The extraction of toxic but valuable metals such as nickel, chromium, lead, and mercury, from wastewaters produced in various industries such as semiconductor and mining has been a serious challenge to these industries.
Unlike the commonly used ion-exchange resins that bind with metals unspecifically, a newly developed phosphine-functionalized resins bind with metals selectively via coordination chemistry. The new material allows a cheaper but efficient and selective capture of metals in wastewaters that could be a greener replacement for mining and metal recovery.
A wet chemistry method developed in Ecole Polytechnique, a premium research laboratory in France, is currently being applied in Magpie Polymers, a startup company. The method is a two-step synthesis (polymer synthesis and polymer modification) of the functionalized resins that uses cheap raw materials.
The polymers synthesized in just one step are subsequently modified to attach various types of functional groups – neutral phosphine, phosphine oxide, and phosphine sulfide – depending on the metals to be captured. The usage of these resins can be arranged in a certain order such that all of the metals present in wastewater can be collected. The metals can then be retrieved from the resins by a simple acid wash, which also allows easy and fast regeneration of the adsorbent.
Each gram of the new resin has high coordination chemistry that allows high adsorption capacity (2 eq/kg for copper). Magpie Polymers co-founder Etienne Almoric said, “A single litre of this patented resin can treat five to 10 cubic metres of waste water and recover 50 to 100 grammes of precious metal, equivalent to 3,000 to 5,000 euros ($3,900 to $6,500).”
“We leave only a microgramme per litre,” adds Steve van Zutphen, founder of Magpie Polymers.