Ram B. Gupta

Advancements in Crude Oil Spill Remediation Research After the Deepwater Horizon Oil Spill

An estimated 4.9 million barrels of crude oil and natural gases was released into the Gulf of Mexico during the Deepwater Horizon oil spill of 2010. The Deepwater Horizon oil spill affected the aquatic species in the Gulf of Mexico, vegetation, and the human population along the coast. To reduce the effect of the spilled oil on the environment, different remediation strategies such as chemical dispersant, and mechanical booms and skimmers were utilized. Over 2.1 million gallons of dispersants was applied to minimize the impact of the spilled oil. However, environmental and human toxicity issues arose due to the perceived toxicity of the dispersant formulations applied. After the Deepwater Horizon oil spill, various studies have been conducted to find alternative and environmentally benign oil spill response strategies. The focus of this manuscript is to demonstrate an objective and an overall picture of current research work on oil spill response methods with emphasis on dispersant and oil sorbent applications. Current trends in oil spill sorbent and dispersant formulation research are presented. Furthermore, strategies to formulate environmentally benign dispersants, as well as the possible use of photoremediation, are highlighted.

Hierarchical nitrogen-doped porous carbon derived from lecithin for high-performance supercapacitors

The development of renewable carbon sources for sustainable energy storage applications is of significance importance. Herein, we report the synthesis of three-dimensional N-doped carbons derived from lecithin via a simple route. Hierarchical porous carbons with high surface area (up to 1803 m2 g−1) and nitrogen-doping level (up to 9.2 wt%) were successfully prepared by hydrothermal carbonization and a subsequent thermal annealing. The electrochemical performance of the carbon electrodes was examined with both two and three-electrode cell configurations in 1 M KOH and 1 M H2SO4 electrolytes. The as-prepared NC-800 electrode features a large specific capacitance (285 F g−1 at 0.5 A g−1), high-rate capacitive behavior, and long-term cycling stability (8% loss after 20 000 cycles). Furthermore, NC-800 exhibits an energy density of 24.7 W h kg−1 at a power density of 500 W kg−1 in 1 M H2SO4. The excellent electrochemical performance of N-doped carbons is attributed to the unique hierarchical porous frameworks along with pseudocapacitive effect. This work opens up a new approach for preparation of hierarchical N-doped porous carbon materials with tailored properties for supercapacitor applications.

Interfacial adsorption and surfactant release characteristics of magnetically functionalized halloysite nanotubes for responsive emulsions

Magnetically responsive oil-in-water emulsions are effectively stabilized by a halloysite nanotube supported superparamagnetic iron oxide nanoparticle system. The attachment of the magnetically functionalized halloysite nanotubes at the oil-water interface imparts magnetic responsiveness to the emulsion and provides a steric barrier to droplet coalescence leading to emulsions that are stabilized for extended periods. Interfacial structure characterization by cryogenic scanning electron microscopy reveals that the nanotubes attach at the oil-water interface in a side on-orientation. The tubular structure of the nanotubes is exploited for the encapsulation and release of surfactant species that are typical of oil spill dispersants such as dioctyl sulfosuccinate sodium salt and polyoxyethylene (20) sorbitan monooleate. The magnetically responsive halloysite nanotubes anchor to the oil-water interface stabilizing the interface and releasing the surfactants resulting in reduction in the oil-water interfacial tension. The synergistic adsorption of the nanotubes and the released surfactants at the oil-water interface results in oil emulsification into very small droplets (less than 20μm). The synergy of the unique nanotubular morphology and interfacial activity of halloysite with the magnetic properties of iron oxide nanoparticles has potential applications in oil spill dispersion, magnetic mobilization and detection using magnetic fields.

Rapid transformation of heterocyclic building blocks into nanoporous carbons for high-performance supercapacitors

The ever-increasing global energy consumption necessitates the development of efficient energy conversion and storage devices. Nitrogen-doped porous carbons as electrode materials for supercapacitors feature superior electrochemical performances compared to pristine activated carbons. Herein, a facile synthetic strategy including solid-state mixing of benzimidazole as an inexpensive single-source precursor of nitrogen and carbon and zinc chloride as a high temperature solvent/activator followed by pyrolysis of the mixture (T = 700–1000 °C under Ar) is introduced. The addition of ZnCl2 prevents early sublimation of benzimidazole and promotes carbonization and pore generation. The sample obtained under the optimal carbonization temperature of 900 °C and ZnCl2/benzimidazole weight ratio of 2/1 (ZBIDC-2-900) features a moderate specific surface area of 855 m2 g−1, high N-doping level (10 wt%), and a wide micropore size distribution (∼1 nm). ZBIDC-2-900 as a supercapacitor electrode exhibits a large gravimetric capacitance of 332 F g−1 (at 1 A g−1 in 1 M H2SO4) thanks to the cooperative advantages of the electrochemical activity of the nitrogen functional groups and the accessible porosity. The excellent capacitance performance coupled with robust cyclic stability, high yield and straightforward synthesis of the proposed carbons holds great potential for large-scale energy storage applications.

Heparin depolymerization by immobilized heparinase: A review

Heparin is a member of the glycosaminoglycan (GAG) family composed of glucosamine and uronic acid units containing O-sulfo, N-acetyl and N-sulfo groups, which are alternating in the chain and linked by 1→4 manner. It is a naturally occurring anticoagulant that prevents the formation of clots and their growth within blood. Certain low molecular weight heparins (LMWHs) are considered as better therapeutic agents than natural heparin because of the reduced side effects and smaller risk of bleeding. LMWHs can be produced from heparin by chemical or enzymatic depolymerizations. Heparinases catalyze the cleavage of glycosidic linkage between amino sugars and uronic acids in heparin. There are three kinds of heparinases which are frequently used for depolymerization of heparin. Despite wide range of applications of heparinases in health care, their use still has been hampered due to poor stability and high cost. To overcome this problem heparinases are recommended for immobilization to reduce the cost of product and enhance stability. Heparinases have been successfully immobilized using various methods and supports, mostly for deheparinization of blood through extracorporeal devices. The focus of this review is to present the current status of heparinase immobilization including various supports and methods used, stability and applications.

Biofuels in Air and Ground Transportation

Use of biofuels in aviation and ground transportation is increasing. The advantages of biofuels include their broad availability, carbon neutrality, environmental friendliness with potential economic and social benefits for the local communities. Bioethanol and biodiesel are by far the most prominent because of their ease of substitution of the conventional fossil fuels. Due to stringent quality standards in the aviation industry, rigorous testing of the biofuels is crucial. A number of feedstocks and technological routes are being explored for biofuel production including hydrotreated vegetable oils, Fischer-Tropsch fuels, synthesized iso-paraffinic fuels and alcohol-to-jet fuels. Some commercial flights have started using biofuels. Even though bioethanol and biodiesel are being blended with conventional fuel, there are still technological and economical challenges that prevent this fuel type to completely replace fossil fuels. The concept of bio-refinery which will utilize all parts of the biomass and transform all the co-products to value-added chemicals will give the biofuel industry a more competitive economic edge. Biofuels are promising alternatives and their use will continue to increase in the near future.

Immobilization alters heparin cleaving properties of heparinase I

We report here a novel observation that immobilization of heparinase I on CNBr-activated Sepharose results in heparin degradation properties that are different from heparinase I in the free solution form. Studies over a range of pHs (5-8) and temperatures (5-50°C) as well as under batch and flow conditions show that immobilized heparinase 1 displays altered pH and temperature optima, and a higher propensity for generation of longer chains (hexa- and octa-) with variable sulfation as compared to that in the free form, which is known to yield disaccharides. The immobilized enzyme retained good eliminase activity over at least five cycles of reuse. In combination, results suggest that heparinase I immobilization may offer a more productive route to longer, variably sulfated sequences.