Science

Foam made from natural materials removes oil from contaminated water – synthesis

Everyone knows that water and oil don’t mix because of everyday experiences at home or school, and because of stains in the ocean after major leaks. Less well known is the use of foam, porous and absorbent materials to eradicate these catastrophes and other episodes of water contamination, similar to the sponges used in household cleaning, capable of absorbing contaminants by separating water.

Porous materials – foams, sponges and airgel – which are generally used as an alternative to traditional decontamination methods, have the disadvantage that, depending on non-renewable resources, they are made from petroleum and are not biodegradable. Research at the National Center for Energy and Materials Research (CNPEM) has led to innovations that can replace these materials with a new foam based on cellulose and latex, which is highly efficient and produced in a simple and clean process.

Nanocellulose is already used in porous materials for various applications. Some of its advantages are its abundance and low cost, which can be obtained from biomass such as sugarcane bagasse or paper-making waste. In addition, it has very suitable properties for obtaining three-dimensional porous structures.

However, cellulose is inherently hydrophilic – that is, it has an affinity for water rather than pollutants – and is fragile when wet. Thus, for use in the absorption of oils and other hydrophobic compounds (such as toluene and chloroform), several steps are usually required in the manufacture of cellulosic foams and even in the use of solvents which can be environmentally harmful.

The solution found at CNPEM combined the association between nanocellulose obtained from eucalyptus and natural rubber latex with a one-step production process. Latex gives the material structural strength and affinity for the pollutants that cellulose lacks. But the strangest thing is the way to get the foam. Solid materials – cellulose and latex – make up only 2% of a mixture with water, which is frozen and then lyophilized. This means that the water changes from the solid (ice) to the gaseous state during the freeze-drying process, with the pores remaining in its place, which absorb the pollutants in a proportion up to 50 times greater than the mass of the cellulose foam.

The analyzes carried out in the CNPEM laboratories showed the high porosity of the material and other morphological properties, its ability to absorb oil and other substances, as well as its durability after several cycles of use. The developed material has already been registered for a patent and is available for licensing and use as a sustainable alternative to the remediation of contaminated water. The results were published in a cover article in the November issue of the international journal ACS Applied Nano Materials.

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