Stabilization of mercury-containing waste

DETAILED DESCRIPTION OF THE INVENTION Many types of industrial processes generate waste containing toxic metals, including mercury.
Two common types of such waste to which the present invention is applicable are sludge wastes generated during the production of chlorine and caustic by electrolysis of concentrated brines, known in the industry as mercury cell chlor-alkali production.
These types of sludges are referred to sometimes hereinafter as K071 waste, a designation used in experimental work by the present inventors and used by the EPA is categorizing this type of waste in RCRA.
These types of waste are considered hazardous because of mercury contamination.
Present K071 waste generation in the U.
S.
is estimated to be on the order of from 20,000 to 30,000 tons/year.
In particular, two types of K071 sludges, sodium chloride (naCl) and potassium chloride (KCl) have been tested extensively as representative mercury-containing waste.
The laboratory studies discussed herein demonstrate the effectiveness of cement kiln dust (CKD) and sulfur (and caustic (NaOH) in preferred embodiments) stabilization for NaCL K071 sludge.
These two particular mercury-containing NaCl and KCl sludges were generated at plants owned and operated by Occidental Chemical Corporation in Muscle Shoals, Alabama and Delaware City, Delaware.
The KCl K071 waste is a mixture obtained from clarifier and filter operations in the production of chlorine and caustic by electrolysis of concentrated brines.
The waste primarily contains KCl (40-60%) and water (35-60%).
The waste further contains CaCO.
sub.
3 and hydroxides of iron, aluminum and magnesium.
The sludge typically consists of fine particles and will not dewater easily.
This type of KCl waste typically contains more mercury than the NaCl sludge.
NaCl K071 sludge is a mixture of sludges from such clarifier, filter press and saturator operations.
However, clarifier and filter press produce a somewhat liquid homogenous sludge whereas the saturator operation produces a dry, coarse, sandy waste containing rock salt particles about one-quarter inch in diameter