Bulk sorbents
These sorbent products do not have any particular shape of their own and are made up of particles without any links between them.
AFNOR type A
Many such products are available on the market. They can be powders or short fibres, of mineral origin (treated substances: expanded perlite, vermiculite...), vegetable origin (treated or not: sawdust, peat...) or may be synthetic (polymers: polyurethane, polypropylene, polystyrene, epoxy...).
In practice, the volume of sorbent needed is at least twice the volume of pollutant to be recovered. Floating bulk sorbents can therefore only be used to recover small amounts of oil, especially when we consider the cost involved and the technical and logistical difficulties linked to the products' properties and their use. Furthermore, the spreading of these products makes recovery difficult.
Bulk sorbents can be spread in several ways:
- manually (irregular spreading and only applicable to small amounts of pollution)
- using a hydro-ejector (e.g. foam hose)
- using an air projector.
Whatever the method chosen, all personnel must be protected (masks, goggles), due to the effect of the wind on the sorbent and the possibilty of irritation caused by the product. After spreading the sorbent on the oil, agglomerates are formed, which may be more or less consistent depending on the type of product, the type of oil and the sea state. For recovery using nets, the mesh of the net must be smaller than the average particle size of the sorbent.
Sorbents can even be used on viscous hydrocarbons (several thousand cSt). However the sorption time depends on the viscosity. In the case of high density pollutants, near 1 (for example, reverse emulsion of water on the surface), contact between the oil and the sorbent is difficult to obtain, because of the presence of a film of water on the surface of the slick.