Removal of complexed heavy metals from waste effluents

Claim 3

A method according to claim 1 wherein the step of contacting the waste solution with a mixture of peroxide and ozone comprises mixing peroxide with the waste solution while also bubbling ozone through the waste solution.

Claim 4

A method according to claim 2 wherein the ozone is bubbled through the waste solution in an amount not substantially exceeding that which can be absorbed in the mixture.

Claim 5

A method according to claim 2 wherein the peroxide comprises hydrogen peroxide, and the peroxide is mixed with the waste solution in an effective amount up to about five percent by volume.

Claim 8

A method according to claim 5 wherein the step of precipitating the heavy metals from the solution comprises raising the pH of the solution to at least about 12 to precipitate insoluble oxides and hydroxides of the heavy metals, and thereafter contacting the alkaline solution with a sulfide to further precipitate the heavy metals.

Claim 9

A method according to claim 6 wherein the step of precipitating the heavy metals from the solution also includes contacting the alkaline solution with a phosphate to additionally precipitate the heavy metals as insoluble heavy metal phosphates.

Claim 10

A method according to claim 5 including the additional steps of lowering the pH of the waste solution after separating the insoluble precipitates, and discharging the thus treated waste solution substantially free of the heavy metals.

Claim 11

A method according to claim 5 wherein the waste solution comprises concentrated photographic processing wastes containing heavy metals tightly bound by one or more of said complexing agents.

Claim 12

A method according to claim 5 wherein the step of contacting the waste solution with a mixture of peroxide and ozone comprises mixing hydrogen peroxide with the waste solution in an effective amount up to about five percent by volume while also bubbling ozone through the mixture of waste solution and hydrogen peroxide in an amount not substantially exceeding that which can be absorbed in the mixture.

Claim 13

A continuous method for the treatment of waste solutions which contain heavy metals tightly bound by one or more complexing agents selected from the group consisting of EDTA, NTA and thiosulfate to recover the heavy metals and reduce pollution of streams by the heavy metals, said method comprising directing the waste solution containing the heavy metal complexes into a reaction vessel and introducing hydrogen peroxide into the reaction vessel and into contact with the waste solution while also bubbling ozone through the waste solution to oxidize and destroy the complexing agents and convert the heavy metals into a readily separable form, directing the solution from the reaction vessel to a causticizing vessel and introducing a causticizing agent to raise the pH of the solution to at least about 12 and precipitate some of the heavy metals as insoluble heavy metal oxides and hydroxides, directing the solution from the causticizing vessel to a polishing vessel and introducing sodium sulfide into the solution to bring about additional precipitation of the heavy metals as heavy metal sulfides, directing the solution and insoluble precipitates from the polishing vessel and separating the insoluble heavy metal precipitates from the waste solution leaving the solution substantially free from the heavy metals.

Claim 14

A continuous method for the treatment of waste solutions which contain heavy metals tightly bound by one or more complexing agents selected from the group consisting of EDTA, NTA and thiosulfate to recover the heavy metals and reduce pollution of streams by the heavy metals, said method comprising directing the waste solution containing the heavy metal complexes into a reaction vessel and introducing hydrogen peroxide into the reaction vessel and into contact with the waste solution while also bubbling ozone through the waste solution to oxidize and destroy the complexing agents and convert the heavy metals into a readily separable form, directing the solution from the reaction vessel to a causticizing vessel and introducing a causticizing agent to raise the pH of the solution to at least about 12 and precipitate some of the heavy metals as insoluble heavy metal oxides and hydroxides, directing the solution from the causticizing vessel to a polishing vessel and introducing sodium sulfide into the solution to bring about additional precipitation of the heavy metals as heavy metal sulfides, directing the solution and insoluble precipitates from the polishing vessel and separating the insoluble heavy metal precipitates from the waste solution leaving the solution substantially free from the heavy metals.

Claim 15

A method according to claim 11 wherein the solution and precipitate is directed from the polishing vessel to a holding vessel, and including the step of holding the solution for at least about 24 hours prior to separation of the precipitate therefrom to allow time for complete precipitation of the insoluble heavy metals.