Prachi Varshney

Bio: Prachi Varshney is an academic researcher from Banaras Hindu University. The author has contributed to research in topics: Chlorella sorokiniana & Integrated gasification combined cycle. The author has an hindex of 3, co-authored 3 publications receiving 591 citations.

Isolation and biochemical characterisation of two thermophilic green algal species- Asterarcys quadricellulare and Chlorella sorokiniana, which are tolerant to high levels of carbon dioxide and nitric oxide

Abstract: Atmospheric levels of carbon dioxide (CO2) and nitric oxide (NO) have been on the rise ever since the beginning of industrialisation. A significant fraction of this increase can be attributed to the emissions from stationary sources such as thermal power plants and steel plants. While there has been an impetus in recent times towards sequestration of these greenhouse gases at source, current technologies are not commercially viable. In this context, microalgae-mediated CO2 capture and utilization has attracted attention, although several technological challenges remain to be addressed. Importantly, this process will require algal strains that grow fast and are tolerant to high light, temperature and flue gases. The majority of the reported algal strains fail in at least one of these requirements. On account of this, we have isolated two novel green algal strains, which have been identified as Asterarcys quadricellulare and Chlorella sorokiniana, from water bodies that are located in and around a steel plant in India. These are relatively fast-growing strains with specific growth rates of up to 0.06 h− 1 and 0.1 h− 1, respectively. Furthermore, these strains can tolerate high temperatures of up to 43 °C, high light intensity and high CO2 and NO levels. When exposed to high CO2 levels, 55–71% of the dry cell weight comprised of carbohydrates. Additionally, exposure to NO gas along with CO2 led to an enhanced lipid accumulation of 44%–46% of dry biomass. The high lipid content makes these strains valuable feedstock in biodiesel production, and the high carbohydrate content makes the lipid extracted biomass an attractive source of carbon for biochemical conversion to ethanol. We believe that these strains are promising and ready to be tested with real flue gases under outdoor conditions.

Effect of elevated carbon dioxide and nitric oxide on the physiological responses of two green algae, Asterarcys quadricellulare and Chlorella sorokiniana

Abstract: Algae have the potential to capture carbon dioxide (CO2) and nitric oxide (NO) from flue gases. However, the effects of high concentrations of these gases on the photophysiology of algae are poorly understood. To that end, we used the techniques of chlorophyll fluorescence to study the effect of industrially relevant levels of CO2 and NO on the photophysiology of two green microalgae, Asterarcys quadricellulare and Chlorella sorokiniana, that are tolerant to these gases. Measurements of maximum quantum yield (Fv/Fm) and maximum relative electron transport rate (rETRmax) show an enhanced performance of photosystem II (PSII) under high CO2 levels. In C. sorokiniana, high CO2 stimulated non-photochemical quenching (NPQ), while the opposite effect was observed in A. quadricellulare. Light-saturated photosynthetic rates (Pmax) of both species were highest at 10% CO2. Further, the tested levels of NO did not show adverse effect on the performance of PSII. OJIP chlorophyll fluorescence transients suggest that in C. sorokiniana, the energetic communication between PSII units declined at 15% CO2. However, in A. quadricellulare, this decline was visible even at 10% CO2 with complete inhibition of cell growth at 15% v/v. Overall, our results suggest that although photosynthesis was regulated differently in the two microalga, both species exhibited enhanced PSII performance under reasonably high levels of CO2 and NO. Thus, the two species are potential candidates for bio-fixation of CO2 and NO from flue gases.

Copper corrole immobilized onto reduced graphene oxide: An efficient electrocatalyst for hydrogen evolution reaction

Abstract: First-row transition metal complexes derived from corrole-based ligands are considered efficient catalysts for hydrogen evolution reaction (HER). They are known to enhance the rate of hydrogen production by lowering the energy barrier in the water-splitting process. Here, the synthesis and characterization of a copper corrole complex (CuN2CA) having amine functionality on corrole has been reported. This complex is immobilized onto reduced graphene oxide (CuN2CA-rGO) that exhibited excellent electrocatalytic activity towards hydrogen evolution reaction (HER) with a significantly lower onset potential of -0.57 V vs. NHE efficiency of the corrole complex has significantly been improved when combined with reduced graphene oxide (rGO).

Recent advances in solid sorbents for CO2 capture and new development trends

Abstract: Carbon dioxide (CO2) capture using solid sorbents has been recognized as a very promising technology that has attracted intense attention from both academic and industrial fields in the last decade. It is astonishing that around 2000 papers have been published from 2011 to 2014 alone, which is less than three years after our first review paper in this journal on solid CO2 sorbents was published. In this short period, much progress has been made and the major research focus has more or less changed. Therefore, we feel that it is necessary to give a timely update on solid CO2 capture materials, although we still have to keep some important literature results published in the past years so as to keep the good continuity. We believe this work will benefit researchers working in both academic and industrial areas. In this paper, we still organize the CO2 sorbents according to their working temperatures by classifying them as such: (1) low-temperature ( 400 °C). Since the sorption capacity, kinetics, recycling stability and cost are important parameters when evaluating a sorbent, these features will be carefully considered and discussed. In addition, due to the huge amounts of cost-effective CO2 sorbents demanded and the importance of waste resources, solid CO2 sorbents prepared from waste resources and their performance are reviewed. Finally, the techno-economic assessments of various CO2 sorbents and technologies in real applications are briefly discussed.

Formic acid as a hydrogen storage material – development of homogeneous catalysts for selective hydrogen release

Abstract: Formic acid (FA, HCO2H) receives considerable attention as a hydrogen storage material. In this respect, hydrogenation of CO2 to FA and dehydrogenation of FA are crucial reaction steps. In the past decade, for both reactions, several molecularly defined and nanostructured catalysts have been developed and intensively studied. From 2010 onwards, this review covers recent advancements in this area using homogeneous catalysts. In addition to the development of catalysts for H2 generation, reversible H2 storage including continuous H2 production from formic acid is highlighted. Special focus is put on recent progress in non-noble metal catalysts.

Ionic liquid-based materials: a platform to design engineered CO2 separation membranes

Abstract: During the past decade, significant advances in ionic liquid-based materials for the development of CO2 separation membranes have been accomplished. This review presents a perspective on different strategies that use ionic liquid-based materials as a unique tuneable platform to design task-specific advanced materials for CO2 separation membranes. Based on compilation and analysis of the data hitherto reported, we provide a judicious assessment of the CO2 separation efficiency of different membranes, and highlight breakthroughs and key challenges in this field. In particular, configurations such as supported ionic liquid membranes, polymer/ionic liquid composite membranes, gelled ionic liquid membranes and poly(ionic liquid)-based membranes are detailed, discussed and evaluated in terms of their efficiency, which is attributed to their chemical and structural features. Finally, an integrated perspective on technology, economy and sustainability is provided.