CHAPTER 29
DISPOSAL OF SMALL-SCALE SPILLS Margaret-Ann Armour Department of Chemistry, University of Alberta, Edmonton
29.1 29.1.1
INTRODUCTION Applicability
Small-scale spills of hazardous chemicals can occur in laboratories in educational institutions, quality control and testing laboratories, hospitals, greenhouses, and wherever small quantities of hazardous chemicals are handled. Such spills have less potential to cause widespread problems than spills on an industrial scale. However, they pose a risk to the health of workers in the laboratory or at the site of the spill from the inhalation of fumes, from the potential hazards of reactive chemicals, and, in the case of liquids, from slipping on wet floors. It is recognized that small spills should be cleaned up as quickly, responsibly, and efficiently as possible. Workplaces must have a protocol for handling spills and provide spill kits in appropriate locations. It is important that such kits be readily available in locations where they are easily accessed when needed. Furthermore, a plan needs to be in place to guide what is to be done with the residues from cleanup of the spills (National Research Council, 1995). Since 1981, we have been developing and testing in the laboratory, methods for the onsite disposal of small quantities of a variety of hazardous chemicals (Armour, 1996a). We have been able to apply many of the methods to disposing of the residues from the cleanup of spills of these chemicals. The application of several of the methods to spills of commonly used hazardous chemicals is described in subsequent paragraphs. The quantity of spilled material to which the disposal procedures are applicable varies with the hazard of the material spilled. In general, these procedures can be applied to the quantities of chemicals normally handled and transported in laboratories. As a guide, the disposal procedures are applicable to spills of up to about 4 L of liquid.
29.1.2
Requirements for Effective Handling of Small-Scale Spills
One of the most important requirements in handling small-scale spills is speed of reaction. The site of the spill should be isolated and workers not directly involved in the spill cleanup kept at a safe distance. For identifiable spills, the hazards are considered and appropriate personal protection worn with breathing apparatus if necessary. For spills of unknown substances it is best to wear full personal protection, including breathing apparatus. Solids that 29.1
29.2
CHAPTER TWENTY-NINE
do not present a health or reactive hazard can be scooped up and either disposed of on-site using an appropriate method or packaged and labeled for disposal off-site. Reactive solids or those posing a health hazard should be covered with a powder form of absorbent and the mixture should be scooped into a container and disposed of according to an acceptable method. Liquid spills are absorbed using absorbent pillows or powdered absorbent, and the mixture is scooped into a container and disposed of appropriately. The area of the spill is washed with soap and water or with a suitable reagent solution. 29.1.3
Factors in the Disposal of Residues from Spill Clean-up
Cleanup of a spill results in residues of the chemical itself, or of absorbent material containing the spilled chemical. These require disposal. In deciding how to dispose of the absorbed material, a critical question is related to the reactivity of the spilled chemical. Workers who are knowledgeable about the properties of the spilled chemical are often the best people to perform the cleanup and disposal of the spill. If the spill was of a single known chemical or its solution, it may be possible for the laboratory worker to denature the chemical for onsite disposal, thus avoiding the risks of storage and transportation for off-site disposal. Specific procedures that can be used to convert the hazardous material at the laboratory bench to nonhazardous products are provided later in the chapter. Alternatively, the residue can be packaged and labeled for off-site disposal. If the spill was of a mixture or the identity of the spilled chemical is not known, the disposal may present a more difficult problem. The issue of spilled unknowns is discussed in more detail in Section 29.3.9.
29.2
SPILL MIX FOR THE ABSORPTION AND COVERAGE OF SMALL SPILLS Many chemical supply companies sell spill kits that include absorbents. These may be in the form of loose powders or pillows. Frequently there are different absorbents for different types of spill. For example, one pillow is used for aqueous acid spills, another for aqueous alkaline spills, and a third for organic liquids. We have developed an absorbent that we have found to be practical and effective for all types of spills. It is easily prepared and is inexpensive so that containers of it can be available wherever hazardous chemicals are being used. The spill mix is particularly useful in schools and in the teaching laboratories of academic institutions since it can be made available at many locations.
29.2.1
Contents of Spill Mix
The spill mix contains sodium carbonate (soda ash, often available from swimming pools), bentonite (clay cat litter), and dry sand (Armour et al., 1999). The rationale for choosing these components for the spill mix was as follows. The sodium carbonate at least partially neutralizes any acid in the spill, thus rapidly reducing the corrosive impact of the acid on the surface where the spill occurred. The bentonite absorbs liquid and vapors effectively, and the sand moderates and helps to smother any reaction that may occur (for example, in a spill of a solution of lithium aluminum hydride in ether, there is a risk of fire). 29.2.2
Preparation of Spill Mix
The preparation of the spill mix is very simple. Equal volumes of sodium carbonate, bentonite, and dry sand are placed in a plastic container with a lid. The container is shaken until the components are mixed. It is also good to shake the container before use.
DISPOSAL OF SMALL-SCALE SPILLS
29.2.3
29.3
Method for Testing Spill Mix
We have tested the spill mix in the laboratory on simulated spills of over 250 hazardous chemicals and their solutions. Three characteristics were measured. First, we looked at the ability of the spill mix to absorb liquids and eliminate toxic and / or flammable fumes. Secondly, we assessed its effectiveness in reducing the danger of highly reactive solids catching fire. Thirdly, we determined methods by which the spill mix containing the absorbed spill could be converted to environmentally safe products for disposal. Samples of the hazardous chemicals were spilled in a large evaporating basin. Spill mix was added to the basin until the liquid was completely absorbed or the solid was covered. With a plastic scoop, the mixture was transferred to a plastic or glass container and the container placed in the fume hood. Depending on the nature of the chemical that had been spilled, a method was selected to convert the hazardous chemical into nontoxic and environmentally acceptable products. The residues after the conversion reaction were identified. The concentration of the metal ion remaining after precipitation by sodium silicate was measured by ICP (Leco Plasmarray ICP Spectrometer, argon gas plasma, or, for lead ions, ICP / MS Elan Model 250, argon gas plasma). From the results of testing in the laboratory, appropriate treatment methods for specific spills have been documented.
29.2.4
Use of Spill Mix
The general procedure for using spill mix is to pour the spill mix onto the spill of liquid or reactive solid so that all of the liquid is absorbed or all of the reactive solid is completely covered. The residue is scooped up using a plastic scoop and placed in a plastic pail. For off-site disposal, the residue is packaged, labeled appropriately, and sent for disposal. In many cases the residue can be converted at the laboratory bench to nontoxic and nonhazardous residues for easier disposal. Some of the methods developed and tested in the laboratory to facilitate on-site disposal are described in Section 29.3. To ensure a fast cleanup, spill kits including gloves, goggles, plastic pail, plastic scoop, and step-by-step cleanup procedures should be readily available.
29.3 29.3.1
DISPOSAL OF RESIDUES FROM SPILL CLEANUP Liquid Spills of Mineral Acids
To treat a spill of a mineral acid, such as concentrated hydrochloric, sulfuric, or nitric acids, breathing apparatus must be worn in addition to appropriate protective equipment. If the spill is of a dilute aqueous solution of a mineral acid, breathing apparatus may not be necessary. The spill is covered with spill mix until all of the liquid is absorbed. A plastic pail is three-quarters filled with water and the residue is transferred into the pail of water using a plastic scoop. The pail is transported to a fume hood. The pH of the solution is measured and, if necessary, the solution is neutralized by the addition of sodium carbonate or dilute (5%) aqueous sodium hydroxide solution. Table 29.1 lists the approximate quantities of spill mix required for spills of 100 mL of the given liquids and the approximate volumes of 5% aqueous sodium hydroxide needed to neutralize the resultant solution when the spill mix is added to 5 L of water. After standing in the fume hood until the solids have settled, the liquid containing sodium chloride, sodium sulfate or sodium nitrate in aqueous solution is poured into the drain. The solids, bentonite and sand, are treated as normal garbage. When the aqueous acidic solution is neutralized with sodium carbonate or aqueous 5% sodium hydroxide solution, the acids are converted to their sodium salts as shown in Eqs. (29.1) and (29.2) respectively
29.4
CHAPTER TWENTY-NINE
TABLE 29.1 Quantities of Spill Mix Required to Absorb Some Acids and Bases and Volumes
Required to Neutralize the Resulting Solutions
Liquid ‘‘spilled’’ (100 mL) Sulfuric acid Nitric acid Phosphoric acid Hydrochloric acid 20% Sodium hydroxide Glacial acetic acid
Weight of spill mix used 255 165 220 185 125 150
g g g g g g
Volume of 5% aqueous NaOH to give pH 7
Volume of 5% aqueous HCl to give pH 7
1.68 L 360 mL 700 mLa 72 mL 250 mL 600 mLa
a Phosphoric acid and acetic acid form buffer solutions with aqueous sodium hydroxide. For these acids, enough 5% aqueous sodium hydroxide solution should be added to bring the solution to pH 5 rather than pH 7. This is the quantity indicated in the table.
2HCl ⫹ Na2CO3 → 2NaCl ⫹ H2O ⫹ CO2 H2SO4 ⫹ 2NaOH → Na2SO4 ⫹ 2H2O 29.3.2
(29.1) (29.2)
Liquid Spills of Bases
Spills of aqueous solutions of sodium and potassium hydroxide and of ammonia are discussed in this section. Aqueous solutions of bases such as sodium or potassium hydroxide are covered with sufficient spill mix so that all of the liquid is absorbed. With a plastic scoop, the mixture is slowly added to a plastic pail about three-quarters full of cold water. The pail is transported to the fume hood. The pH of the solution is measured and it is brought to a pH of between 5 and 8 by the addition with stirring of solid sodium bisulfate or 5% aqueous hydrochloric acid. Table 29.1 lists the approximate quantity of spill mix required for a spill of 100 mL of 20% sodium hydroxide solution and the volume of 5% aqueous hydrochloric acid required to bring the solution formed by the addition of the absorbent to 5 L of water to pH 7. After the solids have settled, the neutral aqueous liquid is decanted to the drain and the solid residue, consisting of sand and bentonite, can be discarded as normal garbage or washed with water, dried, and reused in spill mix. Neutralization of the spilled base with sodium bisulfate or 5% aqueous hydrochloric acid solution occurs according to Eqs. (29.3) and (29.4) respectively. NaOH ⫹ NaHSO4 → Na2SO4 ⫹ H2O KOH ⫹ HCl → KCl ⫹ H2O
(29.3) (29.4)
Spills of ammonia present two hazards. Laboratory workers may slip in the spill or be overcome by the vapors, especially if the ammonia is a concentrated solution. Thus, the worker handling the spill should wear breathing apparatus and other people should remain a safe distance away. The spill is covered with sufficient spill mix to absorb all of the liquid and maintain a dry layer of spill mix on top. The mixture is scooped into a container and transported to the fume hood. In the fume hood it is slowly added to a plastic pail of cold water. The liquid is neutralized by the addition, with stirring, of either solid sodium bisulfate or 5% aqueous hydrochloric acid. The aqueous solution is decanted into the drain and the solid, sand / bentonite, disposed as normal garbage or washed with water, dried, and reused
DISPOSAL OF SMALL-SCALE SPILLS
29.5
to prepare spill mix. The addition of sodium bisulfate to the ammonia solution yields ammonium sulfate [Eq. 29(5)], while the addition of hydrochloric acid yields ammonium chloride [Eq. (29.6)].
29.3.3
2NH4OH ⫹ NaHSO4 → (NH4)2SO4 ⫹ 2H2O
(29.5)
NH4OH ⫹ HCl → NH4Cl ⫹ H2O
(29.6)
Spills of Compounds with Highly Toxic Fumes
Breathing apparatus must be worn to manage spills of chemicals that have highly toxic fumes. Bromine is an example of a liquid with this characteristic, and iodine is an example of a solid. Everyone except those managing the spill must be instructed to stay at a safe distance from the spill. A spill of bromine is covered as quickly as possible with spill mix to eliminate the fumes. When all of the bromine has been absorbed, the mixture is transferred using a plastic scoop to an empty plastic or glass container. The container is placed in the fume hood and the bromine / spill mix mixture is slowly added to a pail of cold water. During stirring, a 10% aqueous solution of sodium bisulfite is added to the liquid in the pail until it is colourless. The pH is measured and, if necessary, the liquid is neutralized by the addition, with stirring, of solid sodium carbonate or 5% aqueous sodium hydroxide solution. The liquid is decanted to the drain and the solid residue, consisting of a mixture of sand and bentonite, can be treated as normal garbage. The area of the spill can be washed with a 10% aqueous solution of sodium bisulfite to remove any remaining traces of bromine. When sodium bisulfite is added to the bromine / spill mix / water mixture, the bromine is converted to sodium bromide according to Eq. (29.7). Br2 ⫹ 4NaHSO3 → 2NaBr ⫹ Na2SO4 ⫹ 3SO2 ⫹ 2H2O
(29.7)
Iodine is a solid at room temperature, but it sublimes readily and the fumes are highly toxic. Therefore, covering the spilled crystals of iodine with spill mix avoids the danger of inhalation of the fumes. Spills of solutions of iodine can be treated similarly. The mixture of iodine and spill mix is scooped into a container and, in the fume hood, added to a pail of cold water. During stirring, a 10% aqueous solution of sodium bisulfite is added to the liquid in the pail until it is colorless and no crystals of iodine remain. The mixture is allowed to stand in the fume hood for at least 12 hours, stirred, and if the color of iodine has returned, more sodium bisulfite solution is added until the liquid is again colorless. If necessary, the aqueous solution is neutralized by the addition, with stirring, of solid sodium carbonate or 5% aqueous sodium hydroxide solution. The liquid is decanted to the drain and the solid residue, consisting of a mixture of sand and bentonite, is treated as normal garbage. As in the case of the bromine spill, the area of the iodine spill can be washed with a 10% aqueous solution of sodium bisulfite to remove remaining traces of iodine. When sodium bisulfite is added to the iodine / spill mix / water mixture, the iodine is converted to sodium iodide according to Eq. (29.8) I2 ⫹ 4NaHSO3 → 2NaI ⫹ Na2SO4 ⫹ 3SO2 ⫹ 2H2O 29.3.4
(29.8)
Spills of Flammable Solvents
Examples of flammable solvents are methanol, ethanol, acetone, diethyl ether, and hexane. Several of these liquids have toxic fumes but the greatest hazard of spills of these highly flammable liquids is the risk of fire. When a spill occurs, all ignition sources should be immediately shut off. Covering the spilled liquid with spill mix rapidly eliminates further
29.6
CHAPTER TWENTY-NINE
evaporation and so reduces the risk of ignition. Sufficient spill mix should be used to completely absorb the liquid and provide a top layer of dry solid. Using a plastic scoop to avoid the chance of sparks, the mixture is transferred to a container and transported to the fume hood, where it is packaged and labeled for off-site disposal. In some jurisdictions the spill mix with the absorbed liquid may be allowed to stand in an open container in the fume hood until all of the liquid has evaporated. The remaining solid is added to water to dissolve the sodium carbonate and the residue is treated as normal garbage.
29.3.5
Spills of Organic Bases
Many organic bases have highly toxic vapors; pyridine has an especially nauseating odor. The following is an example of the oxidative destruction of an absorbed spill of pyridine or aniline using acidic aqueous potassium permanganate. The spill is covered with sufficient spill mix to absorb the liquid. The mixture is scooped into a container with a plastic scoop and transported to the fume hood. Enough water is added, with stirring, to dissolve the sodium carbonate present in the spill mix. After the solids have settled, the liquid is decanted into a glass or plastic container. Enough 6 M sulfuric acid is added to the liquid (frothing will occur) to give a pH of 2. (To prepare 6 M sulfuric acid, slowly add 10 mL of concentrated acid, with cooling if necessary, to 20 mL of cold water. Always add the acid to water, never the other way around.) Sufficient solid potassium permanganate is added to the stirred solution that the liquid remains purple. (A drop of the liquid placed on a piece of filter paper will show a purple ring.) The mixture is allowed to stand at room temperature for 48 hours and more permanganate is stirred in if the color is no longer purple. Solid sodium bisulfite is stirred into the solution until it is colorless, and then the solution is neutralized by adding solid sodium carbonate (frothing will occur) or 10% aqueous sodium hydroxide solution. The clear solution is decanted into the drain and any brown solid (manganese dioxide) discarded with normal garbage.
29.3.6
Spills of Aqueous Solutions Containing Heavy Metal Ions
Spills of aqueous solutions containing heavy metal salts present a disposal problem since many of these salts are highly toxic and should not be disposed in such a way that they will contaminate groundwater. The spill is covered with sufficient spill mix to absorb all of the liquid. The mixture is scooped into a container and transported to the fume hood. Sufficient water is added to dissolve the sodium carbonate in the spill mix. The solids are allowed to settle and the supernatant liquid decanted into another container. The solids are washed with water, allowed to settle, and the washings are added to the decanted liquid. An aqueous solution of sodium metasilicate (Na2SiO3 䡠 5H2O, 12.5 g per 100 mL of water) is added, with stirring, until there is no further precipitation of solid. The pH of the solution containing the metal silicate should be adjusted, using 2 M sulfuric acid, to the pH shown in Table 29.2 for the metal ion that was present in the spilled aqueous solution. The pH listed in Table 29.2 is that at which maximum precipitation of the metal ion occurs. (To prepare 2 M sulfuric acid, slowly add 10 mL of concentrated acid, with cooling if necessary, to 50 mL of cold water. Always add the acid to water, never the other way around.) The mixture is allowed to stand at room temperature for 12 hours to ensure complete precipitation has occurred. The solid can be collected by filtration or the liquid allowed to evaporate in a large evaporation dish in the fume hood. The dry solid is packaged and labeled for disposal in accordance with local regulations. The reaction is shown in Eq. (29.9).
DISPOSAL OF SMALL-SCALE SPILLS
29.7
TABLE 29.2 The Optimum pH for the Precipitation of Metal
Ions as Silicates Metal ion
pH
Metal remaining in solution (ppm)
Pb(II) Fe(II) Fe(III) Zn(II) Al(III) Cu(II) Co(II) Mn(II) Ni(II)
10.5 9.5 to 10 10 to 10.5 8.5 8.5 10.5 to 11 9.5 to 10 9.5 to 10 9.5 to 10
0.8 5 2 ⬍0.5 ⬍2 0.03 0.08 0.2 0.3
M2⫹ ⫹ Na2SiO3 → MSiO3 ⫹ 2Na⫹ divalent metal ion
sodium silicate
(29.9)
metal silicate (insoluble)
Dichromate salts are particularly toxic and can be present in dichromate cleaning solutions or in plating baths. From our laboratory testing, we have developed a method for the handling of spills of aqueous solutions containing dichromate ions that precipitates the dichromate as a flocculent (rather than a gelatinous) precipitate of highly insoluble chromium hydroxide. The spilled aqueous solution containing dichromate ions is covered with sufficient spill mix to absorb all of the liquid. The mixture is scooped into a container and transported to the fume hood. Enough water is added to the mixture to dissolve the sodium carbonate in the spill mix. After the solids have settled, the liquid is decanted into a second container. The solids are washed with water, the solid is allowed to settle, and the washings are added to the decanted liquid. The acidity of the liquid is adjusted to pH 1 with 6 M sulfuric acid. (To prepare 6 M sulfuric acid, slowly add 10 mL of concentrated acid, with cooling if necessary, to 20 mL of cold water. Always add the acid to water, never the other way around.) During stirring, solid sodium thiosulfate (Na2S2O3 䡠 5H2O) is added until the solution changes from orange to blue and cloudy. The solution is neutralized by the addition of sodium carbonate, and after a few minutes a blue-grey flocculent precipitate forms. The precipitate can be allowed to settle and the liquid decanted into the drain. The solid is allowed to dry in a large evaporating dish in the fume hood. The decanted liquid contains less than 0.5 ppm of dichromate. The dry solid is packaged and labeled for disposal in accordance with local regulations. The reaction of dichromate with thiosulfate proceeds according to Eq. (29.10). Cr2O72⫺ ⫹ 3Na2S2O3 ⫹ 2H3O⫹ → 2Cr(OH)3 ⫹ 3Na2SO4 ⫹ 3S dichromate
29.3.7
sodium thiosulfate
(29.10)
chromium hydroxide (insoluble)
Spills of Some Potentially Carcinogenic Materials
When a chemical is especially hazardous to the worker handling the spill, it is advisable to try to neutralize the spill before absorption onto spill mix. Such treatment is especially recommended when the spilled material is a known human carcinogen. Many of the chemicals used in chemotherapy are known to be mutagenic and therefore have the potential to be carcinogens. For example, daunorubicin is deactivated with acidic potassium permanga-
29.8
CHAPTER TWENTY-NINE
nate solution (Castegnaro et al., 1985). If a solution containing daunorubicin is spilled, a solution of freshly prepared acidic potassium permanganate is poured over the spill. (This solution is prepared by adding 17 mL of concentrated sulfuric acid to 83 mL of water, cooling, and adding 4.7 g of potassium permanganate.) The appropriate quantity of potassium permanganate solution to use can be found by estimating the weight of daunorubicin in the spilled liquid and allowing 10 mL of solution per 50 mg of daunorubicin. The area of the spill must be isolated since the reaction should be allowed to proceed for at least two hours. A saturated solution of sodium bisulfite (10 g of sodium bisulfite, NaHSO3, in 35 mL of water) is poured onto the spill to decolorize the potassium permanganate solution. The liquid is absorbed on spill mix and the mixture scooped into a container with a plastic scoop and transported to the fume hood. The clear liquid can be decanted to the drain and the solid residue treated as normal garbage.
29.3.8
Spills of Pesticides
Commercial concentrated pesticide formulations may be spilled when workers are preparing the diluted solution for treatment of plants. In some instances the surface on which the spill occurred may be somewhat porous. Then, in addition to the spill being cleaned up, it is important that the site of the spill be decontaminated so that the pesticide is not carried on the footwear of workers walking through the area. Spill management methods for Diazinon, Chlorpyrifos, and 2,4-D are described here (Armour et al., 1996). Diazinon is an insecticide used to control sucking and chewing insects on a wide variety of crops. Chlorpyrifos is used to control insects and mites in stored grain and various pests on fruit, vegetables, and other crops. When a spill of the concentrated formulation of Diazinon or Chlorpyrifos occurs, it is suggested that the liquid be absorbed on spill mix and the solid scooped into a plastic pail. If the liquid has been spilled on a porous surface, the site of the spill should be decontaminated by isolating the area and pouring household chlorine bleach onto the site. The excess liquid is absorbed on spill mix and the solid residue combined with the solid from absorption of the pesticide in the plastic pail. The pail is transported to a fume hood or to a very well ventilated area, preferably out of doors. The volume of concentrate spilled is estimated, and for each 1 mL, 100 mL of household chlorine bleach is added to the solids. The mixture is stirred and allowed to stand in a secure and very well ventilated area for at least 18 hours. The liquid is poured into the drain and the solids washed with water and treated as normal garbage. The herbicide 2,4-D is widely used for weeding cereal and other crops. The most commonly used form is the iso-octyl ester. Spills of the ester are treated by absorbing on spill mix and either packaging and labeling the residue for off-site disposal or scooping the residue into a plastic pail for on-site denaturation. To decompose the absorbed 2,4-D iso-octyl ester, enough water is added to the residue in the pail to dissolve the sodium carbonate in the spill mix. A solution of aqueous acidic potassium permanganate is prepared as follows. Concentrated sulfuric acid (17 mL) is added slowly to 70 mL of cold water. The solution is allowed to cool to room temperature and 4.7 g of potassium permanganate is dissolved in the solution. The volume of the solution is brought to 100 mL with cold water. The amount of 2,4-D isooctyl ester in the spill is estimated, and 100 mL of acidic potassium permanganate solution is added for each 200 mg of 2,4-D iso-octyl ester. Foaming will occur due to the presence of sodium carbonate from the spill mix. The mixture is allowed to stand in a secure, well ventilated place (a fume hood is ideal) for 96 hours. Solid sodium bisulfite is added with stirring until the liquid is colorless. The pH is adjusted to between 6 and 8 by the addition with stirring of either solid sodium carbonate or 5% aqueous sodium hydroxide. The solids are allowed to settle, the liquid is decanted to the drain, and the solids are treated as normal garbage.
DISPOSAL OF SMALL-SCALE SPILLS
29.3.9
29.9
Spills of Unknown Substances
Spills of unknown substances produce a difficult situation. Fortunately, they are a rare occurrence, and even if the exact identity of the spilled chemical is unknown, it is usually not difficult to narrow the possibilities. For spills of solid unknown substances, a judgment has to be made about the probable hazard of the spill. It is always wise to assume the worst-case scenario and wear complete personal protective equipment with breathing apparatus. If it is known that the solid is not dangerously reactive, then it can be scooped into a container, packaged, and labeled as accurately as possible for disposal. If there is a possibility that the spill is of a metal hydride or other solid that may spontaneously catch fire, it should be covered with spill mix, scooped into a plastic pail using a plastic scoop, and transported to the fume hood. Slowly and cautiously, butanol is added with stirring to the mixture. The weight of hydride spilled is estimated and about 40 mL of butanol is allowed for each 1 g of mixture If the spill is of a liquid, it should be covered with spill mix as quickly as possible until all the liquid is absorbed and there is a dry layer of spill mix on top. If the spill is known to be of a flammable organic solvent, although the exact identity of the liquid is unknown, the adsorbed residue can be treated as described under Section 29.3.5. Similarly, if the spill is known to be of an aqueous solution containing heavy metal ions, the procedure described in Section 29.3.7 can be followed. If the nature of the liquid is completely unknown, either it can be analyzed to discover its identity and the residue can then be treated appropriately, or the residue from absorption on spill mix can be packaged, labeled as accurately as possible, and sent off-site for disposal.
29.4
CONCLUSIONS For the over 250 hazardous chemicals that we have spilled and tested with spill mix, it has been found that liquids are rapidly absorbed and fuming is quickly eliminated. Because the spill mix is relatively inexpensive, containers of it can be kept in laboratories or other areas where hazardous chemicals may be spilled. This allows for very rapid covering of the spill with spill mix and the control of many of the risks associated with the spill. The spill mix we have developed is versatile and provides a practical way of reducing the danger of spills of hazardous chemicals. When the identity of the spilled chemical is known, it is often possible to convert the absorbed mixture to environmentally acceptable products using reactions that have been tested in the laboratory.
29.5
REFERENCES Armour, M. A. 1996. Hazardous Laboratory Chemicals Disposal Guide, 2nd ed., CRC Press, Boca Raton, FL. Armour, M. A., C. Nelson, P. Sather, Y. Briker, E. Crown, K. B. Rigakis, and N. Kerr. 1996. ‘‘Decontamination of Spills and Residues of Pesticides and Protective Clothing Worn during Their Handling,’’ in Proceedings of the Pacific Basin Conference on Hazardous Waste, Pacific Basin Consortium for Hazardous Waste Research and Management, Kuala Lumpur, Malaysia, pp. 44–54. Armour, M. A., D. Ashick, and J. Konrad. 1999. ‘‘Tested Methods for the Handling of Small-Scale Spills,’’ Chemical Health and Safety, vol. 6, no. 1, pp. 24–27. Castegnaro, M., J. Adams, M. A. Armour, J. Barek, J. Benvenuto, C. Confaloneri, C. Goff, S. Ludeman, D. Reed, E. B. Sansone, and G. Telling. 1985. Laboratory Decontamination and Destruction of Carcinogens in Laboratory Wastes: Some Antineoplastic Agents, International Agency for Research on Cancer, Lyons, France. National Research Council. 1995. Prudent Practices in the Laboratory. Handling and Disposal of Chemicals, National Academy Press, Washington, DC.
