GRAFTA Nanotech
Petroleum Hydrocarbons and BTEX removal from Industrial Wastewater.
Solving Hydrocarbon Contamination
Petroleum hydrocarbons and BTEX (benzene, toluene, ethylbenzene and xylene) can enter surface water and groundwater resources through leakage or spillage from gas stations, oil and gas operations, fuel storage tanks and surface runoff in urban areas.​
It should be noted that the initial release of PHCs in most cases is in form the free phase product, technically characterized as Lower (than water) Non-Aqueous Phase Liquid (LNAPL). The LNAPL then diffuses and dissolves in water and migrates in dissolved form.
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PHCs include a wide range of hydrocarbon molecules that are categorized based on the number of carbon atoms in their structure. From a regulatory perspective, PHCs are categorized into four categories with different solubility, volatility and biodegradation rate.​
Fraction 1 (F1) encompasses the range of ECN from C6 to C10. It represents the volatile fraction of most hydrocarbon mixtures. BTEX representing the aromatic compounds also fall within this fraction (i.e. benzene, toluene, ethylbenzene and xylenes, BTEX).​
Fraction 2 (F2) encompasses the range of ECN from C>10 to C16. It represents the semi-volatile fraction and comprises aromatic and aliphatic subfractions in the ranges C>10 to C12 and C>12 to C16.​
Fraction 3 (F3) encompasses the range of ECN from C>16 to C34. It includes both aromatics and aliphatics in the C>16 to C21 and C>21 to C34 ranges.​
Fraction 4 (F4) encompasses compounds with ECN of C>34 to C50+. PHC within this range often make up a significant proportion of crude oils and petroleum products, although the fraction is generally considered to be of low mobility (volatility and solubility).
Fractions 1 and 2 comprise compounds that are both soluble and volatile, whereas Fractions 3 and 4 comprise fewer mobile compounds.
GRAFTA™ shows outstanding performance in removing PHCs and BTEX from contaminated groundwater and surface water as well as industrial process waters, following is a technical overview of GRAFTA™'s mechanisms, performance metrics, and application requirements for targeting hydrocarbons.
GRAFTA™ Product Line
GRAFTA™ comprises micro-scale inert particles embedded with numerous layers of graphene and graphene oxide nanosheets. The product is available in two formulations:
GRAFTA™ 1.0 (G1)
Designed for the adsorption of heavy metals and organic compounds. The core graphene based solution targeting metals, petroleum hydrocarbons, PAHs, BTEX, wide range of VOCs and Semi-VOCs including but not limited to chlorinated solvents (e.g. PCE, TCE, etc.), PCBs and a range of inorganics such as ammonia and phosphate.
GRAFTA™ 2.0 (G2)
GRAFTA™2.0 is engineered to add chemical reduction capability targeting reductive removal of metals particularly in higher oxidation states to target contaminants like selenium present as selenate followed by adsorption within the same matrix.
GRAFTA™ particles
For Petroleum hydrocarbons and BTEX, the graphene oxide content of GRAFTA™1.0 is the main ingredient that provides high adsorption capacity.
The unique structure of GRAFTA™ provides a massive surface area for adsorption, ensuring exceptional contaminant removal efficiency.
Hydrocarbon Removal Process using GRAFTA™
The graphene and to some extent graphene oxide content of GRAFTA are responsible for the adsorptive removal of dissolved PHCs and BTEX molecules, mainly through non-covalent Van der Waals forces and possibly through π-π stacking.
It should be noted that while GRAFTA is highly capable of absorbing free phase PHCs (and other oils), the objective of using GRAFTA (G1) is to remove the dissolved fraction of PHCs and BTEX.
GRAFTA is also effective in adsorbing the excess concentrations of PHCs and BTEX that are in many cases present in water or wastewaters in excess of solubility limits.
Hydrocarbon Removal Performance
Performance of GRAFTA has been applied and tested for a variety of waters contaminated with PHCs, BTEX and other types of hydrocarbons and heavy metals.
In one case, groundwater from a PHC impacted plume with relatively high concentrations of PHCs was tested and the results indicated that the removal of various fractions was achieved to non-detectable levels in the effluent.
In another application, where relatively high F3 concentration of F3 in a contaminated industrial cooling water was subject to removal, GRAFTA reduced the concentration from 1190 µg/L to non-detectable levels.
Influencing Factors
G1 performance in removal of PHCs, BTEX and other types of hydrocarbons is not hindered by environmental factors such as temperature or some of the typical chemical composition of the water subject to treatment.​
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There is no need to adjust the pH of water prior and after removal by G1. In most cases, it is expected to have other ions and metals be present in waters subject to PHC removal.
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Comprehensive testing has showed that other contaminants including metals, are also removed simultaneously.
Application Requirements
Large-scale application of G1 for PHCs and BTEX removal is simple and can be achieved by using any type of above ground vessel (tanks of various sizes and shapes, and made of either polyethylene or steel), that can house G1 and accommodate a preferably upflow hydraulic regime provided by minimal pumping requirement where gravity feed is not viable.
Retention time (Empty Bed Contact Time (EBCT)) of less than 10 minutes would typically result in over 99% removal of PHCs and BTEX.
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In addition to above ground treatment systems, G1 can also be injected into the groundwater system to form an adsorptive permeable reactive barrier (PRB) as part of in-situ risk management measures where required. Injection of G1 into groundwater contaminated with PHCs and BTEX has shown promising results in both injection hydraulics and PHC and BTEX removal efficiencies.
A standard GRAFTA™ system
End-of-Life Management
GRAFTA™ exhibits minimal leaching of adsorbed contaminants, ensuring environmental safety.
Toxicity Characteristic Leaching Procedure (TCLP) tests have confirmed that leachate concentrations are below regulatory limits, facilitating safe disposal or repurposing of spent media.
Further Case Studies
GRAFTA™ has extensive applications in the removal of hydrocarbons from water:
An industrial site releasing process water that after an oil-water separator the water contained polyacrylic hydrocarbons (PAHS) as well as phenolics. Read More...
The contaminated site impacts the local aquifer and lake with petroleum hydrocarbon released over time through an underground fuel storage tank on a private property. Read more...
GRAFTA™: A Hydrocarbon Removal Solution
GRAFTA™1.0 (G1) offers a highly effective solution for the removal of PHCs and BTEX from contaminated waters and wastewaters, achieving non-detectable effluent concentrations with relatively short retention times.
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To have a discussion about how GRAFTA™ can solve your hydrocarbon contamination issues contact us today.