The adsorption of polyoxyethylated nonylphenol on calcium carbonate in aqueous solution

Universal scaling of adsorption of nonionic surfactants on carbonates using cloud point temperatures

HYPOTHESIS

Nonionic surfactants alter the wettability of oil-wet carbonate surfaces to a water-wet state. The degree of surfactant adsorption is expected to determine the extent of the wettability alteration. Furthermore, the structure of the hydrophobic and hydrophilic units of the surfactant should affect the degree of adsorption and correlate with the wettability alteration.

EXPERIMENTS

The adsorption on Indiana limestone was measured for nonionic surfactants with two different types of hydrophobic units and hydrophilic polyethoxylate units ranging from 15 to 40 mers. Measurements were conducted for several surfactant concentrations and temperatures.

FINDINGS

Adsorption increased with temperature and for surfactants with fewer hydrophilic groups. The adsorption occurs as micelles rather than individual surfactant molecules. An increase in adsorption is observed for the more hydrophobic surfactants at higher temperature and is attributed to the increase in micelle sizes. Adsorption collapses onto a universal curve as a function of the difference between cloud point of the surfactant and system temperature. At the same time wettability alteration was found to have a direct correlation with surfactant adsorption. These findings are critical for judicious selection of nonionic surfactants for analysis and design of wettability alteration for oil reservoirs.

Mechanisms of the inhibition of enzymatic hydrolysis of waste pulp fibers by calcium carbonate and the influence of nonionic surfactant for mitigation

Recycled paper mills produce large quantities of fibrous rejects and fines which are usually sent to landfills as solid waste. These cellulosic materials can be enzymatically hydrolyzed into sugars for the production of biofuels and biomaterials. Paper mill wastes also contain large amounts of calcium carbonate which inhibits cellulase activity. The calcium carbonate (30%, w/w) decreased 40-60% of sugar yield of unbleached softwood kraft pulp. The prime mechanisms for this are by pH variation, competitive and non-productive binding, and aggregation effect. Addition of acetic acid (pH adjustment) increased the sugar production from 19 to 22 g/L of paper mill waste fibers. Strong affinity of enzyme-calcium carbonate decreased free enzyme in solution and hindered sugar production. Electrostatic and hydrogen bond interactions are mainly possible mechanism of enzyme-calcium carbonate adsorption. The application of the nonionic surfactant Tween 80 alleviated the non-productive binding of enzyme with the higher affinity on calcium carbonate. Dissociated calcium ion also inhibited the hydrolysis by aggregation of enzyme.

Theoretical estimation of stability ratios for hexadecane-in-water (H/W) emulsions stabilized with nonylphenol ethoxylated surfactants

The effect of steric interactions on the stability of oil-in-water emulsions is studied here by means of emulsion stability simulations (ESS). For this purpose, a new steric potential based on a modification of the one formerly proposed by Vincent et. al. is employed. The parameters of the calculation correspond to hexadecane in water emulsions stabilized with nonylphenol ethoxylated surfactants of different chain lengths (NPEm). Stability ratios (W) were calculated using the half life time of the number of drops per unit volume of these systems. A functional relationship between W and the repulsive potential barrier, (DeltaV), similar to the one previously found by Prieve and Ruckenstein for electrostatically stabilized suspensions was obtained. However, according to our simulations there exists a threshold for the stability of emulsions with respect to coalescence which is approximately located around 12.7 k(B)T.

Effect of nonionic surfactants on aqueous primidone suspensions

The following interactions between the soluble surfactant, octoxynol 9, and the very slightly soluble, finely powdered drug, primidone, in aqueous suspension were investigated: adsorption/desorption of the surfactant, micellar solubilization of the drug, and deflocculation of its particles. The last effect, measured by the sedimentation volume of the suspensions, was also investigated for other octoxynols. The adsorption of octoxynol 9 on solid primidone was proportional to the equilibrium surfactant concentration up to the critical micelle concentration. It leveled off at higher concentrations, reaching saturation at completion of a close-packed surfactant monolayer. The adsorption was essentially completely reversible. The solubility of primidone in water was very slight; its micellar solubilization was even less extensive. The sedimentation volume of primidone suspensions decreased with increasing equilibrium concentration of octoxynol 9 and began to level off at the critical micelle concentration of 0.018%. At about twice that concentration, the sedimentation volume became almost constant, but reached its lowest value only at less than or equal to 0.5%. Slow rotation of suspensions prior to sedimentation promoted flocculation and higher sedimentation volumes between 0.01 and 0.03% octoxynol 9. Octoxynols with higher hydrophilic-lipophilic balance than octoxynol 9 produced considerably larger sedimentation volumes at comparable concentrations, due to a lower surface activity and a lesser tendency to adsorb on primidone.

Adsorption of non-ionic surfactants at the griseofulvin-solution interface

The adsorption from solution onto griseofulvin powder of a series of non-ionic detergents of the polyoxyethylene glycol mono alkyl ether type is described. Results are also given for polyethylene glycol 400 and a new detergent, pentaerythritol mono-n-octyl ether, whose synthesis and purification is reported. The effect of temperature on the adsorption is studied and possible explanations of the variation of adsorption with temperature are based on the orientation of the molecules at the interface; this is deduced from measured molecular areas.