Coal Sorbent System for the Extraction and Disposal of Heavy Metals and Organic Compounds

The Coal Sorbent System (CSS) utilizes a newly developed coal-based sorbent, which has the combined characteristics of an activated carbon and ion exchange resin. The low cost and excellent combustion characteristics (including very low sulfur and ash) of the coal sorbent enabled the development of a system to extract metals and organics from aqueous streams, concentrate them on the sorbent and encapsulate the metals (destroy organics) utilizing developed incineration or vitrification processes. Coal Sorbent is produced by the chemical leaching of ordinary coal using the TRW Molten Caustic Leaching (MCL) process. The coal sorbent produced from the MCL process is much like activated carbon with a large internal surface area (up to 1000 m2/g). In addition to its high surface area, the coal sorbent, unlike activated carbon, has inherent carboxyl groups much like ion exchange resins that can remove heavy metals from wastewater. Heavy metal capacities up to 70 mg/g (7%) of coal sorbent have been demonstrated. The coal sorbent has both a high surface area and a large concentration of carboxyl groups on the surface. These two features enable the Coal Sorbent to be used as a wastewater treating medium to remove both organics (high carbonaceous surface area) and heavy metals (carboxyl ion exchange groups). Once the heavy metals and organics are adsorbed on the virtually sulfur and ash- free coal sorbent, the spent coal sorbent can be processed by commercially available combustion/vitrification processes to encapsulate the metals and destroy the organics. Waste volume reductions as high as 420,000:1 have been demonstrated for uranium groundwater applications at an estimated cost through disposal of <$0.001/gallon water treated.