Background

Elemental sulfur is a by-product of the refining of crude oil. Recent research has demonstrated that it is possible to produce stable polymeric materials from this incredibly cheap chemical feedstock. It has been demonstrated that these polymers have an incredible affinity for aqueous mercury, and are capable of removing mercury from even below concentrations of 1 ppm.

Mercury is a global health hazard and there is no ‘safe’ level of mercury in water. It is a common industrial effluent pollutant and is often handed over to specialist treatment facilities and buried in hazardous waste sites located in salt mines.

There are three incumbent materials applied as mercury sorbents: conventional activated carbon, ion exchange resin, and metal sulfide. However, all of them have critical disadvantages, such as low capacity, high cost, and limiting conditions.

Researchers at the University of Liverpool hope to produce materials that are able to remove mercury in an incredibly simple and effective manner and to produce an alternative to traditional disposal methods that both lower the cost of disposal and enhance safety.

Technology Overview

In its most simple form, the technology is a polymeric material from sulfur, a by-product of the oil and gas industry, resulting in a low price, around 100 USD/ton. Elemental sulfur has been used to synthesize sulfur-containing polymers and their derivative materials via the new technology of Inverse Vulcanisation. This approach is highly novel, and hasn’t been yet implemented in industry.

All these materials show high efficiency and high selectivity to heavy metals and precious metals. The most outstanding result is that at extremely low concentration (below 10 parts per million), ThioTech materials adsorb 15 times more mercury than conventional activated carbon. From a realistic mixed metal ion solution, mercury is selectively captured by ThioTech materials, without inhibition by the other metals. Moreover, toxic mercury is potentially reduced into stable compounds, such as HgS, which could be disposed of with no extra treatment. 

The nanoparticles are able to be formed into membrane composites that can be used in membrane filtration. The coatings are able to be formed into polymer-coated silica powders that can be used in filtration beds and the same process is possible for the sulfur-doped activated carbons.

Stage of Development

The polymer and polymerisation process is not patent-protected, however, the subsequent critical processing of the polymer is patent protected. Researchers have developed the polymers produced into coatings (TRL4), nanoparticles(TRL4), and sulfur-doped activated carbons (TRL4). 

They are currently in the process of scaling up the chemistry from the lab-scale (500 g) to a 10 kg scale with the intention to push for pilot manufacture. And are also actively seeking opportunities for validation studies. 

Benefits

• Highly selective like ion-exchange resins, but are more comparable on a cost basis to activated carbon.
• Incredibly cheap, one of the bulk monomers (elemental sulfur) can be sourced at around ~$100 / tonne. 
• There is evidence that highly stable HgS is formed when the material is spent. This material is much safer to store and handle. 

Applications

• Remediation of tailing water from coal mining
• Remediation of mercury-contaminated water 

Opportunity

Actively seeking partners for validation studies of the materials.