The Art-and-Craft Material That Could Clean Our Oceans

Worldwide, a shocking 2.7 billion litres of oil makes its way into our oceans every year.[1] Oil spills are detrimental to the environment and to the species that live within and nearby the sea. The substance coats the feathers of birds and the bodies of mammals, causing them to lose their ability to regulate their temperature and leading to hypothermia, which often becomes fatal. Additionally, the pollutant is often toxic, poisoning and potentially killing organisms that come into contact with or ingest it.[2] The removal of oil from our oceans is therefore paramount.

Although there exist methods to reduce the effect of oil spills, more effective techniques are currently being developed.

A popular method is the use of lipophilic (oil-liking) sorbents; a type of material with the ability to soak up specific liquids or gases and remove them from another medium, similar to sponges.[3] Although sorbents could be used as an effective substance to extract and clear away oil, the majority do not fit the necessary criteria to make them a worthwhile investment for rigs. In order to be deemed effective, they must float on the surface to maximise oil absorption and efficiently absorb the pollutant. Additionally, they would ideally be multipurpose upon the rig, so that they do not take up unnecessary storage space.

Professor Qian and his research group at the Shanghai institute of Ceramics are currently producing an exciting new material that could change the way we respond to these spills. They have created a material—an ultra-light graphene composite that can absorb up to 41 times its own weight in oil from the ocean’s surface—that fulfills each of the previously stated criteria.[4]

They created the material using poly(vinylidene chloride) (PVDC) clay, more commonly known due to its use as an art-and-craft material for children. It has an excellent ability to be moulded into any desired size and shape. Once treated, pores that form within the material are separated by graphene (an arrangement of carbon that is only one atomic layer thick). The resulting composite has the ability to soak up the oil into 74% of their pore volume, thus removing it from the ocean. The high porosity of these sorbents combined with the hydrophobic nature of the graphene mean that the material does not sink below the ocean’s surface. This in turn fulfils the first criteria point of maximising absorption by floating on the surface, even when saturated with oil.

Not only is the starting material extremely mouldable, it’s also incredibly strong – the final composite can support more than one ton of force per square metre. The pairing of these two attributes, strength and mouldability, gives the material the ability to have a secondary purpose on a rig or tanker. Professor Qian claims that these will not require their own storage because they can be ‘used as floor or surface tiles’, making them particularly appealing for use in rigs and tankers due to their versatile and multipurpose nature.

One problem arises as a result of extremely low temperature in the ocean: oil becomes more viscous and difficult to absorb. However, since graphene can absorb energy from the sun, the composite material can reach a surface temperature of 78°C and retain its heat well. This energy is then transferred to the surrounding oil, decreasing its viscosity and thus making it easier for the material to absorb. Once the sorbent is saturated, this energy can be used in a self-combustion reaction to reduce the oil from a physical pollutant into H2O and CO2. Although CO2 is an air pollutant, Professor Qian states that ‘the cost of CO2 emission is small relative to the risk of uncontained oil spillage.’ The self-combustion aspect of this material enables it to be reusable as, after each regeneration, it can still hold up to 90% of its previous oil retaining ability – allowing it to be reused over 15 times.

Professor Qian’s sorbents are far more effective than the current naturally occurring organic and inorganic sorbents (e.g. peat moss and clay, respectively).[5] The new material is capable of absorbing almost five times as much oil, is reusable, and—unlike its naturally occurring counterparts—remains on the ocean’s surface. Although other synthetic sorbents (similar to plastic polymers) can absorb roughly 40% more of their weight than Professor Qian’s material, they do not remove oil through self-combustion, nor are they reusable. Additionally, this material is the only known type that has alternative uses upon rigs and tankers,

As yet, the timescale for when these tiles could be implemented is unknown. The team created this sorbent as a proof of concept and so may be looking into scalability going forward. Professor Qian does not report how this would work in a real-life situation. If these tiles are being used as flooring, would the tiles be secured to the floor? If so, how would they be removed if a spill were to occur? Although Professor Qian has been contacted with these questions, there has been no response as of yet.

Overall, this new sorbent could be an extremely useful material to reduce the impact of oil spills. Professor Qian states that they could ‘provide the crucial first-response kit for mitigating oil-spill disasters,’ thus reducing the immediate devastation that spills can cause, and ultimately help keep our ocean as clean as possible.

References

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