Method and Composition For Sorbing Toxic Substances

Abstract

Toxic substances such as heavy metals are extracted from a medium using a sorbent composition. The sorbent composition is derived by sulfidation of red mud, which contains hydrated ferric oxides derived from the Bayer processing of bauxite ores. Exemplary sulfidizing compounds are H 2 S, Na 2 S, K 2 S, (NH 4 ) 2 S, and CaS x . The sulfur content typically is from about 0.2 to about 10% above the residual sulfur in the red mud. Sulfidized red mud is an improved sorbent compared to red mud for most of the heavy metals tested (Hg, Cr, Pb, Cu, Zn, Cd, Se, Th, and U). Unlike red mud, sulfidized red mud does not leach naturally contained metals. Sulfidized red mud also prevents leaching of metals when mixed with red mud. Mixtures of sulfidized red mud and red mud are more effective for sorbing other ions, such as As, Co, Mn, and Sr, than sulfidized red mud alone.

1 . A process of treating a medium comprising (i) flue gas from coal- or oil-fired power plants, (ii) a hydrocarbon stream containing heavy metal ions, (iii) a dry or wet mixture containing heavy metal ions, or (iv) elemental mercury, the process comprising contacting the medium with a sorbent comprising sulfidized red mud. 
     
     
         2 . The process of  claim 1 , wherein the medium comprises flue gas from coal- or oil-fired power plants, and the medium is flowed through a dry or wet scrubber containing said sorbent comprising sulfidized red mud.