Removal of Mercury from Waste Water: Large-Scale Performance of an Ion Exchange Process

Abstract

Duolite™ GT-73 ion exchange resin routinely reduces the mercury content of a waste water stream to less than the permitted level of 10 ppb. Effluent concentrations from the ion exchange facility (IEF) are consistently between 1 to 5 ppb, even though the feed contains a varying concentration of mercury (0.2 to 70 ppm). Two operational problems have been encountered at that facility, however. Firstly, the stated capacity of the resin for mercury was not being achieved. The abnormally low capacity was traced to analytical laboratory waste which was intermittently treated by the resin. That waste contained hydrochloric acid, stannous chloride, and potassium permanganate, among other chemicals, which presumably eluted sorbed mercury from the resin and also oxidized the thiol (SH) functional groups on the resin and rendered them inactive. The net effect was that the resin had to be replaced more frequently than anticipated. Secondly, the IEF was temporarily shut down because the mercury content of the waste water could not be reduced to below the permitted level, even with fresh resin. That problem was caused by slow settling solids composed mainly of iron which apparently adsorbed some of the mercury and allowed it to pass through the resin untreated. The solids were presumably a result of processing waste water abnormally high in iron which may have co-precipitated with mercury and other elements in the feed and caused a residual buildup of solids throughout the IEF. The problem was remedied by installing a 0.2 µm cartridge filter between the feed tank and the columns.

Potential of Mercury-Resistant Marine Bacteria for Detoxification of Chemicals of Environmental Concern

“…was a successful demonstration of the detoxifying efficiency of the MRB. Common methods to remove Hg 2+ from contaminated waters are mostly based on sorption to materials such as ion exchange resins 31,35) . One of the initial efforts to retain mercury in bacterial bioreactors was made by 7) Canstein et al 10) , who demonstrated the removal of mercury from chloralkali electrolysis wastewater by a mercury resistant Pseudomonas putida strain.…”

Mercury Contaminated Material Decontamination Methods: Investigation and Assessment

“…Mercury in the form of anionic complexes, such as HgCl 3 -, can be treated by anion exchange resins. The thiol resin, Duolite GT-73, is reported to be selective for mercury in any of its three oxidation states (Ritter and Bibler 1992).…”

“…A full-scale ion exchange process at a defense processes facility has consistently removed mercury via ion exchange from 0.2 to 70 mg/L down to levels of 1 to 5 µg/L, following 0.2 µm prefiltration (Ritter and Bibler 1992). This system utilizes a macroporous, weakly acidic, polystyrene/divinylbenzene cation resin, with thiol (-SH) functional groups.…”

Technology Evaluation for Waterborne Mercury Removal at the Y12 National Security Complex

“…This is because cation or anion exchangers without strong chelating ability are vulnerable to complexation of Hg 2+ in the water. Among the tested commercial chelating resins, Duolite GT-73 from Rohm and Haas (now a subsidiary of Dow) stands out as the most investigated one and has exhibited good mercury adsorption capacity (Ritter and Bibler, 1992). In a DOE report evaluating selective ion exchange resins for removal of ppb levels of mercury from groundwater, seven resins were studied including cation exchanger CG8 (Resin Tech), anion exchanger Dowex 21K (Dow), cation exchanger containing thiol functional groups GT 73 and SR-4 (Sybron Chemical), chelating resin Chelex 20, and Hg-specific chelating resin SIR-200 (Resin Tech) and S-920 (Purolite) (Monson et al, 2000).…”