Screening for synergistic interactions in dilute polysaccharide solutions

©1995. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ This document is the Accepted, version of a Published Work that appeared in final form in Carbohydrate Polymers. To access the final edited and published work see https://doi.org/10.1016/0144-8617(95)00098-4A simple viscometric approach has been used to screen for binding interactions between different polysaccharides in very dilute solution where exclusion effects should be negligible. The method involves preparing stock solutions to approximately the same, low, viscosity (ηsp ≈ l), dialysing to identical ionic conditions, mixing in various proportions, and looking ror departures from the initial common viscosity. Mixtures of xanthan or de-acetylated xanthan with locust bean gum (LBG) or konjac glucomannan (KM) show massive enhancement of viscosity, as anticipated from the formation of synergistic gels at higher concentrations. However, no viscosity changes on mixing with LBG or KM were observed for other conformationally ordered bacterial polysaccharides (welan and rhamsan) or for alginate and pectin with sufficient Ca2+ to induce almost complete conversion to the dimeric ‘egg box’ form, demonstrating that conformational rigidity is not, in itself, sufficient for other polysaccharides to form heterotypic junctions with mannan or glucomannan chains. Interactions of carrageenans with LBG appear to depend on both conformation and the extent of aggregation. Mixtures of LBG with K+ kappa carrageenan in 100 mM KCl (which is known to promote extensive aggregation of double helices) gave erratic values for rotational viscosity and showed typical gel-like mechanical spectra under low-amplitude oscillation. Disordered carrageenans (K+ kappa in water and lambda in 100 mM KC1) showed no evidence of interaction with LBG. Negative results were also obtained for iota carrageenan under ionic conditions believed to promote ordering without significant aggregation (100 mM KCl). However, under conditions where limited aggregation might be expected (iota carrageenan in 90 mM CaC12; Me4N+ kappa carrageenan in 150 mM Me4NI), significant reductions in viscosity were observed on mixing with LBG, which may indicate some intermolecular association but without the formation of an extended network structure

Investigation of Changing Pore Topology and Porosity during Matrix Acidizing using Different Chelating Agents

Core flooding acidizing experiments on sandstone/carbonate formation are usually performed in the laboratory to observe different physical phenomena and to design acidizing stimulation jobs for the field. During the tests, some key parameters are analyzed such as pore volume required for breakthrough as well as pressure. Hydrochloric acid (HCl) is commonly used in the carbonate matrix acidizing while Mud acid (HF: HCl) is usually applied during the sandstone acidizing to remove damage around the well bore. However, many problems are associated with the application of these acids, such as fast reaction, corrosion and incompatibility of HCl with some minerals (illite). To overcome these problems, chelating agents (HEDTA, EDTA and GLDA) were used in this research. Colton tight sandstone and Guelph Dolomite core samples were used in this study. The experiments usually are defined in terms of porosity, permeability, dissolution and pore topology. Effluent samples were analyzed to determine dissolved iron, sodium, potassium, calcium and other positive ions using Inductively Coupled Plasma (ICP). Meanwhile Nuclear Magnetic Resonance (NMR) was employed to determine porosity and pore structure of the core sample. Core flood experiments on Berea sandstone cores and dolomite samples with dimensions of 1.5 in × 3 in were conducted at a flow rate of 1 cc/min under 150oF temperature. NMR and porosity analysis concluded that applied chemicals are effective in creating fresh pore spaces. ICP analysis concluded that HEDTA showed good ability to chelate calcium, sodium, magnesium, potassium and iron. It can be established from the analysis that HEDTA can increase more amount of permeability as compared to other chelates

Physico-chemistry of (1,3)-β-glucans

This chapter describes the methods and results of studies into the conformations adopted by (1,3)-β-glucans in solid, solution and native states, and characterization of the physical behavior of (1,3)-β-glucans in dilute solutions, concentrated solutions and gel networks. The physico-chemical properties exhibited by (1,3)-β-glucans are based primarily on the nature and stability of ordered conformations that are present under hydrated conditions. X-ray fiber diffraction analysis has shown unambiguously that a triple helix can be formed under both anhydrous and hydrated solid state conditions for linear (1,3)-β-glucans; similar diffraction behavior for side-chain-substituted (1,3)-β-glucans suggests a similar triple helical form with reduced lateral aggregation of glucan backbones due to the presence of side chains. Solid state 13C nuclear magnetic resonance (NMR) provides evidence that triple helical conformations are present within gels and some native forms of (1,3)-β-glucans. Light scattering, electron microscopy and atomic force microscopy data show the presence of triple helices for a range of substituted (1,3)-β-glucans in dilute aqueous solution, and are consistent with single-chain forms in solutions of alkali and dimethyl sulfoxide (DMSO)