COM MUN ICAT IONS
Disposal of Mercury Wastes from Water Laboratories Robert B. Dean, Robert T.Williams,l and Robert H. Wise Environmental Proteotion Agency, Water Quality Office, Cincinnati, Ohio 45226
Procedures for the ecologically satisfactory recovery or disposal of mercury-containing wastes, generated at water laboratories and other laboratories, are described. Suggestions for the prevention of potentially hazardous conditions in the laboratory are also presented.
W
A
ny form of mercury that is discharged into water may be converted by bacterial action into volatile methyl mercury compounds. In this form mercury is up to a hundred times as toxic as inorganic mercury salts. Furthermore, methyl mercury is accumulated in food chains and can reach prohibited levels in fish and wildlife. We should be concerned about mercury discharges if they exceed 1 gram per working day or 0.5 lb a year, EPA laboratories will set a national example by doing everything reasonable to avoid discharges of mercury from their operations. Mercury is used in significant quantities-as the liquid metal in manometers and other instruments, and as chemical compounds used as catalysts, reagents, or preservatives. Common water analyses for COD, ammonia, and TKN consume about 2.5 lb per year of mercury at just one water research laboratory. The following procedures have been worked out at the Robert A. Taft Water Research Center for the safe disposal of mercury and will serve as guides to eliminate significant mercury contamination from all water laboratories.
Waste or Dirty Metallic Mercury It is hazardous and expensive to attempt to purify metallic mercury in a laboratory that is not specially equipped to control and condense mercury vapors and to dispose of mercury-rich residues and extracts. Most laboratories will find it safer and less expensive to collect mercury in properly sealed strong containers and ship it to a commercial reprocessor for recovery. Standard steel flasks which hold 76 lb of mercury are available from reprocessors for storage and return shipment of dirty mercury. A number of firms have stated that they will accept waste mercury for reprocessing. Arrangements should always be made before shipment. A list of reprocessors who will supply shipping flasks is included in Table I. It is not intended to be limiting and is offered only for convenience. Mercury metal has a high vapor pressure and an appreciable solubility in water. Exposed surfaces of mercury are hazardous to health. If metallic mercury is spilled at any time, the spill should be cleared up immediately, even if it has occurred inside a fume-hood. Spilled mercury can be sucked up with an aspirator pump fitted with a trapbottle, and small drops can be swept together with a wet dust brush to avoid scattering. To whom correspondence should be addressed. 1044 Environmental Science & Technology
Solutions of Inorganic Mercury Salts Introduction. Mercury salts are necessary components of the wastes from COD, Kjeldahl and Nessler determinations and are frequently used to preserve water samples. The safest way to capture and retain mercury salts is as the sulfide at a high pH. Acidic solutions such as COD wastes should be carefully neutralized and combined with alkaline wastes from Kjeldahl and Nessler analyses and water samples containing mercury preservatives. The most convenient source of the sulfide ion is sodium thiosulfate which is already present in Kjeldahl analyses to precipitate the mercury catalyst. The chief problem when using sodium thiosulfate is to avoid the rapid decomposition to elemental sulfur if solutions are acidified. The sulfur which precipitates increases the volume of sludge which must be
Table I. Reprocessors of Mercury Bethlehem Apparatus Co., Inc. Front and Depot Sts. Hellertown, Pa. 18055 Phone: (215) 838-7034 Goldsmith Division, National Lead Co. 11 1 North Wabash Chicago, Ill. 60602 Phone: (3 12) 726-0232
M
M
Mallinckrodt Chemical Works MCO 223 West Side Ave. Jersey City, N.J. 07303 Phone: (201) 432-2500 (Mr. Frank L. Mackey, Eastern Branch Plant Manager) Quicksilver Products, Inc. 350 Brannan St. San Francisco, Calif. 94107 Phone: (415) 781-1988 (Miss Grace Emmans, Owner and President)
MC
Sonoma Mines, Inc. P. 0. Box 226 Guerneville, Calif. 95446 Phone: (707) 869-2013 (Mr. C. 0. Reed, President)
C
Wood Ridge Chemical Corp. Park Place East Wood-Ridge, N.J. 07075 Phone: (201) 939-4600 (Mr. E. L. Cadmus, Technical Director) M = Supplies flasks for return of metallic mercury.
MC
C = Will accept mercury sulfide for reprocessing. 0 = Will accept certain organic mercury chemicals. Special approval must always be obtained before shipment is made to a reprocessor.
stored and processed. Sodium sulfide should not be used to precipitate mercury because the precipitate may redissolve in excess alkaline sulfides. Mercury sulfide is insoluble and is stable with regards to most reagents except aqua regia and bromine. Bacterial conversion to methyl mercury can be prevented by maintaining a pH above 10. Mercury sulfide is the principal mercury ore and some refiners are willing to accept shipments of mercury sulfide precipitates, thus recycling the metal instead of polluting the environment. Procedure. Dilute combined COD and other acidic wastes to about twice their original volume by slowly adding them to water, then adjust the pH to greater than 7 by slowly adding sodium hydroxide solution (40 to 50% w/v) with vigorous stirring; this neutralization typically generates a large amount of heat, and dangerous spattering may occur if the sodium hydroxide is added carelessly. Combine the neutralized COD waste (with stirring) with any previously pooled wastes resulting from Kjeldahl nitrogen and Nessler ammonia determinations. At this point, the combined wastes should have a p H of 10 or higher; if not, add sodium hydroxide solution until a pH of 10 to 11 has been reached. While the combined alkaline wastes are still warm, intermittently stir in small portions of sodium thiosulfate solution (40 to 50% w/v) until no further precipitation seems to be occurring; this step is important, and it requires careful observation coupled with judgment. Immediately set the mixture aside, and allow the precipitate to begin settling. As soon as a few milliliters of clear supernatant can be drawn off, make sure its pH is still above 10, then add an equal volume of sodium thiosulfate solution. If the supernatant thus being tested still contains dissolved mercury, additional precipitate will rapidly form, indicating that sodium thiosulfate must again be added to the main batch of waste slurry.
After an appropriate settling period, decant or siphon off the clear, previously tested supernatant and discard it. Slurry-wash the precipitate twice with water containing a trace of NaOH to remove sodium sulfate, allowing for reasonably complete settling each time; discard both of the clear washings. Dry the washed precipitate, first in airi.e., at room temperature-then in an oven at a temperature not exceeding 110°C. Store the dry solids thus obtained until a sufficient quantity has accumulated to justify shipment to a commercial reprocessor. Several firms have tentatively agreed to accept such mixed mercury-containing wastes for recovery of the mercury involved, provided that the dry wastes are shipped to them with freight or postage prepaid (Table I ) . Special approval for shipment must always be obtained from the processor.
Waste Organomercury Compounds
We presently cannot recommend a generally applicable disposal method for waste organomercurials. Sulfides do not break the mercury-carbon bond and the precipitates which do form have unknown stability. The high toxicity and high volatility of organomercurial compounds make careful storage the only safe way to protect the environment. The Mallinckrodt Chemical Works (Table I) has agreed to accept certain mercury chemicals for disposal, including some of the less volatile organomercurials, provided they have been contacted and have given their consent and appropriate shipping instructions in each case. All other organomercury wastes should be carefully stored by the owner until reprocessing facilities become available. Received for review April 23, 1971. Accepted June 21, 1971.
Chemiluminescent Reactions of Ozone with Olefins and Sulfides W. A. Kummer, J. N. Pitts,
Jr.,1
and R. P. Steer2
Department of Chemistry, University of California, Riverside, Calif. 95202
Chemiluminescence spectra from the gas-phase reactions of ozone with several olefins and organic sulfides in the mm pressure range have been recorded and the integrated emission intensities relative to ethylene have been calculated. Possible uses of these reactions in monitoring low concentrations of ozone and sulfur-containing pollutants are discussed.
T
here has been considerable interest recently in developing sensitive instrumental techniques for monitoring low concentrations of ozone and other atmospheric pollutants. Some of the techniques developed for ozone analysis are based upon measurements of the intensity of the chemiluminescence produced when ozone reacts with specific reagents either in heterogeneous systems (Regener, 1960 To whom correspondence should be addressed. Present address: Department of Chemistry and Chemical Engineering, University of Saskatchewan, Saskatoon, Sask.,Canada.
and 1964) or in homogeneous gas-phase systems. The latter technique seems more convenient from the standpoint of continuous air pollution monitoring. Thus Nederbragt et al. (1965) and Warren and Babcock (1970) have developed a method based upon the chemiluminescence produced in the reaction between ozone and ethylene at atmospheric pressure. Fontijn et al. (1970) have utilized the low-pressure chemiluminescent reaction between NO and O3for the detection of NO and have suggested that this method might be used equally well for the analysis of ozone. In the present paper, we wish to report studies of homogeneous gas-phase chemiluminescent reactions of ozone with a number of olefins and organic sulfides. Emphasis will be placed on the possibility of using these reactions as a sensitive, quantitative method of ozone analysis. Experimental
Emission studies were performed in a flow system shown schematically in Figure 1. The reaction vessel consisted of a 3-liter, Pyrex flask having a 2 in. diameter planar, Pyrex window, and was silvered on the outside for increased light Volume 5, Number 10, October 1971 1045
