Process for treating iron-containing waste streams

Abstract

The invention is a process for treating an iron-containing waste stream. The process comprises dividing the waste stream into a first and a second stream, then adding a neutralization agent (e.g., calcium hydroxide) to the first stream to form a partially neutralized slurry, and combining this partially neutralized first stream with the second stream to form a combined stream. The combined stream comprises ferrous chloride and metal hydroxide precipitates, which are separated.

1 . A process for treating an iron-containing effluent produced by the chlorination of a titaniferous feedstock, the process comprising:
 (a) dividing the iron-containing effluent into a first stream and a second stream;   (b) adding a neutralization agent to the first stream to form a partially neutralized first stream having a pH of 4.7 or greater;   (c) combining the partially neutralized first stream with the second stream to form a combined stream comprising ferrous chloride and metal hydroxide precipitates, and having a pH of 3.2 to 4; and   (d) separating the ferrous chloride from the metal hydroxide precipitates.   
     
     
         2 . The process of  claim 1  wherein the titaniferous feedstock is selected from the group consisting of anatase ores, ilmenite deposits, slags, and tar sands. 
     
     
         3 . The process of  claim 1  wherein the first stream contains 25 to 45 percent of the iron-containing effluent. 
     
     
         4 . The process of  claim 1  wherein the first stream contains 30 to 40 percent of the iron-containing effluent. 
     
     
         5 . The process of  claim 1  wherein the neutralizing agent is selected from the group consisting of calcium hydroxide, calcium oxide, and mixtures thereof. 
     
     
         6 . The process of  claim 4  wherein the neutralizing agent is calcium hydroxide. 
     
     
         7 . The process of  claim 1  wherein the partially neutralized first stream has a pH of 4.7 to 5.3. 
     
     
         8 . The process of  claim 1  wherein the combined stream has a pH of 3.2 to 3.7. 
     
     
         9 . The process of  claim 1  wherein the ferrous chloride is separated from the metal hydroxide precipitates by a method selected from the group consisting of filtration, decantation, and centrifugation.