Hydrology: Cleanup Surfactant - Research Paper Example

Hydrology; Cleanup Surfactant Hydrology; Cleanup Surfactant Introduction Groundwater contamination as well as soil by petroleum products and organic solvents has become a significant environmental concern in the world today. These compounds tend to seep in the subsurface as NAPL (non- aqueous-phase liquid) or a separate organic-phase. When NAPL is being transported downwards as a result of capillary and gravitational forces, a part of organic liquid tend to be retained in the soil pores. They are retained as ganglia or immobile globules. The retention of the organic liquid as immobile globules takes place as a result of interracial forces. The residual organic liquid facilitates for an aquifer contamination. This takes place as water dissolves in the soil to join the rest of the ground water (Brusseau et al., 2009). It is hence evident that the contaminants are stored in the soil. In other words soil is also contaminated. It had been long believed that pump and treat methods were helpful in cleaning up contaminated soil. However, it has been discovered that these methods are neither economical nor effective means of recuperating residual NAPL from the contaminated aquifers. The inefficiency is attributed to low aqueous solubility of most NAPL as well as large interracial tension that exist between NAPL and groundwater. These aspects prevent displacement of residual NAPL globules at realistic pumping velocities. Aqueous surfactant solutions have instead been approved as the best criteria of removing NAPL from the contaminated aquifers (McCray et al., 2001). BioSolve and PetroSolve are examples of the aqueous surfactant solutions used in cleaning up soil in the world today. Various aspects are linked to these products which imply why these products are recommendable in the clean-up process as the document discusses. Discussion There are two main reasons why aqueous surfactants are recommendable in soil clean-up process. One of the reasons is that they tend to increase the superficial solubility of NAPLs. Secondly, they reduce interracial tension available between organic and aqueous phases. These phases help in inducing the mobilization of the residual organic liquids. The BioSolve and PetroSolve surfactants cleanup facilitate the removal of deposited and sorbed polychlorinated biphenyls (PCBs), the diesel fuels from the soil as well as the polycyclic aromatic hydrocarbons (PAHs). These techniques have succeeded as a result of critical micelle concentration. This aspect dramatically enhances the aqueous solubility of the hydrophobic organic compounds (Carroll & Brusseau, 2009). BioSolve can be defined as a superior alkaline cleaner that is designed specifically to remove stubborn build ups of heavy organic soiling. It is made of high alkaline blend of anionic, non-ionic and amphoteric surfactants. They are usually dissolved in an aqueous solution that incorporates a sequrstrant. The aqueous solution helps in achieving superior hard water performance. PetroSolve, on the other hand, is an extremely effective cleanup agent made of petroleum based agents. The ingredients used in the manufacture of PetroSolve include the light petroleum distillates (Brusseau et al., 2009). The petroleum distillates include materials such as Naphtha and parafins. Other component that is incorporated in PetroSolve is aromatic and benzene. There are number of cheap and effective surfactants in the society. Nanoremediation is one mode cheap mode of surfactants used in the society. It encompasses the use nano-sized reactive agents. These agents tend to immobilize or degrade contaminants. In groundwater or soil nanoremediation, the nanoparticles tend to be brought into contact with contaminants via the in situ injection. Pump and treat process can also be used. The nanomaterials then degrade the available organic contaminants. The degradation of these contaminants is done through the redox reactions or adsorption to and immobilization of metals like arsenic or lead. This technology has been used in the commercial sector in groundwater remediation. Research on whether the nanoparticles can be used in cleaning up gases is also on going. Nanomaterials are very reactive as a result of their great surface area per unit mass (McCray et al., 2001). This technology is relatively cheaper but it is effective hence accepted by many. Bioremediation is another process of decontamination through the biological means. It is among the cheapest type of surfactants. However, it is effective. It entails treating the environment using particular plants for example the use of phytoremediation. Bioremediation is at times used together with the pump and treat system. In bioremediation all bacteria either are specially bred or have naturally occurred are made to consume the contaminants from the extracted groundwater. The system is at times referred to as the bio-gac system. Most of the times, the groundwater tends to be recycled so as to allow a continuous flow of water. This enhances growth of bacteria population. Mycoremediation is a bioremediation form. It is a process of making use of fungi in returning an environment that have been contaminated by the pollutants (Carroll & Brusseau, 2009). This is an effective system although it is relatively cheap. The BioSolve and the PetroSolve surfactants have been indicated in various works as being used in various clean up processes in the society. In cleanup processes recorded in articles BioSolve have been indicated being used as the BioSolve Pinkwater. In this form it is represented as the water-based, proprietary, biodegradable formulation of both surfactants and performance additives. When in a dilute aqueous solution, the BioSolve Pinkwater creates the micro-emulsions (micelles) when they are applied vigorously to hydrocarbon contaminants (Smith & Burns, 2002). The article indicates that when BioSolve is being used micellular emulsions usually take palce. These emulsions perform three functions that are very essential. These functions form the basic requirements across the diverse mitigation applications. These requirements include increasing solubility, improving bioavailability and reducing volatility. It has been indicated that BioSolve surfactant was formulated and tested from 1970s to 1980s. For the last 30 years, BioSolve surfactants have been in a constant use by professionals in addressing wide range of applications attributed to hydrocarbon contamination. One of the applications is the odor control at fuel spills and excavations and hydrocarbon vapor suppression. Professionals have also been using the BioSolve surfactants in in-situ soil bioremediation and remediation, spill cleanup and equipment cleaning as well as tank and pipeline degassing (Thomson & International Conference of Groundwater Quality, 2005). Sludge removal is another aspect that BioSolve surfactants have been used to solve. It has been indicated that the BioSolve Pinkwater has withstood the test of time thus becoming hydrocarbon leading product. It has been defined by customers as being easy in its use as well as highly effective. It has also been indicated as worker friendly and environmentally responsible. It has been used by environment remediation contractors and engineers, major oil companies, and industrial maintenance contractors among others. BioSolve products have gained overwhelming recommendation across North America and other parts of the world. There are six distribution centers of the BioSolve surfactants in USA and 17 in foreign countries (Brusseau et al., 2009). This implies that BioSolve products have been in use. BioSolve became a renowned hydrocarbon mitigation agent due to its proven effectiveness, safe as well as easiness in its use. Its use has been attributed to a number of benefits. One of the benefits is that it removes stubborn hydrocarbons aggressively. The non-ionic surfactants formulation in BioSolve products is strongly oil-loving and lipophilic. When the BioSolve products have been applied in a given surface whether be it stone, sand, cement or steel, hydrocarbons get pulled out aggressively. The hydrocarbon that had been mobilized tends to be emulsified within the BioSolve pinkwater solution. This makes the hydrocarbon to become non-combustible, non-volatile and miscible in water (Carroll & Brusseau, 2009). The dual functionality tends to be of universal benefit when it comes to addressing contamination in hydrocarbon. When BioSolve is applied hazardous vapors are transformed to become non-volatile, contaminating sludge and grease is removed and residual NAPL is solubilized and mobilized. In terms of its use BioSolve is neither a solvent nor a foam but a water-based solution. The working solution is 94% to 98% typically water. This aspect makes it easy to handle, easy to mix and easy to apply. It has a benefit in its predictable performance. It has a stable formula in that it holds incompatible ingredients together in water-based solution. It has also been noted as broadly effective. It works with brackish and fresh water and works on a range of surfaces soil types inclusive. They can also be used in gaseous and liquid hydrocarbons that are insoluble in water. BioSolve products are also recommendable since they do not contain hazardous ingredients (McCray et al., 2001). The BioSolve Pinkwater is usually sold as a viscous concentrate. It is usually diluted in most of its applications except when being used in the oil wells, bilges and sewer systems. In a typical working solutions, the strength of BioSolve range from 2% to 6% by volume. After it has been added in water which in a tank having considered the contents, the mixture is usually stirred to acquire a uniform solution (Smith & Burns, 2002). The main markets of BioSolve pinkwater include the industrial maintenance, emergency response and soil remediation. For hydrocarbon contaminate emulsification to be achieved four elements are usually incorporated. Method of agitation can be used in emulsification of hydrocarbon contaminate. Agitation can take various forms like vacuum extraction, water jet, mixing, pumping, soil tilling, scrubbing and others. Agitation can also be defined as the mechanical energy. They are broadly used by the contractors. BioSolve is used in accelerating natural bioremediation of the contaminated soil either on lands applied to biopiles or on site via surface application. When Biosolve is mixed with contaminated soils the hydrocarbons tend to come into contact with strong lipophilic surfactant. The bacteria transform hydrocarbons into digestible material. The surfactants then solubilize the contaminants hence pulling them into an aqueous solution. When it is sprayed directly onto an oil spill the BioSolve Pinkwater eliminates explosion and fire hazard (National Research Council (U.S.), 1997). An aggressive agitation combined with a course stream ends up reducing volatilization. The application of BioSolve Pinkwater facilitates the roadway cleanup and also eliminates hazardous oil sheen. PetroSolve is another aqueous surfactant solution that is widely used in cleaning up NAPL contaminated sites. It is in the class of biosurfactant. It can also be referred to as a non-ionic biosurfactant. It is formulated specially to be used in the remediation treatments. The PetroSolve application can be used in remediating a wide range of contaminants including the heating oil, chlorinated solvents as well as diesel. It can be applied through a number of ways. The ways include pump and treat enhancement, direct injection and the groundwater recirculation with the use of ISD equipment. The ETEC technology can help in designing a surfactant flushing application that will fit every site’s unique features. Most applications have the potential of utilizing the site infrastructure which will lead to a treatment that is cost effective (Brusseau et al., 2009). The PetroSolve technique has similar features to those of BioSolve. For example, they it has features which have the potential of increasing solubility of NAPLs. This is a crucial aspect that makes them to outdo other forms of contamination clean up. They also tend to reduce the interracial tension that tends to exist between the aqueous and organic phases. Documents and records are available that reveal that PetroSolve have been in use (National Research Council (U.S.), 1997). This technique plays a pivotal role when it comes to cleaning up surfaces of any nature contaminated with oil based contaminants. It is, however, worth noting that water is the main store of these contaminants. It is also applicable in decontamination or cleaning up tools and equipment used at the remediation sites on drilling rigs, in refineries, in the industrial maintenance operations and following spill cleanup. Most tar and oil build-up can easily be washed away on contact. The PetroSolve technique has been in use for about two decades. It has been greatly used for the surfactant enhanced remediation in the attempts of mobilizing and solubilizing the residual NAPL. It also facilitates its recovery as well as disposal. Depending on the plume and soil characteristics the PetroSolve decontaminant can reach the contaminated zones via the deep injection wells or by gravity fed via injection galleries from the surface (Thomson & International Conference of Groundwater Quality, 2005). After the residual NAPL have been desorbed from the soil surfaces on contact, the PetroSolve solubilizes the hydrocarbons in an aqueous emulsion. This enables these hydrocarbons to be extracted. Rapid turnaround has been essential when fuel or oil storage tank is scheduled for maintenance or stripped for repair. Unpumpable sludge and high vapor levels can frustrate this time-sensitive process. Such challenges were well addressed by the PetroSolve. In the process of removing as well as repairing the fuel storage tanks PetroSolve has proven to be an effective tool. It plays a pivotal role in suppressing the volatile organic vapors that tend to feature when one is working with the fuel tanks (Smith & Burns, 2002). The PetroSolve assists in loosening as well as removing tank bottom sludge. The PetroSolve is a major construction and remediation work-sites where the excavation of contaminated soils can release the hazardous VOCs or noxious organic odors. The dilute solution of the PetroSolve tends to be directly sprayed onto new exposed stockpiles or soil surfaces of contaminated material where volatilization is going on. In the society, there are several plant-based surfactants. In New York City brownfield, S-ISCO also known as a surfactant-enhanced ISCO system was implemented. It was a system that was meant for coal tar contamination remediation. It was implemented solely to remediate the coal tar that was present as residual NAPL that is held within the pore spaces of predominately silty and sandy soil. A patented, co-solvent mixture/plant-based surfactant and an alkaline-activated sodium persulfate were delivered in the subsurface through the pressure-pulsing injection enhancement technology (National Research Council (U.S.), 1997). This was between October 2010 and March 2011. The supplier injected S-ISCO for five months. It destroyed 90% of the coal tar that was related contaminants. These contaminants included naphthalene, PAHs and BTEX in a targeted interval. This indicates that there are available and effective plant-based surfactants. Critical micelle concentration (CMC) can be defined as surfactant’s concentration in a bulk phase, above the aggregates of tenside molecules. These molecules are termed as micelles. As the surfactant’s concentration tends to increase, adsorption takes place on a surface until overlaid. This corresponds to minimum value of Surface Tension. A CMC’s knowledge is very crucial when using surfactants. Since the surface tension does not reduce above the CMC. In various processes CMC tends to specify the limiting concentration for a meaningful use. When micelles’ formation is desirable, the CMC is hence a measure of the surfactant’s efficiency. Scientific characterization variables of the surface adsorption can be derived from CMC as well. Examples include the surface excess and area per molecule. The last variables that can be used in determining the coefficient of adsorption from the measurements are done with a bubble pressure tensiometer (McCray et al., 2001). In other words measurement of CMC of PetroSolve and BioSolve surfactants was done through a tensiometer. The tensiometer executes this mandate by measuring the concentration series’ surface tension. There are various types of bubble pressure tensiometer such as BP50 and BP 100. The figure below is of a BP100. A bubble pressure tensiometer is a crucial apparatus used to determine dynamic surface tension. It measures the highest internal pressure of a gas bubble formed in a liquid being tested. The whole set-up incorporates the Young-Laplace equation in determining the factor in subject. Where p is the internal pressure of the spherical gas bubble, r is the radius of the curvature and σ is the surface tension. Once a gas bubble gets produced in a liquid at the capillary’s tip the curvature increases and then decreases. This eventually triggers the occurrence of pressure maximum. The greatest curvature and thus the greatest pressure happen when the curvature’s radius equals the capillary’s radius as demonstrated in the figure below. Pressure characteristic for the bubble pressure measurement, position of pressure maximum If the capillary’s radius is known, the surface tension can easily be calculated from the maximum pressure Pmax. As the capillary gets immersed in the liquid, P0 the hydrostatic pressure resulting from the liquid’s density and immersion depth has to be deducted from the pressure measured. This eventually gives rise to this formula. The value that will be achieved is equivalent to surface tension at a particular surface age. The surface age can be defined as the time from when the bubble starts forming to when the pressure maximum will occur. The surface tension’s dependence on surface age tends to be measured by varying the speed through which bubbles are produced. The bubble pressure measurements tend to enable the calculation of the surfactant rate parameters like adsorption coefficient and diffusion coefficient. Dependency of the surface tension on the surface age After achieving the SFT (surface tension), CMC can easily be achieved graphically. The CMC of the BioSolve and PetroSolve was found to be approximately 150 mg/l. CMC is achieved when a straight line passing via a plateau intersects with the regression straight line as demonstrated in the figure below. Determination of the CMC with a tensiometer The PetroSolve and BioSolve surfactants need to be pure. The surface tension is usually dependent on concentration logarithm over a large range. Above CMC, SFT is independent of concentration extensively. The results of CMC lie from intersection between regression straight line of linearly dependent region and a straight line passing via the plateau. In other words the tensiometer reading is represented on a graph coupled with lines composing it (Thomson & International Conference of Groundwater Quality, 2005). One locates the value by considering these lines whereby CMC exists at intersection of regression line and straight line passing via the plateau. Sorption isotherm tends to describe the equilibrium of a material’s sorption at a surface at constant temperature. It is a representative of materials that are bound on a surface as a function of material available in the solution or gas phase. The sorption isotherms are usually used like empirical models. Freundlich adsorption isotherm is the technique that was used in collecting data for PetroSolve and BioSolve surfactants in terms of sorption isotherm (Smith & Burns, 2002). It is an empirical relation between solute concentrations on an adsorbent surface to the solute concentration in a liquid. The adsorbed amount is measured in mol/kg. The particles of the PetroSolve and BioSolve surfactants were measured by the nanosight range instruments. They operate in a mode of light scatter. All the particles in the instrument can be easily visualized and measured after being studied by this instrument. The instrument is capable of operating in fluorescence mode when the fluorescent nanoparticles are measured. The nanosight range instrument measures both the particles size and their concentration. This could be the main reason why it was preferred mode to measure the BioSolve and PetroSolve surfactants’ particles (National Research Council (U.S.), 1997).  The NanoSight range machine is capable of visualizing, Sizing as well as determining the Concentration of the liquid being tested. This implies that when the sample of the PetroSolve or BioSolve surfactant is presented in the machine, the machine will offer the researcher with an opportunity of visualizing the particles of the surfactant. It will also measure the sizes of these particles automatically as well as determine the surfactant’s concentration. The NanoSight range machine makes use of the Nanoparticle Tracking Analysis also referred to as (NTA) so as to characterize the nanoparticles in the solution. The machine is capable of analyzing each particle individually. They are, however, analyzed simultaneously through direct observation as well as measurement. The particle by particle strategy produces very high resolution results for the distribution of particle sizes as well as concentration. The visual validation makes NanoParticle range machines preferable. This is because they offer additional confidence in the data received. Both the concentration and particle size are measured while the fluorescence mode offers the differentiation naturally and labeled particles. The sizes of the BioSolve and PetroSolve surfactants range between 0.7 to 0.99 Micron. Surface tension can be defined as the elastic tendency of liquids that tend to make them acquire the least possible surface area. In terms of surface tension, surfactants acts like compounds lowering interfacial tension or surface tension. Surfactants may act as wetting agents, foaming agents, dispersants or emulsifiers. The collection of data of PetroSolve and BioSolve surfactants’ surface tension was done through classical techniques. One of the techniques is the spinning drop method. The apparatus used in obtaining data related with surface tension of PetroSolve and BioSolve surfactants is the maximum bubble pressure apparatus. The surfactant layers of these surfactants are well studied by x-ray reflectivity or ellipsometry (Carroll & Brusseau, 2009). Conclusion It is evident from the discussion above that contamination in the world today is at a very high level. Industrialization as well as increased use of chemicals is the leading cause of contamination being experienced especially in the soil and the groundwater. This contamination is a threat to the human life because the ground water will find its way to the river or get used in farming. Similarly, soil gets contaminated as well. This implies that the plants that will be planted will be growing in a contaminated environment. There are, therefore, high chances of these plants’ fruits or products to have contents of contaminants. This means that when consumed by human beings they can impart advance impacts to the human beings. Similarly, if the contaminated water seeps to the river, all the aquatic animals will have adverse effects. These effects will easily be passed over to the human life. This shows how important it is for cleaning up both the soil and the groundwater for the safety of all living things. References Brusseau, M., Narter, M., Schnaar, S. & Marble, J. (2009). Measurement and Estimation of Organic-liquid/Water Interfacial Areas for Several Natural Porous Media. Environmental Science & Technology 43(10): 3619-3625. Carroll, K., & Brusseau, M., Dissolution, (2009). Cyclodextrin-enhanced Solubilization, and Mass Removal of an Ideal Multicomponent Organic Liquid. Journal of Contaminant Hydrology 106(1-2): 62-72. McCray, J., Bai, G., Maier, R., & Brusseau, M. (2001). Biosurfactant-Enhanced Solubilization of NAPL Mixtures. Journal of Contaminant Hydrology 48(1-2), 45-68. National Research Council (U.S.). (1997). Innovations in ground water and soil cleanup: From concept to commercialization. Washington, D.C: National Academy Press. Smith, J. A., & Burns, S. E. (2002). Physicochemical groundwater remediation. New York: Kluwer Academic. Thomson, N. R., GQ 2004, & International Conference of Groundwater Quality: Bringing Groundwater Quality Research to the Watershed Scale. (2005). Bringing groundwater quality research to the watershed scale. Wallingford: International Association of Hydrological Sciences. Read More