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Table 4. Qualitative cost comparison of each example of sponge material models per gram for precursors, manufacture, and the environmental amenability of the product.

Table 4 Qualitative cost comparison of each example of sponge material models per gram for precursors, manufacture, and the environmental amenability of the product.

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Figure 2. Intermolecular and intramolecular polarity control the observed hydrophilic and hydrophobic properties of a surface and surface interactions with molecules. These physical properties manifest themselves both on the molecular level as the boiling/melting points of the target for bulk properties, such as adhesive and cohesive contact angles. Melting points are provided and serve to show how intermolecular forces caused by polarity affect physical properties, such as the boiling point.
Figure 2. Intermolecular and intramolecular polarity control the observed hydrophilic and hydrophobic properties of a surface and surface interactions with molecules. These physical properties manifest themselves both on the molecular level as the boiling/melting points of the target for bulk properties, such as adhesive and cohesive contact angles. Melting points are provided and serve to show how intermolecular forces caused by polarity affect physical properties, such as the boiling point.
Table 1. Properties of different types of crude oil as measured at 77 °F (25 °C). Distilled water is provided for comparison. Table 2. Different types of nonpolar targets, their viscosity, and density. Viscosity and density can affect the sorption speed and efficacy of sorption methods and which demonstrate qualitatively how nonpolar a sorbent surface is. robustness and resilience requires a lot of trial and error to opti- mize both precursors and manufacture, and often, it is more effective to design these materials for a specific intended use.
Table 1. Properties of different types of crude oil as measured at 77 °F (25 °C). Distilled water is provided for comparison. Table 2. Different types of nonpolar targets, their viscosity, and density. Viscosity and density can affect the sorption speed and efficacy of sorption methods and which demonstrate qualitatively how nonpolar a sorbent surface is. robustness and resilience requires a lot of trial and error to opti- mize both precursors and manufacture, and often, it is more effective to design these materials for a specific intended use.
shown in Fig. 3. Once oil can enter the sorbent, the porous capacity of an oil sponge is governed by its relative density defined by Gibson and Ashby as p*/p,, where p* is a material’s total density and p, is the density of the solid struts, which retain the sponge’s shape.”° “Porosity” is then equal to 1 - p*/p, and represents the total proportion of open space for oil to be con- tained in a material. The internal surface area of sorbents, usu- ally defined as meter?/gram sorbent, is often determined using gas adsorption techniques.”° Porous material structures have been theorized and computationally modeled to optimize parameters, such as relative density, pore geometry, and surface area. An added feature and advantage of sorbent materials with high structural porosity is buoyancy, which is enhanced by closed pores, but this extra space displaces the target fluid. Removing structural material to increase void space and porosity can also degrade mechanical sturdiness and so elastic properties in sorb- ents are often ideal because removing the oil can be achieved by deformation of the material that we know as “squeezing” or “wringing” seen in household sorbents. Striking a balance between maximum porosity and surface area with mechanical
shown in Fig. 3. Once oil can enter the sorbent, the porous capacity of an oil sponge is governed by its relative density defined by Gibson and Ashby as p*/p,, where p* is a material’s total density and p, is the density of the solid struts, which retain the sponge’s shape.”° “Porosity” is then equal to 1 - p*/p, and represents the total proportion of open space for oil to be con- tained in a material. The internal surface area of sorbents, usu- ally defined as meter?/gram sorbent, is often determined using gas adsorption techniques.”° Porous material structures have been theorized and computationally modeled to optimize parameters, such as relative density, pore geometry, and surface area. An added feature and advantage of sorbent materials with high structural porosity is buoyancy, which is enhanced by closed pores, but this extra space displaces the target fluid. Removing structural material to increase void space and porosity can also degrade mechanical sturdiness and so elastic properties in sorb- ents are often ideal because removing the oil can be achieved by deformation of the material that we know as “squeezing” or “wringing” seen in household sorbents. Striking a balance between maximum porosity and surface area with mechanical
Figure 4. CAG is the primary comparative test for hydrophobic properties of surfaces. The adhesive and cohesive forces between a sorbent material surface and water are often measured as the angle between the surface and the arc of the water drop, shown above.*? This allows a quantitative measure how water repellent and usually oil adsorbent the surface is with an angle range of 0° <0 < 180°. As discussed in the earlier sections and depicted in Fig. 2, there are many alkyl, aliphatic, and aryl liquid organic com- pounds, which are nonpolar due to low AEN and orthogonal EN vectors across bonds in the medium. It is then expected that the surfaces of organic polymers composed of these kinds of nonpo- lar molecular structures would have similar nonpolar intermo- lecular interactions and high sorbent adhesion properties with nonpolar fluids. The plastic industry has matured to the point where the degree of polymerization, crystallinity, functional group/structure selection, and physical morphology of poly- mers can be finely tuned in a bottom-up synthesis to optimize porosity, surface area, and the elastic mechanical properties desired to remove oil by squeezing. High surface area plastic structures can be synthesized using an arsenal of techniques, including supercritical drying, autoclaving, and gelling approaches, which can be used to create both polydisperse and monodisperse pore sizes.??-74 One crucial disadvantage of these materials is that many plastics cannot break down naturally and The loose, hierarchical classification methods we use here divide synthetic sorbents in two: they can be assembled from either a “bottom-up” synthesis from raw, unstructured chemi- cal precursors or “top-down” synthesis, which uses a previously existing material’s porous structure as a template for the new sorbent.*! The latter is a popular method throughout the recent literature because the method exploits the recognizable elastic mechanical properties of readily obtained household/industrial
Figure 4. CAG is the primary comparative test for hydrophobic properties of surfaces. The adhesive and cohesive forces between a sorbent material surface and water are often measured as the angle between the surface and the arc of the water drop, shown above.*? This allows a quantitative measure how water repellent and usually oil adsorbent the surface is with an angle range of 0° <0 < 180°. As discussed in the earlier sections and depicted in Fig. 2, there are many alkyl, aliphatic, and aryl liquid organic com- pounds, which are nonpolar due to low AEN and orthogonal EN vectors across bonds in the medium. It is then expected that the surfaces of organic polymers composed of these kinds of nonpo- lar molecular structures would have similar nonpolar intermo- lecular interactions and high sorbent adhesion properties with nonpolar fluids. The plastic industry has matured to the point where the degree of polymerization, crystallinity, functional group/structure selection, and physical morphology of poly- mers can be finely tuned in a bottom-up synthesis to optimize porosity, surface area, and the elastic mechanical properties desired to remove oil by squeezing. High surface area plastic structures can be synthesized using an arsenal of techniques, including supercritical drying, autoclaving, and gelling approaches, which can be used to create both polydisperse and monodisperse pore sizes.??-74 One crucial disadvantage of these materials is that many plastics cannot break down naturally and The loose, hierarchical classification methods we use here divide synthetic sorbents in two: they can be assembled from either a “bottom-up” synthesis from raw, unstructured chemi- cal precursors or “top-down” synthesis, which uses a previously existing material’s porous structure as a template for the new sorbent.*! The latter is a popular method throughout the recent literature because the method exploits the recognizable elastic mechanical properties of readily obtained household/industrial
Figure 3. Creating an open architecture of trusses, lumen, and pores to allow particles to flow in and out of sorbents can increase reusability. Ideally, particles (1 & 2) can move completely through the material without getting stuck in internal voids (3). Closed or “blind” pores (4) can limit the working capacity of a sorbent but are inevitable in all materials.
Figure 3. Creating an open architecture of trusses, lumen, and pores to allow particles to flow in and out of sorbents can increase reusability. Ideally, particles (1 & 2) can move completely through the material without getting stuck in internal voids (3). Closed or “blind” pores (4) can limit the working capacity of a sorbent but are inevitable in all materials.
Figure 5. Many top-down approaches in oil sponge research utilize prefabricated inner porous structures and use chemical deposition/etching to fabricate an oleophilic outer surface. A thin metal oxide surface layer is installed into a substrate architecture, such as polyurethane, which is then reacted with silyl alkyl chlorides leaving behind an extremely fine, even surface of alkyl chains (alk) which are shown to have excellent superhydrophobic contact angle properties. Silanol and alkylsilane-based materials are becoming increas- ingly popular, especially for their use in top-down syntheses using surface coatings on commercially obtained sponges. The common method of preparation of these surface-coated top- down sorbents is to take a porous architecture and place a metal oxide coating on the surface via electrolytic deposition, oxida- tion, or washing/evaporation. Once this coating has set a metal oxide layer on the surface of the already porous material, silyl alkyl chlorides, such as methyltrichlorosilane MeSiCls, are applied to the surface by liquid or gas methods (Fig. 5). Silicon-oxygen bonds form in favor of silicon-chlorine bonds, and HCl gas is released as by-product with the alkyl portion of the silane remaining. This new polar covalent network of polar silicon- oxygen bonds attached to the sponge anchors a usually superhy- drophobic, nonpolar alkyl surface. Because these layers are so Carbon allotrope materials, such as graphene, graphite, and carbon nanotubes (CNTs), are known to have a nonpolar sur- face structure of hexagonal rings with 120° sp? geometry, which makes them extremely symmetrical, uniformly electron- egative, and therefore very nonpolar. Graphene sheets are a mere 0.3 nm thick and have the ability to be folded, bent, and perforated to accommodate nonpolar fluids on a surface and so are similar to alkylsilanes and silanols because they can be set in place by treatment, which anchors them to the surface of a sponge or template.!? Carbonization of already porous carbon-based materials can create nonpolar domains of both crystalline carbon materials (graphene, graphite, CNTs) and nonpolar amorphous carbon. Top-down materials are especially advantageous because they can be made from almost any carbon-based precursor and heat treated, which allows for them to be made out of waste materials, such as plastics, lignocellu- losic biomass, or other persistent waste materials, which can
Figure 5. Many top-down approaches in oil sponge research utilize prefabricated inner porous structures and use chemical deposition/etching to fabricate an oleophilic outer surface. A thin metal oxide surface layer is installed into a substrate architecture, such as polyurethane, which is then reacted with silyl alkyl chlorides leaving behind an extremely fine, even surface of alkyl chains (alk) which are shown to have excellent superhydrophobic contact angle properties. Silanol and alkylsilane-based materials are becoming increas- ingly popular, especially for their use in top-down syntheses using surface coatings on commercially obtained sponges. The common method of preparation of these surface-coated top- down sorbents is to take a porous architecture and place a metal oxide coating on the surface via electrolytic deposition, oxida- tion, or washing/evaporation. Once this coating has set a metal oxide layer on the surface of the already porous material, silyl alkyl chlorides, such as methyltrichlorosilane MeSiCls, are applied to the surface by liquid or gas methods (Fig. 5). Silicon-oxygen bonds form in favor of silicon-chlorine bonds, and HCl gas is released as by-product with the alkyl portion of the silane remaining. This new polar covalent network of polar silicon- oxygen bonds attached to the sponge anchors a usually superhy- drophobic, nonpolar alkyl surface. Because these layers are so Carbon allotrope materials, such as graphene, graphite, and carbon nanotubes (CNTs), are known to have a nonpolar sur- face structure of hexagonal rings with 120° sp? geometry, which makes them extremely symmetrical, uniformly electron- egative, and therefore very nonpolar. Graphene sheets are a mere 0.3 nm thick and have the ability to be folded, bent, and perforated to accommodate nonpolar fluids on a surface and so are similar to alkylsilanes and silanols because they can be set in place by treatment, which anchors them to the surface of a sponge or template.!? Carbonization of already porous carbon-based materials can create nonpolar domains of both crystalline carbon materials (graphene, graphite, CNTs) and nonpolar amorphous carbon. Top-down materials are especially advantageous because they can be made from almost any carbon-based precursor and heat treated, which allows for them to be made out of waste materials, such as plastics, lignocellu- losic biomass, or other persistent waste materials, which can
Figure 6. Carbon biomass sources are abundant and most carbon biomass can be pyrolyzed under inert conditions at temperatures >350 °C. Crude graphene oxide has relatively nonpolar/hydrophobic bulk properties due to a very minor difference in chemical EN across the surface structure. Hydrogen gas and other reductants can further reduce the structure to become very nonpolar reduced graphene oxide or amorphous carbon. I a I a aR a a a way to create environmentally benign waste and pollutants from sponges deployed in oil spills. Many morphologies in nature are well adapted for oil collection, such as fibers and stems, because they contain capillaries, which can draw nonpo- lar liquids into their lumen or onto their surfaces depending on the nature of these materials. Cyclodextrins are well studied for their ability to contain nonpolar materials in their cavities, and synthetic adaptations of these molecules have been used with success.*® Cellulose, which is the most abundant form of carbon in the biosphere, is well known for its nonpolar, highly insolu- ble properties caused by the crystallinity and regularity of its glucose-based structure.*? Using aerogel formation and drying techniques, many normally dense natural materials can be physically altered to become porous. While novelty of synthetic biomaterial sorbents claim more attention, there is much to be said of materials, which are used as-is or barely processed from nature. Human hair, silk fibers, and kapok fibers have all been used to sorb oil for early oil spills.4° These biologically produced biomaterials do not really fit into the bottom-up or top-down classification because they are not manufactured and thus have the advantage to being as abundant and available as they can be grown or collected in case of an oil spill. The challenge of apply- ing both synthetic and collected materials effectively to a large-scale oil spill comes from supply issues and the ease of
Figure 6. Carbon biomass sources are abundant and most carbon biomass can be pyrolyzed under inert conditions at temperatures >350 °C. Crude graphene oxide has relatively nonpolar/hydrophobic bulk properties due to a very minor difference in chemical EN across the surface structure. Hydrogen gas and other reductants can further reduce the structure to become very nonpolar reduced graphene oxide or amorphous carbon. I a I a aR a a a way to create environmentally benign waste and pollutants from sponges deployed in oil spills. Many morphologies in nature are well adapted for oil collection, such as fibers and stems, because they contain capillaries, which can draw nonpo- lar liquids into their lumen or onto their surfaces depending on the nature of these materials. Cyclodextrins are well studied for their ability to contain nonpolar materials in their cavities, and synthetic adaptations of these molecules have been used with success.*® Cellulose, which is the most abundant form of carbon in the biosphere, is well known for its nonpolar, highly insolu- ble properties caused by the crystallinity and regularity of its glucose-based structure.*? Using aerogel formation and drying techniques, many normally dense natural materials can be physically altered to become porous. While novelty of synthetic biomaterial sorbents claim more attention, there is much to be said of materials, which are used as-is or barely processed from nature. Human hair, silk fibers, and kapok fibers have all been used to sorb oil for early oil spills.4° These biologically produced biomaterials do not really fit into the bottom-up or top-down classification because they are not manufactured and thus have the advantage to being as abundant and available as they can be grown or collected in case of an oil spill. The challenge of apply- ing both synthetic and collected materials effectively to a large-scale oil spill comes from supply issues and the ease of
Table 3. Sorbent materials are hard to compare effectively across the literature because they have different sorption capability testing methods and test different materials. One of the most universal materials used in sorbent testing are vacuum pump oils, which are often a mixture of alkyl hydrocarbons, siloxanes, and mineral oils.
Table 3. Sorbent materials are hard to compare effectively across the literature because they have different sorption capability testing methods and test different materials. One of the most universal materials used in sorbent testing are vacuum pump oils, which are often a mixture of alkyl hydrocarbons, siloxanes, and mineral oils.
Metal-coated silane/alkylsiloxane nr = not reported, GO = graphene oxide, rGO = reduced graphene oxide.
Metal-coated silane/alkylsiloxane nr = not reported, GO = graphene oxide, rGO = reduced graphene oxide.
Table 5. Cost of cleaning Deepwater Horizon (DH) incident-size spill (4.9 million barrels) with materials based on cost parameters. Combining the best known performance parameters at a cost of $0.50 a gram gives a price of $9.23 x 10’. stockpiled, and deployed immediately at spills, their use would also offer enhanced outcomes for the local economy and nearby populations of people and, if designed to be rigorously benign in the ecology, the wildlife too. Instead of offering the monetary amount for each kind of technology, which can change with respect to the global mar- ket for the price of individual precursors, a generalized esti- mation for a theorized material is offered. For Material A, which can contain 1 g of crude oil per gram of sorbent the, cost to manufacture the material, precursors included, will be con- servatively $1 per gram. Material A will only be able to be used 1 time and disposed of immediately, hazardous waste disposal/ handling costs notwithstanding. The Deepwater Horizon inci- dent released 4.9 million barrels of crude oil (465,307 metric tonnes, 4.65 x 10!! ¢).3 Each advancement that moves these actors forward can quickly lower the price. If the cheapest precursors, such as lignocellulosic biomass, which is an abun- dant waste product, could be sourced for $0.01 per gram, the price would be 100* cheaper (Material B) and would cost less than BP’s settlement of $5.5B. If this material could then be enhanced to increase its capacity (Material C), be reused mul- tiple times by enhancing the collection strategy on the ground (Material D) or both this price can goes down another two order of magnitude based on values seen thus far in materials found in the literature.
Table 5. Cost of cleaning Deepwater Horizon (DH) incident-size spill (4.9 million barrels) with materials based on cost parameters. Combining the best known performance parameters at a cost of $0.50 a gram gives a price of $9.23 x 10’. stockpiled, and deployed immediately at spills, their use would also offer enhanced outcomes for the local economy and nearby populations of people and, if designed to be rigorously benign in the ecology, the wildlife too. Instead of offering the monetary amount for each kind of technology, which can change with respect to the global mar- ket for the price of individual precursors, a generalized esti- mation for a theorized material is offered. For Material A, which can contain 1 g of crude oil per gram of sorbent the, cost to manufacture the material, precursors included, will be con- servatively $1 per gram. Material A will only be able to be used 1 time and disposed of immediately, hazardous waste disposal/ handling costs notwithstanding. The Deepwater Horizon inci- dent released 4.9 million barrels of crude oil (465,307 metric tonnes, 4.65 x 10!! ¢).3 Each advancement that moves these actors forward can quickly lower the price. If the cheapest precursors, such as lignocellulosic biomass, which is an abun- dant waste product, could be sourced for $0.01 per gram, the price would be 100* cheaper (Material B) and would cost less than BP’s settlement of $5.5B. If this material could then be enhanced to increase its capacity (Material C), be reused mul- tiple times by enhancing the collection strategy on the ground (Material D) or both this price can goes down another two order of magnitude based on values seen thus far in materials found in the literature.
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