Solid Soil Removal

Solid Soil Type and Size. Different soHd soils differ greatly in ease of removal and redeposition behavior. These differences can be traced to particle size and soil—substrate bonding. The effect of particle size variation on detergency has been studied with soil removal and redeposition techniques. 

In this method lg of soil is refluxed with 2M sodium hydroxide after centrifuging to remove solids. The clean extract is digested with perchloric acid-nitric acid at 265 °C. The iodine content of the extract is determined by the catalytic action of iodine on the oxidation of arsenic III ions with cerium IV ions. Between 96 and 97% recovery of added iodine spikes to soil were obtained by this method. 

Waste water, soil, sediment, solid waste Extraction (liquid-liquid, Soxhiet, sonication) with organic solvent such as dichloromethane, removal of water, volume reduction. GC/MS (EPA method 8270) 20 g/L (ppb) for wastewater 1,300 g/kg (ppb) for low soil, sediment 110 at 100 g/L (100 ppb) EPA 1986a... 

Precleaning inspections of the parts may also help in establishing the proper temperature and concentration at which to operate the bath. Quite often, bath temperatures and/or concentrations are increased in an attempt to improve efficiency. While this works in many cases, some soils can become set at higher temperatures and concentrations. When bath oils and solids are present on a part, the rapid removal of the oil due to higher bath temperature creates a difficult-to-remove solid. Proper cleaning may require a lower temperature, longer soak time, and some form of agitation. 

Skjemstad, J. O., Clarke, P,Taylor, J. A.,Oades, J. M., and Newman, R. H. (1994a).The removal of magnetic materials from surface soils. A solid state 13C CP/MAS NMR study. Aust. J. Soil Res. 32,1215-1229. 

Time - resolved spectra of a solid hydrocarbon layer on the surface of an internal reflection element, interacting with an aqueous solution of a nonionic surfactant, can be used to monitor the detergency process. Changes in the intensity and frequency of the CH2 stretching bands, and the appearance of defect bands due to gauche conformers indicate penetration of surfactant into the hydrocaibon layer. Perturbation of the hydrocarbon crystal structure, followed by displacement of solid hydrocaibon from the IRE surface, are important aspects of solid soil removal. Surfactant bath temperature influences detergency through its effects on both the phase behavior of the surfactant solution and its penetration rate into the hydrocaibon layer. 

The results obtained with C19 and as model soils suggested that the crystal form of the hydrocarbon can affect surfactant penetration and hence removal. Hexacosane (C26), with a melting point of 57 °C, allows investigation of the effect of temperature over a wider range than the systems described above. Additional details about the relationship of surfactant phase behavior to solid soil removal can be obtained, and the efficiency of the displacement mechanism can be explored further, using C2g as a model soil. 

Adsorption of bath components is a necessary and possibly the most important and fundamental detergency effect. Adsorption is the mechanism whereby the interfacial free energy values between the bath and the sohd components (solid soil and substrate) of the system are lowered, thereby increasing the tendency of the bath to separate the solid components from one another. Furthermore, the sohd components acquire electrical charges that tend to keep them separated, or acquire a layer of strongly solvated radicals that have the same effect. If it were possible to follow the adsorption effects in a detersive system, in all their complex ramifications and interactions, the molecular picture of soil removal would be greatly clarified. 

In line with cleaning efficacy, solid particles have also been incorporated into some light-duty liquid formulations with the objective of increasing the effectiveness of the products in removing solid caked-on or baked-on soiling from articles. 

Anionic and nonionic surfactants can reduce the work required to remove solid particles. This is because these surfactants adsorb to hair or hydrophobic soils with their hydrophobic tails in contact with the hydrophobic surfaces and their hydrophilic heads oriented toward the bulk solution. This has the effect of reducing ypw and ypw and, thus, Wa. Even more importandy, anionic surfactants remove particulates as a result of the increase of negative potentials on soil and hair upon anionic adsorption to these surfaces. This increases mutual repulsion between particulate and fiber, thus facilitating soil removal. 

Particulate Soil Removal of particulate solid soil by aqueous baths is accomplished by the following mechanisms ... 

Figure 33-3 shows two types for liquids. The side tube is a reservoir for the sample when gas is not flowing. The sample is added to the tube on the left and connected to the apparatus. Gas then is admitted into the top of the right tube. If a solution is the sample, then a frit is used to disperse the gas. If a soil or solid is the sample, then the frit is removed. 

The most frequently discussed topic in washing is the role of solubilisation processes. Many investigators [76] attract attention to the fact that the surfactant concentration in a washing solution is much lower than CMC, and in this connection, solubilisation of oils is principally excluded due to absence of surfactant micelles. At the same time, the review of recent works [85, 86] show that solubilisation can play a dominant role both in washing fabrics and in the removal of soils from solid surfaces. These views are based on the following mechanisms. Surfactants adsorb at w/o interfaces under formation of densely packed adsorption layers which leads to a high local surfactant concentration as compared with the rather low concentration in the washing solution. After that, noticeable penetration of water into the oily soil is possible, under formation of liquid-crystal phases. Then, mesomorphic phases are swelled and destroyed under the formation of emulsion droplets. 

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