Recent Innovations in Chemical Engineering - Volume 12, Issue 1, 2019

Background: Scaffolds can be used to substitute the extracellular matrix and to favour the generation of tissues and organs. Until now, various processes have been implemented for scaffolds generation, but they are characterized by several limits. Methods: In this work, we tested a supercritical fluids assisted process for the generation of nano-structured biopolymeric scaffolds; it is characterized by three steps: generation of a polymeric gel (loaded with a porogen), drying of the gel using supercritical CO2, waterwashing to remove the porogen. Results: 3D Poly(D,L-lactic acid) scaffolds have been obtained, characterized by very high porosity (> 90%) and surface are (> 200 m2/g), and by a fibrous nanostructure (fibres ranging between 60 and 400 nm) superimposed to a micrometric cellular structure. Conclusion: Moreover, suitable mechanical properties (up to 125 KPa) and very low solvents residue (< 5 ppm) have been obtained.

Background: Bridging the gap between different phenomena, mechanisms and levels of description, different design methods can converge in a unitary way of formulation. This protocol consolidates the analogy and parallelism in the description of any unit operation of separation, as is the particular case of sedimentation. This holistic framework is compatible and complementary with other methodologies handled at length, and tries to contribute to the integration of some imaginative and useful - but marginal, heuristic or rustic- procedures for the design of settlers and thickeners, within well founded and unified methodology. Objective: Classical models for hindered sedimentation allow solid flux in the direction of the gravity field to be formulated by analogy to changes obeying a potential, such as molecular transfer in the direction of the gradient and chemical transformation throughout the reaction coordinate. This article justifies the fundamentals of such a suggestive generalized analogy through the definition of the time of the sedimentation unit (TSU), the effective surface area of a sedimentation unit (ASU) and the number of sedimentation units (NSU), as elements of a sizing equation. Methods: This article also introduces the generalization of the model ab initio: Analogy is a well known and efficient tool, not only in the interpretation of events with academic or coaching purposes, but also in the generalized modelling, prospective, innovation, analysis and synthesis of technological processes. Chemical Engineering protocols for the basic dimensioning of Unit Operations driven by potentials (momentum, heat and mass transfer chemical reaction) are founded in macroscopic balances of mass and energy. Results: These balances, emphatically called “design equations”, result from the integration of mechanistic differential formulations at the microscopic level of description (“equations of variation”). In its turn, these equations include phenomenological terms that may be formulated in corpuscular terms in the field of Chemical Physics. The design equation correlates requirements in equipment (e.g. any practical forms of size and residence or elapsed time for an efficient interaction) to the objectives of the operation (e.g. variations in mass or energy contents of a confined or fluent system). This formulation allows the identification of different contributions: intrinsic terms (related to mechanistic kinetics of the phenomena) and circumstantial terms (related to conditions and variables of operation). Conclusion: In fact, this model suggests that temporal or spatial dimensions of the equipment may be assumed to depend irrespectively on two design contributions: the entity of a representative “unit of operation (or process)” - illustrated by a descriptor of this dimension- and the “number of (these) units” needed to achieve the separating or transformative objectives of the operation.

Objective and Background: Synergistic extraction was introduced to replace single extraction due to enhanced extraction efficiency of heavy metal. Methodology: In order to improve extraction efficiency, di-(2-ethylhexyl) phosphoric acid (D2EHPA) was mixed with isodecanol to provide a synergistic effect together with leaching solution which is thiourea. From the single extraction system, the optimum temperature is found at 30°C producing the highest yield of %E of 91.30%. The single extraction also happened better with the presence of Fe(III) solution and thiourea as the %E is at 91.23%. Results and Conclusion: It was found that the synergistic D2EHPA-isodecanol extraction is successful as it yields higher %E than the single D2EHPA extraction.

Background: A molybdenum sulfide (Mo3S4) nanorod photocatalyst was synthesised through the facile hydrothermal method and applied in the degradation of Rhodamine B and Methyl Blue dyes under visible light irradiation. Methods: The Mo3s4 nanorod was synthesised using sodium molybdate, sodiumdiethyldithiolcarbonate and ethylenediaminetetraacetic acid as molybdenum and sulfur sources, and capping agent respectively. The photocatalyst was characterized by using XRD, FTIR, TEM, SEM, EDS and UV-Vis spectroscopies. Results: SEM result shows that the synthesised sample has a rod-like shape made up of several thin sheets. The XRD result revealed the Mo3S4 nanorod to exist in the Rhombohedral phase. The energy band gap of the sample was calculated to be 2.02 eV. The synthesised Mo3S4 nanorod showed great potential in the removal of both RhB and MB in aqueous solution. 85.46% and 99.78% removals of RhB and MB dyes respectively were achieved in 90 min. Conclusion: It was also observed that the photodegradation of both RhB and MB follows pseudo-first order kinetics, with apparent rate constants of 0.0089 min-1 and 0.0118 min-1 for RhB and MB respectively.

Background: In this paper, we have studied the improvement of the physical and chemical properties of the fiber-matrix interface of a Biocomposite based on the copolymer polylactic acid (PLA). Methodology: We have developed an analytical model using a genetic approach to locate the interface damage under the effect of mechanical stress, temperature and humidity. Our simulation is based on Weibull's probabilistic approach and the law of water diffusion in polymer matrix, the diffusion is generated by Fick's law. Results: Our results show that the interface of Biocomposite (Starch-PLA) is the most resistant to the different constraints applied and that the physical and chemical properties of this material are much more improved compared to other materials studied by the same genetic model. Conclusion: Our calculations coincide perfectly with the conclusions of Antoine et al. who determined that natural fibers improve the physical properties of composite materials.

Objective: The classical mass transfer theory is not applicable for modeling the mass transfer of chemical, absorption, adsorption and catalytic processes in column apparatuses, where the velocity distributions and interphase boundaries are unknown. The modeling of these processes is related with the creation of new type of convection-diffusion models (for qualitative analysis) and average-concentration models (for quantitative analysis), where the surface reactions are replaced by equivalent volume reaction, while the velocity and concentration distributions are replaced by average velocity and concentrations. The effect of the radial non-uniformity of the velocity in the average-concentration models is introduced by model parameters, which must be obtained experimentally. Methods: The new convection-diffusion and average-concentration models are obtained in the cases of different processes in column apparatuses: simple and complicated chemical reactions, physical and chemical absorption, physical and chemical adsorption, heterogeneous catalytic processes (physical and chemical adsorption mechanism). These models are presented in the monograph Chr. Boyadjiev, M. Doichinova, B. Boyadjiev, P. Popova-Krumova, “Modeling of Column Apparatus Processes” (Second edition), Springer- Verlag, Berlin Heidelberg, 2018. Results: Two hydrodynamic situations are considered, when the radial velocity component is equal to zero, in the cases of an axial modification of the radial non-uniformity of the axial velocity component and when the radial velocity component is not equal to zero. Conclusion: The use of experimental data, for the average concentrations at the column end, for a concrete process and column, permits to obtain the model parameters, related with the radial non-uniformity of the velocity. These parameter values permit to use the averageconcentration models for modeling of different processes.