Greenhouse gas absorption

Serpentine, a commonly-occurring form of magnesium silicate hydroxide, is a natural absorber of carbon dioxide.

However, it works slowly - geologically slowly. Researchers from Penn State University in Pennsylvania have now found a process which can speed the absorption rate up to the scale of hours, rather than eons, raising the possibility of a serpentine-based absorber for industrial boilers.

The secret, according to research leader Mercedes Maroto-Valer, is to grind up the serpentine and dissolve it in sulphuric acid. This converts the silicon in the mineral into silicon dioxide - sand - which sinks to the bottom of the solution. The magnesium becomes magnesium sulphate.

Adding some sodium hydroxide to the mixture converts some of the sulphate into the hydroxide, and the mixture of magnesium sulphate and hydroxide in solution is an efficient CO2 absorber.

The process would not create any further pollutants, the team claim, because all the by-products are saleable. Passing CO2 through the solution generates magnesium carbonate, which has markets both in construction, for making building blocks, and in the cosmetics industry. Even the silica can be used, as a sorbent to capture sulphur dioxide from flue gases, which can in turn be converted into sulphuric acid.