Use of surfactant

Contemporary concern about pollution has made it important to dispose of oil slicks from spiUs. The suitable use of surfactants may reverse the spreading of the slick, thereby concentrating the slick for easier removal. 

The focus of more recent work has been the use of relatively low concentrations of additives in other oil recovery processes. Of particular interest is the use of surfactants (qv) as CO2 (4) and steam mobiUty control agents (foam). Combinations of older EOR processes such as surfactant-enhanced alkaline flooding and alkaline—surfactant—polymer flooding show promise of improved cost effectiveness. 

The WAG process has been used extensively in the field, particularly in supercritical CO2 injection, with considerable success (22,157,158). However, a method to further reduce the viscosity of injected gas or supercritical fluid is desired. One means of increasing the viscosity of CO2 is through the use of supercritical C02-soluble polymers and other additives (159). The use of surfactants to form low mobihty foams or supercritical CO2 dispersions within the formation has received more attention (160—162). Foam has also been used to reduce mobihty of hydrocarbon gases and nitrogen. The behavior of foam in porous media has been the subject of extensive study (4). X-ray computerized tomographic analysis of core floods indicate that addition of 500 ppm of an alcohol ethoxyglycerylsulfonate increased volumetric sweep efficiency substantially over that obtained in a WAG process (156). 

One reason for widespread interest in the use of surfactants as gas mobihty control agents is the effectiveness at concentrations of <0.1 wt % (156,163). Some surfactants are effective below their critical micelle concentration (164). This low chemical requirement can significantly improve process economics. 

Chemically Modified Waxes. Hydrocarbon waxes of the microcrystaHine, polyethylene, and polymethylene classes are chemically modified to meet specific market needs. In the vast majority of cases, the first step is air oxidation of the wax with or without catalysts (11). The product has an acid number usuaHy no higher than 30 and a saponification number usuaHy no lower than 25. An alternative step is the reaction of the wax with a polycarboxyHc acid, eg, maleic, at high temperature (12). Through its carboxyl groups, the oxidised wax can be further modified in such reactions as saponification or esterification. Oxidised wax is easily emulsified in water through the use of surfactants or simple soaps, and is widely used in many coating and poHsh appHcations. 

Property of liquid, whereby molecular forces at the surface tend to minimize the contained volume, hence water droplets. Water has high surface tension which makes it poor at wetting thus requiring use of surfactant materials for certain processes. 

The use of surfactants has been an important positive factor for several reasons. They form O/W microemulsions, which must have low viscosity and contain a high oil content later on this oil must be separated fairly easily. 

Studies on mechanisms are described by Balzer [192]. In the case of anionics the residual oil in the injection zone is removed via displacement into the adjacent reservoirs ether carboxylates show their good adaptation to differences in temperature and salinity. Further it was found from interfacial tension measurements, adsorption and retention studies, and flooding tests that use of surfactant blends based on ether carboxylates and alkylbenzensulfonates resulted... 

Therefore in many countries the use of surfactants derived from phosphonic acid are limited by law, especially for surfactants of mass products like household detergents that will flow into wastewater effluents. The difficulty in formulating detergents without inorganic polyphosphates is discussed in Ref. 206. 

As for PAHs, attempts have been made to increase bioavailability by use of surfactants, and a complex picture has again developed (Fava and Di Gioia 1998). Triton-100 exerted both positive and negative effects in soil slurries even though it was not metabolized by the soil microflora, it adversely affected the degradation of chlorobenzoate intermediates, whereas in fixed-bed reactors, depletion of PCBs was enhanced. 

In general, the cleanup of oiled shorelines has been by mechanical, labor-intensive means. The use of surfactants to deterge and lift the oil from the surface results in more complete and rapid cleaning. Not only is the cleaning process more efficient, but it can also be less environmentally damaging because potentially less human intrusion and stress on the biologic community occurs and because the chemicals can make the washing more effective at a lower temperature. 

Table 6 Relationship Between the Use of Surfactants in the Preparation of Pharmaceutical Dosage Forms, Their Dispersibility in Water and Their HLB Values...

Surfactants. The use of surfactants is greatly restricted in formulating ophthalmic solutions. The order of surfactant toxicity is anionic > cationic >> nonionic. Several nonionic surfactants are used in relatively low concentrations to aid in dispersing steroids in suspensions and to achieve or to improve solution clarity. Those principally used are the sorbitan ether esters of oleic acid (Polysorbate or Tween 20 and 80), polymers of oxyethylated octyl phenol (Tyloxapol), and polyoxyl 40 stearate. The lowest concentration possible is used to perform the desired function. Their effect on preservative efficacy and their possible binding by macromolecules must be taken into account, as well as their effect on ocular irritation. The use of surfactants as cosolvents for an ophthalmic solution of chloramphenicol has been described [271]. This com-... 

In suspension polymerization, the monomer is agitated in a solvent to form droplets, and then stabilized through the use of surfactants to form micelles. The added initiator is soluble in the solvent such that the reaction is initiated at the skin of the micelle. Polymerization starts at the interface and proceeds towards the center of the droplet. Polystyrene and polyvinyl chloride are often produced via suspension polymerization processes. 

The use of surfactants to achieve low (<10 mN/m) interfacial tensions between oil and water as a means of enhancing recovery from partially depleted conventional reservoirs is well recognized I ll. In steam injection processes... 

The proposed mechanism of effect of surfactant and ultrasound is reported in Fig. 7.5. The long chain surfactant molecules attach to surface of nanoparticles due to physical adsorption. Only thin layer is adsorbed onto the CaC03 nanoparticles. Due to presence of ultrasound and use of surfactant will control the nucleation. Surfactant keeps the particles away from each other by preventing flocculation due to change in surface tension of reaction mass. The concentration of additives was changed from 0.2 to 1.0 g/L. Addition of 0.2 g/L tripolyphosphate shows the increase in the rate of precipitation which is determined from the Ca(OH)2 consumption. Polyacrylic acid shows the least rate of precipitation (0.115 mol/1), which... 

In summary, intratracheal instillation of CNTs has shown that their potential in eliciting adverse pulmonary effects is influenced by exposure time, CNT dose, CNT biopersistence, surface defects, and metal contamination [71, 72]. Despite the use of surfactants, all studies showed that intratracheal instillation caused major difficulties due to the agglomerative nature of CNTs in a biological environment. More realistic exposure methods, namely inhalation rather than intratracheal administration, are therefore needed for determining the pulmonary toxicity [59, 65, 73]. Several investigations have been performed by using administration different from intra-... 

Nerurkar, M. M., Burton, P. S., Borchardt, R. T., The use of surfactants to enhance the permeability of peptides through Caco-2 cells by inhibition of an apically polarized efflux system,... 

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