Volume 19, Issue 8 - Special Issue: Dedicated to the International Conference “Advances in Chemical Engineering-2020 (AdChE-2020)” UPES, Dehradun, India; Guest Editors: Santosh K. Gupta and Ajay K. Ray

Cerium oxide (ceria) contains two stable states of cerium ions (Ce 3+ and Ce 4+ ). The presence of these two states and the ability to swap from one state to another (Ce 3+ ↔ Ce 4+ ) by scavenging the highly reactive oxygen species (ROS) generated from radiolysis of water, ensure the enhanced stability of polysulfone (Psf) membranes in the γ-radiation environment. In this study, the ROS scavenging ability of ceria was studied. Ceria nanoparticles were found to scavenge ROS like hydroxyl radicals and hydrogen peroxide (H 2 O 2 ). The H 2 O 2 scavenging is due to the peroxidase-like catalytic activity of ceria nanoparticles. The ROS scavenging is responsible for offering protection to the Psf host matrix and in turn the stability to the Psf-ceria mixed-matrix membranes (MMMs) in γ-radiation environment. Thus, presence of ceria nanoparticles provides an opportunity for utilizing Psf-ceria MMMs in ionizing radiation environment with increased life span, without compromise in the performance.

The magnetohydrodynamic nanofluid flow comprised of dust particles is carried out in the current investigation. The role of dust nanoparticles on the flow characteristics is vital. The radiative heat phenomena for the interaction of Cu nanoparticle are deliberated in this discussion. However, both water and oil (kerosene) are treated as conventional fluids. Regarding the current applications on nanofluid in industries for the production of several materials, it is important to use the nanoparticles as a coolant. In recent applications, for the CPU cooler Cu-nanoparticle is used because of its high thermal conductivity and as a good conductor of heat. The governing flow characteristics involved with nonlinear properties of partial differential equations are transformed into ordinary differential equations using suitable similarity variables. Further, numerical treatment is imposed using the in-build Matlab code bvp5c. The imitation is carried out for the various profiles using physical parameters and presented graphically. The numerical values for the rate coefficients are presented via tables and deliberated briefly.

Thermal degradations of biomass corn leaves were studied for kinetic modeling. Thermogravimetric-differential analyzer runs at 5, 10, 20, and 30 °C min −1 heating rates were employed. Apparent activation energy and frequency factor values were calculated for first-order kinetics using several procedures. The procedure of Coats and Redfern showed 28.89 to 31.78 kJ mol −1 apparent activation energy and 15.5 to 157.12 min −1 frequency factor, respectively. Calculation of the apparent activation energy and frequency factor using Kissinger–Akahira–Sunose procedure gave 229.9–364.2 kJ/mol and 8.567 × 10 23 and 1.13 × 10 31 (min −1 ), respectively as the conversion increased from 0.1 to 0.9. The newly introduced excel solver procedure indicates a distribution activation energy over the entire range of conversion. For first-order reaction kinetics, the calculated apparent activation energy magnitudes ranged between 5.0 kJ mol −1 with frequency factor equals to 0.239 and 196.2 kJ mol −1 with frequency factor 2.89 × 10 12 in the studied range. The low or high magnitudes of the calculated activation energy are not associated with a particular value of the conversion. The calculated apparent activation energies are related to the direct solution of the simultaneous equations that constitute the basis of the excel solver.

The grape juice production generates an industrial wastewater that has a high concentration of organic matter and several polyphenols, such as ethanol. Therefore, the discharge of this wastewater can produce environmental problems. The aim of this work was to determine the optimal concentration of the reagents involved in a solar photo-Fenton process in the treatment of wastewater coming from juice. The process was analysed in a factorial design, as a function of H 2 O 2 (900, 1000, 1100 mg/L) and Fe 2+ (90, 100, 110 mg/L) concentration. The grape juice wastewater presents high organic content (20,500 mg/L COD and 5.4 mg/L polyphenols). Also, the presence of alcohols such ethanol, ethyl acetate and 2-metil-1-propanol was confirmed. The results showed that highest COD (>27%) and polyphenols removal (>36%) were obtained in experiments with 1100 mg H 2 O 2 /L and 100 mg Fe 2+ /L. In treatments with higher COD removal, 2-metil-1-propanol was detected as an intermediate of ethanol oxidation. These results proved that solar photo-Fenton is a suitable approach for treating the refractory organic matter from grape juice.

An intermittent supply of energy from renewable or unconventional resources has resulted in the use of phase change materials (PCM) in thermal energy storage (TES) systems. In this work, melting and heat transfer characteristics in a rectangular enclosure of different aspect ratios (width to height) filled with a phase change material (PCM) have been studied numerically. The n -octadecane has been selected as the PCM (melting temp = 301.35 K, Prandtl number ∼ 60). We considered five different aspect ratios (AR) of the enclosure to delineate the effects of 9-fold variation in the aspect ratio. The simulations were carried out using ANSYS Fluent 19.2. In particular, extensive results have been presented and discussed in terms of the temperature contours, rate of melting and energy storage, and total time required to reach the fully melt condition. Additionally, the effect of the mushy zone parameter ( A mush ) on the melting performance has also been investigated. Low values of the A mush were seen to predict the higher rate of melting. At a fixed value of A mush , ∼ 3 times faster melting rate was observed as the value of AR was reduced from 3 to 1/3. Finally, it can be concluded that melting and energy storage rate largely depends on the aspect ratio of the enclosure and the optimal choice of the value of the A mush .

Simulation studies of n-heptane/toluene system were performed using Aspen Plus. The comparative study of different entrainers: N-Methyl-2-Pyrrolidone (NMP), Phenol, and Sulfolane for separation of this system was done. Sensitivity analysis was carried out to optimize flowsheets. The criteria to determine the appropriate solvent for the said system included, the total cost calculated by the Aspen Process Economic Analyzer, amount of the solvent consumed, cost of the solvent, and purity obtained during the separation process. For the given system, sulfolane was found to be the appropriate solvent.

Heterogeneous photocatalysis refers to the series of oxidation and reduction reactions on a semiconductor surface by the electrons and holes generated by absorption of light by the catalyst. This method is widely used for the degradation of dyes and their mixtures present in the textile effluent, and involves two main aspects, viz. a photocatalyst, and a photoreactor. TiO 2 nanoparticles are well explored and among the best known photocatalysts used worldwide. Annular slurry bubble-column reactor is a commonly used photoreactor for dye(s) degradation. This research paper explores the effects of different parameters like air-flow rate, photocatalyst loading, and initial dye concentration on the dye degradation in an annular slurry bubble-column photoreactor. The results showed that the best dye degradation efficiencies were reported at an aeration rate of 1.7 × 10 −4  m 3 /s and at a catalyst loading of 1.5 kg/m 3 . Higher the initial concentration of dye, the greater is the time taken for complete degradation and mineralization. A kinetic-invariant method, which is based on the dimensionless representation of existing data to predict the new experimental results, is used to develop a semi-empirical reactor performance equation. It can be used to predict the concentration of dye undergoing degradation in the photocatalytic reactor at any time without a need for further experimentation.

The turmeric rhizome ( Curcuma longa ) contains curcuminoids embedded in the starch matrix. It is thus important to target starch hydrolysis to enhance extraction of curcuminoids. In the case of starch hydrolysis, α-amylase is more efficient when the starch is in a gelatinised form than when it is in its natural form. The present work includes hydrolysis of turmeric starch in its natural and gelatinised forms using α-amylase in hydrotrope solution (HS) and sc CO 2 . The optimum rate of starch hydrolysis was obtained using 200 IU cm −3 of α-amylase, at reaction conditions of 6.5 pH at 328 K when 10% w/w of turmeric powder was stirred at 900 rpm in HSs. The hydrolysis in 15 MPa sc CO 2 at room temperature required a phase modifier and 40 min of residence time (RT). The enzyme treatment of turmeric powder in HSs increased the filtration rate for curcuminoid extraction (gelatinised and native) compared to untreated turmeric powder.

The supercritical antisolvent (SAS) recrystallization process is one of the most promising recrystallization techniques for the particle formation of pharmaceutical compounds. In this process, a solution of active pharmaceutical ingredient (API) is sprayed into the supercritical carbon dioxide (SC CO 2 ) environment. The mass transport of both the solvent and the antisolvent results in supersaturation followed by the crystallization of the API. In this work, a model is developed to estimate the supersaturation profile of solute in a droplet falling in the SC CO 2 environment. The droplet consists of paracetamol as a solute and ethanol as a solvent. It moves down in the antisolvent (supercritical CO 2 ) environment. Interestingly, the present model predicts a rise in supersaturation followed by a fall for a while and then a sharp increase. The competing phenomena of nucleation and growth mechanisms are used to justify this variation in the supersaturation.