PROCESS FOR REMOVAL AND STABILIZATION OF ARSENIC AND SELENIUM FROM AQUEOUS STREAMS AND SLURRIES
A process for removing or stabilizing arsenic and/or selenium from aqueous streams or slurries is provided that includes contacting the streams or slurry with a composition containing lanthanum chloride. The lanthalum chloride composition can optionally contain various lanthanides. The composition can optionally contain ferric or ferrous sulfate. The process is preferably conducted by adjusting the pH of solution to between about 8 or 10, adding 2 moles of lanthanum chloride for every mole of arsenic or selenium ions present in solution, adding 5 to 6 moles ferric or ferrous ions for every mole of arsenic or selenium ions present in solution and adjusting the oxidation potential of the solution to between 200-400 mV for removal of selenium ions and between 100-200 mV for removal of arsenic ions. Using the processes of this invention, the selenium and arsenic concentrations can be reduced to less than currently acceptable limits and arsenic and selenium can be stabilized from leaching, decomposition or other degradation processes.