Treatment system for alkaline or acidic solution containing heavy metals

Claim 1

A method of continuously treating an alkaline solution containing heavy metal ions comprising hexavalent chromium and at least one metal ion selected from the group consisting of iron, nickel, zinc, and copper to lower the pH of the solution and reduce the amount of said heavy metal ions contained therein, comprising: (a) providing a body of said aqueous solution; (b) contacting the body with CO 2 gas to lower the pH thereof; (c) maintaining said CO 2 gas in contact with said solution at a pressure in the range of 25 to 675 psig during said contacting; (d) adding metal ions selected from the group consisting of Fe +2 and Mn to the solution having lowered pH to reduce said hexavalent chromium to trivalent chromium and to form metal hydroxide precipitates and chromium hydroxide; and (e) separating the heavy metal hydroxide precipitates from the treated solution to provide a solution having a reduced amount of heavy metal ions contained therein and having a lowered pH.

Claim 2

A method of continuously treating an alkaline solution containing heavy metal ions comprising hexavalent chromium and at least one metal ion selected from the group consisting of iron, nickel, zinc, and copper to lower the pH of the solution and reduce the amount of said heavy metal ions contained therein, comprising: (a) providing a body of said aqueous solution; (b) contacting the body with CO 2 gas to lower the pH thereof; (c) maintaining said CO 2 gas in contact with said solution at a pressure in the range of 25 to 675 psig during said contacting; (d) adding metal ions selected from the group consisting of Fe +2 and Mn to the solution having lowered pH to reduce said hexavalent chromium to trivalent chromium and to form metal hydroxide precipitates and chromium hydroxide; and (e) separating the heavy metal hydroxide precipitates from the treated solution to provide a solution having a reduced amount of heavy metal ions contained therein and having a lowered pH.

Claim 14

A method of treating an alkaline solution on a continuous basis, the solution having a pH in the range of 10.5 to 13.8 and containing heavy metal ions selected from the group consisting of Cr +6 , Ni, Cu, Fe, and Zn, the method reducing the pH to a pH in the range of 7 to 8.2 and providing reduced amounts of heavy metal ions therein, the method comprising: (a) providing a body of said alkaline solution; (b) pumping a stream of alkaline solution from said body to a reaction vessel, the stream having a nozzle located therein to inject CO 2 gas into said solution in a direction counter current to the direction of flow of said stream, the velocity of said stream being in the range of 0.2 to 300 ft/sec; (c) injecting said CO 2 gas into said stream at a supersonic velocity exiting said nozzle to lower the pH of the solution to a pH in the range of 7.5 to 10.5; (d) maintaining said CO 2 gas in contact with said solution at a pressure in the range of 25 to 500 psig in said reaction vessel; (e) electrolytically adding Fe ions to the solution having lowered pH, the Fe ions reducing said heavy metal ions to form heavy metal hydroxide precipitates and simultaneously therewith lowering the pH of the solution; and (f) separating the heavy metal hydroxide precipitates from solution to provide a solution having lowered pH and reduced amounts of heavy metal ions.

Claim 15

A method of treating an alkaline solution on a continuous basis, the solution having a pH in the range of 10.5 to 13.8 and containing heavy metal ions selected from the group consisting of Cr +6 , Ni, Cu, Fe, and Zn, the method reducing the pH to a pH in the range of 7 to 8.2 and providing reduced amounts of heavy metal ions therein, the method comprising: (a) providing a body of said alkaline solution; (b) pumping a stream of alkaline solution from said body to a reaction vessel, the stream having a nozzle located therein to inject CO 2 gas into said solution in a direction counter current to the direction of flow of said stream, the velocity of said stream being in the range of 0.2 to 300 ft/sec; (c) injecting said CO 2 gas into said stream at a supersonic velocity exiting said nozzle to lower the pH of the solution to a pH in the range of 7.5 to 10.5; (d) maintaining said CO 2 gas in contact with said solution at a pressure in the range of 25 to 500 psig in said reaction vessel; (e) electrolytically adding Fe ions to the solution having lowered pH, the Fe ions reducing said heavy metal ions to form heavy metal hydroxide precipitates and simultaneously therewith lowering the pH of the solution; and (f) separating the heavy metal hydroxide precipitates from solution to provide a solution having lowered pH and reduced amounts of heavy metal ions.

Claim 19

A method of treating a high pH alkaline solution containing heavy metal ions selected from the group consisting of Cr +6 , Ni, Cu, Fe, and Zn to lower the pH and reduce the level of heavy metal ions contained therein comprising: (a) providing a body of said alkaline solution; (b) flowing a stream of said solution from said body to a reaction vessel; (c) injecting CO 2 gas through a nozzle into said stream of solution in a direction counter current to flow of said stream, the injecting performed at a velocity in the range of Mach 1 to March 5; (d) thereafter adding metal ions selected from the group consisting of Fe +2 and Mn to reduce said heavy metal ions and to cause precipitation of heavy metal hydroxide precipitates and further lower the pH of said solution; and (e) separating the heavy metal hydroxide precipitates from the solution to provide a solution having a reduced amount of heavy metal ions contained therein and having a lowered pH.

Claim 20

A method of treating a high pH alkaline solution containing heavy metal ions selected from the group consisting of Cr +6 , Ni, Cu, Fe, and Zn to lower the pH and reduce the level of heavy metal ions contained therein comprising: (a) providing a body of said alkaline solution; (b) flowing a stream of said solution from said body to a reaction vessel; (c) injecting CO 2 gas through a nozzle into said stream of solution in a direction counter current to flow of said stream, the injecting performed at a velocity in the range of Mach 1 to March 5; (d) thereafter adding metal ions selected from the group consisting of Fe +2 and Mn to reduce said heavy metal ions and to cause precipitation of heavy metal hydroxide precipitates and further lower the pH of said solution; and (e) separating the heavy metal hydroxide precipitates from the solution to provide a solution having a reduced amount of heavy metal ions contained therein and having a lowered pH.

Claim 30

A method of treating an alkaline solution containing heavy metal ions selected from the group consisting of Cr +6 , Ni, Cu, Fe, and Zn to to reduce the amount of heavy metal ions contained therein comprising: (a) providing a body of said alkaline solution; (b) pumping a stream of said solution from said body to a reaction vessel; (c) injecting CO 2 gas through a nozzle into said stream at a supersonic velocity exiting from said nozzle to lower the pH; (d) maintaining said CO 2 gas in contact with said solution at a pressure in the range of 25 to 675 psig in said reaction vessel, the reaction vessel containing a packing material in a lower portion thereof and said stream being introduced into said lower portion of said reaction vessel to permit said solution containing CO 2 gas to pass therethrough; (e) removing solution from said reaction vessel and adding Fe +2 ions to said solution removed from said reaction vessel to reduce said heavy metal ions to form heavy metal hydroxide precipitates; and (f) separating the heavy metal hydroxide precipitates from the solution to provide a solution having a reduce amount of heavy metal ions contained therein and having a lowered pH.

Claim 31

A method of treating an alkaline solution containing heavy metal ions selected from the group consisting of Cr +6 , Ni, Cu, Fe, and Zn to to reduce the amount of heavy metal ions contained therein comprising: (a) providing a body of said alkaline solution; (b) pumping a stream of said solution from said body to a reaction vessel; (c) injecting CO 2 gas through a nozzle into said stream at a supersonic velocity exiting from said nozzle to lower the pH; (d) maintaining said CO 2 gas in contact with said solution at a pressure in the range of 25 to 675 psig in said reaction vessel, the reaction vessel containing a packing material in a lower portion thereof and said stream being introduced into said lower portion of said reaction vessel to permit said solution containing CO 2 gas to pass therethrough; (e) removing solution from said reaction vessel and adding Fe +2 ions to said solution removed from said reaction vessel to reduce said heavy metal ions to form heavy metal hydroxide precipitates; and (f) separating the heavy metal hydroxide precipitates from the solution to provide a solution having a reduce amount of heavy metal ions contained therein and having a lowered pH.

Claim 35

A method of continuously treating an alkaline solution containing metal ions selected from the group consisting of Cr +6 , Ni, Cu, Fe, and Zn to reduce the amount of said metal ions contains therein comprising: (a) providing a stream of said alkaline solution at a pressure in the range of 10 to 175 psig and flowing at a velocity of 0.2 to 300 ft/sec; (b) injecting CO 2 gas through a nozzle into said stream in a direction substantially counter current to said stream, the CO 2 gas exiting said nozzle at a velocity in the range of Mach 1 to Mach 5, the CO 2 gas effective in lowering the pH of the solution; (c) continuously introducing said stream of solution containing said CO 2 gas to a reaction vessel; (d) permitting excess CO 2 gas to separate from said solution by escaping to an upper region of said vessel and exhausting a portion of said CO 2 gas from said upper region; (f) maintaining said CO 2 gas in said upper region at a pressure in the range of 10 to 175 psig over said solution in said vessel; (g) withdrawing a stream of solution substantially depleted of CO 2 gas from said vessel, the stream of solution having a lowered pH; (h) adding Fe ions to said solution having a lowered pH to reduce said heavy metal ions and to form metal hydroxide precipitate; and (i) separating the heavy metal hydroxide precipitate from the solution to provide a solution having a reduced amount of heavy metal ions contained therein and a lowered pH.

Claim 36

A method of continuously treating an alkaline solution containing metal ions selected from the group consisting of Cr +6 , Ni, Cu, Fe, and Zn to reduce the amount of said metal ions contains therein comprising: (a) providing a stream of said alkaline solution at a pressure in the range of 10 to 175 psig and flowing at a velocity of 0.2 to 300 ft/sec; (b) injecting CO 2 gas through a nozzle into said stream in a direction substantially counter current to said stream, the CO 2 gas exiting said nozzle at a velocity in the range of Mach 1 to Mach 5, the CO 2 gas effective in lowering the pH of the solution; (c) continuously introducing said stream of solution containing said CO 2 gas to a reaction vessel; (d) permitting excess CO 2 gas to separate from said solution by escaping to an upper region of said vessel and exhausting a portion of said CO 2 gas from said upper region; (f) maintaining said CO 2 gas in said upper region at a pressure in the range of 10 to 175 psig over said solution in said vessel; (g) withdrawing a stream of solution substantially depleted of CO 2 gas from said vessel, the stream of solution having a lowered pH; (h) adding Fe ions to said solution having a lowered pH to reduce said heavy metal ions and to form metal hydroxide precipitate; and (i) separating the heavy metal hydroxide precipitate from the solution to provide a solution having a reduced amount of heavy metal ions contained therein and a lowered pH.

Claim 45

A method of continuously treating an acidic solution containing heavy metal ions comprising hexavalent chromium and at least one metal ion selected from the group consisting of iron, nickel, zinc, and copper to raise the pH of the solution and reduce the amount of said heavy metal ions contained therein, comprising: (a) providing a body of said acid solution; (b) contacting the body with NH 3 gas to raise the pH thereof; (c) maintaining said NH 3 gas in contact with said solution at a pressure in the range of 25 to 675 psig during said contacting; (d) adding metal ions selected from the group consisting of Fe +2 and Mn to the solution having raised pH to reduce said hexavalent chromium to trivalent chromium and to form metal hydroxide precipitates and chromium hydroxide; and (e) separating the heavy metal hydroxide precipitates from the treated solution to provide a solution having a reduced amount of heavy metal ions contained therein and having a raised pH.

Claim 46

A method of continuously treating an acidic solution containing heavy metal ions comprising hexavalent chromium and at least one metal ion selected from the group consisting of iron, nickel, zinc, and copper to raise the pH of the solution and reduce the amount of said heavy metal ions contained therein, comprising: (a) providing a body of said acid solution; (b) contacting the body with NH 3 gas to raise the pH thereof; (c) maintaining said NH 3 gas in contact with said solution at a pressure in the range of 25 to 675 psig during said contacting; (d) adding metal ions selected from the group consisting of Fe +2 and Mn to the solution having raised pH to reduce said hexavalent chromium to trivalent chromium and to form metal hydroxide precipitates and chromium hydroxide; and (e) separating the heavy metal hydroxide precipitates from the treated solution to provide a solution having a reduced amount of heavy metal ions contained therein and having a raised pH.

Claim 56

A method of continuously treating an acidic solution containing metal ions selected from the group consisting of Cr +6 , Ni, Cu, Fe, and Zn to reduce the amount of said metal ions contained therein comprising: (a) providing a stream of said acidic solution at a pressure in the range of 10 to 175 psig and flowing at a velocity of 0.2 to 300 ft/sec; (b) injecting NH 3 gas through a nozzle into said stream in a direction substantially counter current to said stream, the NH 3 gas exiting said nozzle at a velocity in the range of Mach 1 to Mach 5; (c) continuously introducing said steam of solution containing said NH 3 gas to a reaction vessel; (d) permitting excess NH 3 gas to separate from said solution by escaping to an upper region of said vessel and exhausting a portion of said NH 3 gas from said upper region; (e) maintaining said NH 3 gas in said upper region at a pressure in the range of 10 to 500 psig over said solution in said vessel; (f) withdrawing a steam of solution substantially depleted of NH 3 gas from said vessel; (g) adding Fe ions to said solution to reduce said heavy metal ions and to form metal hydroxide precipitate; and (h) separating the metal hydroxide precipitate from the solution to provide a solution having a reducing amount of heavy metal ions contained therein.

Claim 57

A method of continuously treating an acidic solution containing metal ions selected from the group consisting of Cr +6 , Ni, Cu, Fe, and Zn to reduce the amount of said metal ions contained therein comprising: (a) providing a stream of said acidic solution at a pressure in the range of 10 to 175 psig and flowing at a velocity of 0.2 to 300 ft/sec; (b) injecting NH 3 gas through a nozzle into said stream in a direction substantially counter current to said stream, the NH 3 gas exiting said nozzle at a velocity in the range of Mach 1 to Mach 5; (c) continuously introducing said steam of solution containing said NH 3 gas to a reaction vessel; (d) permitting excess NH 3 gas to separate from said solution by escaping to an upper region of said vessel and exhausting a portion of said NH 3 gas from said upper region; (e) maintaining said NH 3 gas in said upper region at a pressure in the range of 10 to 500 psig over said solution in said vessel; (f) withdrawing a steam of solution substantially depleted of NH 3 gas from said vessel; (g) adding Fe ions to said solution to reduce said heavy metal ions and to form metal hydroxide precipitate; and (h) separating the metal hydroxide precipitate from the solution to provide a solution having a reducing amount of heavy metal ions contained therein.