Arsenic and TOC are removed from drinking water or wastewaters by use of
finely-divided metallic iron in the presence of powered elemental sulfur or other
sulfur compounds such as manganese sulfide, followed by an oxidation step. A premix
may be produced for this process, by adding the iron, sulfur and oxidizing agent
to water in a predetermined pH range. The iron and sulfur are mixed for a period
of time dependent upon the temperature and pH of the water and the presence of
complexing or sequestering minerals and organic acids in the water. An oxidizing
agent is added to the mixture and agitating is continued. In a preferred embodiment
the oxidizing agent is hydrogen peroxide. Water is decanted from the mixture after
a sufficient reaction time, to produce a concentrated premix. This premix can be
added to water intended for drinking or to industrial effluents containing toxic
materials. Use of various gradations and mixtures of this sulfur-modified iron
(SMI) premix have been successfully demonstrated to remove the following toxic
substances from water: arsenic (arsenite and arsenate); disinfection byproducts
and precursors; copper; chrome VI; sulfate; and chlorinated solvents including
trichloroethene. Metals removed may be present in the untreated water in either
the dissolved state or as a fine particulate. SMI has been fabricated using sulfur
in the amount of up to 50% of the weight of the iron. SMI premix has been manufactured
using a wetted but non-fluid mix at room temperature and at elevated temperature.
SMI has been successfully demonstrated in pressure and gravity contact beds in
both upflow and downflow modes. It has been prepared in uniformly-graded media
similar in size and gradation to commercially-available filter media. Spent SMI
can be recycled as a non-hazardous material as feed material to a steel production facility.
