The separation of ionic and organic mercury from water using milk proteins, xanthates and keratin
The interaction and removal of divalent mercury, monomethyl mercury and dimethyl mercury from water solutions with milk proteins, xanthates, and structural proteins have been investigated. Milk proteins, including lactalbumin, casein, whey and whole milk were tested in concentrations of one part protein per 500 parts water. Once filtered, these proteins removed up to 90% of divalent mercury from 10 ppm solutions, up to 80% of methyl mercury from a 6.5 ppm solution and about 50% of dimethyl mercury from limited tests at 10 ppm (Mercury concentrations expressed as Hg⁺⁺).
Using one part of sodium isopropyl xanthate per 2200 parts of solution followed by hexane extraction, removals of 98% (2 hexane washes) of divalent mercury from 10 ppm solutions, and 95% removal of methyl mercury from 10 ppm solutions were achieved. The xanthates are commercially used as reagents in ore flotation, and removal by flotation would probably be more desirable in a practical waste treatment process using xanthates.
Unusually good mercury removals were achieved using a sulfur containing structural protein, keratin (hair). Degreased human hair from a local barbershop achieved an 83% removal of divalent mercury from a 10 ppm solution using one part hair per 500 parts solution. When the solution was well agitated, one part of this hair per 500 parts solution removed 98% of the mercury from solutions containing 10 ppm and also ppb of divalent mercury. Removal was similar for monomethyl mercury and about 50% for dimethyl mercury.
The use of these complexing agents for the removal of mercury from waste water is encouraging and likely similar removals would be expected for other trace metals.