pH Adjustment Method Research Articles

Controlled Synthesis of Phase‐Pure Zeolitic Imidazolate Framework Co‐ZIF‐9

AbstractThe synthesis of phase‐pure Co‐ZIF‐9, an important cobalt‐based zeolitic imidazolate framework, could be achieved by modification of the reported synthesis procedure through pH adjustment of the starting synthesis mixture. The phase‐pure Co‐ZIF‐9 material obtained has been characterized by a combination of UV/Vis, FTIR, and Raman spectroscopy as well as by thermogravimetric analysis (TGA) and XRD and possesses a lower overall crystallinity. This can be explained by the addition of the base for the pH adjustment method. On the basis of these findings, a synthesis pathway for the formation of the secondary phase, cobalt formate, is proposed along with its relationship to the flexibility of the coordination environment of cobalt ions. The crystal structures of both phases have been determined by single‐crystal X‐ray crystallography, and the resolved structures also reflect the coordination flexibility of the framework cobalt ions.

Direct synthesis of mesoporous molecular sieves of Ni-SBA-16 by internal pH adjustment method and its performance for adsorption of toxic Brilliant Green dye

An ordered mesoporous novel material Ni-SBA-16 has been synthesized by internal pH-adjustment method. The synthesized material has been characterized by small angle XRD (SXRD), wide angle XRD (WXRD), Scanning Electron Microscope (SEM), High-Resolution Transmission Electron Microscope (HRTEM), Fourier-transform Infra-red (FTIR) spectroscope and Nitrogen Adsorption desorption techniques. The characterization results have shown that material possesses highly ordered mesostructure with high surface area (736m2/g) and large pore diameter (3.8nm). FTIR and WXRD spectra revealed that nickel was uniformly dispersed on SBA-16 surface. The synthesized material has been used as adsorbent for removal of toxic Brilliant Green dye due to its large surface area and pore size. At optimized conditions, almost 100% of Brilliant Green dye was removed from aqueous solution by Ni-SBA-16. The isotherms analysis indicates that the Langmuir and Hill models provide the best correlation of the experimental data. The maximum adsorption capacity (qmax) of Ni-SBA-16 for Brilliant Green dye was 322.58mg/g.

Synergetic Degradation of Enzyme-Fenton Reagent for Methyl Orange

The effects of pH adjustment method, pH value, UV light, catalase and Fenton reagent on the degradation efficiency of enzyme-Fenton reagent for methyl orange (MO) were investigated, and the synergetic catalytic effects of catalase and Fenton reagent on the catalytic oxidation for methyl orange were found. When under no UV-light, the enzyme can enhance the degradation efficiency of Fenton reagent. The optimum conditions for degrading methyl orange simulated wastewater whose concentration is 0.1 g/L at room temperature are obtained as follows: the pH is tuned with H2SO4, pH is 3.0, concentration of catalase is 5 μg / mL, concentration of H2O2is 0.01%, concentration of FeSO4is 1.8μmol / L. The degradation rate can reach 98% in 60min. When under UV light at the same condition, the degradation rate can reach 94% in only 15min.

Quality by Design Approach for Understanding the Critical Quality Attributes of Cyclosporine Ophthalmic Emulsion

Restasis is an ophthalmic cyclosporine emulsion used for the treatment of dry eye syndrome. There are no generic products for this product, probably because of the limitations on establishing in vivo bioequivalence methods and lack of alternative in vitro bioequivalence testing methods. The present investigation was carried out to understand and identify the appropriate in vitro methods that can discriminate the effect of formulation and process variables on critical quality attributes (CQA) of cyclosporine microemulsion formulations having the same qualitative (Q1) and quantitative (Q2) composition as that of Restasis. Quality by design (QbD) approach was used to understand the effect of formulation and process variables on critical quality attributes (CQA) of cyclosporine microemulsion. The formulation variables chosen were mixing order method, phase volume ratio, and pH adjustment method, while the process variables were temperature of primary and raw emulsion formation, microfluidizer pressure, and number of pressure cycles. The responses selected were particle size, turbidity, zeta potential, viscosity, osmolality, surface tension, contact angle, pH, and drug diffusion. The selected independent variables showed statistically significant (p < 0.05) effect on droplet size, zeta potential, viscosity, turbidity, and osmolality. However, the surface tension, contact angle, pH, and drug diffusion were not significantly affected by independent variables. In summary, in vitro methods can detect formulation and manufacturing changes and would thus be important for quality control or sameness of cyclosporine ophthalmic products.

Synthesis of CoSBA-15: A Comparative Study of pH Adjustment versus Non-pH Adjustment Method

Synthesis of CoSBA-15: A Comparative Study of pH Adjustment versus Non-pH Adjustment Method

A trace‐metal clean, pH‐controlled incubator system for ocean acidification incubation studies

The emerging research field of ocean acidification studies has gained international attention during the past years and recently defined international standards in the Guide to best practices for ocean acidification research and data reporting. However, a combination of ocean acidification studies with trace metal research is very rare and possible trace metal side effects on marine phytoplankton in ocean acidification incubation studies are often not assessed. Here we describe a trace metal clean, pH‐controlled incubator system for laboratory and seagoing ocean acidification research. Seawater pH adjustment is achieved via passing CO2 gas through diffusive silicone tubing to minimize the risk of contamination and to avoid the negative mechanical effects of gas bubbles on phytoplankton. The system measures pH automatically with an accuracy of 0.004 and a precision of 0.001 and includes a feedback regulation to adjust pH during the incubation if required. Mn, Fe, Co, Ni, Cd, and Pb measurements show that our system and the pH adjustment method do not contaminate the samples with any of these metals. We tested this system in laboratory studies as well as during the PINTS voyage in the Tasman Sea.

Preparation of Finite Particles of Nitrate Forms of Layered Double Hydroxides by pH Adjustment with Anion Exchange Resin

Well-defined finite particles of nitrate forms of layered double hydroxides (MgAl and NiAl types) were successfully synthesized from aqueous solution of metal nitrates by the recently developed pH adjustment method, where hydroxide form ion-exchange resin was used to change a starting acidic solution into basic solution for the hydroxide formation. The interlayer nitrate ion of layered double hydroxide was exchanged with such anions as dodecylsulfate and oleate to form intercalation compounds by conventional anion exchange reactions in aqueous media at room temperature, suggesting potential of the methods as well as the present materials for further study on the applications of LDHs.

Preparation of Well-defined Nanometer-sized Layered Double Hydroxides by Novel pH Adjustment Method Using Ion-exchange Resin

Abstract Well-defined finite particles of layered double hydroxides were successfully synthesized from aqueous solution of metal salts by the newly developed pH adjustment method, where hydroxide form ion-exchange resin was used to make acidic starting solution to basic for the hydroxide formation.

Recovery and Characterization of Sardine Oil Extracted by pH Adjustment

A new oil extraction method involving pH adjustment was developed and compared with the traditional heat extraction method. Sardine oil was obtained by adjusting the pH to the isoelectric point (pI) of sardine muscle (pH 5.5) using HCl or food-grade organic acids [with/without calcium (Ca)] followed by centrifugation. Oil extracted with citric acid plus Ca showed the best quality, along with good recovery, the lowest haze value, and the highest n-3 polyunsaturated fatty acid content. All oils extracted by pH adjustment exhibited high stability against oxidation supported by low conjugated dienes and thiobarbituric acid reactive substance level with fewer impurities compared to the heat process. There was a significant beneficial effect of Ca addition prior to pH adjustment in terms of lipid oxidation stability and color of the final products. The pH adjustment method is a novel process for oil extraction and a promising method that can be utilized for high-oil pelagic species such as Pacific sardines.

Characterization of Highly Ordered MCM-41 Silicas Using X-ray Diffraction and Nitrogen Adsorption

Highly ordered MCM-41 silicas were synthesized in the presence of alkyltrimethylammonium surfactants and characterized using powder X-ray diffraction and nitrogen adsorption at 77 K. Samples prepared in the presence of hexadecyltrimethylammonium (HTMA+) and octadecyltrimethylammonium surfactants using the repeated pH adjustment method were found to exhibit a very high degree of structural ordering and (100) interplanar spacings of 4.1 and 4.6 nm, respectively. Using a high-temperature (438 K) synthesis procedure involving HTMA+ surfactants, it was also possible to prepare MCM-41 with the (100) spacing above 5 nm, which exhibited as many as five distinct XRD peaks. The MCM-41 materials had appreciable amounts of secondary mesopores, but no micropores. Pore sizes evaluated from (100) interplanar spacings and primary mesopore volumes using geometrical considerations were found to be in excellent agreement with those calculated using the Barrett−Joyner−Halenda method with the recently reported modified versio...

The elasticity of synthetic phospholipid vesicles obtained by photon correlation spectroscopy

Osmotic-swelling experiments were conducted on a variety of preparations of "uniform" unilamellar vesicle systems. The synthetic lipid preparations included both vesicles produced by extrusion through polycarbonate ultrafiltration membranes and vesicles produced by the pH-adjustment method. The vesicles were monitored by photon correlation spectroscopy during swelling as the osmolarity of the external solution was decreased. Contrary to our previously reported results [Aurora, T. S., Li, W., Cummins, H. Z., & Haines, T. H. (1985) Biochim. Biophys. Acta 820, 250-258; Li, W., & Haines, T. H. (1986) Biochemistry 25, 7477-7483; Li, W., Aurora, T. S., Haines, T. H., & Cummins, H. Z. (1986) Biochemistry 25, 8220-8229; Haines, T. H., Li, W., Green, M., & Cummins, H. Z. (1987) Biochemistry 26, 5439-5447] large unilamellar vesicles produced from acidic lipids by the pH-adjustment technique were highly polydisperse and did not swell in a manner that permitted the computation of a Young's modulus, presumably due to the polydispersity. Also contrary to our previous reports, membranes derived from bovine submitochondrial particles did not produce evidence of swelling when subjected to similar protocols. Analysis of osmotic swelling of extruded unilamellar vesicles has allowed us to assign Young's moduli for bilayers of dioleoylphosphatidylcholine and dioleoylphosphatidylglycerol, in the range (5-8) x 10(8) and (3-6) x 10(8) dyn/cm2, respectively. The diameters and polydispersites obtained with electron microscopy and photon correlation spectroscopy were compared directly and with computer-modeling techniques. While excellent agreement was obtained for distributions with low polydispersity (approximately greater than 0.1), serious disagreement was found when the polydispersity exceeded approximately 0.2.

Elasticity of synthetic phospholipid vesicles and submitochondrial particles during osmotic swelling.

A rapid and accurate method has been developed for measuring the elastic response of vesicle bilayer membranes to an applied osmotic pressure. The technique of dynamic light scattering is used to measure both the elastic constant and the elastic limit of dioleoylphosphatidic acid (DOPA) and DOPA-cholesterol vesicles and of submitochondrial particles derived from the inner membrane of bovine heart mitochondria. The vesicles prepared by the pH-adjustment method are unilamellar and of uniform size between 240 and 460 nm in diameter. The vesicles swell uniformly upon dilution. The observed change in size is not due to any change in the shape of the vesicles. The data also indicate that the vesicles are spherical and not flaccid. The total vesicle swelling in these studies resulted in a 3-4% increase in surface area for vesicles swollen in 0.15 M KCl and a 5-10% increase in surface area for vesicles swollen in 0.25 M sucrose. This maximum represents the elastic limit of the vesicles. Evidence is presented to show that the vesicles release contents after swelling to this maximum, reseal immediately, and reswell according to the osmotic pressure. For DOPA vesicles in a 0.15 M KCl-tris(hydroxymethyl)aminomethane hydrochloride (Tris-HCl) buffer (pH 7.55), the observed membrane modulus is found to be in the range of 10(8) dyn/cm2. The modulus was found to be in the order of 10(7) dyn/cm2 for DOPA vesicles in a 0.25 M sucrose-Tris-HCl buffer (pH 7.55). This is comparable to that of submitochondrial particles in the same sucrose-Tris-HCl buffer. The observed membrane modulus also decreases with vesicle size. Its magnitude and its variation with ionic strength indicate that the major component of bilayer elasticity is neither the inherent elasticity of the bilayer nor the bending modulus. The variation of the membrane modulus with respect to curvature suggests that its principal component may be related to surface tension effects including the negative charges on the vesicle surface. There is considerable variation between vesicles swollen in sucrose and those swollen in KCl in the membrane modulus, in the elastic limit at which the vesicles burst, and in the transbilayer pressure difference at bursting. The latter was found to be 4-6 mosM (10(5) dyn/cm2) in sucrose solution and 20-4 mosM (10(6) dyn/cm2) in KCl solution.

Studies on the Treatment of Night Soil. XIII. Tertiary Treatment of Night Soil. with Hypochlorite by the Two Stage pH Adjustment Method

A method for tertiary treatment of night soil by chlorination with calcium and sodium hypochlorites was studied. Removal of ammonium-nitrogen by hypochlorite was not affected by pH. When an excess of hypochlorite to the break point was added, color and ammonium-nitrogen were completely removed. To eliminate the color, the most effective pH on chlorination was at 1-2. Colored substances in the secondary treated water of night soil, such as humic acid, fulvic acid, hymatomelonic acid, and methanol and water-soluble substances, were easily decolorized by chlorination. Orthophosphate was effectively removed by flocculation at pH 10 or above. Orthophosphate was completely removed by treatment with calcium hypochlorite. But, when sodium hypochlorite was used, calcium hydroxide must be added in order to eliminate orthophosphate. The two-stage pH adjustment method is the most effective for the tertiary treatment of night soil by chlorination.