scholarly journals A Multi-Scale Approach to Microencapsulation by Interfacial Polymerization

Polymers ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 644
Author(s):  
Fabián Ricardo ◽  
Diego Pradilla ◽  
Ricardo Luiz ◽  
Oscar Alberto Alvarez Solano
Keyword(s):  
Interfacial Polymerization ◽  
Process Variables ◽  
Compression Force ◽  
Ph Change ◽  
Ph Measurements ◽  
Kinetics Of Polymerization ◽  
Multi Scale ◽  
Ph Values ◽  
Initial Ph ◽  
Kinetics Of

This work applies a multi-scale approach to the microencapsulation by interfacial polymerization. Such microencapsulation is used to produce fertilizers, pesticides and drugs. In this study, variations at three different scales (molecular, microscopic and macroscopic) of product design (i.e., product variables, process variables and properties) are considered simultaneously. We quantify the effect of the formulation, composition and pH change on the microcapsules’ properties. Additionally, the method of measuring the strength of the microcapsules by crushing a sample of microcapsules’ suspension was tested. Results show that the xylene release rate in the microcapsules decreases when the amine functionality is greater due to a stronger crosslinking. Such degree of crosslinking increases the compression force over the microcapsules and improves their appearance. When high levels of amine concentration are used, the initial pH values in the reaction are also high which leads to agglomeration. This study provides a possible explanation to the aggregation based on the kinetic and thermodynamic controls in reactions and shows that the pH measurements account for the polyurea reaction and carbamate formation, which is a reason why this is not a suitable method to study kinetics of polymerization. Finally, the method used to measure the compressive strength of the microcapsules detected differences in formulations and composition with low sensibility.

scholarly journals Technical note: Stability of tris pH buffer in artificial seawater stored in bags

Ocean Science ◽  
2021 ◽  
Vol 17 (3) ◽  
pp. 819-831
Author(s):  
Wiley H. Wolfe ◽  
Kenisha M. Shipley ◽  
Philip J. Bresnahan ◽  
Yuichiro Takeshita ◽  
Taylor Wirth ◽  
...  
Keyword(s):  
Dissolved Inorganic Carbon ◽  
Technical Note ◽  
Artificial Seawater ◽  
Upper And Lower Bounds ◽  
Sensor Calibration ◽  
Time Data ◽  
Ph Change ◽  
Ph Measurements ◽  
Experimental Conditions ◽  
Initial Ph

Abstract. Equimolal tris (2-amino-2-hydroxymethyl-propane-1,3-diol) buffer in artificial seawater is a well characterized and commonly used standard for oceanographic pH measurements. We evaluated the stability of tris pH when stored in purportedly gas-impermeable bags across a variety of experimental conditions, including bag type and storage in air vs. seawater over 300 d. Bench-top spectrophotometric pH analysis revealed that the pH of tris stored in bags decreased at a rate of 0.0058±0.0011 yr−1 (mean slope ±95 % confidence interval of slope). The upper and lower bounds of expected pH change at t=365 d, calculated using the averages and confidence intervals of slope and intercept of measured pH change vs. time data, were −0.0042 and −0.0076 from initial pH. Analyses of total dissolved inorganic carbon confirmed that a combination of CO2 infiltration and/or microbial respiration led to the observed decrease in pH. Eliminating the change in pH of bagged tris remains a goal, yet the rate of pH change is lower than many processes of interest and demonstrates the potential of bagged tris for sensor calibration and validation of autonomous in situ pH measurements.

scholarly journals Technical note: Interpreting pH changes

2021 ◽  
Vol 18 (4) ◽  
pp. 1407-1415
Author(s):  
Andrea J. Fassbender ◽  
James C. Orr ◽  
Andrew G. Dickson
Keyword(s):  
Technical Note ◽  
Ion Concentration ◽  
Ph Change ◽  
Ph Measurements ◽  
Hydrogen Ion Concentration ◽  
Ph Changes ◽  
The Past ◽  
Initial Ph ◽  
Relative Change

Abstract. The number and quality of ocean pH measurements have increased substantially over the past few decades such that trends, variability, and spatial patterns of change are now being evaluated. However, comparing pH changes across domains with different initial pH values can be misleading because a pH change reflects a relative change in the hydrogen ion concentration ([H+], expressed in mol kg−1) rather than an absolute change in [H+]. We recommend that [H+] be used in addition to pH when describing such changes and provide three examples illustrating why.

Effects of Acetic Acid and Arginine on pH Elevation and Growth of Bacillus licheniformis in an Acidified Cucumber Juice Medium†

2015 ◽  
Vol 78 (4) ◽  
pp. 728-737 ◽  
Author(s):  
ZHENQUAN YANG ◽  
XIA MENG ◽  
FREDERICK BREIDT ◽  
LISA L. DEAN ◽  
FLETCHER M. ARRITT
Keyword(s):  
Acetic Acid ◽  
Citric Acid ◽  
Bacillus Licheniformis ◽  
Pathogenic Bacteria ◽  
Ph Change ◽  
Ph Values ◽  
Vegetable Products ◽  
Initial Ph ◽  
Tomato Products ◽  
Ph Elevation

Bacillus licheniformis has been shown to cause pH elevation in tomato products having an initial pH below 4.6 and metabiotic effects that can lead to the growth of pathogenic bacteria. Because of this, the organism poses a potential risk to acidified vegetable products; however, little is known about the growth and metabolism of this organism in these products. To clarify the mechanisms of pH change and growth of B. licheniformis in vegetable broth under acidic conditions, a cucumber juice medium representative of a noninhibitory vegetable broth was used to monitor changes in pH, cell growth, and catabolism of sugars and amino acids. For initial pH values between pH 4.1 to 6.0, pH changes resulted from both fermentation of sugar (lowering pH) and ammonia production (raising pH). An initial pH elevation occurred, with starting pH values of pH 4.1 to 4.9 under both aerobic and anaerobic conditions, and was apparently mediated by the arginine deiminase reaction of B. licheniformis. This initial pH elevation was prevented if 5 mM or greater acetic acid was present in the brine at the same pH. In laboratory media, under favorable conditions for growth, data indicated that growth of the organism was inhibited at pH 4.6 with protonated acetic acid concentrations of 10 to 20 mM, corresponding to 25 to 50 mM total acetic acid; however, growth inhibition required greater than 300 mM citric acid (10-fold excess of the amount in processed tomato products) products under similar conditions. The data indicate that growth and pH increase by B. licheniformis may be inhibited by the acetic acid present in most commercial acidified vegetable products but not by the citric acid in many tomato products.

scholarly journals Technical note: Interpreting pH changes

2020 ◽  
Author(s):  
Andrea J. Fassbender ◽  
James C. Orr ◽  
Andrew G. Dickson
Keyword(s):  
Technical Note ◽  
Ion Concentration ◽  
Ph Change ◽  
Ph Measurements ◽  
Hydrogen Ion Concentration ◽  
Ph Changes ◽  
The Past ◽  
Initial Ph ◽  
Relative Change

Abstract. The number and quality of ocean pH measurements has increased substantially over the past few decades such that trends, variability, and spatial patterns of change are now being evaluated. However, comparing pH changes across domains with different initial pH values can be misleading because a pH change reflects a relative change in the hydrogen ion concentration ([H+]–expressed in mol kg−1) rather than an absolute change in [H+]. We recommend that [H+] be used in addition to pH when describing such changes and provide three examples illustrating why.

scholarly journals Silica Removal from a Paper Mill Effluent by Adsorption on Pseudoboehmite and γ-Al2O3

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2031
Author(s):  
Ruben Miranda ◽  
Isabel Latour ◽  
Angeles Blanco
Keyword(s):  
Paper Mill ◽  
Ph Adjustment ◽  
Paper Mill Effluent ◽  
Kinetics Studies ◽  
Silica Removal ◽  
Industrial Water Use ◽  
Optimum Ph ◽  
Initial Ph ◽  
Equilibrium And Kinetics ◽  
Kinetics Of

Effluent reuse is a common practice for sustainable industrial water use. Salt removal is usually carried out by a combination of membrane processes with a final reverse osmosis (RO). However, the presence of silica limits the RO efficiency due to its high scaling potential and the difficulty of cleaning the fouled membranes. Silica adsorption has many advantages compared to coagulation and precipitation at high pHs: pH adjustment is not necessary, the conductivity of treated waters is not increased, and there is no sludge generation. Therefore, this study investigates the feasibility of using pseudoboehmite and its calcination product (γ-Al2O3) for silica adsorption from a paper mill effluent. The effect of sorbent dosage, pH, and temperature, including both equilibrium and kinetics studies, were studied. γ-Al2O3 was clearly more efficient than pseudoboehmite, with optimal dosages around 2.5–5 g/L vs. 7.5–15 g/L. The optimum pH is around 8.5–10, which fits well with the initial pH of the effluent. The kinetics of silica adsorption is fast, especially at high dosages and temperatures: 80–90% of the removable silica is removed in 1 h. At these conditions, silica removal is around 75–85% (<50 mg/L SiO2 in the treated water).

Derivatives of isatin in aqueous solution. I. Kinetics of ring opening of Isatin-5-sulfonate

1981 ◽  
Vol 34 (2) ◽  
pp. 365 ◽  
Author(s):  
H Stunzi
Keyword(s):  
Ring Opening ◽  
Rate Of Change ◽  
Spectroscopic Methods ◽  
Ph Values ◽  
Buffer Region ◽  
Pka Value ◽  
Back Titration ◽  
Kinetics Of ◽  
Derivatives Of ◽  
Sulfonate Anion

The reactions of isatin-5-sulfonate anion (si-) which cause a hysteresis in pH titrations were studied by pH-metric and n.m.r, spectroscopic methods. Rapid alkalimetric titrations [I 0.15 M (KNO3),37�] gave the pKa value corresponding to the addition of OH- to si- [pKa(ring) 9.55]. The slow ring opening to the sulfonatoisatate dianion (sia2-) led to a drift of the pH values towards an equilibrium buffer region. Its pKa, value [pKa(eq) 3.44] corresponds to the reaction si-+H2O ↔ sia 2-+H+ Rapid back-titration gave the pKa value of the ring-opened species Hsia- [pKa(open) c. 1.3]. The rate law for the ring opening d[sia]/dt=k2 [siOH](OH)+k1*[si] was obtained from the rate of change of pH. N-Methylisatin-5-sulfonate behaves analogously.

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