mfety in the chemical laboratory
edited by MALCOLM M. RENFREW University of idaho MOSCow, idaho 83843
Tested Disposal Methods for Chemical Wastes M. A. Armour, L. M. Browne, and G. L. W e i r University
of Alberta. Edmonton, Alberta, Canada T6G 262
"How should I dispose of it?" This question was often asked of members of the Chemistry Department Safety Committee at the Universitv of Alherta in reference to ~, chrnmidi m,lmgar needed. Answers t*,such q ~ ~ e r t i owere n s suught m the availat,le mfurmatioo x w w s ( 1 ) . then, to ewuurage the safe and responsible disposal of waste chemicals by all laboratory workers in the department, a manual was prepared in which ~
~~
Margaret-Ann Armour is a 1961 BSc graduate from the University of Edinburgh. She waned as a research chemist in the Da0e.r indusw for five "ears. In 1970. she . recewed a PhD m physlcal organic cnem~strytfrom the Unwers PI 01 A berta where. 10, the as! t *e years, she has oeen %pervisaolaw undeyaduate aganic chemistry laboratories. She is chairperson of the Chemistw Department Safety Comminea and. in collaboration with the other authors 01 this arlicle, is directing a group working on memods fw disposal and recycling of waste chemicals Lois Browne is a 1961 BSc graduate of Uw University of A I M . In 1972 she earned her PhD degree in organic chemistry at lhe University of Alberta studying natural products chemistry and she currently is involved in research in lhis area. Her interest and oarticioatian in the develooment of safe nandllng and d6posa ol wasta chemcals arose from the percewed need for s ~ c h practmcal ,nformat~onto be read !I ava la0 e in the laboratory. She has served as a member of the depanmental safety comminee since her student days. Gordon Weir received a BSc from the University of Calgary in 1969 and an MSc in organic chemistry from the University of Alberta in 1976. He has been with the University d Alberta since then, having served in the oepwt-t of Chemisby as a Sessional Demonstrator and as the Labaratoly Cwrdinator for lhe freshman organic chemistry course. Since 1978 he has been an Administrative Officer in the Depmment 01 Chemistry, a role which includes extensive involvement with the departmental safety camminee.
.
.
.
literature dispaaal methods were collected for over 2M) individual chemicals (2). This manual is given to all those within the department who work with chemicals. During the prepara$ion of the manual, it was reeagnized that *ere was a need for the laboratory testing of sdme of the disposal methods and for the development of methods specific to individual chemicals. As a result, we have been pursuing grant-funded research into methods for the recycling and disposal of waste chemicals from academic laboratories. Dispoaal procedures from the literature have heen tested in the laboratory, and new procedures have been developed. These have been evaluated critically for their safety, reliability and practicality. As has been suggested (3), the tested procedures have been documented in detail, in the style of ''Organic Syntheses," and several have now been checked independently in another laboratory.' We describe here some of the procedures that have been developed.
Chemical Spills I t is rssential that chmm:cals spilled in the laboratory kropidly and clli~ientlynhsorM to avoid the risk of injury from noxious fumes or from workers slipping on the spill. We have found that a 1:l:l mixture by weiaht of soda ash, clay cat litter (benton&), A d sand is very effective in rapidly absorbing liquids, in neutralizing acids, in controlling fumes, and in moderating the hazard due to reactive chemicals. The mixture is economical and easy to prepare. I t has been tested on a large variety of materials from concentrated acids to acid halides and bromine. Calcium carbonate can he substituted for soda ash in the mix. When a soill occurs in the laboratow. the uurker i h d d wear safery ~oggles,g l u k a laboratory coar, and, if necessary, breathing apparatus. The spill is covered with the mix, and after any liquid has been absorbed, the
solid is scooped into a plastic container and transported to the fume hood. Subsequent treatment of the solid depends upon the nature of the chemical soilled. If it was an acid or a cumpound readily hydn,lped tu an add such aa an nod chloride o r anhydride, the mixture is dawly added to a pail of cold water, and, after any reaction has ceased (we usually recommend allowing it to stand in the fume hood for 24 h) the solution is neutralized with soda ash or calcium carbonate and decanted into the drain with a large volume of water. The solid residue can be treated as normal garbage. For chemicals other than acids, the mixture of spill and spill mix is transported to the fume hood and treated appropriately; for example, oxidizing agents plus spill mix would he slowly added to a pail of cold water, then reduced by adding 10% sodium bisulfite solution. The neutralized solution is decanted into the drain with a large volume of water and the solid residue treated as normal refuse. The area of the spill is washed thoroughly with detergent solution.
Dichromate Cleaning Solutlon Although not recommended, haths of dichromate cleaning solution can still he found in laboratories. Because of their poisonous nature, chromium salts must he disposed of in secure landfills designated for toxic substances. Since the cost of such disposal is dependent upon the quantity of the waste, it is desirable to convert the chromium into a dry insoluble salt. For dichromates this is readily achieved by reduction with sodium thiosulfate; huwevcr, frcqumrly a gelatinous preripitat* ir pnduced We h a w tuund that careful control of the vH irf t h wlutiun ~ is needed to yield an easily filtrable salt. The acidity of used dichromate cleaning solution is unknown, therefore it is simplest to neutralize the solution, then reacidify to the required pH. Thus, dichramate cleaning solution (1M) mL) contained in a 500-mL Erlenmeyer flask and stirred magnetically is made neutral to litmus by the slow additionof soda
'
Project directed by K. Simpson. N h e m A I M Institute of Technology. Volume 62
(Continued on page A94) Number 3
March 1985
A93
ash, then reacidified with J M hydrochloric arid (5.5 mL). Withswirling, hydraredsodium thiosulface (40gJ is added and the solution is again neutralized with soda ash (-10 g). A blue-gray flocculent precipitate is formed which can he filtered immediatelv. or. if the mixture is ~- allowed to stand for-&'week. much of the supernaunt liqurd can be de. ranted. The supernatant liquid contains less than 0.5 ppm of chromium. The solid residue is washed with water to remove soluble inorganic salts, dried, packaged and labelled for disposal in a secure landfill. p~~~~~~~~ ~~~~~ ~~~
~
~
~
~
~
Plcrlc Acid Picrie acid is highly explosive in the dry state. I t is supplied as a water-wet solid and as such can he disposed of if handled carefully. On no aeount should acid which has heeome dry be touched or moved. Rather, it should he destroyed by bomb disposal experts. Pieric acid can be converted to a nonexplosive compound by reducing the nitro groups to amino groups with tin and concentrated hydrochloric acid (4). Working behind a safety shield, picric acid (1g) is placed in a 3-neck round-bottomed flask cooled in an ice-water bath and fitted with a dropping funnel and condenser. Any traces of the acid on glassware or equipment are rinsed into the f h k using about 10 mL of water. Granulated tin (4 g) is added and the mixture stirred magnetically. Concentrated hydrochloric acid (15 mL) is placed in the dropping funnel and slowly added dropwise. The initial reaction is vigorous; the rate of addition of the acid may he increased as the reaction moderates. When the addition is complete, the mixture is allowed to warm to room temperature, then heated under reflux for 1 h to complete the reduction. The unreacted tin is filtered, washed with 2 M hydrochloric acid (10 mL) and discarded or reused. The filtrate and washings are neutralized with 10%sodium hvdroxide solution and fdtered to remove tin c h i d e . The solid can be treated as normal garb&e.'l'hc filtrate contains 2.4,6-triaminophenolor itsoxidation product and should be packaged, labelled and sent for inrmeration.This method has been used w destroy havhes of up w 8.5 g of picrir acid at a time: ~~~
~~
~~
~~
~~~
~
Organic Azides Organic azider, frequcntly cnrouncered as reactiun intermediates, can be reduced to nonexplosive products with tin and hydrochloric acid at room temperature (5). Ceric ammonium nitrate oxidation, a frequently cited method useful for inorganic azides, is extremelv slow and not a satisfadorv nroeess. The foll&ing prardure for the reduction uf organic m d r s shuuld k performed in a fume hood hehind a safety shield. To the u i d e A94
Journal of Chemical Education
(0.01 mol) contained in a round-bottomed flask is added concentrated hydmchloric acid (100 mL) and granular tin (0.1 mole). The mixture is stirred mechanically a t room temperature for 12 h. From the reactions performed in our laboratory, this time is sufficient to reduce even relatively stable azides. For example, the times required to reduce the azides which we have tested are as follows: 2-azido-4'-nitrobiphenyl, 8.5 h; Lauroyl azide, 2.5 h; t-hutylazidoacetate, 10 m k , phenyl azide, 11min. When reaction is complete, the unused tin is removed by filtration and discarded or reused; the filtrate is neutralized hv the slow addition of soda ash while stirring &d filtered to remove tin chloride. 7he liquid is packaged in a labelled container for disposal by burning.
The Destruction of Hydroperoxldes In Ethers and Alkenes The formation of peroxides in ethers and alkenes occurs rapidly when these compounds are exposed to air and light (6).Distillation of the liquids leads to concentration of the peroxides in the residue and can result in an explosion (7). Further, the addition of drying agents such as sodium hydride or lithium aluminum hydride to ethers containing peroxides may result in an explosive reaction (8).Hydroperoxides can be readily reduced hy vigorously shaking the ether or alkene (100 mL) in a 250-mL separatory funnel for 3 min with a freshlv orenared 50% aquewa solution of sodium &e&biiulfite (20 mL). This method has the advantage over shaking with ferrous sulfate solution in that even water-soluble ethers such as dioxane form two layers with concentrated sodium metabisulfite solution so that recovery and subsequent drvine. of the ether or alkene is
Dlwosal of Oxalic Acld Oxalic acid and its salts are toxic. Therefore, although they are water soluble, it is preferable to decompose these compounds rather than to wash them into the sewer system. H e a t i oxalic acid or its salts in concentrated sulfuric aeid decomposes them to carbon dioxide, carbon monoxide, and water (9). The procedure must be performed in the hwd. Oxalic acid (5 g) is added to concentrated sulfuric acid (25 mL) in a three-neck, round-bottomed flask fitted with a thermometer. Using a heating mantle, the mixture is heated to 80'-1WT for 30 min. The sulfuric acid can be re-used since the only nonvolatile product is a small quantity of water. If it is desired to dispose of the acid, it should be m l e d and poured slowly into apail of cold water. The solution is neutralized by the addition of sods ash and washed into the drain with a large volume of water. Salts of oxalic acid can he destroyed in a similar manner. Oxalyl chloride must be hydrolyzed to o d i c acid before being decomposed in sulfuric acid. In the fume hood, oxalyl chloride (10 mL) is slowly added to cold water (20 mL) contained in a 250-mL round-bottomed
flask. After atanding at room temperature for one hour, coneencrated sulfuric acid (100 ml.) is wefully poured inm the flask and the mixture heated as for the destruction of oxalic acid. When the reaction is over, the diluted and cooled sulfuric aeid can be slowly wured with stirrine into a nail of cold water. ;he solution .~ ~ . neutrkized -~~~&th soda ash and poured into the drain. These and other p d u r e s that have heen developed in our laboratory are included in the second edition of our manual on hazardous chemicals (10). We believe that the value of the nrocedures lies in the fact that they have b&n carefully tested under laboratory conditions. have been discussed with other professional chemists, and are specific for individual chemicals rather than for groups of chemicals. ~~~~~~~~~
~~
~~
~
Acknowledgment The authors acknowledge the contrihutions of the workers involved in this research, Katherine Ayer, John Cre~ar,Paul Cumming, Donna Renecker, and Richard Young. Financial support for this work has been received from the Occupational Health and Safety Division of Alberta Workers' Health, Safety and Compensation, Waste Management Branch of Alberta Environment, Summer Canada and the Government of Alberta Summer Temporary Employment Program. Gratitude is expressed to Kay Simpson of the Northern Alberta Institute of Technology for arranging to have one of her students independently check several of the procedures.
....- ,-.-,.
(I1 (a) Ridebe, A..andMeiater,R,Anp~np~np. Chom., 49.101 (1936). ib) Rieehe. A,. Angclu. Chem, 70, 261 (19581. (8) Moffett, R B.,Chom. En#. News, 32,4328 (1954). (91 Lichtey, D.M.,J Phys Chem., 11,224 l19Ml. (101 Armour,M.A..Brme,L.M.,and Weir,G.L.."Haaardous ChemieslaInf-~nftititi
and Dispoeal Guide? Znded., Uniuamity olAlborta, (19841.
Volume
Number 3
March
