Sara S t e c k Melford DePaul University Chicago, Illinois 60614
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Sdid Waste Chemistry A different environmental muse
A solid waste chemistnr course has been develooed a t De-
P& to round out a n Lnvironmental chemistry program started five years ago. I t bas had the additional, unexpected feature of providing a n introduction to industrial chemistry and to some engineering concepts, two important areas frequently omitted from liberal arts chemistry sequences. Few guidelines for the course existed then and a suitable approach was not self-evident. The lecture and laboratory could not parallel those for air and water pollution courses because the solid waste problem is too varied to reduce the study to origins, reactions, toxicities, and quantitative measure of ~- the ~-~~ma& chemicals involved. The class. moreover. could not parallel a civil or environmental engineering course because more cbemistrv and less solid waste management had to be presented. The solution was to develop the course around a recoverv and utilization theme. This aooroach oardeled the recent trend in the solid waste field; inaddition, it logically led to discussion of manv industrial chemistry processes and provided a suitable bask for experiments in thk laboratory. ~
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Lecture The lecture oortion of the course is divided into four maior which are outlined below together with a number of the more comnrehensive references that have been used. Over half of the c o & e is devoted to the recovery and utilization section general tone but the other three parts are necessw to set the . and perspective of the subject. I) Introduction:Typesand Amountsof Solid Wastea (1.2) (Urhan,
Industrial, Agricultural, and Mining) 11) Economics and Energy A. Economics in Solid Waste Management and Recycling (35) B. Energy used in Produds that become Solid Waste(Aut0mobiles and Consumer Packaging (6,7)) C. Energy from Solid Wastes (35, 8) (Incineration-high temperature, heat remvery, electricity generation-Pyrolysis. Anaerobic Digestion) 111) &lid Waste Management (1,2,4,5) (Collection and Disposallandfill, incineration,cornpoet) IV) Recovery and Utilization (3-68-10) A. Processing (4,9,10) (Size reduction, Separation, Systems) B. Manufacture and Utilization 1. Ferrous (11) and Non-ferrous (12) (A], Cu, Zn,Ni, Ph) Metals (Foundry wastes (3) end Mining wastes (3,s)) 2. Cement (3) 3. Glass and Ceramics (3) 4. Paper (12) 5. Plastics (3) 6. Rubber and tires 7. Food and agricultural waste8 (9) The introduction begins with defining solid waste and delineating its interrelation with energy and air and water pollution. Components of and statistics for the various types of solid waste are presented in one or two class periods. Agricultural wastes (>50%) and mining wastes (>30%) are included because of their large contribution to the overall oroblem. Because of their importance in any solid waste problem solution, economic restraints and enerw considerations are discussed next. The hard facts of econ&ics, one of which is a market for goods. have led to the demise of many recycling endeavors. An elegant chemical solution to a prohiem 6
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174 1 Journal of Chemlcal Educ~tlon
worthless unless it is economically feasible. As our natural resources dwindle, energy and materials tied up in solid wastes are becoming more important. Free energy analyses of technological methods and recycling by R. Stephen Berry and associates ( 6 7 ) bring a new and interesting approach to this subject. This section presents excellent practical application of chemical thermodynamics calculations. Solid waste management techniques are discussed because the student needs to know what alternatives are available in waste collection and disnosal. Onlv a few lectures are used for this material, which presents a number of engineering practices and concepts to the student. The first topics in the recovery and utilization sections are nrocessine a i d seoaration techniaues because they frequently beterminle the chemical hodge-podge that must be work& with. Necessarilv. most of this section is based on physical rather than chemical properties; the discussion, howe"ei, does show that there is a place for chemistry, especially in the prnpriety chemicals used in froth flotation. In the utilization section, the chemistryof how the product was originally made was introduced firstso that the chemical composition could be used in waste products. Physical, as well as chemical, solutions to a problem were presented because they are frequently more economical. This section applies the type of thinking the student must use in an industrial chemistry position. Lecture material came from manv sources. including- "eovernment and industrial publications, environmental journals, and those given above. The students were expected to consult a significant number of them because a suitable textbook was not available for the course. Lectures were supplemented with a number of solid waste films from the EPA. Appropriate field trips were taken to increase the student's experience with solid waste treatment and industrial operation; ~~~~
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Laboratory Because a chemistry laboratory is not equipped to process mnst solid waste mixtures, suitable exoeriments were difficult to devise. The solution h& been to d G d e the laboratory into four classes of experiments: (1)composition, (2) processing, (3) separation, and (4) utilization of wastes. This scheme better reflects the solid waste field than traditional chemical analysis of d u s u and other manageable wastes. Although outlines for a number of experiments (brieflydescribed helow) are eiven to the students.thev are encouiaeed to imorovise or s h t i t u t e experiments of tieir own desi& One of'the ex~erimentsmust include some orieinal research. Rationale and iesults for all experiments a r e k e p t in an industrial style notebook. Instrumental analysis is encouraged. (1)One composition experiment is to keep a record of the weight and volume of the glass, metal, paper, and food in the family waste for one week (13)and to compare the results with composite figures reported by cities. An experiment on waste properties is to bury and regularly water tin and aluminum can lids. Each week these lids are dug up, washed, dried, and weighed; the weekly weight losses are used to predict and compare the length of time required for their complete degradation (13). Because the weight loss in an-eight week period is less than dramatic, the kinetics need a good error analysis. (2) Cryogenic processing (3d;8 ) of plastic-insulatedwire, metals, and rubber makes an interesting, simply implemented experiment. When hammered, the brittle plastic breaks away from the malleable
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copper in insulated wire that has been dmpped in liquid nitrogen for a short time. Unlike most metals. zincdoes not remain malleable when exposed to cold temperatures; (he Bureau of Mines has developed a separation scheme for the recovery of east zinc in automobile engines using this property. Students cooled various forms of metals in liquid nitrogen and then hammered them; three different types of zinc shattered while all other metals treated, including cadmium, remained malleable. In the third experiment,studenta hammered rubber articles before and after immersion in liquid nitrogen; this processing has been used to reduce the volume of rubber tires. (3) An interesting experiment that does not require sophisticated equipment is density separation of plastics. Common everyday plastics are cut into small pieces with scissors or tin-snips and separated according to the Bureau of Mines scheme (3c,8)outlined in the table. Relatively clean separations have been obtained with untreated mixtures in spite of adhering glue, paper, and air bubbles. Because the suggested solvent washing scheme (3c) partially dissolved the plastic pieces, conscientious students have washed the plastic by stirring it with a sand and detergent water solution to remove some of the sdherine materials: the sand is easilv screened off from the plastic pieres.-~hestudents' results indicate that the amount of polypropylene used in hou~eholdgods has increased greatly in the past couple of years. (4) The recovery and utilization experiments can easily b tailored to the students' analvtieal,oraanic, inowanic, or bioehemieal interests and are therefore most suitable for an in-depth research project. Studentsare exoected to exolore and write un the backeround for the project, the chemical rationale, their experiments, economic considerativns, and any other pertinent information, Some of the problems pursued by DePaul Univernity students are described below. ~~
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Analysls of Nectrlc Furnace DU& with Roposals for Its Utilization Standard quantitative analysis techniques (iron in steel) and atomic absorption spectroscopy have been used to analyze the dust; an emission spectrograph could be used to advantage with this problem but was not available a t DePaul. Chemical com~ositionof the dust is then used to describe its usefulness ( 3 ~ as ) a raw material for steelmaking, a pigment in paint primers, a pelletized aggregate, a soil conditioner, a soil stabilizer, and in original ideas of the student. A similar experiment could he carried out with fly ash. Pyrolysis of Plastics Students have pyrolyzed polystyrene in a vacuum and in nitrogen and helium atmospheres contained in a tube furnaee assembly; they have analyzed the products by gas chromatoeraoh" andmass and infrared soectrometrv. mo. Stvrene nomer is the predominant produciin these experiments; this illustrates the orinciole of destructive distillation. This exto other plastics and to other be periment c o d d ~ a s i l ~ adapted atmospheres. The Bureau of Mines, for instance, has reported (3c) that it is cheaper to transport HCI as PVC, which is pyrolyzed, than as liquid HCI. Use of Agricultural Wastes to Remove Heavy Metal Ions from Water (3dJ Students have made ion-exchanee columns with several t y p e i i f sawdust and have run meta'i ion solutions a t various DH'S throueh them. The sawdust removed siznificant amounts of mercury from solutions analyzed by aGmic sb~
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sorption spectroscopy but did not remove chromium and cobalt from solutions analned bv S~ectronic20 colorimetric analysis. The most efficient was& for metal ion removal have been rewrted to be those which contain tannin or tannin-like materials (3d). Glass Insulation A brick-like type of insulation can be made by foaming . students powdered glass with CaC03 a t about 750°C ( 3 ~ )The sought to determine the effect of different types of glass (soda-lime, Pyrex, window, crystal, and blue) by grinding them separately, combining them with 1-2% CaC03 in porcelain crucibles, and heating them a t several temperatures in a muffle furnace. The students have had only limited success with this experiment. Detinning of Bimetallic Cans Aluminum interferes with the presently used oxidativealkaline process of detinning; the students, therefore, checked to see whether or not the older chlorine treatment could he used to separate the tin from a bimetallic can mixture. Tube furnace experiments auicklv showed that iron in a bimetallic can mixture was tr&sporied by a chlorine gas stream a t temperatures as low as 50°C. Thus the volatility of SnClr could not be used to separate the tin from the mixture. Further study revealed that the volatile iron molecule is FeAICls (14).
Micmrganlsms and the Degradation o r Organic Wastes Students used microbiological techniques to study the types of bacteria aasociated with the normal degradation of various organic wastes. An obvious extension of this experiment is the production of methane and other useful organic compounds by bacterial action on specific organic wastes. Conciuslon
Student response to the c o w has been very g d , the word has spread that the course is an excellent way to learn some practical chemistry. The enrollment tripled the second time the course was taueht. Graduates have indicated that employers are interestid in what they have done in the course. This chemistw class is one of the few that leads to the creative thinking in the laboratory that the students will practice in industrial chemistry; it, moreover, gives them an appreciation of the importance of economic factors. Literature Cited (1) E l i m n . Rolf lConrultanl(. "Sdid Waste Man-enL" US. Cuvt Printinv Office. Washington, D. C., I%9. (2) Small. W ~ l l m nE.." T h d Pollution." Planer Publishera. New York. 1970 ce ( 4 .-pme.di.rn "rthc pirat M ~ ~waste . ~ ~utiiizatiun'sympusium1.. I spmr,red hy I l T R l and the Bumav uf Mines. Chicapo. Ill.. 1968. (bl " P n r d i n r s dthcSecend Mineral Waste Utililatlm Syrnmium.' 1970. Icl "Pmcdinus 01tho Third Mineral Waste Utilizatil~nSvmouaium."1972. ld) " P l e d i n n o f t h e Fnurth Mineral Waste
S.. and Fok, M. F., "Pnducfum and C~~nsumpri~mofAulclmobil~:luly1972. RFIIIII~~ the illin& inatitutelur EnvinmmentalQuaiily.Prinfed in part inScienrs c ondPublic A l l o h , pp. LI-I7.,WO. ( D ~ 197:l). 171 Makinu, Hin,, and Berry. R. S.. "Cmsurnrr Gcmds." June 1978.. Swdv L r illinllia in. %tilutelin Envimm&ldl Quality. (8) "Bureau or Minea Resesrch Prngrams on Recycling and Diapmal of Mineral-Met& Bureau of Mines lnlormation Cireular No. 8595. and Energy-Based Was*:
[email protected]. 1973. (91 "Solid Waste Pnr-ins: Publie Health Service Publication No. 1956, U. S. God. PrintingOffice. Washington,D. C.. 1971. (101 "Recovery and Utilization of Minicipal Solid Waste," Public Health PublicationNo. 180.5 U.S. Gwt. Printingoffice, Washington, D. C., I97i. (111. Mffisnnun, Hamld E. (Editor), "The Msking,Shaping,andTreatiryofStoel," U n i M StatssSWl Curp..Printed by Herbiek and Held, 1971. (lo "AStudy tu Identify Opportunitieslor IncreasedSolid WssteUfi1ization:Prepsred by Baltelle Lahuraturies lor the National Asreistiun of S~mndaryMaterial In. duatries, inc.,June 1972 Vul. IGeneral Report, Vol. Il-VII Metals Report,Vol. V I I I X Paper and Textile Report. (13) Biaustein. E. H.. "Anti-pullution Lab: Sentinel Boob Publishen, Ine.. New York, is72. (14) Fowler, Richard M.,snd Melfurd. Sara S.. "FLAICI~.A Vulatlle Molecule Formed by tho Reaction of Aluminum C h h i d ~ with Ferric Chloride: lnorx. Chrm., is. 47:j (19761. ( 6 ) B a y , R.
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Volume 54, Number 3, March 1977 1 175
