Production of Urea/Acetylated-ligninsulfonate Matrix as SRFs and Investigation the Effect of Hydrodynamic Conditions on the Release Rate Using Biot Number

2022 ◽  
Vol 15 ◽  
Author(s):  
Samira Moradi ◽  
Keivan Shayesteh ◽  
Qasem Mohammad
Keyword(s):  
Mass Transfer ◽  
Biot Number ◽  
Release Rate ◽  
Integral Transform ◽  
Hydrodynamic Condition ◽  
Mechanical Resistance ◽  
Nitrogen Release ◽  
The Matrix ◽  
Slow Release Fertilizers ◽  
Finite Integral

Background: This study aimed to investigate the effect of the hydrodynamic condition on the release rate of urea/acetylated lignin sulfonate (Ac-LS) matrix as slow-release fertilizers (SRFs). Therefore, two models were developed using the mass transfer balance for the finite/infinite volume of fluids, solving finite integral transform/separation of a variable. In these models, the Biot number that verified the hydrodynamic condition appeared. Methods: In the experimental section, the urea/Ac-LS matrix fertilizer was produced. The morphological, thermal, chemical, and mechanical properties of the LS, Ac-LS, urea, and urea/Ac-LS matrix were analyzed using Fe-SEM, TGA, XRD, and SANTAM. Finally, the nitrogen release of the matrix fertilizer was investigated at 25°C for different impeller speeds. Results: The results showed that the thermal and mechanical resistance of urea/Ac-LS, with strong interaction, increased rather than pure urea or Ac-LS. The models were also validated using experimental data. The results further showed that in both states, the external resistance of the mass transfer decreased with increasing impeller speed, and the nitrogen release rate increased with increasing Biot number. Conclusion: It was also observed that, in a given hydrodynamic condition, initially, the release rate in the finite environment was less than the infinite; however, after a while, the type of environment did not affect the release rate

Influence of Formulation Variables and Processing Techniques on Drug Release from Carbopol-971 based Matrix Tablets of Cinnarizine and Nimodipine.

2010 ◽  
Vol 2 (1) ◽  
Author(s):  
Singh K. ◽  
Pandit K. ◽  
Mishra N.
Keyword(s):  
Drug Release ◽  
Release Rate ◽  
Polymer Concentration ◽  
Matrix Tablets ◽  
Wet Granulation ◽  
Weight Variation ◽  
Diffusion Controlled ◽  
The Matrix ◽  
Processing Techniques ◽  
Formulation Variables

The matrix tablets of cinnarizine and nimodipine were prepared with varying ratio of Carbopol- 971P and co-excipients of varying hydrophilicity (i.e. dicalcium phosphate and spray dried lactose) by direct compression and wet granulation using alcoholic mucilage. The prepared tablets were evaluated for weight variation, hardness and friability. The influence of concentration of the matrix forming material and co-excipients on the release rate of the drug was studied. The release rate of Cinnarizine (more soluble drug) from tablets followed diffusion controlled mechanism whereas for nimodipine (less soluble drug), the drug release followed case-II or super case- II transport mechanism based on Korsmeyer- Peppas equation. The results indicated that the drug release from matrix tablets was increases with increase in hydrophilicity of drug and co-excipients. The release of drug also increased with thermal treatment and decreasing polymer concentration.

scholarly journals Preparation and properties of hydrogel based on sawdust cellulose for environmentally friendly slow release fertilizers

2020 ◽  
Vol 9 (1) ◽  
pp. 139-152 ◽  
Author(s):  
Xiao Zhang ◽  
Yanlu Liu ◽  
Panfang Lu ◽  
Min Zhang
Keyword(s):  
Slow Release ◽  
Environmentally Friendly ◽  
Water Absorbency ◽  
The Novel ◽  
Structure And Properties ◽  
Nitrogen Release ◽  
Release Property ◽  
Slow Release Fertilizers ◽  
Grafting Copolymerization ◽  
Cross Linker

AbstractA novel hydrogel slow-release nitrogen fertilizer based on sawdust with water absorbency was prepared using grafting copolymerization. Urea was incorporated as nitrogen source in a hydrogel fertilizer. Potassium persulfate (KPS) and N,N᾽-methylenebis acrylamide (MBA) were used as the initiator and cross-linker, respectively. The structure and properties of the samples were characterized by XPS, EDS, SEM, XRD and FTIR. The effects of various salt solutions, ionic strength and pH on swelling behavior were discussed. The results showed that the largest water absorbency of the sample reached 210 g/g in distilled water. In addition, the sample had the good nitrogen release property. Thus, the novel environmentally friendly hydrogel fertilizer may be widely applied to agricultural and horticultural fields.

Strain shadow “megapores” in mid-crustal ultramylonites - local, transient reservoirs servicing the granular fluid pump?

2021 ◽  
Author(s):  
Florian Fusseis ◽  
Craig Allsop
Keyword(s):  
Mass Transfer ◽  
Transport Properties ◽  
Shear Zones ◽  
Grain Boundary Sliding ◽  
Shear Direction ◽  
Rock Interaction ◽  
The Matrix ◽  
Granular Fluid ◽  
The Individual ◽  
Individual Grains

<p>Shear zones are important conduits that facilitate the bidirectional migration of fluids and dissolved solids across the middle crust. It is a relatively recent revelation that mylonitic deformation in such shear zones can result in the formation of synkinematic pores that are potentially utilised in long-range fluid migration. The pores definitely influence a shear zone’s hydraulic transport properties on the grain scale, facilitating synkinematic fluid-rock interactions and mass transfer. Our understanding of how exactly various forms of synkinematic porosity integrate with the kinematics and dynamics of shear zones is still growing. Here we show a previously undescribed form of synkinematic porosity in an unweathered, greenschist-facies psammitic ultramylonite from the Cap de Creus Northern Shear Belt (Spain). The sizeable, open pores with volumes > 50k µm3 appear exclusively next to albitic feldspar porphyroclasts, which themselves float in a fine-grained, polymineralic ultramylonitic matrix that likely deformed by grain size-sensitive creep and viscous grain boundary sliding. The pores wrap around their host clasts, occupying asymmetric strain shadows and tailing off into the mylonitic foliation. A detailed analysis using high-resolution backscatter electron imaging and non-invasive synchrotron-based x-ray microtomography confirms that the pores are isolated from each other. We found no evidence for weathering of the samples, or any significant post-mylonitic overprint, unequivocally supporting a synkinematic origin of the pores. </p><p>We propose that this strain shadow porosity formed through the rotations of the Ab porphyroclasts, which was governed by the clasts’ shapes and elongation. The ultramylonitic matrix was critical in enabling the formation of pores in the clast’s strain shadows. In the matrix, the individual grains were displaced mostly parallel to the shear direction. As a consequence of clast rotation it can be expected that, in the strain shadows, matrix grains followed diverging movement vectors. As a result, phase boundaries in the YZ plane experienced tensile forces, leading to the opening of pores. We infer that this tensile decoupling among matrix grains established a hydraulic gradient that drained the matrix locally and filled the pores with fluid. The fact that the strain shadow pores remained open in our samples suggests a chemical equilibrium with the fluid. Pore shape and volume will have been subject to continuous modification during ongoing matrix deformation and clast rotation.</p><p>This form of synkinematic porosity constitutes a puzzling, yet obvious way to maintain surprisingly large pores in ultramylonites whose transport properties are otherwise likely determined by creep cavitation and the granular fluid pump (Fusseis et al., 2009). We envisage that the strain shadow megapores worked in sync with the granular fluid pump in the ultramylonitic matrix and, while the overall porosity of ultramylonites may be small, locally, substantial fluid reservoirs were available to service fluid-rock interaction and fluid-mediated mass transfer. Our findings add another puzzle piece to our evolving understanding of synkinematic transport properties of mid-crustal ultramylonites and fluid-rock interaction in shear zones at the brittle-to-ductile transition.</p>

scholarly journals Cyclodextrins and Cyclodextrin Derivatives as Green Char Promoters in Flame Retardants Formulations for Polymeric Materials. A Review

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 664 ◽  
Author(s):  
Maria Paola Luda ◽  
Marco Zanetti
Keyword(s):  
Flame Retardants ◽  
Environmental Concern ◽  
Fire Retardant ◽  
Polymeric Materials ◽  
Poly Lactic Acid ◽  
Mechanical Resistance ◽  
Self Healing ◽  
Cyclodextrin Derivatives ◽  
The Matrix ◽  
Fire Retardance

Polymers are intrinsically flammable materials; hence, fire retardance (FR) is required in their most common applications (i.e., electronic and construction, to mention some). Recently, it has been reported that cyclodextrin (CD) and cyclodextrin derivatives are beginning to be introduced into Intumescent Fire Retardant (IFR) formulations in place of pentaerythritol, which is used in IFRs that are currently on the market. Since IFRs are of less environmental concern than their hazardous halogen containing counterparts, the use of natural origin compounds in IFRs provides a way to comply with green chemistry issues. BCD and BCD derivatives presence in IFR mixtures promotes a higher yield of blowing gases and char when polymeric materials undergo combustion. Both processes play important roles in intumescence. The key rule to obtain in insulating compact char is the good dispersion of the nanoparticles in the matrix, which can be achieved by functionalizing nanoparticles with BCD derivatives. Moreover, CD derivatives are attractive because of their nanosized structure and their ability to form inclusion complexes with many compounds used as FR components, reducing their release to the environment during their shelf life of FR items. Often, fire retardance performed by BCD and BCD derivatives accompanies other relevant properties, such as improved mechanical resistance, washability resistance, self healing ability, thermal conductivity, etc. The application of CD fire retardant additives in many polymers, such as poly(lactic acid), poly(propylene), poly(vinyl acetate), poly(methyl methacrylate), linear low density poly(ethylene), polyamides, and polyesters are comprehensively reviewed here.

scholarly journals Estimation of the Biot Number Using Genetic Algorithms: Application for the Drying Process

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2822 ◽  
Author(s):  
Krzysztof Górnicki ◽  
Radosław Winiczenko ◽  
Agnieszka Kaleta
Keyword(s):  
Mass Transfer ◽  
Biot Number ◽  
Moisture Diffusion ◽  
Absolute Error ◽  
Heat Fluxes ◽  
Coefficient Of Determination ◽  
Drying Process ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Multi Objective Genetic Algorithm

The Biot number informs researchers about the controlling mechanisms employed for heat or mass transfer during the considered process. The mass transfer coefficients (and heat transfer coefficients) are usually determined experimentally based on direct measurements of mass (heat) fluxes or correlation equations. This paper presents the method of Biot number estimation. For estimation of the Biot number in the drying process, the multi-objective genetic algorithm (MOGA) was developed. The simultaneous minimization of mean absolute error (MAE) and root mean square error (RMSE) and the maximization of the coefficient of determination R2 between the drying model and experimental data were considered. The Biot number can be calculated from the following equations: Bi = 0.8193exp(-6.4951T−1) (and moisture diffusion coefficient from D/s2 = 0.00704exp(-2.54T−1)) (RMSE = 0.0672, MAE = 0.0535, R2 = 0.98) or Bi = 1/0.1746log(1193847T) (D/s2 = 0.0075exp(-6T−1)) (RMSE = 0.0757, MAE = 0.0604, R2 = 0.98). The conducted validation gave good results.

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