Susanta K. Mohapatra

Spent Coffee Grounds as a Versatile Source of Green Energy

The production of energy from renewable and waste materials is an attractive alternative to the conventional agricultural feed stocks such as corn and soybean. This paper describes an approach to extract oil from spent coffee grounds and to further transesterify the processed oil to convert it into biodiesel. This process yields 10-15% oil depending on the coffee species (Arabica or Robusta). The biodiesel derived from the coffee grounds (100% conversion of oil to biodiesel) was found to be stable for more than 1 month under ambient conditions. It is projected that 340 million gallons of biodiesel can be produced from the waste coffee grounds around the world. The coffee grounds after oil extraction are ideal materials for garden fertilizer, feedstock for ethanol, and as fuel pellets.

Functionalization of self-organized TiO2 nanotubes with Pd nanoparticles for photocatalytic decomposition of dyes under solar light illumination.

Self-organized, vertically oriented TiO2 nanotube arrays prepared by the sonoelectrochemical anodization method are functionalized with palladium (Pd) nanoparticles of approximately 10 nm size. A simple incipient wetness method is adopted to distribute the Pd nanoparticles uniformly throughout the TiO2 nanotubular surface. This functionalized material is found to be an excellent heterogeneous photocatalyst that can decompose nonbiodegradable azo dyes (e.g., methyl red and methyl orange) rapidly (150-270 min) and efficiently (100%) under ambient conditions using simulated solar light in the absence of any external oxidative radicals such as hydrogen peroxide.

Self-organized TiO2 nanotubular arrays for photoelectrochemical hydrogen generation: effect of crystallization and defect structures

The effect of crystallization and surface chemistry of nanotubular titanium dioxide (TiO2) in connection with the photoelectrochemical process is reported in this investigation. TiO2 nanotubular arrays were synthesized by a simple anodization process in an acidified fluoride electrolyte at room temperature. The TiO2 nanotubes were amorphous in as-anodized condition; their transformation to crystalline phases was a function of annealing temperature and gaseous environment. The anatase phase was observed predominantly after annealing in non-oxidizing atmospheres, whereas annealing in an oxygen environment showed a mixture of anatase and rutile phases. X-ray photoelectron spectroscopy was used to determine the chemical environment of the surface, which revealed the presence of phosphate, oxygen vacancies and pentacoordinated Ti in hydrogen annealed samples. Diffuse reflectance photospectrometry of non-oxygen annealed samples showed long absorption tails extending in the visible region. The photoelectrochemical response of the TiO2 nanotubes annealed in different conditions was investigated. Photoelectrochemical performance under simulated solar light was improved by annealing the nanotubular TiO2 samples in non-oxidizing environment.

Double-Wall Anodic Titania Nanotube Arrays for Water Photooxidation

Vertically oriented double-wall titania nanotube (external diameters of 82 and 206 nm) arrays are synthesized by a sonoelectrochemical anodization technique in combination with a unique room-temperature ionic liquid and organic electrolyte. Compared to similar single-wall nanotubes (0.638 mA/cm(2)) and commercial nanoparticles (0.365 mA/cm(2)), these double-wall nanotube arrays show 2-4 times more photoactivity to split water under solar light illumination to generate hydrogen and oxygen. Partial doping of B and C into the TiO(2) matrix gives rise to these double-wall nanotubes which absorb visible solar light more efficiently than the intrinsic TiO(2). The structural properties of these novel structures have been studied extensively using various spectroscopic, analytical, and electrochemical techniques.

A Green Process for Producing Biodiesel from Feather Meal

This paper describes a new and environmentally friendly process for developing biodiesel from commercial feather meal, a waste product of the poultry industry. Currently, feather meal is used as an animal feed, given its high protein content, and also as a fertilizer because of its high nitrogen content. In this work, we have extracted fat from the feather meal in boiling water (70 degrees C) and then transesterified the fat into biodiesel using KOH and methanol; 7-11% biodiesel (on a dry basis) is produced in this process. ASTM analysis of the prepared feather meal biodiesel confirmed that the biodiesel is of good quality and comparable to other biodiesels made from other common feedstocks. Given the amount of feather meal produced by the poultry industry, it is estimated that this process can create 150-200 million gallons of biodiesel in the United States and 593.2 million gallons worldwide.

Synthesis of TaON nanotube arrays by sonoelectrochemical anodization followed by nitridation: a novel catalyst for photoelectrochemical hydrogen generation from water

This communication reports the synthesis of TaON nanotube arrays as efficient visible light driven photocatalysts for photoelectrochemical generation of hydrogen from water.

The detection of improvised nonmilitary peroxide based explosives using a titania nanotube array sensor

There is a critical need to develop an efficient, reliable and highly selective sensor for the detection of improvised nonmilitary explosives. This paper describes the utilization of functionalized titania nanotube arrays for sensing improvised organic peroxide explosives such as triacetone triperoxide (TATP). TATP forms complexes with titania nanotube arrays (prepared by anodization and sensitized with zinc ions) and thus affects the electron state of the nanosensing device, which is signaled as a change in current of the overall nanotube material. The response is rapid and a signal of five to eight orders of magnitude is observed. These nanotube array sensors can be used as hand-held miniaturized devices as well as large scale portable units for military and homeland security applications.

Formation of chelating agent driven anodized TiO2 nanotubular membrane and its photovoltaic application

Titania (TiO(2)) nanotubular arrays provide an exciting material for dye sensitizing solar cells (DSSC) because of their large surface area, lower recombination losses, and fast charge transport properties along the nanotubes. In this paper, design of a next generation DSSC using a TiO(2) nanotubular membrane is discussed. A single step, green process is developed to produce stable large area, free-standing TiO(2) nanotubular films (in a short time, 30-60 min) by anodizing Ti using an organic electrolyte, containing disodium salt of ethylene diaminetetraacetic acid (Na(2)[H(2)EDTA]) as complexing agent, and subsequent drying. Transparent, crack-free TiO(2) films, 20-41 microm thick containing ordered hexagonal TiO(2) nanotubes are achieved by this process. Films having a geometrical area up to 16.5 cm(2) with pore openings of 182 nm have been obtained. These films have been etched to form membranes which provide an exciting prospect for front side illuminated DSSC with good mass and photon transport properties as well as wettability. A photovoltaic efficiency of 2.7% is achieved using a front side illuminated DSSC compared to 1.77% using back side illumination.

Photoelectrolysis of water using heterostructural composite of TiO2 nanotubes and nanoparticles

Efficient photoelectrolysis of water to generate hydrogen (H2) can be carried out by designing photocatalysts with good absorption as well as charge transport properties. One dimensional (1D), self-organized titania (TiO2) nanotubes are known to have excellent charge transport properties and TiO2 nanoparticles (NPs) are good for better photon absorption. This paper describes the synthesis of a composite photocatalyst combining the above two properties of TiO2 nanocomposites with different morphologies. TiO2 NPs (5?9?nm nanocrystals form 500?700?nm clusters) have been synthesized from TiCl4 precursor on TiO2 nanotubular arrays (~80?nm diameter and ~550?nm length) synthesized by the sonoelectrochemical anodization method. This TiO2 nanotube?nanoparticle composite photoanode has enabled obtaining of enhanced photocurrent density (2.2?mA?cm?2) as compared with NTs (0.9?mA?cm?2) and NPs (0.65?mA?cm?2) alone.

Photo-electrochemical generation of hydrogen using hybrid titanium dioxide nanotubular arrays

Anodization of Ti in acidified fluoride solution resulted in a vertically oriented and an ordered nanotubular titanium oxide surface. Annealing of the TiO2 nanotubular arrays in a carbonaceous or nitrogen containing atmosphere presumably resulted in band-gap states, which enhanced the photo-activity. Composite electrode of nanotubular TiO2 + carbon doping resulted in a photocurrent density of more than 2.75 mA/cm2 at 0.2 V(Ag/AgCl) under simulated solar light illumination. The enhanced photo-activity of the carbon-modified nanotubular TiO2 is highly reproducible and sustainable for longer duration. The charge carrier densities, calculated based on the Mott-Schottky analyses, were in the range of 1-3 x 1019 cm-3 for both the carbon modified and the nitrogen-annealed nanotubular TiO2 samples. The asanodized and oxygen-annealed samples showed a charge carrier density of 5 x 1017 and 1.2 x1015 cm-3 respectively. In this study, the measured photo current density was not directly related to the charge carrier densities of the nanotubes. Presence of different phases, such as amorphous, anatase and rutile, influenced the photo activity more than the charge carrier density.