Alkali Dissolution Research Articles

Alkaline dissolution and dyeing properties of sea-island type polyethylene terephthalate ultramicrofiber knitted fabrics

Sea-island type polyethylene terephthalate ultramicrofibers with a single fiber diameter of ca. 600 and 800 nm have been produced over the last 4 years. Alkaline dissolution behavior and dyeing properties of the ultramicrofiber fabrics were investigated. It was found that the dissolution ratio was dependent upon temperature in the alkali treatment. When the fabric was treated with 1 wt% sodium hydroxide solution at 95 °C, the dissolution ratio reached the theoretical value in about 30 min. Alkali dissolution behavior could be monitored indirectly by the cationic dye staining method and observed directly by SEM analysis. The color yield of the ultramicrofiber fabric dyed with disperse dye was dependent on the dyeing temperature and K/S value decreased as the dyeing temperature increased. Build-up property was generally good and K/S value of dyed fabric from ca. 800 nm fiber was higher than that from ca. 600 nm fiber. Wash fastness was poor to moderate for ca. 800 nm fabric and poor for ca. 600 nm fabric. Light fastness was very poor.

Preparation of silica nanoparticles from waste silicon sludge

In order to reduce the release of hazardous waste silicon sludge (WSS) into the environment, we report a novel method to transform the WSS into silica nanoparticles and simultaneously to separate abrasive silicon carbide (SiC) particles. Alkali dissolution and acid precipitation processes were utilized to prepare silica nanoparticles effectively. The alkali dissolution process was carried out by sodium hydroxide to produce sodium silicate solution, from which SiC was separated by filtration. Afterward, the silica nanoparticles were prepared by acid precipitation method using hydrochloric acid. Box–Behnken design (BBD) was used to optimize the process variables affecting the dissolution efficiency, namely, mass ratio of NaOH and WSS, reaction temperature, and reaction time, and to determine the optimum conditions for the reaction process. Ultraviolet-visible spectrophotometer was used to measure the silica concentration in the solution. Characterized by XRD, FTIR, TEM, and BET surface area analysis, the silica with average pore size (10.52nm), high specific surface area (430.9m2/g) was obtained, and the particle size was about 20–45nm.

Alkali-templated surface nanopatterning of chalcogenide thin films: a novel approach toward solar cells with enhanced efficiency.

Concepts of localized contacts and junctions through surface passivation layers are already advantageously applied in Si wafer-based photovoltaic technologies. For Cu(In,Ga)Se2 thin film solar cells, such concepts are generally not applied, especially at the heterojunction, because of the lack of a simple method yielding features with the required size and distribution. Here, we show a novel, innovative surface nanopatterning approach to form homogeneously distributed nanostructures (<30 nm) on the faceted, rough surface of polycrystalline chalcogenide thin films. The method, based on selective dissolution of self-assembled and well-defined alkali condensates in water, opens up new research opportunities toward development of thin film solar cells with enhanced efficiency.

Biooxidation of Gold-, Silver, and Antimony-Bearing Highly Refractory Polymetallic Sulfide Concentrates, and its Comparison with Abiotic Pretreatment Techniques

Effectiveness of different pure and mixed cultures of three moderately thermophilic, extremely acidophilic bacterial strains (Acidimicrobium ferrooxidans ICP, Sulfobacillus sibiricus N1, Acidithiobacillus caldus KU) were investigated for biooxidation of highly refractory polymetallic gold ore concentrates. Despite of its complex mineralogy and the presence of a mixture of potentially inhibitory metals and metalloids, the concentrate was readily dissolved in defined mixed cultures including both iron and sulfur oxidizers, releasing as much as 80% of soluble Fe and 61% of soluble As. Factors to affect microbial mineral dissolution efficiencies (i.e. microbial As(III) oxidation ability, formation of secondary mineral precipitation (e.g. jarosite, elemental sulfur, scorodite, anglesite), and microbial population dynamics during biooxidation) were studied, based on which roles of individual microbes and their synergistic interactions during biooxidation were discussed. Applying the biooxidation pretreatment using the most efficient mixed cultures containing all three strains significantly improved the recovery of both Au (from 1.1% to 86%) and Ag (from 3.2% to 87%). Finally, this study provides one of the very few available comparisons of the effectiveness of different pretreatment techniques for refractory gold ore concentrates: Compared with other abiotic pretreatment approaches (roasting, pressure oxidation, and alkali dissolution), biooxidation was shown to be one of the most effective options in terms of the recovery of Au and Ag.

Preparation and properties of PMMA modified silica aerogels from diatomite

Diatomite was used as raw material to prepare sodium silicate with a modulus of 3.1 by alkali dissolution method and the resulted sodium silicate solution was employed as a precursor. Methyl methacrylate monomers were introduced in wet gels through solution-immersion, and upon heating at 70 °C, the mesoporous surfaces throughout the skeletal framework were coated with the polymer layer. PMMA modified silica aerogels were successfully synthesized via ambient pressure drying. The properties were investigated by FTIR, NMR, TGA, nitrogen adsorption-desorption, FESEM and nano-indentation, etc. Results indicate that with the increasing of PMMA incorporated into silica aerogels, the bulk density and the BET surface area increase, the porosity decreases. Through the observation of FESEM, it is found that the interconnecting pores and the big pores add, the pore size distribution expands from 5–17 to 28–150 nm. By comparison, the PMMA modified silica aerogels achieve a 52-fold increase in hardness and a 10-fold increase in modulus.

Alkali dissolution behaviour of sea–island‐type polyethylene terephthalate ultramicrofibre knitted fabrics

Sea–island‐type polyethylene terephthalate ultramicrofibre (0.007 denier per filament) with a single fibre diameter of ca. 800 nm has been produced over the last 4 years. Three kinds of sea–island‐type polyethylene terephthalate knitted fabric manufactured from this ultramicrofibre were alkali treated, and their dissolution behaviour was investigated. It was found that the dissolution ratio was dependent upon temperature and sodium hydroxide concentration in the alkali treatment. Practical dissolution ratios mostly reached the theoretical values after alkali treatment with 1.0% (w/w) sodium hydroxide solution at 95 °C for 40 min in all samples. Alkali dissolution of the sea component and revealing of the island component were confirmed by differential scanning calorimetry and scanning electron microscopy. Alkali dissolution behaviour could also be monitored indirectly by the cationic dye staining method. While all untreated samples exhibited high colour yield values after cationic dyeing, alkali‐treated samples showed reduced colour yield values with increasing alkali treatment time and a final levelling‐off point.

An Experimental Study on Production of Silica Aero-Gel Using Fly Ash from Coal-Fired Power Plants

silica aero-gels were synthesized from coal fly ash at ambient pressure. The experimental procedure for silica aero-gels production included alkali dissolution of fly ash, surface hydrophobic treatment of the wet-gel, followed by drying of the wet-gel samples at ambient pressure wasinvestigated. Optimized experimental parameters for production of silica aero-gels from fly ash were obtained through systematic studies. BET, SEM and FTIR and contact angle measurement were used in order to investigate the structure and characteristics of the silica aero-gel powders.

Thermal transformation of pyrophyllite and alkali dissolution behavior of silicon

Thermochemical behavior of pyrophyllite was characterized by using XRD, FTIR, TG-DTA and MAS NMR techniques. Pyrophyllite experiences a series of solid-state phase transformations during thermal treatment. Dehydroxylation of pyrophyllite is completed at 880°C, and the original layered framework is inherited in dehydroxylated pyrophyllite. Up to 1100°C, the layered framework is collapsed thoroughly, with formation of amorphous SiO2 and mullite. Above 1200°C, cristobalite crystallizes from amorphous SiO2, and mullitization is promoted dramatically. The alkali leaching results show that amorphous SiO2 in the thermally activated pyrophyllite is soluble in caustic soda liquor, while mullite is not, and the formation of sodium aluminosilicate hydrate of 0.95Na2O·Al2O3·3.25SiO2·4.79H2O during alkali leaching diminishes the dissolution ratio of silica. The alkali dissolution behavior of silicon demonstrates an innovative process for removing silica from pyrophyllite by using thermochemical activation (TCA) followed by alkali leaching, which can be applied to desilication of bauxite ore and preparation of alumina-base porous material. A desilication of 84% was obtained from the tested ore containing 90% pyrophyllite at the optimal thermochemical activation conditions of temperature 1100–1150°C and time 90–20min. The good alkali dissolution characteristic of silica also is a cogent evidence on the formation of amorphous silica during the thermal treatment of pyrophyllite.

Mechanically induced reactivity of gibbsite: Part 1. Planetary milling

Gibbsite [γ-Al(OH)3] precipitated from Bayer leach liquor is mechanically activated in a planetary mill at ambient conditions. Mechanical activated (MA) gibbsite is characterized in terms of particulate characteristics, structural characteristics and reactivity. Physicochemical changes during MA involved (1) size reduction in the initial stages followed by particle aggregation in the later stages and changes in particle size distribution, and (2) progressive decrease in crystallite size, and increase in microstrain leading to eventual amorphisation. Reactivity of milled gibbsite (measured in terms of (1) decrease in its dehydroxylation temperature, and (2) increase in alkali dissolution) is found to increase with mechanical activation. Increased reactivity of milled gibbsite is correlated with various physicochemical characteristics.

Studies on separation and purification of fission 99Mo from neutron activated uranium aluminum alloy

A new method has been developed for separation and purification of fission 99Mo from neutron activated uranium–aluminum alloy. Alkali dissolution of the irradiated target (100mg) results in aluminum along with 99Mo and a few fission products passing into solution, while most of the fission products, activation products and uranium remain undissolved. Subsequent purification steps involve precipitation of aluminum as Al(OH)3, iodine as AgI/AgIO3 and molybdenum as Mo-α-benzoin oxime. Ruthenium is separated by volatilization as RuO4 and final purification of 99Mo was carried out using anion exchange method. The radiochemical yield of fission 99Mo was found to be >80% and the purity of the product was in conformity with the international pharmacopoeia standards.

600 nm급 폴리에스터 해도형 초극세사 편성물의 감량 및 염색 특성

The weight reduction and dyeing properties of circular-knitted fabric manufactured from sea-island-type polyethylene terephthalate (PET) ultramicrofiber were investigated. The diameter of a single fiber was approximately 600 nm. The results of scanning electron microscopy (SEM) analysis, alkali dissolution ratio measurements, and cationic dye staining method revealed that the dissolution of the sea component from each ultramicrofiber was completed through alkali treatment with 1% NaOH aqueous solution for 30-40 min at <TEX>$95^{\circ}C$</TEX>. The color yield of the disperse dye on the fabric was observed to be dependent on the dyeing temperature. The color yield increased with an increase in the dyeing temperature up to <TEX>$120^{\circ}C$</TEX>, and then decreased at <TEX>$130^{\circ}C$</TEX>. The build-up property was generally good. The wash fastness was poor and the light fastness was very poor.

석회석과 제강슬래그를 이용한 오염토양 안정화에 따른 비소 및 중금속의 식물체 전이도 평가

This study estimated stabilization efficiency of As and heavy metal contaminated agricultural soil in abandoned mine through pot experiment. Also contaminants uptake of plant (lettuce) was compared as function of amendment (limestone, steelmaking slag and the mixture of these) addition. In soil solution analysis, concentration of contaminants in soil solutions which added limestone or steelmaking slag were lower than that of the mixture. Especially in As analysis, concentration with 5% (wt) addition of steelmaking slag showed the lowest value among those with other amendments. This seems that As stabilization happens through Fe adsorption during precipitation of Fe by pH increasing. Leachability of As in stabilized soil by TCLP was represented similar result with soil solution analysis. However leachability of heavy metals in stabilized soil was similar with that of non-stabilized soil due to dissolution of alkali precipitant by weak acid. Contaminants uptake rate by plant was also lower when limestone or steelmaking slag was used. However this study revealed that concentration of contaminants in soil solution didn't affect to the uptake rate of plant directly. Because lower <TEX>$R^2$</TEX> (coefficient of determination) was represented in linear regression analysis between soil solution and plant.

Study of the Formation and Influence Factors of Silica Scale in ASP Flooding

ASP Flooding has a better displacement efficiency, but there is still a serious problem of wells scaling. Researched on formation mechanism and influence factors of silica scale in ASP flooding with alkali, the formation of silica scale is mainly due to the alkali dissolution reaction of reservoir rock to produce the soluble silicon ions and form silica scale in formation conditions. Laboratory experiments simulated formation mineralization aqueous solution, analyzed the morphology of silica scale by scanning electron microscopy, and studied the role played by calcium, magnesium, aluminum ion, polyacrylamide, surfactant. The experimental results show that: calcium, magnesium, aluminum ions, polyacrylamide, and surfactant can promote the formation of silica scale, and the morphology characteristics of silica scale are different.

A suggested alternative procedure for processing of monazite mineral concentrate

An alternative procedure for the processing of monazite mineral concentrate has been suggested. This procedure is based on a prior separation of the REEs and Th oxalates from the sulfate liquor of the hydrous oxide cake obtained after alkali breakdown of monazite concentrate.From the mixed oxalate precipitate, it was possible to optimize the selective alkali dissolution of Th using a mixed Na2CO3/NaHCO3 solution. Highly pure oxide products of the three interesting metal values; viz REEs, Th and U have properly been prepared.

Influence of metakaolin characteristics on the mechanical properties of geopolymers

The relationship between the properties of geopolymers and the characteristics of metakaolin samples used in their preparation has been investigated. Three commercial metakaolin samples have been characterised using 27Al-NMR to determine the coordination number of Al (IV, V and VI), and by acid and alkali dissolution to determine the reactive Si and Al content. The setting and mechanical properties of geopolymers formed from the metakaolin samples under identical conditions are reported, using Weibull statistics to analyse strength data. Although the metakaolin samples contained different levels of five coordinated aluminium (Al (V)) the mechanical properties of the geopolymers formed were very similar. The reactive fraction of metakaolinite determined by dissolution in 8M NaOH provides the most relevant long-term indicator of geopolymer performance.

Percutaneous Nephrolithotomy in Autosomal Dominant Polycystic Kidney Disease: Is it Different from Percutaneous Nephrolithotomy in Normal Kidney?

Objectives: Nephrolithiasis has been reported in 20-28% of patients, of whom 50% are symptomatic for stone disease and 20% require definite urologic intervention. The management of nephrolithiasis includes oral alkali dissolution therapy, extracorporeal shock wave lithotripsy and surgical treatment. In such patients, percutaneous nephrolithotomy (PNL) as a method of stone treatment has been reported in few cases with limited experience. The aim of this study is to present our experience of PNL in autosomal dominant polycystic kidney disease (ADPKD) and assessing the outcome results. Material and Methods: From 2002 to 2011, 22 patients (26 renal units) suffering from ADPKD with stone were managed by PNL. Demographic characteristics, operative parameters and postoperative complications were recorded and analysed. Result: The overall success rate of PNL was 82.1% and PNL with extracorporeal shock wave lithotripsy for clinically significant residual fragments was 92.85% respectively. The hematuria required blood transfusion (n = 9), postoperative fever due to cyst infection (n = 4) and paralytic ileus (n = 3) were recorded. Conclusion: The PNL in ADPKD PNL is safe and effective but have more postoperative complications such as bleeding requiring transfusions, fever due to cyst infection and paralytic ileus.

Effect of denaturation during extraction on the conformational and functional properties of peanut protein isolate

Abstract Peanut protein isolate (PPI) was extracted by alkali dissolution and acid precipitation from defatted peanut flour. The effects of extraction conditions on the denaturation and functional properties of PPI were investigated. In comparison with native peanut protein (NPP) which was extracted by ammonium sulfate, the PPI extracted by alkali dissolution and acid precipitation had a higher extent of denaturation. Arachin was affected more easily by the extraction process than conarachin and led to a noticeable decrease of thermal stability of PPI. PPI contained much lower sulfhydryl and disulfide bond contents than NPP. The analyses of intrinsic fluorescence spectra indicated a more compacted tertiary conformation of NPP than PPI. Extraction process influenced the functional properties of PPI, such as protein solubility, emulsifying activity index and foaming capacity. The relatively poor functional properties of PPI might be associated with protein denaturation/unfolding and subsequent protein aggregation. Industrial relevance Peanut is an important oilseed crop and a well-accepted food. After oil production through thermal treatment, the defatted peanut flour is the main byproduct, which possesses a large amount of proteins. However, due to the low extraction yield and poor functional properties of these proteins, they are not well utilised in industry till now. In this work, peanut proteins were extracted by two techniques. The results indicated that extraction technique could significantly modify the functional properties of peanut proteins. Therefore, this work is helpful for industrial utilisation of peanut proteins.

Preparation of Ultrafine Aluminum Hydroxide from Coal Fly Ash by Alkali Dissolution Process

A new two-step alkali dissolution technique was used to prepare ultrafine aluminum hydroxide from coal fly ash in this study. The first step alkali dissolution was to leach SiO2 from the coal fly ash using sodium hydroxide solution for obtaining the desilicated product with higher Al2O3/SiO2 ratio. The leaching efficiency of SiO2 reached to 40% when the coal fly ash was leached with 8 M sodium hydroxide solution at 95°C for 150 min. The second step alkali dissolution was that the mixtures of the as-desilicated product and white lime were leached with 20 M sodium hydroxide solution at 260°C for 60 min for extracting alumina from the desilicated product. The alumina extraction efficiency was up to 89%. The sodium aluminates solution obtained from the second alkali dissolution was used to synthesize ultrafine Al(OH)3 after treating by lime and NaHCO3 solution respectively. The results of XRD, SEM and chemical analysis revealed that the prepared ultrafine aluminum hydroxide with monoclinic structure was in the form of spherical particles with the average size of 80∼150 nm.

Effect of leaching behaviour by quenching of bottom ash from MSW incineration

Bottom ashes (BA) obtained from a municipal solid waste incineration plant, have shown different pH and lead concentrations in leachate for different lines. In order to explain this behaviour, combustion tests were performed concerning the lines and the effect of the type of wastes. The BA obtained from the same waste has shown the same raw chemical composition, but different leachate characteristics for the different lines. The bottom ash from different wastes burned on the same line instead showed very similar leachate behaviour. The results suggest that the quality of leach ate depends on the plant and process conditions (in particular the ash quenching phase) and not on the composition of the waste. During ash quenching, the formation and dissolution of soluble alkalis depends on the washing ratio and on the residence time. A different washing degree leads to a different residual alkalinity in the bottom ash, and consequently to a different value of leachate pH with different metal releases. Therefore, with the practical aim of establishing the best conditions for the final disposal of bottom ash, a careful planning of this phase could be proposed as an alternative to a weathering process.

Transformation of silica fume into chemical mechanical polishing (CMP) nano-slurries for advanced semiconductor manufacturing

Silica nanoparticles have been synthesized from silica fume using alkali dissolution–precipitation process. The dissolution efficiency of 99% at a temperature of 80 °C and a time of 20 min was achieved. Sodium silicate solution was obtained by dissolving the fume with NaOH solution. Then, silica nanoparticles were precipitated using sulfuric acid. Silica nanoparticles (175 nm) were achieved using 12% sulfuric acid at pH 7 and 200 ppm sodium dodecyl sulfate (SDS). The silica morphologies appeared as a spherical shape with narrow particle size distribution. The silica samples were used for the formulation and testing of chemical mechanical polishing (CMP) slurries. The morphology of the polished wafer surface and its roughness were examined by atomic force microscope (AFM).The results indicated that the surface roughness was greatly improved after application of CMP. It was found that the surface roughness of the polished wafer is 0.226 nm at an applied pressure of 7 psi. The removal rate was found to be 1200 Å. These values confirm the quality of polished wafers.