Howard S. Kimmel and Don G. Lambeti 1 Physical Chemistry for

Newark College of Engineering Newark, New Jersey 07102 ( Environmental Engineers

Developing a course a t Newark College of Engineering in physical chemistry applied to environmental problems presented several challenges. First, the students were Civil Engineering juniors or seniors with only a general chemistry background. Second, although the students had taken a course in mechanical engineering thermodynam- ics, they had no appreciation of the applications of ther- modynamics to chemistry, and almost no background in chemical kinetics. Third, no textbook with quantitative applications of physical chemistry to environmental prob- lems is availahle, although a useful supplement is now availahle (1).

The approach decided upon was to assign readings and problems in an elementary physical chemistry text (2) to provide a background for the applications being consid- ered in the lecture. Students were encouraged to partici- pate in the discussions of applications with which they were familiar as well as to bring in material which they might have. Since the students had not dealt with chem- istry for two or three years, the first week was devoted to a review of stoichiometry using combustion processes as an example. Specifically, the burning of one ton of coal containing 1% sulfur was considered, with how much SOz, SOa, and HzSOI could be produced, and how much iron could the sulfuric acid react with. These figures were then related to the reduction of SO2 in New York City air and to the more general problem of power production (3). Stu- dents later suggested that determination of oxygen and the difference in chemical oxygen demand and biochemi- cal oxygen demand (4) could have been discussed a t this point.

Treatment of gases was begun by computing amounts of each gas in unpolluted air, then giving estimates of each material being put into the environment (5). Next, some

of the sources of pollution were discussed along with the chemistry involved (6). In particular, the ratios of SO31 SO2 in smokestacks were noted, along with possible pro- cesses for conversion of SOz to So3 in the atmosphere. Also, the NOz/NO ratio in smokestacks and automobile exhausts was presented and the question was raised as to whether NO, production is not simply a constant indepen- dent of the fuel used. One student hrought specifications for an experimental automobile using liquid propane fuel which had about ten times less NO then conventional cars, which lead to a discussion of the factors favoring NO production. The inherent difficulty of reducing both NO and CO in auto emissions was pointed out. During this time the problems in the text an gases were assigned and problems which gave the students difficulty were done in class. Later the students indicated that this survey of the chemistnr of air pollution was a valuable introduction to a subject with which they were not familiar.

The first law of thermodynamics was approached from a practical viewpoint. A problem based o n a recent proposal to use steam at 250°C from power plants to heat houses was nresented and was criticized hv students who knew aboui the maze of underground plpea in urban areas. Xext quantitative problems dealing with space heating for houses were presented to rlnrify the conrept of a system. 'I'he basic components of power plants were discussed, and one student hrought some literature about the cooling towers for a new nuclear power plant. With this back- ground, the first law of thermodynamics was developed and applied to the systems previously mentioned, as well as heat transfer in humans (7). the formation of clouds on mountains (ti), and a quantitative derivation of the adia- batic lapse rate (9) which the students had seen men- tioned in a previous course in environmental engineering.

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The second law was introduced by asking what is the theoretical efficiency of a power plant, which led immedi- ately to the Carnot cycle. The implications of the second law to thermal pollution was emphasized by showing ac- tual efficiencies of power plants and engines. Efficiency of utilization of sunlight by organisms (10) was related to the question of whether we should eat algae or steak (11). This led to a discussion of the thermodynamics of utiliza- tion of food (12) and the efficiency of various organisms in food utilization (13). Some of the important cycles, such as that involvine nitrogen (14) were used to illustrate the application of thermod;na&ci in understanding these cy- cles. Next the entropy was develo~ed from the statistical point of view and--qualitative &dictions of entropy changes in phase changes and chemical reactions were confirmed by citing numbers. The concept of the free energy was then developed and applied particularly to the combustion of carbon, nitrogen, and sulfur. It was shown that the SO2 and SOs formation reactions are spontane- ous, while the formation of NO is non-spontaneous. After a review of solutions, the thermodynamics of some water treatment processes for removing calcium ion were dis- cussed, and the reverse osmosis process was derived from the point of view of free energy.

Several systems were used to illustrate chemical equi- librium. The solubility of oxygen in water (15) was shown to lead to an equilibrium constant. The synthesis of am- monia was discussed in some detail as a typical equilibri- um and also to provide a basis for discussion of the prob- lem of nitrates in agricultural water. Some students-com- mented that this discussion was valuable because tertiary treatments of water are just beginning to be operative. Next the combustion of carbon, nitrogen and sulfur were presented with for example S03/SOz ratios computed at various temperatures in air. It was gratifying to the stu- dents to see that a t 100O0C, the S03/S02 ratio is calculat- ed as about 0.05, consistent with the 0.02-0.03 ratio actu- ally observed, while a t 25T, the ratio becomes large, con- sistent with the observed conversion of SO2 in the atmo- sphere. The thermodynamics of some of the proposed con- version processes (6) was also examined.

Ionic equilibrium was introduced by first discussing some practical ways to shift equilibria in solution (4), and the solubility of A~(OH)J and Fe(OH)2, used as water coagulants, was then calculated as a function of pH. The topic of acid-base equilibria was illustrated by consider- ation of the activated sludge process (4) for sewage treat- ment, where the carhonate-bicarbonate buffer system is important. It was shown how the system no longer func- tions if the acid concentration becomes too high. The stu- dents had seen a sewage treatment plant but they were unaware of the chemical principles involved. Next, the problem of hardness in water was examined by computing solubilities of limestone in the presence and absence of

carbon dioxide, and the results were related to the calci- um contents of natural rivers and lakes. Complex ion equilibria were introduced through the observation (16) that more mercury dissolves in salt water than in pure water, and i t was shown that the solubility of HgClz in salt water is 45 times its solubility in pure water, in agree- ment with the observed 50-60 times for NaCl of the same concentration. Finally, the problem of treatment of cya- nide-containing wastes containing transition metal ions was considered to show the necessity of destroying the cy- anide ion before removing the metal ions was attempted.

Ideally, a t least the topics of electrochemistry and ki- netics should be discussed in a course of this sort, and plans are being made to incorporate these topics next year. The approach outlined above will still be used, that is, to present up-to-date examples of the application of physical chemistry to environmental problems, while using a good fundamental texthook for developing the basic ideas.

Student reaction to this approach was uniformly enthu- siastic, because they felt there was a dialog between them and the instructors. Several students commented that they now saw how to apply thermodynamics to environ- mental problems involving chemical reactions, and they understood the fundamentals of thermodynamics better. One student reported that he had been apprehensive about taking another chemistry course at first, but now if he needed more chemistry, he had confidence in his ahili- ty to understand the subject. Also several students said that they had a much clearer idea about their senior re- search projects in Civil Engineering after they finished the course. The instructors found the course challenging, that is, to find and to present the current state of the art and to relate this to fundamental principles was satisfying. Persons who wish to try this approach to teaching physi- cal chemistry for environmental engineering students are invited to correspond with the authors. Literature Cited

(11 Miller. G. Tyler Jr.. "Energetin, Kineties and Life." Wadsworth Publishing Co., Inc.,Belmonl. CsMornia, 1971.

(2) Crockford. H. D. and Knight. Samuel B.. 'Tundammtals of Physical Chemistw.- Semnd Edition, John Wiley& Sona. Inc. NevYork, 1967.

(3) SLsrr. Chauncey. Sei. Amer., 224 131.36 (1971). (4 S~svyar. Ciair N. end McCsrty, Peny L., "Chemistry for Sanitary Engineers" (2nd

Ed.), McGraw-HillBook Co..lne., NeuYork. 1967. (5) Hodges, Laurenf. "Lacture N o t e in Environmental Pollution." Phyrien Depf.. lows

SfateUniv.. Amos, Iowa, 1970.p. 46. (61 Berry. R.S.andLehman, P.A.,Ann. Rsu. P h p . Chrm.. 22,17 (19711. (7) Baas, David E. andCarraher, ChsrlesE. h., J. CHEM.EDUC., 49, 112(1972). (81 Stevenson. P. E , d . CHEM. EDUC., 17.272(1970). 191 Msgill, Paul L., Holden, Francis R. end Ackley, Charles. Editors. "Air Pollution

Handbook."McCraw~Hill Book Co., h c . , New York, 1956. 1101 bates, DavidD., SCL Amcr.. 225 (31.88 (1971). I l l ) Bent. Henry A . J . CHEM. EDUC.,48,692l19711. 1121 Margaria. Rudolfo. Sci. Amer.. 226 131.84 (p72 ) . I131 Tucker, Vance. Sci. Arne,.. 220ii1.70(1969). (141 Delwiche.C.C..Sci.Arnsr., 225(31, 136l1970). (151 Barron. Gordon M.. "General Chemistry." Wadrwarfh Publishing Co., Ine.. Bel-

mont. California, 1912. (16) Perisic, M.and Cuenod,M.,Scienc~. 175.142 119721.

412 /Journal of Chemical Education