Department of Chemical Engineering
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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 Review: Hydrogen adsorption and storage through a spillover mechanism in palladium-integrated metal organic frameworks(Springer, 2025-10) Kuncharam, Bhanu Vardhan Reddy; Gupta, SureshHydrogen spillover, a mechanism involving the disassociation of molecular hydrogen on a metal catalyst and subsequent diffusion of atomic hydrogen to a support material, provides an effective approach for enhancing hydrogen adsorption and storage at ambient conditions. Among porous materials, metal organic frameworks (MOFs) stand out because of their large surface area, tunable porosity, and structural versatility. This review presents a comprehensive examination of hydrogen storage via the spillover mechanism in palladium integrated MOFs. These adsorbents demonstrate synergistic interactions between metal sites and MOF, contributing to improved hydrogen chemisorption and physisorption through spillover. Particular emphasis is placed on various Pd incorporation techniques, the influence of synthesis methods on spillover efficiency, and the physicochemical factors governing hydrogen uptake. The extent of hydrogen uptake depends strongly on the Pd loading, nanoparticle size, and the nature of the MOF support. Overloading of Pd often results in particle agglomeration, reducing the active surface area and thereby diminishing storage performance. Despite these advancements, challenges remain, particularly in achieving reproducible synthesis, optimizing Pd dispersion, and understanding the kinetics of spillover. The review highlights recent progress and critical challenges in developing Pd@MOF systems for practical hydrogen storage applications.Item Metal–organic framework (MOF) as adsorbents for hydrogen separation from steam methane reforming: an in-depth review(Springer, 2025-10) Kuncharam, Bhanu Vardhan Reddy; Gupta, SureshHydrogen (H2), acknowledged as a clean and advanced fuel, has attracted research focus for its production, purification, and energy generation in accordance with the Sustainable Development Goal (UN-SDG 7). H2 is produced by both fossil fuel (such as reforming, pyrolysis, gasification) and non-fossil fuel–based technologies (such as water electrolysis). Currently, fossil fuel–based hydrogen production predominates in meeting the current demands. However, hydrogen obtained through these methods is impure and requires purification before application. Metal–organic frameworks (MOFs) are emerging novel adsorbent materials that surpass conventional adsorbents owing to their favorable physicochemical characteristics and adaptability. This review elucidates the influences and correlations between MOF adsorbents and the performance of the pressure swing adsorption (PSA) process in the separation of H2 from steam methane reforming (SMR) off-gas. The PSA performance is dictated by the adsorbent’s properties and the operational parameters. The gas separation on MOF adsorbents occurs through equilibrium, kinetic, or size exclusion mechanisms. The H2 separation is largely governed by the van-der Waals interaction of various components of SMR off-gas with the MOF, and the gases interact in the order CO2 ≫ CH4 > CO > N2 > H2. It is noted that the MOF–gas interaction can be tuned by functioning MOFs with polar (e.g., -OH, NO2, SO3H) and non-polar functional groups (e.g., ester and alkanes). The operational parameters influence PSA performance indicators, and a general trend is seen among them. This review presents the critical analysis, summary, challenges, and outlook of the MOF-based PSA hydrogen separation, providing notable examples of MOFs reported.Item High-throughput computational screening of metal organic frameworks (MOFs) for CO2 selective separations: trends, challenges, and future perspectives(Elsevier, 2026-01) Kuncharam, Bhanu Vardhan Reddy; Gupta, SureshEfficient separation of CO2 from industrial gas mixtures such as CO2/N2, CO2/CH4, CO2/H2, and CH4/H2 is central to carbon capture, clean fuel production, and hydrogen purification. While metal organic frameworks (MOFs) offer an unparalleled design space for addressing these separations, the vast chemical and structural diversity of MOFs renders experimental evaluation impractical. High-throughput computational screening (HTCS), enabled by molecular simulations, has therefore emerged as a powerful approach to systematically evaluate and rank MOFs across multiple separation targets. This review critically examines HTCS methodologies for both adsorption and membrane-based separations, with a unified analysis of four industrially important gas systems. Further, emerging structure-property relationships to extract general design principles for CO2-selective separations are also highlighted. The review emphasizes that the choice of appropriate simulation inputs such as modelling the framework, force field and charge assignment significantly influence the screening and ranking of MOFs. CO2 typically exhibits strong electrostatic interactions with MOF surfaces, resulting in higher adsorption affinity compared to other gases, whereas the smaller and lighter H2 molecule displays rapid diffusivity. In kinetic separation, mixture diffusivity data is crucial in determining membrane performance. There exists a correlation between MOF structural features and their separation performance. In general, MOFs with narrow pores (3-5 Å) and moderate porosities (0.5-.75) perform better for CO2 separation. This review details the approaches adopted in HTCS of MOFs and the screening outcomes to guide future HTCS-driven MOF discovery.Item Unraveling the kinetics, mass transfer, and multi-omics for environmentally sustainable CO2 bio-mitigation using Bacillus cereus for bioenergy feedstock production(Elsevier, 2025) Gupta, Suresh; Raghuvanshi, SmitaThis research provides a cost-competitive solution to the conflict between ever-increasing energy demand and hazardous carbon dioxide (CO2) emissions reduction from the industries. The paper outlines the use of chemolithotrophic bacteria (B. cereus SSLMC2) for the bio-mitigation of 10, 15, 20, and 25 % CO2 conducted using a 20 L bubble column bioreactor. For 10, 15, 20, and 25 % CO2 (g), the maximum biomass productivity achieved was 0.042, 0.035, 0.032, and 0.051 g L−1 h−1, respectively. The highest percentages of CO2 (g) removal achieved were 91.68, 86.83, 84.86, and 93.43 %, respectively. The effect of parameters on biomass growth and total carbon (C) assimilation was investigated to determine the correlation between the mitigation of CO2 (g) and the growth of B. cereus SSLMC2. The gas chromatography-mass spectrometry (GC-MS) examination of biomass confirmed the formation of potential products during the bio-mitigation process. The nuclear magnetic resonance (NMR) metabolomics technique identified up to 25 metabolites associated with probable bio-mitigating CO2 (g) pathways. Kinetic models such as Monod, Haldane, Powell, Webb, and Luong provided a mathematical depiction of bacterial growth dynamics. Additionally, the mass and heat transfer characteristics crucial to the bio-mitigation process were determined. By demonstrating high CO2 removal efficiencies and the production of valuable by-products, this research highlights the potential of integrating bio-based technologies into existing industrial processes.Item Spillover technique for enhancement of hydrogen adsorption capacity of metal organic frameworks(Taylor & Francis, 2025-04) Kuncharam, Bhanu Vardhan Reddy; Gupta, SureshThis review presents an overview of the hydrogen spillover process, a viable approach to enhance H2 adsorption capabilities of metal-organic frameworks (MOFs). Three primary strategies can increase the effectiveness of spillover namely, physical mixing, carbon bridge building, and doping. Spillover by physically mixing supported noble-metal catalyst and MOF increases the proximity between the catalyst and MOF, facilitating an effective diffusion of disassociated H atoms. However, physical mixing leads to partial destruction of the MOF structure. Spillover by carbon bridge building on the other hand, ensures intimate contact between the catalyst and MOF leading to enhanced H2 adsorption. Doping is another technique to optimize spillover by efficient dispersion of metal nanoparticles. Besides dispersion, the size of nanoparticles also plays a crucial role in spillover by doping. MOFs doped with small sized and well dispersed nanoparticles are ideal candidates for an effective spillover process. The future of spillover depends on enhancing bridge building techniques, creating smaller catalysts, and improving their dispersion on the MOF surface. A thorough study of spillover technique is critically analyzed and frameworks for further improvements are provided.Item Sustainable approach for simultaneously reducing CO2 and NO emissions from synthetic industrial flue gases using bacterial consortium and domestic wastewater in a suspended glass bioreactor(Springer, 2023-02) Raghuvanshi, Smita; Gupta, SureshThe current study showed how a bacterial consortium (Bacillus tropicus SSLMC1 and Bacillus cereus SSLMC2) isolated from the harsh environment of Sambhar Salt Lake could simultaneously remove carbon dioxide (CO2) and nitric oxide (NO) while using domestic wastewater (DWW) as nutrients and an energy source. A 3-L suspended glass bioreactor was used for the lab tests to see how well the bacterial consortium would be able to fix CO2 and NO from three different gaseous mixtures (only CO2, only NO and a mixture of CO2 and NO). The simultaneous removal of CO2 and NO was shown to have the highest values of biokinetic parameters such as biomass productivity, specific growth rate, fixation efficiency, fixation rate, utilization efficiency and nutrient utilization efficiency. The starting and final amounts of nutrients and pollutants present in DWW were examined for checking the simultaneous removal of CO2 and NO. The presence of fatty acids, fatty alcohols and long-chain hydrocarbons found in cell lysate and cell-free supernatant was analysed using Fourier-transform infrared spectroscopy (FT-IR) and gas chromatography-mass spectroscopy (GC–MS). The potential mechanism for the bio fixation of CO2 and NO was presented based on the findings of the experimental work and the product analysis. The resulting biokinetic characteristics were compared to those from earlier studies and showed that using DWW as a nutrient and energy source would allow bacterial consortia to simultaneously biofix CO2 and NO.Item Optimization of bacterial biorefineries for sustainable biodiesel production and flue gas reduction: a holistic approach to climate change mitigation and circular economy(RSC, 2025) Raghuvanshi, Smita; Gupta, SureshThe primary obstacles to addressing the current climate change problem include a rise in worldwide energy consumption, a restricted availability of fossil fuels, and the escalating carbon emissions associated with fossil fuels. Consequently, there is a pressing need to investigate sustainable alternatives to fossil fuels. Biorefineries present a potentially viable avenue for the sustainable production of fuel, as they employ a range of technologies to convert biomass into biofuels. This research aims to examine the cultivation of bacterial biomass and biodiesel production using a biorefinery approach. This process achieves a removal efficiency of 96, 93, and 98% for CO2, SO2, and NO, respectively, and a bacterial biomass of 274 g cultivated in a 20 L integrated bioreactor. The biomass entails extracting lipids (58% w/w) to generate biodiesel (91% w/w). The metabolic pathway followed by bacteria to reduce flue gas and produce lipids was analyzed to improve the production of lipids and biodiesel. A life cycle assessment was performed to assess the environmental impacts during the process. Implementing alternative and safe chemicals can potentially mitigate the adverse effects of processes and GWP100. The techno-economic analysis aimed to systematically examine the capital investment required to set up a bacterial biorefinery as compared to conventional fuel refineries. The findings indicated that the bacterial biorefinery had a net present value of $193 per litre of biodiesel produced. A bacterial biorefinery holds promise in fostering a circular economy characterized by sustainable practices and systems that aim to minimize waste, optimize resource utilization, and encourage the reuse and recycling of materials.Item Industrial scale-up of flue gas bio-mitigation with chemolithotrophs in packed bed reactors: Exploring metabolite synthesis, mass transfer, and techno-economic analysis(Elsevier, 2025-03) Raghuvanshi, Smita; Gupta, SureshElevated emissions of flue gases deteriorate the quality of air, impacting both terrestrial and aquatic ecosystems through their contribution to acid rain and eutrophication. This study examines the bio-mitigation process in a packed bed reactor and its capacity to concurrently decrease the environmental consequences of industrial flue gases (CO2, NO, and SO2) and wastewater by employing mixed bacterial consortia. The highest biomass productivity achieved during the growth phase was 0.002 g L−1 h−1 in the aqueous medium and 0.006 g L−1 h−1 in the PU foam. The highest level of CO2 removal efficiency was 86.60%, while for NO and SO2, it was 77.03% and 82%, respectively. The comprehensive nutrient balance analysis revealed that the flue gas was primarily utilized for biomass assimilation. The FT-IR and GC-MS analysis detected metabolites, including carboxylic acids, esters, and fatty alcohols, that were produced during the process. The NMR study examined alterations in the concentration of metabolites within the cell, indicating metabolic pathways such as the TCA cycle, alanine, pyruvate, butanoate metabolism, and glycolysis. The mass transfer coefficient estimated for the gas-liquid-solid phase was ∼2.0 m s−1 for the flue gases. The scale-up of the reactor based on the mass transfer coefficient up to 20,000 L gives a net present value of $2,66,116.13 with a benefit-to-cost ratio of 1.47. Therefore, this study suggests that employing bacteria is a viable and energy-efficient approach to mitigate the adverse effects of flue gas on air quality. Additionally, it aids industries in minimizing waste and repurposing it for advantageous purposes, thereby diminishing their environmental footprint.Item Reforming CO2 bio-mitigation utilizing Bacillus cereus from hypersaline realms in pilot-scale bubble column bioreactor(Springer, 2024-03) Raghuvanshi, Smita; Gupta, SureshThe bubble column reactor of 10 and 20 L capacity was designed to bio-mitigate 10% CO2 (g) with 90% air utilizing thermophilic bacteria (Bacillus cereus SSLMC2). The maximum biomass yield during the growth phase was obtained as 9.14 and 10.78 g L−1 for 10 and 20 L capacity, respectively. The maximum removal efficiency for CO2 (g) was obtained as 56% and 85% for the 10 and 20 L reactors, respectively. The FT-IR and GC–MS examination of the extracellular and intracellular samples identified value-added products such as carboxylic acid, fatty alcohols, and hydrocarbons produced during the process. The total carbon balance for CO2 utilization in different forms confirmed that B. cereus SSLMC2 utilized 1646.54 g C in 10 L and 1587 g of C in 20 L reactor out of 1696.13 g of total carbon feed. The techno-economic assessment established that the capital investment required was $286.21 and $289.08 per reactor run of 11 days and $0.167 and $0.187 per gram of carbon treated for 10 and 20 L reactors, respectively. The possible mechanism pathways for bio-mitigating CO2 (g) by B. cereus SSLMC2 were also presented utilizing the energy reactions. Hence, the work presents the novelty of utilizing thermophilic bacteria and a bubble column bioreactor for CO2 (g) bio-mitigation.