Floyd N. Toll

Collagen and glycopolymer based hydrogel for potential corneal application.

6-Methacryloyl-alpha-D-galactopyranose (MG) was synthesized, and characterized by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectrometry, and single-crystal X-ray diffraction. A series of interpenetrating polymer network (IPN) hydrogels was fabricated by simultaneously photocuring MG crosslinked by poly(ethylene glycol) diacrylate and chemically crosslinking type I collagen with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide. The successful incorporation of the glycopolymer, polymer MG, into collagen hydrogel was confirmed by FTIR and solid-state (13)C NMR. The optical characteristics of the IPN hydrogels are comparable to those of human corneas. The tensile strength and modulus of the hydrogels are enhanced by incorporation of polymer MG in comparison to that of the control collagen hydrogel. Biodegradation results indicated that polymer MG enhanced the stability of the composite hydrogels against collagenase. In vitro results demonstrated that the IPN hydrogel supported the adhesion and proliferation of human corneal epithelial cells and outperformed human cornea in blocking bacteria adhesion. Taken together, the IPN hydrogel might be a promising material for use in corneal lamellar keratoplasty.

Agglomeration-flotation: recovery of hydrophobic components from oil sands fine tailings

Laboratory agglomeration-flotation tests were used to evaluate the recovery of residual bitumen from a sample of Suncor oil sands fine tailings, using ground coal as a bitumen absorbent. To improve its effectivness, the coal was preconditioned with no. 2 fuel oil, subjected to 30 s high-shear mixing and collected by flotation over 3 min. This oil-conditioned coal was then contacted with mature fine tailings for 5 min with low-shear mixing. Flotation for 5 min resulted in the recovery of 93% of the residual bitumen, compared with 85% after 40 min mixing achieved in earlier tests. Equipment to accomplish this separation has already been designed, scaled and operated for fine coal recovery from washery wastes.

An experimental and numerical study of particle size distribution effects on the sintering of porous ceramics

A single-step processing method has been established to prepare asymmetric porous alumina microstructures by a controlled sedimentation technique. Fine powder from an aqueous suspension is consolidated over a casting slab. Metastable surface chemical control of the suspension properties was able to induce a highly porous flat disc structure with a continuously increasing mean pore size from top to bottom. Formation of this gradient structure was facilitated by using a powder with a very broad particle size distribution. These structures can be used as either ultrafiltration media or as substrates for inorganic membrane making. Sintering can readily introduce defects into functionally gradient ceramics. Despite these problems, the asymmetric structures considered in this paper can be readily sintered without warpage or cracking. In this regard, a finite element method numerical simulation had been developed to model the sintering characteristics of functionally gradient ceramic structures. The key for being able to predict a non-warped structure was the incorporation into the model of the powder particle size distribution as a field variable. Across the vertical section of the structure, the distributions were broad and overlapping, all with a significant fines tail. These characteristics accelerate and homogenize local sintering rates, such that the net result is a non-warped fused structure. This paper presents recent advances with the simulation, where sample geometry, porosity and particle size distribution evolutions were traced alongside measurements made on physical specimens. In general the model corresponded well with the experimental observations. The correct accounting of observed trends lends confidence to the underlying sintering mechanisms incorporated into the model.

Fixation of lead in contaminated soils by co‐agglomeration with metal binding agents*

Abstract Adsorption of lead from an aqueous solution by both agricultural peat moss and soil has been measured. The results may be described by a Langmuir isotherm model. Adsorption isotherms fitted the “H”; type described in the Giles classification. Saturation adsorption was reached at equilibrium lead concentrations > 3000 mg/L for peat, compared with ∼ 250 mg/L for soil. Calculation of the isotherm parameters showed the maximum lead adsorption to be 150 mg lead/g of peat. This compared with only 12.64 mg/g of lead for soil alone. Several tests were carried out to evaluate the lead binding capacity of peat in a spiked soil sample. Results from leaching tests (Environmental Protection Agency, EPA, Toxicity Characteristic Leaching Procedure, TCLP, at pH 2.9) on soil‐peat mixtures confirmed the excellent metal binding capacity of peat in the samples tested. The amount of lead leached from a soil sample, spiked with 1840 mg/kg of water‐soluble lead, decreased with increasing amounts of peat loading. Total ...

Beneficiation of coal-heavy oil coprocessing residue by oil-phase agglomeration☆

Surface characterization techniques (scanning electron microscopy and X-ray photoelectron spectroscopy) were used to examine toluene-insoluble solids from coprocessing of coal and heavy oil in order to evaluate their physical separation potential. Washability studies, using float-sink tests, were also carried out to provide an empirical estimate of the ash separation attainable. On the basis of the results, agglomeration tests were performed in an attempt to optimize the beneficiation of the organic matter in the residue pitch. Ash rejection in these tests ranged from 30 to 40%. Analysis of the ash from the agglomerated and reject fractions suggested that most of the iron was retained in the agglomerates.