mfety in the chemical laboratory
edited by MALCOLM M . RENFREW University of Idaho
MOSCOW, Idaho 83843
The AC Approach to Liquid Spill Cleanup Norman S. Nelson USDA Forest Service, Southern Forest Experiment Station, Forest Hydrology Laboratory, Oxford. MS 36655
Suppose t h a t someone, possibly you, dropped a beaker containing 400 ml of concentrated sulfuric acid. How would you react to the accident? What steps should be taken to minimize the spill hazards and clean up the mess? In a real spill accident situation, you do not have the luxury of being able mentally t o work your way out of the emergency. You must quickly take corrective action, perhaps under difficult, stressful circumstances. Emergency cleanup procedures should be simple and easy to use, safety equipment and cleanup materials must be ready for use, and trained personnel must be ready to use them. Is your laboratory ready? Test yourself with a real chemical-spill cleanup problem. The test will take only a few minutes. Use a flat baking tray (24 X 12 X 1 in.) and any of the chemicals, safety materials, and equipment now in your laboratory. Place the tray on the floor, pour 400 ml of concentrated sulfuric acid into the tray, and then demonstrate your ability t o minimize the spill hazards and clean up the mess. Do not move the tray until it is clean. Was your cleanup procedure safe and efficient? You might have assumed that you could safely handle a serious spill accident, hut I am certain that many experienced chemists, chemical technicians, and most chemistry students could not safely and efficiently clean up 400 ml of spilled eoneentrated sulfuric acid, even under controlled conditions. This paper describes an effeetive approach to chemical-spill cleanup that can he easilv taueht and imolemented. In
Norman Nel-n received his BS in 1957 from Wisconsin State Colleae at Platteviile and n s MS in 1960 from tne Jntversoty of W sconsm he nas t a ~ g h lehemstry at Chabor and Merrm Co eges in Cal~fomla He is currently working as a chemist at the Forest Hydrology Laboratory, where two messy spill accidents taught him how not to clean UD willed chemicals.
The AC Approach Most classes of liquid spills can be cleaned up using a simple, safe emergency approach to eleanup that does not involve direct deaetivation of spilled chemicals. The primary objective in this approach is t o achieve safe containment of the spilled chemical, i.e., to get the spilled chemical up from the spill surface, into a container, and transferred t o a safe place. A chemically inert absorbent must first he used to accomplish safe containment of the suilled chemical: hence. I will call this approach the "Absorption and Containment" (AC) approach to chemicalspill eleanup. The National Research Council (NRC) Committee on Hazardous Substances in the Laboratory provides the rationale for the AC approach (I). "Chemicals occur in almost limitless (and ever-increasing) varieties. For this reason, general precautions for handling almost all chemicals are needed, rather than specific guidelines far each chemical.. . .Accordingly, we have recommended general procedures, applicable to all chemicals, that are designed to minimize the exposure of the lahoratory worker to any chemical." Personnel directly involved with a chemical spill will likely be in a n emotional frame of mind, so that a general, easy-to-remember and easy-to-carry-out eleanup procedure will minimize hazards posed by the spill. The AC eleanup procedure described is general, easy to learn and remember, reasonably quick and easy to carry out, and intrinsically safe. Also, the basic eleanup materials and safety equipment needed t o carry out this procedure are readily available and reasonably priced. Without question, the best all-around liquid absorbent is drv sand. Sand is readilv dinarily comes in a mixture of particle sizes. Sand is a very good absorbent for most laboratory liquids, even low-viscosity, volatile liquids. Although i t will not reduce the vapor pressure of a flammable, volatile liquid, sand will reduce the amount of vaporization when applied to a volatile liquid spill. Sand is not slippery when wet and can be easily spread over a dispersed spill. Finally, the
sandlabsorbed chemical mixture is convenient t o handle and can be quickly removed from the spill surface with appropriate SCOOpS. Regular safety clothing and equipment used for handling lahoratory chemicals will he needed when carrying out an AC spill cleanup, including respirators, face shields, goggles, gloves, towels, sponges, brooms, and mops. In addition, each laboratory should have a t least two heavy-duty plastic pails (3 gal), one containing two flat polyethylene scoops (8 in. 1 X 5 in. ul X 3 in. h), the other one-half full of sand. The pails should be labeled "FOR SPILL CLEANUP ONLY" and kept in an accessible location. Extra sand should he available. All laboratory personnel should learn and practice the AC spill cleanup procedure. When a spill accident happens:
1) Insure the safety of laboratory personnel. a) Be certain that nochemical h u m or poisoning will result. Remove any clothing that came in contact with chemicals, and immediately flush the skin with water. h) Put on necessary protective safety gear. e ) If flammable solvents were spilled, turn off electrical equipment that might spark. d ) Alert other personnel, and block off the spill area. 2) Absorb and contain the spill. a) Liberally spread sand around the perimeter, damming t h e spill. Spread additional sand over the spill until the spilled liquid no longer wets the surface of the sand. b) Scoop the sandlabsorbed chemical mixture toward the center of the spill area and into a plastic pail. Transfer the pail with its contents to a safe place (sink or fume hood).
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3) Clean and deactivate the spill surface. Steps used here will depend on the properties of the chemical spilled, the nature of the spill surface, and the ex(Continued o n page A168)
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tent of the spill. Chemical deactivation might be used, or the surface might he washed with solvent and wiped dry with a towel. Deactivation can be used a t this time because the hazards caused by the spilled chemical will essentially have been eliminated. 4) Dispose of the sandlabsorbed chemical mixture. Steps used here will depend on the nature and quantity of absorbed chemical, laboratory disposal regulations, community disposal ordinances, etc. Chemical deactivation might be required, or t h e absorbed chemieal might be safety eluted from the sand with water and flushed down the sink drain. There are other alternatives, hut the important point is that the disposal procedure can be carefully selected and carried out under controlled conditions.
The AC procedure is clearly general and elementary, both important characteristics of any emergency procedure. The simplicity and efficiency of this procedure are evident when contrasted with recommended procedures for cleanup of acid or alkali spills found in chemical safety literature.
Current Recommended Procedures for Splll Cleanup Two laboratory safety handhooks indude spill cleanup and disposal procedures for manv classes of chemicals. The cleanuo orored& I'M spilled acid and alkaline s o h tims are poor emergency procedures ttr follot,, whether you are a beginning 5tudent in chemistry or an experienced chemist.
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1) "Guide For Safety in the ChemicalLahoratory" From the chapter on safety in the instructional laboratow . (2): . . "Neutralize spilled caustic solutions with acetic or hydrochloric arid solution. Neutralhe acids hg sprinkling rodium bicerhonate on the spill area". From the dr*puaal procedure lor causticalkali and ammonia ( 3 ) :"Spills: 50lution-Neutralize and mop up or use water-vac". From the disposal procedure for inorganic acids (4): "Spills: Cover the eontaminated surface with sodium bicarbonate or a soda ash-slaked lime mixture (50-50). Mix and add water if necessary to form a slurry". 2) "Hazards in the Chemical Lahoratory" "Spread sodaash liherally over the [inorganic acid] spillage and mop up cautiously with water.. (5).
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Neutralization of a spilled alkaline solution should not be attempted using acetic or hydrochloric acids directly on the spill. Accomplishing quantitative neutralization would be difficult. Excess acid would be dangerous, heat would be produced, fumes evolved, and chemicals spread over a larger area. Neutralization of spilled acid solution
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by pure sodium hicarbanate or sodium carbonate could produce excessive heat, cause vigorous evolution of carbon dioxide, and matter acid. Addine water to "form a slurry" would most certainly compound the eleanup problems. Other laboratory safety references (6-9) recommended similar procedures for acid and alkali spills, emphasiring chemical deactivation. I\ different approach is taken by a well-known laboratory safety reference ( l o ) where , the only mention of spill cleanup is in the recommendation that ".. . every large Laboratory huilding should have a wet A vacuum for controlling liquid spills reference handbook for chemical technicians (11) recommends flushing acid and alkali spills to a floor drain, and picking up volatile solvents with raga, toweling, or a mop and pail. The ACS handbook for chemical technicians (12) omits the topic of chemical spill cleanup.
Journal of Chemical Education
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Classroom Tralnlng In Splll Control Wet-run training of chemical-spill cleanup procedures should be given to all new lahoratory personnel, but formal demonstrations of the procedures are rarely given t o students in introductory chemistry courses. Where given, the demonstration would typically proceed as follows: "Students, observe how we eliminate the danger of this acid spill by sprinkling on sodium bicarbonate. When no more carbon dioxide is produced hy the reaction:
the acid is effectively neutralized and we are left with a harmless salt solution which can he ..." This simple demonstration would teach and promote a bad approach to chemical spill control, with the initial objective being chemical deactivation of the spilled chemical. The lack of emphasis on practical spillcontrol procedures in chemical education may result from the fact that the chemicals spilled in academic chemistry laboratories are freauentlv water solutions or relativelv unreactive orgamc wlvenr%,suggestmg that cleanup prohlema are elementary. The best, most effective, emergency procedures for handling chemical spills are not obvious or intuitive, however, even to experienced chemists or chemical technicians.
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Commercial Spill Control Materials Commercial availability of chemical-spill cleanun materials should be heloful to the laboratory manager, but comparative evaluation of the materials is somewhat difficult. The follawmg excerpts from the manufacturers' directions for use are needed to evaluate the spill eleanup material 1) Acid neutralizer powder. "Apply. . . t o the spill. .Foaming will ...hegin and a color change will initiate . . . Add additional neutralizer unIf the slurrv til the foamine.. stons . appears dry but isstill red in color, add a small amount ofwatrr and additional powder. Mix agnin . . Following neutralization, the slurry may be cleaned up."
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For about $25, you would get a few pounds
of chemicals that would react like a mixture of sodium carbonate and indicator, along with directions on bow to neutralize acids on the floor. 2) Sandlsoda ash mixture. "Spread evenly over the spill area. Discontinue application if unexpected reactions occur. Discard used material immediately. Wear gloves and safety goggles. FOR ABSORBING ACID AND ALKALI SPILLS"
For about 825, you would get abour 11 lb of sand, 1 lhof sodaash, a scoop, and some very sketchy directions for use. Three major chemical manufacturers have developed spill cleanup kits. Each con. tnins special materials formulated for cleanup of acid, alkali, and organic solvent spills. 3) Spill eleanup kit A. "Acids, Alkalis: .Add sufficient ABSORBENT to trao all free liouid .. . Add appropriate ~ E U T R A L I Z E Rto deactivate thearid or slkalr nnd tudry the mixture. Collect wrth BRUSH and PAN .
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Cleanup procedure with kit A would he much better if neutralizer were not used until after the absorbentlchemical spill mixture has been scooped into a container and transferred to a safe place (sink or fume hood). Chemical neutralization is the primary obiective of eleanuu kits B and C. Both kits have procedures that call for the additron of water to iniure runtact between ahrorbed chemicals and neutralizer: 4) Spill cleanup kit B. "Sprinkle [acid neutralizerlabsorber] .. . into acid spill area. Mix thoroughly until the color change has developed. Additions of small amounts of water aids in obtaining complete neutralization.. . Scoop u p . . ." "Dilute liquid alkali spills of over 50% concentration with equal volume of water. Sprinkle [alkali] neutralizer into diluted spill and add water until color changes.. Sprinkle absorbent into neutralized spill and mix until all liquid is absorbed. Scoop u p . . ."
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Diluting concentrated alkali with an equal volume of water would spread the spill over twice the area, but the neutralization would still be a hot reaction. 5) Spill cleanup kit C. "Apply [acid neutralizerlabsorber] to the spill.. . Foaming will begin, indicating neutralization.. I f . color indicates an acidic condition. add water and additional [neutralizerlahcolor sorber] .. Mix . .. until appears.. DO NOT proceed until foaming has ceased. .Pick up. .with scoops. ." ". .apply [alkali neutralizerlabsorber] to the caustic spill.. . Thoroughly mix the slurry.. . until it changes to a , . color. Add additional [neutralizer/ to obtain absorber] andlor water the above color reaction.. This step will be accompanied by slurry boiling if concentrated caustic solutions are treated. Scoop up. . ."
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Kit C contains an efficient absorbent for organic solvents. Hedberg (13)has pointed out that because of the high heat of ahsorption that occurs with this absorbent and similar activated carbons, it would he easy to lose 20% of the spill by evaporation during the initial mixing, and possibly heat class 1A flammable liquids dangerously close to their flash points. The following materials use the absarption approach to spill cleanup: 6) Gelling agent for liquid spills. "... organic powder that absorbs and solidifies . . . polar and non-polar organics, halogenated hydrocarbons, organic and inorganic acids, or bases, and aqueous solvents."
Other commercial spill-cleanup materials are available. Any of the commercial aeidspill-cleanup materials described could be used to clean up a concentrated mineral aeid spill; however, the procedures that depend on chemical deactivation will still have the disadvantaees characteristic of soill deactiw r w n pnrpdurea. T ~ P S pPm r e d u m ~prw mure and propagate the misleading d e n that there are many classes of chemical spills that must he chemically deactivated before they can be safely cleaned up.
I ) A porous polyolefin hag containing an amorphous silicate. At Least two manufacturers produce these hags in various sizes. They rapidly absorb most liquids, including concentrated acids, alkalis. and organic solvents. The silicate is chemically in& except for hydrofluoric aeid solutions. The svstem should work well
Conclusions The laboratory floor is a poor place to carry out chemical reactions. There is a greater chance of personal injury and damage to the spill surface when chemical deactivation is carried out directly on a spill. Production of heat, spreading of chemicals, and extra time needed to clean up the spill surface aremore likely when using the deaetivation approach. The inherent faults of this approach to emergency spill cleanup should he recognized and taught in our lahoratories. The deactivation aooroach should he de-emphasized in the c h e k e a l lahoratory safety literature. By comparison, the Absorption and Containment (AC) approach is the hasis for a rational, safe, effective procedure for handling laboratory spills. The AC spill cleanup procedure is general, easy to learn, quiek and easy to carrvout. and inherentlv safe to
solvent "to reduce its dangerous properties".
cient, inert absorbent for nearly all labora. tory liquids.
The user of the gelling agent is cautioned to keep the material away from eyes and face, and to avoid inhalation and contact with skin. The eelline aeent is flammable. which mieht rest& its use in case of a flammable solvent spill. It should not he used fur cleanup of a r m g oxidizer? such as pen,xid~ror perchloric acid.
Literature Clted 11) NRC Committee on Hazsrdoua Suh%taneesin the Lsborstow"Prudent Practices for Handling Hazardous Chcmiesls in Laboratorid'; National Academy, washington, 1981:p 10. (2) Manufacturing Chemists' Association "Guide For Safety in the Chemical Laboratory", 2nd ed.; Van Nostrand Reinhold: New York, 1972;pp 29.31. 13) Ref2.0460 (4) Ref2, 479. (5) Bretherick.L..Ed. "Hazards m the Chemical Lahora-
p
P 115. (7) Glean. M.E.;Turk, A. "Safety in Working with Chemics1s";Mscmillan: New York, 1978;p 115. IRI Ref i n 116 (9) ACS Committee on Chemicalsafety,"safetyin Academic Chemistry Laboratories". 4th ed.: American Chemical Society: Washington, 1985:p 36. 110) Steere, N. V., Ed. "CRC Handbwk of Laboratory Ssiety";2nd ed.:CRC: Boes Raton, FL, 1971: p 20.
(11) Shu8ar.G. J.;Shugar,R.A.:Bauman,L.;Bauman,R. S. "Chemical Technicians' Ready Reference Handbmk': 2nded.:McGraw-Hill: N e w York.1981: or,28, ~
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29. (12) Writing Team far the ACSChemieslTeehnieisn Cur-
riculum Prolect. "Chemiesl T e c h n o l w H a n d b w k
Pecsok.R.L.:Chspman.K.;Ponder,W.,Eds.:Ameri-
can Chemical Society:Washington, 1975.
(13) Hedhorg, D. D. Chem. En#.NOUS1981,59(31),3.
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