Hydrothermal flames for subaquatic, terrestrial and extraterrestrial applications.

Hydrothermal flames are formed in supercritical water in the presence of a fuel and an oxidant (usually air or oxygen). Integrating hydrothermal flames as the heat source for supercritical water oxidation helps to minimize the reaction time (to milliseconds), improve the reaction kinetics and reduce the chances of corrosion and reactor plugging. This review outlines state-of-the-art research on hydrothermal flames including the impacts of process parameters on flame ignition. The ignition and sustainability of hydrothermal flames are dependent on several factors such as the type of fuel and its concentration, type of oxidant (air and oxygen) as well as the temperatures and flow rate of the feed and oxidant. The article describes some novel applications of hydrothermal flames for clean energy production, geothermal energy recovery, deep well spallation, wastewater treatment, degradation of recalcitrant nitrogen-containing compounds and heavy oil upgrading. Finally, the challenges and future perspectives of hydrothermal flame applications are discussed. This review also highlights some technical considerations relating to hydrothermal flames such as the choice of organic solvent and its characteristics, preheating, ignition mechanism, flame stability and propagation, advanced reactor configurations, mixing with subcritical and supercritical components, recirculation zones, cooling mechanisms, corrosion and salt precipitation.

Optimization studies for hydrothermal gasification of partially burnt wood from forest fires for hydrogen-rich syngas production using Taguchi experimental design.

Forest fires significantly affect the wildlife, vegetation, composition and structure of the forests. This study explores the potential of partially burnt wood recovered in the aftermath of a recent Canadian forest fire incident as a feedstock for generating hydrogen-rich syngas through hydrothermal gasification. Partially burnt wood was gasified in hydrothermal conditions to study the influence of process temperature (300-500 °C), residence time (15-45 min), feed concentration (10-20 wt%) and biomass particle size (0.13 mm and 0.8 mm) using the statistical Taguchi method. Maximum hydrogen yield and total gas yield of 5.26 mmol/g and 11.88 mmol/g, respectively were obtained under optimized process conditions at 500 °C in 45 min with 10 wt% feed concentration using biomass particle size of 0.13 mm. The results from the mean of hydrogen yield show that the contribution of each experimental factors was in the order of temperature > feed concentration > residence time > biomass particle size. Other gaseous products obtained at optimum conditions include CO2 (3.43 mmol/g), CH4 (3.13 mmol/g) and C2-C4 hydrocarbons (0.06 mmol/g).

Techno-economic evaluation and sensitivity analysis of a conceptual design for supercritical water gasification of soybean straw to produce hydrogen.

This paper proposes a conceptual design for the catalytic supercritical water gasification of soybean straw. The design consists of four process units for pretreatment, gasification, separation, purification and combustion. The economic feasibility of hydrogen production was evaluated based on a comprehensive cash flow analysis. The economic analysis suggested a minimum selling price of U.S. $1.94/kg for hydrogen. The cost of hydrogen produced is relatively lower compared to that of other biomass conversion processes. Besides, the net rate of return (NRR) estimated was 37.1%. A positive NRR value indicates that the project is profitable from an economic perspective. Sensitivity analysis indicates that the minimum selling price of hydrogen is affected by the feedstock price, utility cost, tax rate and labor cost. Moreover, feedstock price and labor cost show the greatest effect. Other factors such as land cost, working capital and utility cost showed the least effect on the minimum selling price.

Fermentative production of butanol: Perspectives on synthetic biology.

Apprehensions relating to global warming, climate change, pollution, rising energy demands as well as fluctuating crude oil prices and supply are leading to a shift in global interest to find suitable alternatives to fossil fuels. This review aims to highlight the many different facets of butanol as an advanced next-generation transportation biofuel. Butanol has fuel properties almost on a par with gasoline, such as high energy content, low vapor pressure, non-hygroscopic nature, less volatility, flexible fuel blends and high octane number. The paper reviews some recent advances in acetone-butanol-ethanol fermentation with special emphasis on the primary challenges encountered in butanol fermentation, including butanol toxicity, solvent intolerance and bacteriophage contamination. The mechanisms for butanol recovery techniques have been covered along with their benefits and limitations. A comprehensive discussion of genetic and metabolic engineering of butanol-producing microorganisms is made for the prospective development of industrially-relevant strains that can overcome the technical challenges involved in efficient butanol production.

Fabrication of Highly Porous Nonspherical Particles Using Stop-Flow Lithography and the Study of Their Optical Properties.

A microfluidic flow lithography approach was investigated to synthesize highly porous nonspherical particles and Janus particles in a one-step and high-throughput fashion. In this study, using common solvents as porogens, we were able to synthesize highly porous particles with different shapes using ultraviolet (UV) polymerization-induced phase separation in a microfluidic channel. We also studied the pore-forming process using operating parameters such as porogen type, porogen concentration, and UV intensity to tune the pore size and increase the pore size to submicron levels. By simply coflowing multiple streams in the microfluidic channel, we were able to create porous Janus particles; we showed that their anisotropic swelling/deswelling exhibit a unique optical shifting. The distinctive optical properties and the enlarged surface area of the highly porous particles can improve their performance in various applications such as optical sensors and drug loading.

Wrinkling Non-Spherical Particles and Its Application in Cell Attachment Promotion.

Surface wrinkled particles are ubiquitous in nature and present in different sizes and shapes, such as plant pollens and peppercorn seeds. These natural wrinkles provide the particles with advanced functions to survive and thrive in nature. In this work, by combining flow lithography and plasma treatment, we have developed a simple method that can rapidly create wrinkled non-spherical particles, mimicking the surface textures in nature. Due to the oxygen inhibition in flow lithography, the non-spherical particles synthesized in a microfluidic channel are covered by a partially cured polymer (PCP) layer. When exposed to plasma treatment, this PCP layer rapidly buckles, forming surface-wrinkled particles. We designed and fabricated various particles with desired shapes and sizes. The surfaces of these shapes were tuned to created wrinkle morphologies by controlling UV exposure time and the washing process. We further demonstrated that wrinkles on the particles significantly promoted cell attachment without any chemical modification, potentially providing a new route for cell attachment for various biomedical applications.

Valorization of horse manure through catalytic supercritical water gasification.

The organic wastes such as lignocellulosic biomass, municipal solid waste, sewage sludge and livestock manure have attracted attention as alternative sources of energy. Cattle manure, a waste generated in surplus amounts from the feedlot, has always been a chief environmental concern. This study is focused on identifying the candidacy of horse manure as a next generation feedstock for biofuel production through supercritical water gasification. The horse manure was gasified in supercritical water to examine the effects of temperature (400-600°C), biomass-to-water ratio (1:5 and 1:10) and reaction time (15-45min) at a pressure range of 23-25MPa. The horse manure and resulting biochar were characterized through carbon-hydrogen-nitrogen-sulfur (CHNS), inductively coupled plasma-mass spectrometry (ICP-MS), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and scanning electron microscopy (SEM). The effects of alkali catalysts such as NaOH, Na2CO3 and K2CO3 at variable concentrations (1-2wt%) were investigated to maximize the hydrogen yields. Supercritical water gasification of horse manure with 2wt% Na2CO3 at 600°C and 1:10 biomass-to-water ratio for 45min revealed maximum hydrogen yields (5.31mmol/g), total gas yields (20.8mmol/g) with greater carbon conversion efficiency (43.1%) and enhanced lower heating value of gas products (2920kJ/Nm(3)). The manure-derived biochars generated at temperatures higher than 500°C also demonstrated higher thermal stability (weight loss <34%) and larger carbon content (>70wt%) suggesting their application in enhancing soil fertility and carbon sequestration. The results propose that supercritical water gasification could be a proficient remediation technology for horse manure to generate hydrogen-rich gas products.

Functional polymer sheet patterning using microfluidics.

Poly(dimethylsiloxane) (PDMS)-based microfluidics provide a novel approach to advanced material synthesis. While PDMS has been successfully used in a wide range of industrial applications, due to the weak mechanical property channels generally possess low aspect ratios (AR) and thus produce microparticles with similarly low ARs. By increasing the channel width to nearly 1 cm, AR to 267, and implementing flow lithography, we were able to establish the slit-channel lithography. Not only does this allow us to synthesize sheet materials bearing multiscale features and tunable chemical anisotropy but it also allows us to fabricate functional layered sheet structures in a one-step, high-throughput fashion. We showcased the technique's potential role in various applications, such as the synthesis of planar material with micro- and nanoscale features, surface morphologies, construction of tubular and 3D layered hydrogel tissue scaffolds, and one-step formation of radio frequency identification (RFID) tags. The method introduced offers a novel route to functional sheet material synthesis and sheet system fabrication.

Preparation and sorption studies of glutaraldehyde cross-linked chitosan copolymers.

Chitosan-glutaraldehyde copolymer sorbents were synthesized by reacting variable weight ratios (low, medium, and high) of glutaraldehyde with fixed amounts of chitosan. Two commercially available chitosan polymers with low (L) and high (H) relative molecular weights were investigated. The chitosan-glutaraldehyde (Chi-Glu) copolymer sorbents are denoted as CPL-X or CPH-X where X denotes the incremental level (X=-1, -2, -3) of glutaraldehyde. The copolymers were characterized using FT-IR spectroscopy and TGA. The solid-solution sorption isotherms in alkaline aqueous solution for the copolymers were characterized using absorbance and emission based spectroscopic methods for p-nitrophenol (PNP) and the arsenate oxoanion HAsO4(2-) species, respectively. The Sips isotherm model was utilized to obtain sorption parameters at pH 8.5 and 295K (i.e. sorbent surface area, sorption capacity and removal efficiency) for each copolymer sorbent. The sorbent surface areas for the low molecular weight chitosan copolymers are listed in parentheses (m(2)g(-1)), as follows: CPL-1 (124), CPL-2 (46.7) and CPL-3 (31.6). The high molecular weight chitosan copolymers are as follows: CPH-1 (79.8), CPH-2 (64.7) and CPH-3 (96.3). The removal efficiencies depend on the pH, temperature, and the relative amounts of sorbate and sorbent. The sorbent removal efficiencies for p-nitrophenol ranged between 7.1% and 49%, and the values for H2AsO4(2-) ranged between 31% to 93% for the low and high molecular weight copolymers.

Preparation and sorption studies of ß-cyclodextrin-chitosan-glutaraldehyde terpolymers.

ß-Cyclodextrin-chitosan-glutaraldehyde terpolymers were synthesized by reacting variable weight fractions of ß-cyclodextrin (ß-CD) and chitosan (Chi), with a constant amount of crosslinker (glutaraldehyde). The ß-CD:Chi:Glu terpolymer sorbents were characterized by FT-IR spectroscopy and TGA. The solid-solution sorption isotherms in aqueous solution for the copolymers were characterized using two spectroscopic methods (UV-Vis and ICAP-OES) for p-nitrophenol (PNP) and the arsenate oxoanion (HAsO(4)(2-)) at alkaline pH conditions. The Sips isotherm model was utilized to obtain sorption parameters at pH 8.5 and 295 K (i.e. sorbent surface area, sorption capacity and removal efficiency) for each copolymer sorbent. The sorbent surface area estimates for the terpolymers at low (T1), medium (T2), and high (T3) weight fractions of ß-CD are listed in parentheses (m(2) g(-1)), as follows: T1 (161), T2 (51.2) and T3 (275). The removal efficiencies are dependent on the relative weight fraction of the polysaccharide components (i.e. ß-CD and Chi); whereas the removal efficiencies for p-nitrophenolate ranged between 7.3% and 28%, and H(2)AsO(4)(2-) ranged between 23% and 55%.

Biosorption of Pb(II) and Cr(III) from aqueous solutions: breakthrough curves and modeling studies.

The sorption capacity parameters obtained for batch studies provide useful information about biosorption system. However, such data fail to explain the process under continuous-flow conditions. The present study is an attempt to explore the biosorption of Pb(II) and Cr(III) by straw from local wheat (Triticum aestivum). The biosorbent has been characterized by using Fourier transform infrared spectroscopy and surface area and elemental analyses and found to be porous and polyfunctional. S-shaped breakthrough curves were obtained at different column heights for the both metal ions. Various breakthrough parameters and saturation times have been determined. The column data have been successfully used to study the Bohart-Adams' bed depth service time (BDST) model and Yoon and Nelson's model. It was found that BDST model quite efficiently explained the whole column data whereas Yoon and Nelson model could explain it below 90% breakthrough concentration. The predicted and calculated BDST parameters were in agreement with each other. Yoon and Nelson's constant decreased with an increase in the column height for both metal ions. Effect of change in flow rate on the Pb(II) biosorption has also been discussed with respect to BDST approach.

Contaminant source identification within a building: Toward design of immune buildings.

The level of protection of a building against the intentional or accidental release of chemical agents is crucial. Both scenarios could endanger life and safety of the buildings occupants. Equipping buildings with appropriate chemical sensors can alert the building occupants about the contaminant release. The readings of these sensors can be employed to trace the location of release, and help to take the appropriate actions to minimize the casualties. However, only a limited number of them can be installed due to their initial and operating cost. Moreover, there is no information about the source strength, release time and possible source location. This paper reports the development of a methodology to identify the source location using sensors reading from limited locations. The methodology uses the artificial neural network (ANN) as a statistical analysis integrated with a multi-zone airborne contaminant transport model, CONTAM. To evaluate the applicability of this method, the contaminant dispersion within a building was modeled and the results were integrated to an ANN for the source identification. The prediction made by the trained ANN was then evaluated by predicting the source of the contaminant in 40 extra cases, which had not been seen by the network during the training session. The model was able to predict the source location in more than 90% of the cases when the building was monitored by three or more sensors. The results show that the method can be used to help building designers decide the optimum configuration of the sensors required for a space based on the accuracy level of the source detection.

Biosorption of heavy metal ions using wheat based biosorbents--a review of the recent literature.

Conventional technologies for the removal/remediation of toxic metal ions from wastewaters are proving expensive due to non-regenerable materials used and high costs. Biosorption is emerging as a technique offering the use of economical alternate biological materials for the purpose. Functional groups like carboxyl, hydroxyl, sulphydryl and amido present in these biomaterials, make it possible for them to attach metal ions from waters. Every year, large amounts of straw and bran from Triticum aestivum (wheat), a major food crop of the world, are produced as by-products/waste materials. The purpose of this article is to review rather scattered information on the utilization of straw and bran for the removal/minimization of metal ions from waters. High efficiency, high biosorption capacity, cost-effectiveness and renewability are the important parameters making these materials as economical alternatives for metal removal and waste remediation. Applications of available adsorption and kinetic models as well as influences of change in temperature and pH of medium on metal biosorption by wheat straw and wheat bran are reviewed. The biosorption mechanism has been found to be quite complex. It comprises a number of phenomena including adsorption, surface precipitation, ion-exchange and complexation.

Reaction chemistry and phase behavior of lignin in high-temperature and supercritical water.

Decomposition of organosolve lignin in water/phenol solutions was studied in a 50 nL micro-reactor coupled with optical, Raman and infrared microscopies at temperatures up to 600 degrees C and water densities up to 1165 kg/m3. It was found that when phenol was used with {lignin+water} mixtures that a homogenous phase was formed that seemed to promote the decomposition of lignin into phenolic fragments by hydrolysis and pyrolysis. Phenol, along with the homogenous reaction conditions also inhibited re-polymerization of the phenolics and promoted oil formation. On the other hand, in the absence of phenol, lignin remained as a heterogeneous phase with water over the range of conditions studied. The homogeneous conditions and conditions for inhibiting char formation by phenol were elucidated and it was found that mixtures of phenol and lignin become homogeneous at 400-600 degrees C and high water densities of 428-683 kg/m3, corresponding to maximum pressures of 93 MPa. These results were further used to propose reaction paths.

New Methodology for the Application of a TGF-FTIR to Study Low Temperature Treatment of Waste Oil.

A new methodology was developed using a Thermo-Gravi-metric Furnace coupled to a Fourier Transform Infrared Spectrometer (TGF-FTIR) to study the low temperature treatment of waste lubricating oils. The sample was heated from room temperature to a final temperature of 1,000 °C at an initial heating rate of 3 °C/min, to slow down the oxidative pyrolysis process allowing for the events taking place to be observable. It was found that the majority of the process in terms of weight loss and gas-phase evolution was over by 650 °C, and thus, the remainder of the sample heating was accomplished at a rate of 5 °C/min. The sample was kept at a temperature of 1,000 °C for 60 minutes in order to allow the remaining solid material to achieve a state of equilibrium (necessary for the solid morphological study). The applicability of TGF-FTIR using this methodology to research in the environmental field was proven to be quite successful, since it allowed for precise control over environmental conditions while simultaneously allowing for data gathering on both sample weight and gas-phase evolution. The developed methodology proved to be reliable, giving repeatable results. The information gathered was used to understand and explain the evolution of the waste oil from initial liquid state to a final solid ash state. It was accomplished in four steps, including (1) release of moisture/light hydrocarbons, (2) bulk volatilization of hydrocarbons, (3) solid material deposition, and (4) solids oxidation.