lignin, which has not been as thoroughly investigated. Acetates of several metals were infused into organosolv cornstover lignin at a concentration of 1.0mmol AAEM cation per gram lignin followed by pyrolysis at 300–800°C.One of the most notable effects was an increase in the yield of char with alkali metals producing more char than alkaline earth metals. Char yield was correlated to the electropositivity of the infused metal cations. Alkali metals increased the overall yield of volatile aromatic compounds while alkaline earth metals had the opposite effect.The infusion of AAEMs into lignin led to an increase in methanol and a decrease in alkenyl side chains on the aromatic products. Methanol is hypothesized to result from cleavage of β-carbons from the 3‐hydroxyprop-1-enyl side chains of lignin linkages while the alkenyl side chains are hypothesized to result from cleavage of γ-carbons. Therefore, alkali metals appear to catalyze cleavage of linkages in the lignin structure.

Effects of alkali on protein polymerization and textural characteristics of textured wheat protein

The impact of alkali addition on the degree of gluten polymerization and textural characteristics of textured wheat protein was investigated. Results showed that the extrusion process increased the average molecular weight of gluten as evidenced by SDS-PAGE and SDS extractable protein. The addition of alkali not only promoted the degree of gluten polymerization, but also induced dehydroalanine-derived cross-linking. Alkali addition decreased the content of cystine and increased the contents of dehydroalanine and lanthionine. The obvious decrease of free SH showed that dehydroalanine-derived cross-linking was quantitatively less crucial than disulfide cross-linking. Furthermore, the protein cross-linking induced by alkali improved the texture properties of gluten extrudates. SEM analysis showed extrusion under alkaline condition conferred a more fibrous microstructure as a consequence of a compact gluten network.

Effect of Alkali and Silane Treatments on Mechanical and Interfacial Bonding Strength of Sugar Palm Fibers with Thermoplastic Polyurethane

ABSTRACTSugar palm fibers (SPF) are one of valuable natural fibers which are abundantly available in Malaysia as agricultural biomass. The aim of this study to investigate on the effects of alkali, silane, and combination between alkali (6%) and silane (2%) on physical and mechanical properties of SPF to improve interfacial bonding of SPF with thermoplastic polyurethane (TPU) matrices. Scanning electron microscopy and Fourier transform infrared spectroscopy was used to observe the effectiveness of the alkali and saline treatments in the removal of impurities. Silane treated SPF exhibits better tensile strength than those of alkali, alkali-silane treated and untreated SPF. Droplet test indicates that the interfacial stress strength (IFSS) of alkali and silane treated SPF are enhanced whereas silane treated fibers exhibit highest IFSS. It is assumed that fiber treatments will help to develop high performance SPF reinforced polymer composites for industrial applications.

Effect of alkali and enzymatic treatments of banana fibre on properties of banana/polypropylene composites

Banana fibres are among the natural fibres obtained from the waste pseudostem of the banana plant, which can be used as reinforcement in the manufacture of thermoplastic composites due to its high ...

The effect of alkali on the product distribution from black liquor conversion under supercritical water

ABSTRACTLignin in chemical pulping waste, or black liquor (BL), can be converted into various products via supercritical water gasification (SCWG). However, the inherited alkaline contents from the pulping chemicals may affect the product yields and properties. In this research, the influence of the residual alkali on the product distribution via SCWG of soda BL and kraft BL was evaluated. The SCWG was performed in a batch quartz reactor for 10 min at various temperatures (673, 773 and 873 K) and pressures (250, 300 and 400 bar). The highest hydrogen (H2) production occurred at 873 K for the soda BL. The water–gas shift reaction with sodium ions played an important part in the H2 production, while only small amounts of methane and carbon monoxide were detected. Hydrocarbons, carboxylic acids and esters were the dominant substrates in the liquid products, which denoted the potential of this method for bond cleaving of the lignin macromolecule. As a result, BL, which typically contains alkali salt, was an appropriate feedstock for the SCWG reaction to produce renewable fuel. This method not only has a positive influence on the generation of value added products from highly corrosive waste but also helps avoid some technical problems commonly encountered with direct firing in a recovery boiler.

Comparison of the structures and electronic properties of sodalites containing alkali metals and alkali-earth metals and their hydrates

The effects of different alkali and alkali-earth metal ions on the electronic structures and properties of sodalite Mn[AlSiO4]6 (M-SOD) and their hydrates Mn[AlSiO4]6⋅8H2O (M=Li, Na, K, n = 6; M=Ca, n = 3) were studied using density functional theory method. Theoretical calculations predicted that the Al–O–Si bond angle and cation-framework oxide distance in sodalites with alkali metal cations are correlated with cell volumes. The reduced bandwidths in M-SOD (M=Li, Na and K) show that the inter-atomic orbital overlap in sodalites is weaker than those in the hydrate phases. Frontier molecular orbital analysis indicated that oxygen atoms in the frameworks and most metal ions of SOD and their corresponding hydrates exhibit high reactivity. The interactions existing in sodalites and hydrates were qualitative described. The calculated combination energies of metal ions with framework of sodalites are in the order of K+< Na+< Li+< Ca2+. This finding confirms the experimental observation for ion exchange.

Effect of Alkalis on Cementitious Materials:Understanding the Relationship between Composition, Structure, and Volume Change Mechanism

Effect of Alkalis on Cementitious Materials:Understanding the Relationship between Composition, Structure, and Volume Change Mechanism

NO + CO reaction over LaCu0.7B0.3O3 (B = Mn, Fe, Co) and La0.8A0.2Cu0.7Mn0.3O3 (A = Rb, Sr, Cs, Ba) perovskite-type catalysts

In this paper, catalytic reduction of NO by CO over perovskite-type oxides LaCu0.7B0.3O3 (B = Mn, Fe, Co) synthesized by sol–gel method was investigated. LaCu0.7Mn0.3O3 showed the highest activity among LaCu0.7B0.3O3 perovskite catalysts (88% CO conversion and 93% NO conversion at 350 °C). The effect of alkali and alkaline earth metals (Rb, Sr, Cs and Ba) on the structure and catalytic activity of LaCu0.7Mn0.3O3 perovskite catalysts was also investigated. The results showed that catalytic activity was improved by partial substitution of La by alkali and alkaline earth metals. The superior activity of La0.8Sr0.2Cu0.7Mn0.3O3 with respect to other catalysts (93% CO conversion and 96% NO conversion at 350 °C) was associated with a higher reducibility at low temperature, more oxygen vacancies and synergistic effect between Cu and Mn. The catalysts were characterized by XRD, BET, H2-TPR, XPS and SEM.

Effects of Alkali and Thermal Treatment on the Ti6Al4V towards Apatite Deposition in Dulbecco’s Phosphate Buffered Saline (DPBS) Solution

A high biocompatibility apatite coated titanium (Ti) could be achieved by biomimetic method. The method is beneficial in surface modification by lowering the processing cost and flexibility. However, the bond between apatite and titanium implant is weak. The structure and composition of apatite formed is different from the apatite in bone. The aim of this research was to investigate the effects of heat and alkali treatment on the physical and chemical properties of Ti6Al4V surfaces and to observe the formation of apatite in Dulbecco’s Phosphate Buffered Saline with CaCl2 and MgCl2 (DPBS) solution on the treated Ti6Al4V for medical implants. Ti discs were surface modified by alkali etching using 5M NaOH at temperature 60°C for 24 hours. A stable mechanical structure of sodium titanate layer formed on alkali-treated is consolidating by heat treated at 500°C and 600 °C. Treated samples were then incubated at 37°C into DPBS solution for 3 days. The morphology structure, phase changes and chemical composition were characterized by using Field Emission Scanning Electron Microscopy (FESEM) and X-Ray Powder Diffraction (XRD). The results shows that apatite coating in globular shape, a group of flakes was found on the samples’ surfaces that had been pre-treated with 5M NaOH at temperature 60°C without thermal treatment and thermal treated at 500°C.