Liquid Soil Removal

Electroosmosis is used to remove liquid (moisture) from different porous solids (e.g., in drying soil for building purposes, which improves the bond between the foundations and the soil). A combination of electrophoresis and electroosmosis is sometimes used to dry peat or clay. In this way, the water content of peat can be reduced from 90% to 55-60%. Unfortunately, the energy required for a further reduction of the water content is very high. 

U.S. EPA bases its 1 gallon/acre/day leak detection sensitivity on the results of calculations that show that, theoretically, an LDS overlying a composite bottom liner with an intact FML component can detect, collect, and remove liquids from a top liner leak rate <1 gallon/acre/day. This performance standard, therefore, can be met with designs that include a composite bottom liner. Based on numerical studies, one cannot meet the leak detection sensitivity with a compacted soil bottom liner, even one with a hydraulic conductivity of 10-7 cm/s. Therefore, the emphasis of this standard is on selecting an appropriate bottom liner system. 

Figure 2. Liquid soil removal from substrate in the presence of surfactants.

The importance of a surfactant - rich phase, particularly a lamellar one, to detergency performance was noted for liquid soils such as C16 and mineral oil (3.6). Videomicroscopy experiments indicated that middle phase microemulsion formation for C12E04 and Cjg was enhanced at 30 °C, while at 18 °C, oil - in - water, and at 40 °C, water - in - oil microemulsions were found to form at the oil - bath interface (3.6). A strong temperature dependence of liquid soil removal by lamellar liquid crystals, attributed to viscosity effects, has been noted for surfactant - soil systems where a middle - phase microemulsion was not formed (10). 

Laundry formulations are the greatest consumer of LAS, being used as the primary surfactant in powder, tablet and liquid formulations providing good degreasing and soil removal properties. Some soap is normally added to the formulation to control the foaming... 

Since the 1990s enzyme mixtures have been commonly used in heavy-duty liquids. Most products contain a minimum of a protease for removal of proteinaceous soils and an amylase to facilitate starchy food-based soil removal. Some products contain lipases for degrading fatty or oily soils and cellulases to improve fabric appearance by cleaving the pills or fuzz formed on cotton and synthetic blends. 

Light-duty liquid or gel dishwashing detergent compositions having controller pH and desirable food soil removal, rheological, and sudsing characteristics... 

A recent review [32] describes several cases in which the maximum soil removal occurs when the soil is incorporated into an intermediate phase, such as a microemulsion or lamellar liquid crystals. These intermediate phases form at the interface between the soil and the washing bath. The phases grow up to a point and then, as a result of agitation, break off into the bath, where they are emulsified into the aqueous solution. 

The mechanisms underlying the detergency and soil removal process have been reviewed by many authors [164-172], This section briefly summarizes the test methods used to characterize the performance of liquid laundry detergents. There are typically three stages of testing during product development (1) laboratory evaluation, (2) practical evaluation, and (3) consumer tests. 

Removal of Liquid Soil Removal of liquid (oily) soil by aqueous baths is accomplished mainly by a roll-back or roll-up mechanism in which the contact angle that the liquid soil makes with the substrate is increased by adsorption of surfactant from the cleaning bath. 

When surfactants of the proper structure are present in the bath, they will adsorb at the substrate-bath (SB) and liquid soil-bath (OB) interfaces in such a fashion (i.e., with the hydrophilic group oriented toward the aqueous bath) as to reduce jSB and Job, with consequent reduction in the work to remove the soil from the substrate. Reduction in ySB will also cause a decrease in cos 0 and an increase in 0, resulting in the observed roll-back of the liquid soil. Many investigators of oily soil removal,... 

Liquid-crystalline phase or microemulsion formation between surfactant, water, and oily soil accompanies oily soil removal from hydrophobic fabrics such as polyester (Raney, 1987 Yatagai, 1990). It has been suggested (Miller, 1993) that maximum soil removal occurs not by solubilization into ordinary micelles, but into the liquid-crystal phases or microemulsions that develop above the cloud point of the POE nonionic. 

Studies of the soil removal properties of polyoxyethylenated straight-chain primary alcohols on cotton and Dacron-cotton permapress fabric indicate that this detergency maximum with change in the number of oxyethylene units in the POE chain is also shown on these fabrics. In liquid no-phosphate formulations built only with diethanolamine to provide an alkaline pH, optimum removal of both sebum and clay soils from Dacron-cotton permapress at 49°C in 150 ppm hard water occurs with about 5, 9, and 10 oxyethylene units for POE C9-11, C12-15, and C16-18 alcohol mixtures, respectively. For removal of the same soils from cotton at the same temperature, the optimum POE chain lengths are about two oxyethylene units larger (Albin, 1973). 

The effect of changing the hydrophilic group from nonionic to anionic can be seen by comparing the soil removal properties of these same POE alcohols with two series of anionics made from the same hydrophobes, either by sulfating the alcohol mixture directly or after polyoxyethylenation with 3 or 6 mol of ethylene oxide. Using the same liquid no-phosphate formulation and the same laundering conditions at 49°C in 150 ppm hard water, the following results were obtained (Albin, 1973) ... 

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