David W. Larsen

The structure of lamellar lyotropic liquid crystals from lecithin and alkanediols

Abstract Lamellar liquid crystals from lecithin and alkanediols were studied to determine the composition range of stability and geometrical dimensions using low-angle X-ray scattering. An estimation of the dislocation pattern was made from the optical pattern in polarized light. The ethylene glycol gave the widest range of stability for the lamellar structure, the range being reduced toward heptanediol, the longest member to give liquid crystals. The interlayer spacing was reduced with increasing chain length of the diol and the dislocation pattern remained identical.

An activated carbon product prepared from milo (Sorghum vulgare) grain for use in hazardous waste gasification by ChemChar cocurrent flow gasification

An activated carbon was prepared by pyrolysis and subsequent gasification of milo seed utilizing the ChemChar gasification process. This carbon was characterized and further utilized for the destruction of refractory organic wastes and for sequestering metal bearing wastes by the ChemChar waste destruction process.

Proton NMR relaxation in hydrogel contact lenses: correlation with in vivo lens dehydration data

A study of hydrogel contact lenses was undertaken to determine whether NMR relaxation data can be used as a predictor for on-eye lens dehydration. Proton NMR relaxation times (T1 and T2), were determined for a series of contact lenses for which on-eye dehydration data were also available. NMR relaxation times were found to depend upon lens water content, but the dependence was not monotonic. T1 values varied between 100 and 800 msec, and T2 values varied between 6 and 85 msec for the lenses studied. In this study, the NMR signal and corresponding relaxation times are average values, derived both from lens water protons as well as from exchangeable polymer protons. A simple analysis of the data indicates that the mobility of these protons varies by more than a factor of 10 for the lenses studied. A test for linear correlation between NMR relaxation rate, 1/T1 and relative change in lens water mass, % delta mw gave r = -0.830 for all data, and r = 0.904 if one lens was excluded.

Gasification as an alternative method for the destruction of sulfur containing waste (ChemChar process)

Abstract The behavior of a non-incinerative reductive thermal cocurrent flow gasification process (ChemChar Process) when used to treat representative sulfur compounds is reported. Gasification of 1,3-benzenedisulfonic acid, thiomorpholine, and sulfuric acid converts the sulfur in these compounds to H 2 S, OCS, and elemental sulfur. The H 2 S and OCS are released in the synthesis with the gas product from which they can be scrubbed, with the elemental sulfur being deposited on the char matrix. No production of sulfur dioxide was detected. Gasified sulfur products recovered amounted to 89–114% of the total sulfur present in the sulfur compounds gasified, although exact mass balances could not be obtained due to the sulfur present in the char.

Gasification of waste‐contaminated soil by the chem char process

Abstract Reverse‐burn gasification (RBG, the ChemChar Process) has been applied to the treatment of soil contaminated with hydrocarbons, poly‐chlorinated biphenyls (PCBs) and thorium. Overall destruction of the PCBs in excess of 99.9999% (six nines) was achieved. No undesirable dibenzo dioxins or furans were produced, and metals and acid gases are retained in the char residue matrix. An overall hazardous waste treatment system based on gasification is described.

Lyotropic liquid crystals from lecithin, water, and polyethylene glycol

Abstract Lyotropic liquid crystals with lecithin as the amphiphile and with water/polyethylene glycol (PEG) solutions as the solvent were prepared with polyethylene glycol/water ratios from 182 to 0. The liquid crystals were lamellar and the interlayer spacing was independent of the solvent content for water/PEG ratios ⩽1 but increased strongly with the water/PEG ratio. Higher ratios gave increased interlayer spacing with solvent content similar to the variation for liquid crystals with water as solvent but the absolute values of the spacing were higher.

Solvent-Solute Interaction in an Lα Phase Formed With Water, Ethylene Glycol and Lecithin

Abstract The variation in the order parameter with the ethylene glycol/water ratio was determined by deuterium HMR groups in ethylene glycol were determined in an L liquid crystalline phase of lecithin, water and ethylene glycol. In addition, the interlayer spacing was determined by small angle X-ray diffractometry. The results were described using a simple two-component adsorption model and showed no substantial variation between water and ethylene glycol of their binding affinity to the polar groups of the lecithin 31P NMR results supported earlier proton NMR spectra interpretation of an increased disorder of the amphiphiles with greater amount enhanced of ethylene glycol/water ratio.

The destruction of chemical warfare surrogates and subsequent phosphorus distribution during gasification

Abstract The ChemChar process enables gasification of a wide variety of liquid and sludge wastes on a readily handled macroporous granular char. The process produces combustible gas products, largely retains metals and halides on the char matrix, and effectively destroys organohalides without producing SOX, NOX, chlorinated dibenzodioxins or chlorinated dibenzoflirans (which can occur with incineration). To study chemical warfare agent wastes under gasification conditions, the destruction removal efficiencies (DRE) of the chemical warfare surrogates parathion and diethylchlorothiophosphate were determined. DREs of > 99.9996 % and > 99.99998 % were found for parathion and diethylchlorothiophosphate, respectively. Additionally, a study of the distribution of radiolabeled phosphorus (P‐32) after gasification of parathion and tributylphosphate showed essentially complete retention of the phosphorus within the gasification system. This study illustrates that the ChemChar gasification process holds significant ...

The chemical reduction of small inorganic gases in an electrothermal plasma reactor

Abstract Chemical reduction of small inorganic gases is accomplished using an electro-thermal plasma reactor. This benchscale reactor maintains a highly reactive plasma zone in a fluidized bed of carbon particles through which an electrical current is discharged. The carbon particles function as current-controlling media, heat sinks and reaction sites. Chemicals introduced into this medium are subjected to a variety of energy sources and chemically reactive species, which result in chemical reduction. It is shown that the inorganic gases, H2O, CO2, NO, NO2 and SO2, are chemically reduced in the plasma zone of the reactor. The end products consist of hydrogen, carbon monoxide and nitrogen gases. Additionally, elemental sulfur is deposited onto the carbon particles.

The destruction of chlorofluorocarbons during ChemChar gasification

Abstract Due to the hazardous implications of releasing CFCs into the environment, studies on their thermal destruction are necessary. The use of incineration to destroy these compounds, while effective, have produced polychlorinated dibenzodioxins and polychlorinated dibenzofurans (PCDD/PCDF) while releasing large amounts of corrosive HCl and HF. The ChemChar gasification process was evaluated for its ability to destroy two CFCs, l,l,2‐trichloro‐l,2,2‐trifluoroethane (CFC‐113) and dichlorodifluoromethane (CFC‐13). It was found that DRE values of > 99.9998 % are obtained for the destruction of l,l,2‐trichloro‐l,2,2‐trifluoroethane while not producing any PCDD/PCDF. Additionally, the chloride (as the potassium salt) and fluoride (as carbon‐fluoride) that result from the destruction of both CFCs are retained in the gasification system. This study illustrates that the ChemChar gasification process holds significant promise as an alternative to incineration for the safe and complete destruction of CFCs.