Caustic Alkaline Research Articles

Extraction of silica from natural deposits for the production of silicon in photovoltaic applications

The Silica, primarily sourced from silicon dioxide (SiO2) is a common chemical compound abundant in nature, existing in various forms such as quartz, sand, glass, and diverse minerals. It finds extensive use across multiple industries, contributing significantly to glassmaking, ceramics, abrasives, refractory materials, and serving as a crucial component in semiconductor production for electronic chips. This work provides a comprehensive review of the silica elaboration process aimed at obtaining silicon. The initial stage involves the preparation of raw materials, utilizing Algerian sand and diatomite, which undergo meticulous chemical treatment to eliminate unwanted impurities. This method comprises distinct steps, known as the purification process, wherein the sand or diatomite shell is assessed through dissolution in a caustic alkaline solution. This approach indicates the potential to generate high-quality silica from diatomite using an aqueous chemical process. This paper explores the prospect of sand or diatomaceous earth as a novel source of premium-grade silica. It discusses the effects of hydrochloric acid as a solvent for purification. This study contrasts treatment methods before and after acid leaching, focusing on samples with larger particle sizes (ranging from 53 to 300 microns), shorter refining durations (1 to 6 hours), and relatively higher temperatures (30 °C to 70 °C). The findings reveal that the highest purity of silica was attained through HCl treatment (25%).

Theory-Guided Inelastic Neutron Scattering of Crystalline Alkaline Aluminate Salts Bearing Principal Motifs of Solution-State Species.

Aluminate salts precipitated from caustic alkaline solutions exhibit a correlation between the anionic speciation and the identity of the alkali cation in the precipitate, with the aluminate ions occurring either in monomeric (Al(OH)4-) or dimeric (Al2O(OH)62-) forms. The origin of this correlation is poorly understood as are the roles that oligomeric aluminate species play in determining the solution structure, prenucleation clusters, and precipitation pathways. Characterization of aluminate solution speciation with vibrational spectroscopy results in spectra that are difficult to interpret because the ions access a diverse and dynamic configurational space. To investigate the Al(OH)4- and Al2O(OH)62- anions within a well-defined crystal lattice, inelastic neutron scattering (INS) and Raman spectroscopic data were collected and simulated by density functional theory for K2[Al2O(OH)6], Rb2[Al2O(OH)6], and Cs[Al(OH) 4]·2H2O. These structures capture archetypal solution aluminate species: the first two salts contain dimeric Al2O(OH)62- anions, while the third contains the monomeric Al(OH)4- anion. Comparisons were made to the INS and Raman spectra of sodium aluminate solutions frozen in a glassy state. In contrast to solution systems, the crystal lattice of the salts results in well-defined vibrations and associated resolved bands in the INS spectra. The use of a theory-guided analysis of the INS of this solid alkaline aluminate series revealed that differences were related to the nature of the hydrogen-bonding network and showed that INS is a sensitive probe of the degree of completeness and strength of the bond network in hydrogen-bonded materials. Results suggest that the ionic size may explain cation-specific differences in crystallization pathways in alkaline aluminate salts.

Exhaust Gases Purification of Sintering Furnaces Using Under-Sludge Water as a Gas Cleaning Solution

It is proposed to introduce an additional stage of "wet" cleaning of waste gases of caking at RUSAL Achinsk. For experimental industrial research, the work used a multi-vortex scrubber, in which the gas is cleaned in a dispersed water-air layer, formed by the flow of gases from the bottom up through the dispersing lattice. As an absorbent irrigation solution, it is proposed to use pre-heated up to 50 degrees Celsius water (PSH), containing an average of 8.98 g/dm3 and 16.74 g/dm3 of caustic and total alkaline, respectively. The efficiency of gas dust-cleaning was assessed depending on the consumption of PSH (0.2–1.2 l/m3 of gas at feed speeds of 0.2 hp and 0.4 hp), as well as the use of two schemes of its supply (flow and recycling).

Exhaust Gases Purification of Sintering Furnaces Using Under-Sludge Water as a Gas Cleaning Solution

It is proposed to introduce an additional stage of "wet" cleaning of waste gases of caking at RUSAL Achinsk. For experimental industrial research, the work used a multi-vortex scrubber, in which the gas is cleaned in a dispersed water-air layer, formed by the flow of gases from the bottom up through the dispersing lattice. As an absorbent irrigation solution, it is proposed to use pre-heated up to 50 degrees Celsius water (PSH), containing an average of 8.98 g/dm3 and 16.74 g/dm3 of caustic and total alkaline, respectively. The efficiency of gas dust-cleaning was assessed depending on the consumption of PSH (0.2–1.2 l/m3 of gas at feed speeds of 0.2 hp and 0.4 hp), as well as the use of two schemes of its supply (flow and recycling).

The viability of MCM-41 as separator in secondary alkaline cells

The viability of MCM-41 membrane as a separator material in secondary alkaline cell is investigated. The inorganic membrane was employed in an alkaline nickel-zinc system. MCM-41 mesoporous material consists of arrays of hexagonal nano-pore channels. The membrane was synthesized using sol-gel route from parent solution comprising of quarternary ammonium surfactant, cethyltrimethylammonium bromide C16H33(CH3)3NBr (CTAB), hydrochloric acid (HCl), deionized water (H2O), ethanol (C2H5OH), and tetraethylortosilicate (TEOS). Both the anodic zinc/zinc oxide and cathodic nickel hydroxide electrodeposited film were coated with MCM-41 membrane. The Ni/MCM-41/Zn alkaline cell was then subjected to 100-cycle durability test and the structural stability of MCM-41 separator throughout the progression of the charge-discharge cycles is studied. X-ray diffraction (XRD) analysis on the dismantled cell shows that MCM-41 began to transform to lamellar MCM-50 on the 5th cycle and transformed almost completely on the 25th cycle. The phase transformation of MCM-41 hexagonal structure into gel-like MCM-50 prevents the mesoporous cell separator from diminished in the caustic alkaline surround. This work has hence demonstrated MCM-41 membrane is viable to be employed in secondary alkaline cells.

Bauxite residue neutralization with simultaneous mineral carbonation using atmospheric CO2

Simultaneous carbon mineralization during neutralization of bauxite residue, a caustic alkaline by-product of alumina refining, was tested using laboratory batch and a field pilot study in contact with atmospheric CO2. Since CO2 sequestration is limited by the Ca concentration in the bauxite residue, extra Ca sources were added in a semi-soluble mineral and salt form (flue gas desulfurization gypsum or CaCl2) to verify whether this Ca addition accelerated and enlarged the CO2 sequestration obtained as a consequence of neutralization. The results of 55 days of batch and longer-term field tests were in good agreement, and the neutralization rate was accelerated through the addition of both Ca sources. Without the addition of the extra Ca source, atmospheric CO2 contributed to neutralization of pore water alkalinity alone, while Ca addition induced further neutralization through mineral carbonation of atmospheric CO2 to CaCO3. This simple addition of environmentally benign Ca to bauxite residue may provide a feasible bauxite residue management practice that is cost-effective and easy to apply in the field.

Medicinal and cosmetics soap production from Jatropha oil.

Soap is the most useful things which we use our everyday life in various cleansing and cosmetics purposes. Jatropha oil is nonedible oil which has more benefits to soap making. It has also cosmetics and medicinal properties. But the presence of toxic Phorbol esters in Jatropha oil is the main constrains to use it. So it is necessary to search a more suitable method for detoxifying the Jatropha oil before the use as the main ingredient of soap production. This review implies a more suitable method for removing phorbol esters from Jatropha oil. Several parameters such as the % yield of pure Jatropha oil soap, TFM value of soap, total alkali content, free caustic alkalinity content, pH, the antimicrobial activity, and CMC value of general soap should be taken into consideration for soap from detoxified Jatropha oil.

Viability of MCM-41 Inorganic Membrane Separator in Secondary Nickel-Zinc Cell

The viability of MCM-41 inorganic membrane as a separator material in secondary nickel-zinc cell is investigated. MCM-41 mesoporous material consists of arrays of hexagonal nano-channels. The membrane is synthesized by dip-coating procedures from parent solution comprising of quarternary ammonium surfactant, cethyltrimethylammonium bromide C16H33(CH3)3NBr (CTAB), hydrochloric acid (HCl), deionized water (H2O), ethanol (C2H5OH), and tetraethylortosilicate (TEOS). Both the anodic zinc foil and cathodic nickel hydroxide electrodeposited film are coated with MCM-41 membrane. The Ni/MCM-41/Zn alkaline cell is then subjected to 100-cycle durability test. The charge-discharge plot showed typical secondary zinc anode profile – rapid capacity fading. X-ray diffraction analysis on the dismantled cell indicated the transformation of MCM-41 hexagonal matrix structure into MCM-50 lamellar gel form which prevent the mesoporous cell separator from diminished in the caustic alkaline surround.

Preparation and Characterization of Metal Soaps of <i>Cocos nucifera</i> Seed Oil

This study investigated the extraction of Cocos nucifera seed oil (CSO) from Cocos nucifera seed using aqueous processing and the production of metal soaps from the oil and their characterization in terms of colour, pH, free caustic alkalinity, foaming power, foam stability, and corrosion inhibition test. The metal soaps of the oil produced by metathesis were soaps of nickel, calcium, barium, zinc, iron and magnesium. The results of tests of the metal soaps showed that Ni-CSO was greenish in colour, Zn-CSO, Mg-CSO, Ba-CSO and Ca-CSO were white and Fe-CSO had a dark-brown colour. The pH of the metal soaps varied between 6.5 to 8.2. The free caustic alkalinity was low and varied between 0.30 % to 0.43 %. Foam stability was in the order Fe-CSO 0.80, Ca-CSO 0.81, Zn-CSO 0.86, Ni-CSO 0.90, Mg-CSO 0.92 and Ba-CSO 0.93. For corrosion inhibition test Ni-CSO at 100 mg/L, Ca-CSO at 60 mg/L, Mg-CSO, Ba-CSO and Fe-CSO at 40 mg/L inhibited tiger head razor blade corrosion while the other concentrations of the metal soaps showed varied degrees of corrosion.Keywords: Cocos nucifera seed oil; metal soaps; corrosion inhibition; foam stability

Assessment of the Physicochemical Properties of Selected Commercial Soaps Manufactured and Sold in Kenya

Soap is sodium or potassium salt of fatty acid produced by saponification reaction. Soap is used on a day to day basis by households. The physicochemical properties of soaps determine their quality and hence determine their efficiency and their cleansing properties. It remains obscure the quality of the soaps that are sold in the local markets in Kenya and thus the need to assess them. Eight commercial washing soaps were analyzed for Matter insoluble in alcohol, moisture content, total fat matter, free caustic alkalinity, Percentage chloride, pH and Total alkali according to documented methods of analysis. Values of matter insoluble in alcohol ranged between 6.22% to 61.80%, moisture content ranged between 10.91% to 22.69%, total fat matter ranged between 22.64% to 70.51%, free caustic alkali ranged between 0.00% to 0.06%, percentage chloride ranged between 0.07% to 1.01%, pH ranged between 10.63 to 11.71 and total alkali ranged between 0.00% to 0.99%. This study showed that the free caustic alkalinity of all the analyzed soap samples were below the KEBS set limits hence no adverse effects on the cloth or skin, and the pH values for all analyzed soaps were within KEBS limits.

High-Pressure Cold-Sprayed Ni and Ni-Cu Coatings: Improved Structures and Corrosion Properties

Cold spraying is a promising technique for the production of dense metallic coatings. In cold spraying, coating formation is through high velocity impacts of solid particles with high kinetic energy. During impact, particles deform plastically and adhere to the substrate, gradually building-up the coating. This makes it possible to form pure and dense coating structures. These impermeable coatings are advantageous in many applications such as those where corrosion protection is required. Nickel and nickel-copper alloys have good corrosion resistance and therefore, as dense coatings, have high potential for employment as corrosion barrier layers. In this study, the structural and corrosion properties of high-pressure cold-sprayed (HPCS) Ni and NiCu coatings are characterized. NiCu alloys are known to have good corrosion resistance in sulphuric and hydrochloric acids, whereas Ni is resistant to caustic soda and alkaline salt solutions. This study also shows the effect of heat treatments on coating properties. FESEM studies of cross-sectional samples reveal structural details of the HPCS coatings while corrosion properties are evaluated with polarization measurements. The corrosion behavior of both the bulk and substrate material is determined in order to assess the real corrosion protection potential of the coatings.

Preliminary study of efficacy of hyaluronic acid on caustic esophageal burns in an experimental rat model

BackgroundThe aim of this study was to investigate the effectiveness of hyaluronic acid on the prevention of esophageal damage and stricture formation after experimental caustic (alkaline) esophageal injury in rats. Materials and MethodsTwenty-one Wistar albino rats were randomly divided into three groups. A caustic esophageal burn was created following the Gehanno model: Group l (n=7) underwent operation, but no injury; Group 2 (n=7) was injured and left untreated; and Group 3 (n=7) was injured and treated with hyaluronic acid, first topically and then orally by gavage (2×0.3mL; 12.5mg/mL for 7days). The caustic esophageal burn was created by instilling 25% NaOH into the distal esophagus. All rats were euthanized on day 22 for evaluation. The efficacy of hyaluronic acid treatment was assessed histopathologically and biochemically via blood determination of the total antioxidant status (TAS), total oxidant status (TOS), oxidative stress index (OSI), and sulfhydryl group (SH) and lipid hydroperoxidase (LOOH) levels. Statistical analyses were performed. ResultsWeight gain was significantly lower in Group 2 than in the other two groups (P<0.05). The mean stenosis index, histopathologic damage score, TAS, TOS, OSI, and SH and LOOH levels were higher in Group 2 than in the other two groups. The mean stenosis index, inflammation, TAS, SH and OSI in Group 2 were significantly different than those in the other two groups (P<0.05). ConclusionHyaluronic acid treatment is effective in treating damage and preventing strictures after caustic esophageal burn in rats.

Management of internal hemorrhoids by Kshara karma: An educational case report

A 66-year-old male patient came to the anorectal clinic, Outpatient department, AVT Institute for Advanced Research, Coimbatore, Tamil Nadu, with complaints of prolapsing pile mass during defecation and bleeding while passing stool. The case was diagnosed as “Raktarsha” - 11 & 7 ‘o’ clock position II degree internal hemorrhoids, deeply situated, projecting one and caused by pitta and rakta; with bleeding tendency. Kshara karma (application of caustic alkaline paste) intervention was done in this case to internal hemorrhoids under local anesthesia. The pile mass and per rectal bleeding resolved in 8 days and the patient was relieved from all symptoms within 21 days. No complications were reported after the procedure. The patient was followed up regularly from 2004 onward till date and proctoscopic examination did not reveal any evidence of recurrence of the hemorrhoids.

Gel-like properties of MCM-41 material and its transformation to MCM-50 in a caustic alkaline surround

MCM-41 material, prepared by sol–gel method, reveals gel-like properties in a caustic alkaline environment, i.e., 6M potassium hydroxide (KOH) electrolyte. The gellation of MCM-41 starts at a KOH weight ratio of 40wt.%. The structural change of the material is verified with X-Ray diffractograms and supported by observation using Scanning Electron Microscope (SEM). As the KOH weight ratio increases, the MCM-41 hexagonal arrays structure gradually transforms into MCM-50 lamellar structure before disappearing completely at 80wt.% KOH. The MCM gel phase is further characterized by rotational viscometry and texture analysis. The gel phase shows shear thinning or pseudoplastic behavior and possesses homogeneous matrix structure.

ChemInform Abstract: Improvement in the Corrosion Resistance of Alumina in Caustic Alkaline Solutions Obtained by Dispersing Ceria-Doped Tetragonal Zirconia Particles

ChemInform Abstract: Improvement in the Corrosion Resistance of Alumina in Caustic Alkaline Solutions Obtained by Dispersing Ceria-Doped Tetragonal Zirconia Particles

Protective Effects of Dexpanthenol and Y-27632 on Stricture Formation in a Rat Model of Caustic Esophageal Injury

This experimental study was conducted to investigate the effect of dexpanthenol (converted in the body to pantothenic acid) and Y-27632 (a selective Rho-kinase inhibitor) on stricture formation after caustic (alkaline) esophageal injury in rats. Sixty male Wistar albino rats were randomly allocated into six groups. In group 1 (sham) the distal esophagus was isolated and cannulated but no caustic injury was induced. In all remaining groups, a caustic esophageal burn was induced with 50% sodium hydroxide solution for 90 s and drug treatment was given by daily intraperitoneal injection, beginning 24 h after injury and continuing for 21 d. In group 2 (controls), animals were treated with 0.9% saline; in groups 3 and 4, with 50 and 500 mg/kg/d of dexpanthenol, respectively; and in groups 5 and 6, with 0.3 and 3 mg/kg/d of Y-27632, respectively. Rats were sacrificed 22 d after caustic injury and the distal esophagus was isolated for histopathology and biochemical investigation. Stenosis index and collagen deposition scores were significantly lower in both the dexpanthenol and Y-27632 treated groups (P<0.05). Dexpanthenol and Y-27632 treatment markedly depressed esophageal tissue malondialdehyde and hydroxyproline levels. In this experimental model of caustic esophageal stricture, dexpanthenol and Y-27632 significantly attenuated esophageal stricture formation. These findings indicate that inhibition of Rho-kinase or dexpanthenol administration may offer novel therapeutic approaches in the treatment of caustic esophageal injury.

Extensive Tracheobronchitis and Lung Perforation After Alkaline Caustic Aspiration

Corrosive tracheobronchitis and lung perforation after caustic aspiration are not very common. We present a case of life-threatening acute respiratory system corrosion after aspiration of caustic alkaline crystals during a suicide attempt. The patient survived the severe burns of the tracheobronchial tract and the liquefaction necrosis of the lung lobe by aggressive airway protection procedures and surgical resection of the destroyed lung. We report this rare, clinical condition and discuss the possible mechanism and its management.

High-Grade Silica Refined from Diatomaceous Earth for Solar-Grade Silicon Production

A refining processing of high-purity silica from biogenic diatomaceous earth is newly proposed to exploit the steady and stable resource to the solar-power generation industry. The specimens collected from various representative diatomaceous earth deposits, including both marine and freshwater origin, were chemically analyzed. Trace element distribution in diatomaceous earth was influenced by the biotope habitat of diatoms, when compared to that in quartz of igneous origin. Al, K, and Fe were mainly terrestrially derived, while Si and B were from diatom shells. B content in diatomaceous earth specimens from lacustrine sources was less than that in marine origin. Diatomaceous earth was then dissolved into caustic alkaline solution. With a decreasing pH value, amorphous silica precipitated with impurities. Al and Fe were concentrated in silica precipitated in the pH range of 12.5−10.5, while B was more soluble than silica at pH less than 9. Silica can be precipitated in the pH range of 10.5−9.0, followed by...

COMBINING ULTRAFILTRATION PROCESS WITH COAGULATION PRETREATMENT FOR PULP MILL WASTEWATER TREATMENT

Ultrafiltration combined with coagulation pretreatment was used to treat two kraft pulp mill wastewaters from first-stage caustic extraction and alkaline bleaching operations, respectively. Both alum and ferric chloride were tested using standard jar apparatus at different dose, pH and ionic strength conditions. Ultrafiltration tests were conducted using a crossflow flatsheet membrane apparatus operated in the constant transmembrane pressure mode to examine the effects of membrane material, crossflow velocity and transmembrane pressure in terms of permeate flux and treated effluent quality. The results showed that coagulation with both alum and ferric chloride greatly reduced the permeate flux decline rates. In comparison with alum, greater permeate fluxes were obtained with the use of ferric chloride. Among the process parameters examined, coagulant dose was identified as the most important factor affecting the permeate flux. In addition, colour and COD removals were achieved largely by coagulation for alkaline bleaching wastewater while by membrane filtration for caustic extraction wastewater, highlighting the different mechanisms underlying contaminant removal.

Synthesis of ettringite: a way to deal with the acid wastewaters of aluminium anodising industry

Synthesis of ettringite from acid wastewaters of the aluminium anodising industry has been studied as a possible route of reducing the emissions to the environment, recovering at the same time resource materials as a useful marketable mineral. Wastewaters of different concentrations have been subjected to the process of synthesis suspending calcium oxide and calcium aluminate powders at different time and pH conditions. High caustic alkalinity (pH approximately 12) and low sulphate concentrations (<0.1 M) are the most suitable conditions to synthesise ettringite. The mineral characterisation has been performed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential thermal analysis (DTA), proving the high purity of the pursued solid product when hydrated in the appropriate sodium hydroxide concentrations. In such conditions, around 90% of the aluminium initially present in the wastewater solutions is recovered in the form of ettringite.