THIOTEQ^™ Metal

Why mix toxic metal with a pile of gypsum? THIOTEQ^™ Metal technology recovers dissolved metals from liquids by the formation of high purity metal sulfides. These can either be marketed or disposed of in a very compact form. The required sulfide for this process is generated on-site in a bioreactor from a low cost sulfur source at ambient temperature and pressure.

For the simultaneous removal of sulfate and the recovery of metals please refer to SULFATEQ^™.

Compared to precipitation as metal hydroxides, THIOTEQ^™ offers

• Lower metal effluent concentrations
• Revenue from metal sulfides: attractive ROI at metal concentrations > 0.1 g/l
• Capability to deal with complexes and most chelating agents
• Better settling and dewatering characteristics of the metal sulfide sludge

Sulfide precipitation would be applied widely if the high cost of transport, storage or production of sulfide on-site (as NaSH or H₂S) did not hinder its practical application.

The THIOTEQ^™ Metal technology solves this problem with a biogenic sulfide generator that generates sulfide on-site and on demand under ambient conditions. All that is needed to enable production is elemental sulfur, a food source like alcohol and some fertilizer-like nutrients. The sulfide is transported from the generator to one or more contactors via a closed gas recycle.

• Cost-effective sulfide source: lower cost per tonne of metal sulfide produced
• Safe process at ambient conditions
• On-site sulfide production: no transport and storage of hazardous sulfide
• Better selectivity of metals, higher product quality
• Flexible process: production naturally adjusts to demand
• Robust and proven process

The patented Paques THIOTEQ^™ Metal process consists of two stages: a chemical and a biological. The water to be processed only passes through the chemical stage. Sulfide is produced in the biological stage and transported to the chemical (precipitation) stage via a gas recycle.

Biological stage

A biocatalyst produces sulfide from elemental sulfur and an organic feedstock like ethanol or hydrogen. The biocatalyst grows in a bioreactor with a very long hydraulic retention time and is unaffected by the characteristics of the process stream. The conditions in the bioreactor are ambient, which makes it safe to operate.

Chemical stage - contactor

Sulfide is transported via a gas recycle to the chemical stage that consists of a gas-liquid contactor. The H₂S dissolves in the process liquid and reacts virtually instantaneously with the dissolved metal. The metal sulfide that is formed is separated via gravity settling and dewatered. The lean gas is recycled back to the biological stage.

For more information on Metal & Mining and metal recovery from wastewater, please download our brochure. And/or read the scientific publication about established technologies for metal recovery from industrial wastewater streams (including real industrial setups and data).