Department of Chemical Engineering
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Item Separation of reactive dyes from textile effluent by hydrolyzed polyacrylonitrile hollow fiber ultrafiltration quantifying the transport of multicomponent species through charged membrane pores(Elsevier, 2020-03) Bhattacharjee, SaikatA hydrolyzed polyacrylonitrile (PAN) based ultrafiltration grade hollow fiber membrane using sodium hydroxide having high surface potential was developed in this work. Efficacy of this membrane was demonstrated in treatment of textile effluent. Scanning electron microscopy (SEM) clearly showed that hydrolysis of PAN fibers (HPAN) made them dense. Fourier transform infrared (FTIR) spectra clearly indicated the functional groups confirming the hydrolysis of PAN matrix. The molecular weight cut-off of the HPAN fibers was reduced to 5 kDa from 20 kDa of untreated PAN lowering the average pore radius from 3.6 to 1.8 nm. A decline in the water contact angle of HPAN to 54° from 78° indicated the formation of a more hydrophilic membrane. The surface zeta potential of the hollow fiber was lowered to −12 mV from −2 mV imparting the negative potential on the membrane promoting charge-charge interaction between membrane pore and charged species during filtration. The surface roughness of the membrane was reduced almost by one order of magnitude after hydrolysis indicating its antifouling characteristics. The transport of the dyes and the electrolyte through the membrane pores was analyzed using Donnan steric pore model (DSPM) for a multicomponent system applicable for low cut off ultrafiltration. Contribution of various transport mechanisms, i.e., diffusion, convection and electro-migration was quantified. Thus, the novelty of this work includes (i) development of low cut off ultrafiltration grade hollow fibers; (ii) their application in treatment of real life effluent containing four reactive dyes; (iii) development of multicomponent pore transport model using DSPM.Item Prediction of long term filtration by coupled gel layer and pore transport model for salt removal using mixed matrix hollow fiber ultrafiltration membrane(Elsevier, 2020-11) Bhattacharjee, SaikatCharacterization and performance of lanthanum cobalt oxide nanoparticle doped hollow fiber ultrafiltration membrane are reported in this paper. Nanoparticles (1 wt%) having zeta potential −30 mV at pH 7 imparted high surface charge (surface potential ~19 mV) to the hollow fibers. At this composition, the membrane became more hydrophilic with contact angle reduced to 520 from 570 corresponding to without nanoparticles. Permeability of hollow fiber with 1 wt% nanoparticles increased by 40% compared to that without nanoparticle. At this composition, the membrane molecular weight cut off was 4000 Da (with average pore diameter 34 nm) belonging to ultrafiltration range. Rejection of sodium chloride was 47% in 1000 mg/l synthetic solution at transmembrane pressure drop 69 kPa and cross flow rate 20 l/h. Performance of developed hollow fiber membrane was also tested using actual seawater with a rejection of 40% total dissolved solids at 138 kPa at 20 l/h with 15 l/m2h permeate flux. A combined gel polarization and pore flow model was used to quantify the long term flux decline and salt concentration in the permeate as function of time.Item Effects of finite ion size on transport of neutral solute across porous wall of a nanotube(Springer, 2020-07) Bhattacharjee, SaikatEffect of finite ion size on the transport of a neutral solute across the porous wall of a nanotube is presented in this study. Modified Poisson–Boltzmann equation without the Debye–Huckel approximation is used to determine the potential distribution within the tube. Power law fluid is selected for the study, as its rheology resembles closely to the real-life physiological fluids. The flow within the tube is actuated by the combined effects of pressure and electroosmotic forces. Steady-state solute balance equation is solved by the similarity technique in order to track the solute transport across the tube. The effects of ionic radius, ionic concentration, and flow behavioral index on the length-averaged Sherwood number, permeate flux, and permeate concentration are analyzed. This study will be extremely helpful in predicting the transport characteristics of a neutral solute in real physiological systems and also to fine-tune the performance of microfluidic devices having porous wall.Item Electro-kinetically enhanced mass transport of charged macro-solutes through a microchannel with porous walls(Wiley, 2022-08) Bhattacharjee, SaikatElectrokinetics of the solute transport across the porous walls of micro channel is important from its practical application but less explored. Transport of the charged macro-solutes across perm-selective walls in a microchannel is investigated. The extended Nernst–Planck equation describes the charged macro-solutes distribution in the mass transfer boundary layer over the porous wall. The transverse electromigration of the charged macro-solute either augments or suppresses the concentration polarization and the permeation rate depending on the wall and solute surface potential (attractive or repelling). The wall potential is screened due to the electrical double layer interaction of the wall and charged solute. It is observed that the charged solute concentration over the channel wall enhances by two times in case of oppositely charged interactions (unlike solute and channel wall) compared to like charges. The findings of this study can facilitate understanding of electrokinetic based drug delivery and separation systems involving charged solutes.Item The effect of an AC electric field on a colloidal particle near a permeable surface(Elsevier, 2024-09) Bhattacharjee, SaikatFouling of membranes during separation remains an operational drawback and, as such, has driven much research effort aimed at its mitigation. Some of the more recent approaches for fouling suppression include passive means, such as various surface modifications, as well as active means such as applying electric fields. However, use of an AC electric field has not received much attention, despite great potential shown in early studies. Notably, an AC electric field gives rise to a long-range force when applied to an electrolyte solution, due to differences in mobility and/or charge between the cation and the anion. In the present study, this mechanism is studied by solving the Poisson-Nernst-Planck equations numerically to obtain the time-averaged electric field and the resultant force acting on a charged foulant particle advected towards the membrane by permeation flow. The interplay between two oppositely acting forces (electric force and the permeation drag) gives rise to possible equilibrium positions of the particles, at a finite distance from the membrane, vs. cases where they are deposited. Mapping these equilibrium positions vs. the permeation velocity enables identification of a ‘critical’ flux, above which deposition occurs, and its dependence on system parameters. Notably, it is shown that there exists a ‘resonant’ frequency of the applied AC field, for which the critical flux is maximized with respect to the power input. The present study can provide potentially valuable guidelines for finetuning operational parameters for AC-based fouling mitigation in membrane filtration processes.Item Temperature guided foam stability, structure and texture of pulse nugget: exploring traditional food physics for aerated batter applications(Elsevier, 2025-05) Bhattacharjee, SaikatThis paper revamps the traditional knowledge of pulse nugget (PN) preparation by exploring the impact of moisture and temperature on batter aeration, rheology, spreadability and physicochemical properties (texture, and colour) of dried PN. Black gram (Vigna mungo) was soaked in water for 10 h, grounded into the batter at 960 rpm for 8 min, and subjected to various moisture content (60–70 %), temperature (10–70 °C), and whipping process to produce aerated-pulse-batter (APB). The APB was deposited as 3D conical model geometry using a manual deposition and sun-dried (14 h, 20 °C and RH of 60 %) to produce PN. APB's temperature-guided foaming and viscoelastic behavior explore key aspects of aerated foam dispensing, its spreadability, and the physicochemical properties of dried PN. The temperature inversely impacts APB's viscosity, admitting the Carreau model with a temperature-sensitive term. During PN molding, batter's spreadability increased with temperature and moisture content, showing high radial growth (Δr) and a decrease in calculated height (ht). The molded PNs with an optimal moisture content and temperature of 60 ± 2 % and 20 ± 2 °C demonstrated superior stability, air pocket visibility, and dried PN's texture and colour. Therefore, the batter's moisture content and temperature should be considered while developing a mechanized system for PN processing, such as 3D printing (3DP).Item Sustainable CO2 bio-mitigation: a life cycle perspective on chemolithotrophic conversion in bubble column bioreactors(RSC, 2025-09) Gupta, Suresh; Raghuvanshi, SmitaThe urgent need for low-carbon energy alternatives has intensified interest in sustainable biofuel production pathways. This study presents a comprehensive Life Cycle Assessment (LCA) of a chemolithotrophic bacterial platform for simultaneous CO2 mitigation and biodiesel production using Bacillus cereus SSLMC2 cultivated in 10 and 20 L bubble column bioreactors. Unlike phototrophic systems, this process leverages light-independent bacterial metabolism, offering year-round operation, high biomass yield, and compatibility with flue gas as a carbon source. Experimental data were integrated with LCA modeling using Umberto NXT Universal software and the ReCiPe 2016 and CML baseline methods to quantify environmental impacts across cultivation, biomass harvesting, lipid extraction, and transesterification stages. The results identify dewatering and homogenization as major environmental hotspots, contributing significantly to climate change, fossil depletion, and human toxicity categories. Endpoint analysis revealed human health and resource availability as the most impacted areas, primarily due to electricity use and chemical inputs. Cumulative energy demand assessments confirmed that scale-up from 10 to 20 L does not proportionally increase energy use, suggesting promising scalability. Recommendations include replacing centrifugation with membrane-based dewatering, solvent recovery systems, integration of renewable energy, and recycling of CO2 and water. This is the first LCA study to evaluate chemolithotrophic CO2 bio-mitigation coupled with biodiesel production at pilot scale using empirical data. The findings provide critical insights for optimizing microbial biorefineries and support the development of scalable, environmentally efficient carbon capture and utilization technologies.Item Bioprocess scale-up through experimental design and process simulation: a case study of succinic acid and 3-hydroxypropionic acid(AIChE, 2025) Raghuvanshi, SmitaThe bioprocess scale-up is at the center when developing an upstream process for mass production [1]. Process understanding at the laboratory scale can guide the scale-up rules [2-4]. These rules are broadly classified into maintaining (1) the same mixing time, (2) constant power supplied per unit volume (P/V), (3) constant overall mass transfer coefficient (kLa), and (4) impeller flow numbers [3,4]. Accordingly, different scale-up correlations have been derived and are functions of impeller Reynolds number (Re), impeller tip speed, power transfer per unit volume, and agitation rate [2-4]. At different scales, this correlation-based scale-up can produce comparable biomass [4 and 5]. Thus, in the process of SA mass-production via fermentation, different studies have attempted to scale up fermentative succinic acid (SA) production via yeast. In one study, from an engineered Yarrowia lipolytica PSA02004 via two-stage pH regulation between 5-6 in fed-batch mode a SA titer value of 42.2 g.L-1 with 0.38 g.g-1 yield and 0.84 g.L-1.h-1 productivity is obtained [6]. In the same study, the shake flask scale is translated to the lab-scale reactor at 6.7 L (Working volume: 3L) [7]. Another study in batch mode resulted in an SA titer of 18.4 g.L-1 with a yield of 0.23 g.g-1 at pH 3.0. However, in fed-batch mode, with seven-time feeding, a higher titer value of 76.8 g.L-1 is achieved. The study utilizes an in situ fibrous bed bioreactor (isFBB) of volume 2.5 L [8]. In other studies, via batch or fed-batch mode with multiple feeding mostly near pH 6, the SA values titer and yield in the range of 53.6 g.L-1-209.7 g.L-1 and 0.92 g.g-1 are reported, respectively [9, 10]. However, almost all these studies are limited either to shake flask or to the bioreactor total volume in the range of 1-10 L [6-10].Item A review on recent progress in polymer composites for effective electromagnetic interference shielding properties – structures, process, and sustainability approaches(RSC, 2024-09) Etika, Krishna ChaitanyaThe rapid proliferation and extensive use of electronic devices have resulted in a meteoric increase in electromagnetic interference (EMI), which causes electronic devices to malfunction. The quest for the best shielding material to overcome EMI is boundless. This pursuit has taken different directions, right from materials to structures to process, up to the concept of sustainable materials. The emergence of polymer composites has substituted metal and metal alloy-based EMI shielding materials due to their unique features such as light weight, excellent corrosion resistance, and superior electrical, dielectric, thermal, mechanical, and magnetic properties that are beneficial for suppressing the EMI. Therefore, polymer nanocomposites are an extensively explored EMI shielding materials strategy. This review focuses on recent research developments with a major emphasis on structural aspects and processing for enhancing the EMI shielding effectiveness of polymer nanocomposites with their underlying mechanisms and some glimpses of the sustainability approaches taken in this field.Item Hydrothermal synthesis of conductive copper nanowires: effect of oleylamine and dextrose concentrations(RSC, 2025-11) Etika, Krishna ChitanyaOne-dimensional (1-D) metallic nanoparticles (i.e., nanowires, nanorods) exhibit unique properties and are useful in a variety of applications. 1-D copper nanowires (CuNWs) exhibit excellent electrical conductivity making them an economical alternative in applications that typically employ silver or gold nanowires. In this study, CuNWs were synthesized via an environmentally benign and scalable hydrothermal synthesis method using CuCl2 (CuP) as a copper precursor. Oleylamine (OAm) and dextrose (D) were employed as capping and reducing agents, respectively. The focus of this work was to investigate the influence of varying CuP[thin space (1/6-em)]:[thin space (1/6-em)]OAm and CuP[thin space (1/6-em)]:[thin space (1/6-em)]D molar ratios during synthesis on the nanowire growth, morphology, and electrical conductivity. A series of synthesis trials were conducted by only varying CuP[thin space (1/6-em)]:[thin space (1/6-em)]OAm or CuP[thin space (1/6-em)]:[thin space (1/6-em)]D molar ratios, while keeping all other reaction conditions constant. Morphological analysis of the synthesized products suggests that both OAm and D are essential for the formation of CuNWs. A synthesis conducted at a 1[thin space (1/6-em)]:[thin space (1/6-em)]3.75[thin space (1/6-em)]:[thin space (1/6-em)]1.1 CuP[thin space (1/6-em)]:[thin space (1/6-em)]OAm[thin space (1/6-em)]:[thin space (1/6-em)]D molar ratio produced nanowires with average diameter of 96 nm, while higher OAm concentration resulted in CuNWs with larger diameters. X-ray diffraction analysis confirmed the crystalline nature of the synthesized CuNWs, with diffraction peaks corresponding well to those of FCC copper. The capping of CuNWs with OAm was confirmed through FTIR spectroscopy. Thermogravimetric (TGA) studies on CuNWs show that OAm content in CuNWs increases with increasing CuP[thin space (1/6-em)]:[thin space (1/6-em)]OAm molar ratio during synthesis. The electrical conductivity of CuNW pellets was found to decrease with increasing CuP[thin space (1/6-em)]:[thin space (1/6-em)]OAM molar ratio during synthesis. The highest conductivity of 1.38 × 105 S cm−1 was exhibited in the sample made using 1[thin space (1/6-em)]:[thin space (1/6-em)]3.75[thin space (1/6-em)]:[thin space (1/6-em)]1.1 CuP[thin space (1/6-em)]:[thin space (1/6-em)]OAm[thin space (1/6-em)]:[thin space (1/6-em)]D molar ratio. Furthermore, holding CuNWs pellets under ambient conditions for 60 days did not affect their electrical conductivity.