Department of Chemical Engineering

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IIT Jodhpur

World University root node

Stability and Destabilization of Water-in-Crude Oil Emulsion

Polysulfone (Psf) is the most commonly used polymer for the ultrafiltration membrane applications. Though it is regarded as high-performance engineering thermoplastic, it has γ-radiation stability only up to 100 kGy. When exposed to γ-radiation, the polymeric chains undergo scission and cross-linking, leading to a change in the cross-linking density and degradation in membrane performance. For the first time, carboxylated nanodiamonds (CND) are incorporated into Psf matrix in order to enhance the radiation resistant property of the membranes. Psf-CND composite membranes were fabricated with different loadings of CND (0.1–1 wt%) and exposed to different doses of γ-radiation up to 1000 kGy. The nanomaterials and (un) irradiated membranes were characterised using different instrumental techniques like FESEM, TEM, XPS, DSA, UTM, and DSC. It is claimed that CND helps in homogeneous dispersion of nanoparticles in the membrane matrix while protecting it from the radiation environment by scavenging of radiolysed products of water. The membrane with an optimum loading of 0.5% CND was found to be stable up to 1000 kGy of radiation dose which is 10 times as compared to that of control Psf membrane. The present study has significantly opened up opportunities for enhancing the deployment of polymeric membranes in radioactive effluent treatment. © 2019 Elsevier B.V.

Applied Surface Science

Enhancing γ-radiation resistant property of polysulfone membranes with carboxylated nanodiamond: Impact and effect of surface tunability

Tanker-based distribution systems have been prevalent in developing countries to supply clean and pure water in different regions. To efficiently operate such tanker service systems, a large fleet of tanker trucks are required to transport water among several water sources, water treatment plants and consumers spanning across the regions. This requires tighter coordination between water suppliers, treatment plant operations, and user groups to use available water resources in a sustainable manner, along with the assurance of water quality and timely delivery. This paper proposes a novel formulation to assist decision-making for optimizing tanker-based water distribution systems and treatment operations, with an overall objective of minimizing the total operating cost such that all of the constraints related to the water demand, supply operations, and environmental and social aspects are honored while supplying water to a maximum number of users. The problem is formulated and solved as a mixed integer linear programming (MILP) optimization framework and captures all of the nuances related to (i) water availability limitations and quality constraints from different sources, (ii) maintaining water quality as it transports via tankers, (iii) water demands for various end-use purposes, and (iv) transportation across a water supply chain. The proposed novel framework is applied to a realistic urban model to find the optimal tanker delivery schedule, ensuring appropriate treatment and timely delivery of water. The results of the case study conducted on a representative-scale problem also elucidate several aspects of treatment plant operation and consumer demand fulfillment for the efficient planning and management of tanker-based water distribution systems. © 2020 American Chemical Society.

Industrial and Engineering Chemistry Research

A Short-Term Planning Framework for the Operation of Tanker-Based Water Distribution Systems in Urban Areas

A fundamental challenge in emulating kidney tissue formation through directed differentiation of human pluripotent stem cells is that kidney development is iterative, and to reproduce the asynchronous mix of differentiation states found in the fetal kidney we combined cells differentiated at different times in the same organoid. Asynchronous mixing promoted nephrogenesis, and heterochronic organoids were well vascularized when engrafted under the kidney capsule. Micro-CT and injection of a circulating vascular marker demonstrated that engrafted kidney tissue was connected to the systemic circulation by 2 weeks after engraftment. Proximal tubule glucose uptake was confirmed, but despite these promising measures of graft function, overgrowth of stromal cells prevented long-term study. We propose that this is a technical feature of the engraftment procedure rather than a specific shortcoming of the directed differentiation because kidney organoids derived from primary cells and whole embryonic kidneys develop similar stromal overgrowth when engrafted under the kidney capsule. © 2020, The Author(s).

Fulltext

Communications Biology

Asynchronous mixing of kidney progenitor cells potentiates nephrogenesis in organoids

Drop-interface interaction under an electric field is relevant in commercial desalters wherein water droplets suspended in oil coalesce under an electric field, move down under gravity, and eventually coalesce with the water pool at the bottom of the desalter. In this work, we report our observation that the transition from coalescence to partial coalescence can be described by a critical electrocapillary number and is independent of the Ohnesorge number. On the other hand, the partial coalescence to noncoalescence transition depends upon both the electrocapillary number and the Ohnesorge number. The bridge during partial coalescence exhibits an electrocapillary-number-independent growth and collapse dynamics, although the transition time for growth to collapse depends upon the electrocapillary number (CaE). Lastly, contrary to previous studies, our results indicate that the secondary droplet size varies as CaE3/2 unlike the CaE1/2 reported in the literature. Copyright © 2020 American Chemical Society.

Langmuir

Coalescence, Partial Coalescence, and Noncoalescence of an Aqueous Drop at an Oil-Water Interface under an Electric Field

Atomistic molecular dynamics (MD) simulations are performed in order to understand the adsorption behavior of UO2 2+ ions from an aqueous medium. The dibenzo crown ether (DBCE) and dicyclo hexano crown ether (DCHCE) grafted on the polystyrene surface is used as the adsorbent. We investigated the role of grafting density ρs (mol/nm2) of DBCE and DCHCE on the adsorption behavior with increasing UO2 2+ ion concentration Cs (M). The amount of adsorption (qe) (mg/g) increases with an increase in UO2 2+ salt concentration and follows the Langmuir adsorption isotherm model. The maximum amount of adsorption (qmax) (mg/g) increases with increasing grafting density for both DBCE and DCHCE. The DCHCE shows higher qmax values compared to DBCE over the entire range of ρs: 0.25 mol/nm2 &lt; ρs &lt; 2.07 mol/nm2. Overall, qmax show a 5-fold increase for DBCE and DCHCE with an increase in ρs from 0.25 mol/nm2 to 2.07 mol/nm2. The optimum ρs for the maximum adsorption is found to be 1.25 mol/nm2 for both DBCE and DCHCE. The dynamical behavior of the adsorbed UO2 2+ is also investigated by calculating the self-diffusion coefficient (D) and mean residence time (τ). The D value decreases by ∼47% for DBCE and ∼61% for DCHCE, for the entire range of ρs, with an increase in Cs. Similarly, the τ value shows more than a 5-fold increase irrespective of grafting densities for both DBCE and DCHCE with increasing Cs. In the end, we investigate the UO2 2+ binding structure with DBCE and DCHCE. The potential of mean force (PMF) analysis shows a favorable free-energy for the binding of UO2 2+ to DCHCE compared to DBCE. © 2019 American Chemical Society.

Journal of Chemical and Engineering Data

Molecular Dynamics Study on the Adsorption of UO2 2+ from an Aqueous Phase: Effect of Grafting Dibenzo Crown Ether and Dicyclohexano Crown Ether on the Polystyrene Surface

Fused filament fabrication (FFF) is an extrusion-based 3D printing technique for thermoplastic polymers. In this technique, molten polymer is extruded through a print nozzle and is laid down layer by layer to build up the printed object. Currently, FFF is used primarily to print amorphous or low-crystallinity polymers, such as acrylonitrile butadiene styrene copolymer (ABS) or polylactic acid (PLA). Printing of semicrystalline polymers, such as polyethylene or polypropylene remains particularly challenging. During FFF of semicrystalline polymers, large thermomechanical stresses are generated when the polymer solidifies on cooling. These stresses result in warpage of the printed part. Here, we analyse the factors that influence stresses generated during FFF 3D printing of a commercial semicrystalline polymer, isotactic polypropylene. We investigate the effect of height of the printed object on part warpage, as well the effect of infilling during printing. We demonstrate that the stresses generated during FFF can be substantially decreased by incorporation of a ‘brim’, viz. a thin layer at the base of the printed object, and by adhering the brim to the print substrate using common polyvinyl acetate-based glue. We systematically investigate the effect of the brim size on the warpage of the printed object. We support our experimental findings with finite element method (FEM) simulations that explain the mechanism of stress buildup during printing. The trend in stresses calculated in the FEM simulations parallel the warpage measured in the experiments. Thus, this work represents an important methodological advance towards warpage-free FFF printing of semicrystalline polymers. © 2020, Indian Academy of Sciences.

Bulletin of Materials Science

3D printing of semicrystalline polypropylene: towards eliminating warpage of printed objects

Several industrially important liquid phase reactions which involve acetaldehyde as the main reactant are practised in the presence of acidic catalyst. However, under these conditions, acetaldehyde also undergoes oligomerization via self-aldol condensation reactions to form multiple side products thereby reducing the selectivity of the desired product. In this work, we investigate the detailed kinetics of oligomerization over a commonly used commercial cation exchange resin, Amberlyst-15 as catalyst. It is found that, crotonaldehyde and subsequent heavy aldols are formed in the reaction. Molecular weight distribution of the oligomers formed during the reaction is verified with Flory's statistical method. Kinetic studies are performed in an autoclave over a temperature range of 343−363 K. The effect of different parameters such as temperature, concentration, catalyst loading, and catalyst reusability is examined. A kinetic model based on Langmuir-Hinshelwood-Hougen-Watson (LHHW) rate expression is proposed to explain acetaldehyde oligomerization in the presence of acidic resin. © 2020

Applied Catalysis A: General

Kinetic study for oligomerization of acetaldehyde over cation exchange resin

This work contributes to the estimation of new and complementary density data for carbon dioxide (CO2) confined in carbon slit pores at different conditions. Grand canonical Monte Carlo (GCMC) simulations were employed to predict the CO2 adsorption capacities in carbon slit pores of height 20, 31.6, 63.2, 94.85 and 126.5 Å at 673.15 and 873.15 K over a pressure range of 500–4000 kPa, which corresponds to steam reforming of methane process. The bulk densities of CO2 at these temperature and pressure conditions have been estimated via isothermal–isobaric ensemble MC simulations using the Elementary Physical Model. The predicted density shows an excellent agreement with the experimental data. The adsorption capacities of CO2 in all the aforementioned pores at 673.15 and 873.15 K over the pressure range of 500–4000 kPa have also been estimated in the presence of wall–fluid interactions, in addition to the fluid–fluid interactions. The study on the thermodynamic phase behaviour of confined CO2 in the presence of wall–fluid interactions showed the existence of vapour–liquid equilibria at high temperature and pressure conditions. © 2020, Indian Academy of Sciences.

Molecular simulation study of CO2 adsorption in carbon slit pores at high temperature and pressure conditions

Release of lead (Pb) in drinking water from lead service lines has been extensively studied in single pipes, and the importance of water chemistry has been reported. However, the impact of variations in water chemistry parameters during water supply from the treatment plant to the downstream distribution network is crucial to understand toward minimizing lead release rates and has not yet been researched. This study proposes a comprehensive framework for investigating the changes in dissolved lead concentrations resulting from variations in the concentration of water chemistry parameters (such as pH, orthophosphate, free chlorine disinfectant residual, dissolved inorganic carbon and natural organic matter). The framework accounts for changes in the chemistry as water flows in a typical, full-scale water distribution network from the treatment plant to the homes through iron distribution mains and lead service lines under dynamic hydraulic conditions. The approach comprises the development of a multispecies reactive transport model for simulating important water chemistry reactions in distribution mains using EPANET-MSX. This water chemistry model is coupled in the framework with a mass transfer-based model for lead release from service lines. The resulting trends of water chemistry parameters variations with water age are qualitatively verified with general trends from experimental and field studies. The influence of complex water chemistry on the spatial and temporal profile of lead levels are analyzed by generating holistic simulations for a full-scale water distribution network case study. Three relevant treatment scenarios of pH adjustment, disinfectant dosage, and orthophosphate addition are presented to reflect the importance of the causal relationship between water chemistry variations in distribution mains and dissolved lead release from service lines. A strong correlation is observed between % change in dissolved lead levels and variations in pH, free chlorine residual, and orthophosphate residual in distribution mains. Further, practical implications for the use of the proposed framework to identify lead release hotspots, suggest potential sampling locations, and optimize remedial treatment measures to control lead dissolution for safe water supply are discussed. © 2020 American Society of Civil Engineers.