Hydrogen and Energy

Hydrogen is presumably the transportation of the future, and the U.S. Department of Energy has developed a Hydrogen Posture Plan and National Roadmap for transitioning to a hydrogen economy. The hydrogen and energy related research includes production via nuclear energy-driven thermochemical cycles, utilization, life cycle assessment to ascertain the environmental impacts, and evaluation of primary energy sources for future.

Acid Mine Drainage Remediation

Acid mine drainages (AMDs) are contaminated acidic bodies of water that are formed, primarily due to microbial oxidation of sulfidic ores. AMDs containing high concentrations of sulfate and metal ions can be remediated by metal hydroxide precipitation using lime.  However, it requires expensive reagents and results in generation of large quantities of mixed metal hydroxide sludge that has to be treated as hazardous waste. An attractive alternative treatment utilizes sulfate reducing bacteria (SRB) to convert sulfate ion to sulfide, that can then react with metal ions and precipitate metal sulfides that have even lower solubility than hydroxides. The AMD drainage research focusses upon:

    1. Determination of biokinetics of sulfate reduction using mixed cultures of SRB
    2. Determination of toxic/inhibitory impact of metal ions on SRB activity
    3. Quantification of inhibitory effect of  sulfide, and
    4. Development of processes for metal separation/recovery

Biosorption and Biofiltration

Metal ions can be recovered from aqueous waste streams by sorbing them on a biosorbent, such as, activated sludge. Equilibria and kinetics of sorption of copper and zinc on non-viable activated sludge were determined using a packed column. Biosorption study using continuous column configuration represents a significant departure from the suspended, well mixed batch systems used in most biosorption studies.

Technological feasibility of microbial degradation of volatile organic chemicals (VOCs) was demonstrated using air biofiltration. A comprehensive mathematical model was developed for the biofilters. The salient features of the model included: (1). the use of monod kinetics to describe intrinsic biodegradation kinetics, (2)  Incorporation of external mass transfer (gas-liquid) and (liquid-solid) resistances, and (3) consideration of diffusive resistances within the biofilm. Intrinsic biodegradation constants for the target substrates were determined in a microbiofilter. The biokinetic constants were used in numerical simulations of the model and the theoretical predictions correlated well with the experimental observations, indicating the validity of the model.

Multiphase Reactor Design

A number of industrial processes (hydrometallurgical operation, coal desulfurization) utilize three phase (gas, liquid and catalytic/non-catalytic solid) sparged reactors. The reactions of individual solid particles were modeled using shrinking core and simultaneous diffusion with reaction models. These models combined with the flow models for the reactors led to overall models for fluidized bed and bubble column slurry reactors. Simulations of overall process models yielded performance charts that relate the conversion of the solid phase with respect to the residence time in the reactor. The conversion, or extent of reaction is a function of the operating conditions and properties of the reactants. The validity of the models was tested by comparison of the predicted conversions with the observed experimental data.
 

Recent Publications

"Nanometallic fuels for transportation: a well-to-wheels analysis," Int. J. Energy Res., In press.

"Life cycle assessment of ISPRA Mark 9 thermochemical cycle for nuclear hydrogen production," J. Chem. Technol. Biotechnol., 81, 1753-1759, 2006.

"Energy forecasting: predictions, reality and analysis of causes of error," Energy Policy, 34, 3087-3092, 2006.

"Life cycle assessment of high-temperature water-vapor electrolysis for nuclear hydrogen production," Int. J. Hydrogen Energy, 31, 939-944, 2006.

"Safety of compressed hydrogen fuel tanks: leakage from stationary vehicles," Technol. Soc., 27, 315-320, 2005.

"Constant mole fractions in reacting systems with phase change," Chem. Educator, 10, 329-332, 2005.

"Assessment of metal toxicity to sulfate reducing bacteria through metal concentration methods," in Techniques in Aquatic Toxicology, Vol. 2, Ostrander GK (ed.), CRC Press, Boca Raton, Fla., pp. 169-177, 2005.

"Toxicity of metals and metal mixtures: analysis of concentration and time dependence for zinc and copper," Wat. Res., 38, 3651-3658, 2004.

“Quantification of Toxic and Inhibitory Impacts of Copper and Zinc on Mixed Cultures of Sulfate-Reducing Bacteria,” Biotechnol. Bioeng., 82, 306-312, 2003.