green chemistry, current and future issues

History

The term green chemistry was first used in 1991 by P.T. Anastas in a special program launched by the US Envi-ronmental Protection Agency (EPA) to implement sustain-able development in chemistry and chemical technology byindustry, academia and government. In 1995 the annual USPresidential Green Chemistry Challenge was announced.Similar awards were soon established in European coun-tries. In 1996 the Working Party on Green Chemistry wascreated, acting within the framework of International Unionof Applied and Pure Chemistry. One year later, the GreenChemistry Institute (GCI) was formed with chapters in 20countries to facilitate contact between governmental agen-cies and industrial corporations with universities and re-search institutes to design and implement new technolo-gies. The first conference highlighting green chemistry washeld in Washington in 1997. Since that time other similarscientific conferences have soon held on a regular basis.The first books and journals on the subject of green chem-istry were introduced in the 1990s, including the Journal

of Clean Processes and Products (Springer-Verlag) and

Green Chemistry, sponsored by the Royal Society ofChemistry. Other journals, such as Environmental Science

and Technology and the Journal of Chemical Education,have devoted sections to green chemistry. The actual infor-mation also may be found on the Internet.

The Idea of Green Chemistry

The concept of green chemistry has appeared in theUnited States as a common research program resultingfrom interdisciplinary cooperation of university teams,independent research groups, industry, scientific societiesand governmental agencies, which each have their ownprograms devoted to decreasing pollution.

Green chemistry incorporates a new approach to thesynthesis, processing and application of chemical sub-stances in such a manner as to reduce threats to healthand the environment. This new approach is also knownas:

• Environmentally benign chemistry• Clean chemistry• Atom economy• Benign-by-design chemistry

Review

Green Chemistry — Current and Future Issues

W. Wardencki*, J. Cury³o, J. Namieœnik

Department of Analytical Chemistry, Chemical Faculty, Gdañsk University of Technology, Narutowicza 11/12 , 80-952 Gdañsk-Wrzeszcz; Poland

Received: May 5, 2004

Accepted: December 10, 2004

Abstract

The beginning of green chemistry is frequently considered as a response to the need to reduce thedamage of the environment by man-made materials and the processes used to produce them. A quick viewof green chemistry issues in the past decade demonstrates many methodologies that protect human healthand the environment in an economically beneficial manner. This article presents selected examples of theimplementation of green chemistry principles in everyday life in industry, the laboratory and in educa-tion. A brief history of green chemistry and future challenges are also mentioned.

Keywords: green chemistry, green analytical chemistry, clean chemistry, atom economy, sustainabledevelopment.

*Corresponding author: e-mail: [email protected]

Polish Journal of Environmental Studies Vol. 14, No 4 (2005), 389-395

Green chemistry is commonly presented as a set oftwelve principles proposed by Anastas and Warner [1].The principles comprise instructions for professionalchemists to implement new chemical compounds, newsyntheses and new technological processes.

The first principle describes the basic idea of greenchemistry — protecting the environment from pollution. Theremaining principles are focused on such issues as atomeconomy, toxicity, solvent and other media using consump-tion of energy, application of raw materials from renewablesources and degradation of chemical products to simple,nontoxic substances that are friendly for the environment.

The 12 Principles of Green Chemistry

1. Prevention

It is better to prevent waste than to treat or clean upwaste after it has been created. 2. Atom Economy

Synthetic methods should be designed to maximizethe incorporation of all materials used in the process intothe final product. 3. Less Hazardous Chemical Syntheses

Wherever practicable, synthetic methods should bedesigned to use and generate substances that possess lit-tle or no toxicity to human health and the environment. 4. Designing Safer Chemicals

Chemical products should be designed to effect theirdesired function while minimizing toxicity. 5. Safer Solvents and Auxiliaries

The use of auxiliary substances (e.g. solvents, sepa-ration agents, etc.) should be made unnecessary wherev-er possible and innocuous when used.

6. Design for Energy Efficiency

Energy requirements of chemical processes should berecognized for their environmental and economic impactsand should be minimized. If possible, synthetic methodsshould be conducted at ambient temperature and pressure. 7. Use of Renewable Feedstocks

A raw material or feedstock should be renewablerather than depleting whenever technically and economi-cally practicable. 8. Reduce Derivatives

Unnecessary derivatization (use of blocking groups,protection/deprotection, temporary modification of phys-ical/chemical processes) should be minimized or avoid-ed if possible, because such steps require additionalreagents and can generate waste. 9. Catalysis

Catalytic reagents (as selective as possible) are supe-rior to stoichiometric reagents. 10. Design for Degradation

Chemical products should be designed so that at the endof their function they break down into innocuous degrada-tion products and do not persist in the environment. 11. Real-time analysis for Pollution Prevention

Analytical methodologies need to be further devel-oped to allow for real-time, in-process monitoring andcontrol prior to the formation of hazardous substances. 12. Inherently Safer Chemistry for Accident Prevention

Substances and the form of a substance used ina chemical process should be chosen to minimize the po-tential for chemical accidents, including releases, explo-sions, and fires.

The selected examples for implementing the 12principles in laboratory and industry are presented inTable 1.

390 Wardencki W., et al.

Table 1. Examples of implementation of green chemistry principles into practise.

Examples of Implementation of Green Chemistry Principles Into Practise

In some industrial chemical processes, not only wasteproducts but also the reagents used for the production,may cause a threat to the environment. The risk of expo-sure to hazardous chemical compounds is limited in dailywork by protective equipment such as goggles, breathingapparatus, face-guard masks, etc. According to the prin-ciples of green chemistry, a threat can be eliminated in asimpler way, by applying safe raw materials for produc-tion process.

Large amounts of adipic acid [HOOC(CH2)

4COOH]

are used each year for the production of nylon, polyure-thanes, lubricants and plasticizers. Benzene — a com-pound with convinced carcinogenic properties — isa standard substrate for the production of this acid.Chemists from State University of Michigan developedgreen synthesis of adipic acid using a less toxic substrate.Furthermore, the natural source of this raw material —glucose — is almost inexhaustible. The glucose can beconverted into adipic acid by an enzyme discovered ingenetically modificated bacteria [12]. Such a manner ofproduction of this acid guards the workers and the envi-ronment from exposure to hazardous chemical com-pounds.

Green chemistry tries, when possible, to utilize be-nign, renewable feedstocks as raw materials. From thepoint view of green chemistry, combustion of fuels ob-tained from renewable feedstocks is more preferable thancombustion of fossil fuels from depleting finite sources.For example, many vehicles around the world are fueledwith diesel oil, and the production of biodiesel oil is apromising possibility. As the name indicates, biodieseloil is produced from cultivated plants oil, e.g. from soyabeans. It is synthesized from fats embedded in plant oilsby removing the glycerine molecule (Fig. 1) — a valu-able raw material for soap production.

Biodiesel oil also can be obtained from wasted plantoils, e.g. oils used in restaurants. In the technologicalprocess, a potential waste product is transformed intovaluable fuel. (Combusted biodiesel oil smells like friedpotatoes.) The advantages of using biodiesel oil are ob-vious. It’s fuel from renewable resources and contrary tonormal diesel oil, the combustion of biodiesel does not

generate sulphur compounds and generally does not in-crease the amount of carbon dioxide in the atmosphere.CO

2formed in the combustion of fuel was removed ear-

lier by plants [12].The great threats to the environment are organic sol-

vents applied in many syntheses. They are released intothe environment by a volatilization process, especiallyin the case of volatile organic compounds (VOCs) andas a result of leakage. The emission of such compoundsis significant because in many syntheses their amountsexceeds the amount of reagents. The new solutions forpractical synthesis aim at complete elimination of sol-vents or to substitute the compounds belonging to VOCsby cheap technological media, harmless for humans andthe environment.

The use of supercritical fluids (SCFs) in chemicalprocesses is becoming more and more prevalent [13-17]. The term “supercritical fluids” comprises the liq-uids and gases at temperatures and pressures higherthan their critical temperatures and pressures (Fig. 2).Above the critical point the liquid-vapour phaseboundary disappears while the formed phase exhibitsproperties between those of gas and liquid. High com-pressibility of supercritical fluids in the vicinity of thecritical point makes it easy to adjust density and solu-tion ability by a small change of temperature or pres-sure. Due to this, the supercritical fluids are able todissolve many compounds with different polarity andmolecular mass. Among many possible supercriticalfluids, fulfilling the green chemistry demands as thereaction media are carbon dioxide (scCO

2) and water

(scH2O).

Carbon dioxide as a supercritical fluid is most frequent-ly used as medium for reactions. It is inflammable, easilyavailable (from natural sources, from power engineering)and cheap. Its application gives considerable energy sav-ings because the critical point is easy to reach due to a lowevaporation heat of CO

2. Carbon dioxide as a supercritical

fluid dissolves non-polar compounds and some polar (e. g.methanol, aceton) like fluorocarbon solvents. The discov-

Green Chemistry ... 391

Fig. 1. Reaction for biodiesel oil productionFig. 2 Phase diagram showing supercritical fluid region.

ery of a new surfactant with high surface activity in super-critical carbon dioxide opened a way to new processes intextile and metal industries and for dry cleaning of clothes.Micell Technologies Company offers technology for re-moval of stains using liquid carbon dioxide instead of theperchloroethylene more commonly applied [18].

Most of the common liquids (e.g., water, ethanol, ben-zene, etc.) are molecular. That is, regardless of whetherthey are polar or non-polar, they are basically made up ofmolecules. However, since the early 1980s an exciting newclass of room-temperature liquids have become available.These are the ambient-temperature ionic liquids. Unlikethe molecular liquids, regardless of the degree of associa-tion, they are basically constituted of ions. This gives themthe potential to behave very differently from conventionalmolecular liquids when they are used as solvents.

Room-temperature ionic liquids are considered to beenvironmentally benign reaction media because they arelow-viscosity liquids with no measurable vapor pressure.However, the lack of sustainable techniques for the re-moval of products from the room-temperature ionic liq-uids has limited their application. Professors Brenneckeand Beckman have shown that environmentally benigncarbon dioxide, which has been used extensively, bothcommercially and in research for the extraction of heavyorganic solutes, can be used to extract nonvolatile organ-ic compounds from room temperature ionic liquids [19].They found that extraction of a material into carbon diox-ide represents an attractive means for recovery of prod-ucts from ionic liquids because:(a) CO

2dissolves in the ionic liquid to facilitate extrac-

tion, and (b) the ionic liquid does not dissolve appreciably in the

CO2,

so that the product can be recovered in pure form. The re-search groups of Professors Brennecke and Beckman haveshown that ionic liquids (using 1-butyl-3-methylimidazoli-um hexafluorophosphate as a prototype) and CO

2exhibit

extremely unusual, and very attractive, phase behavior.The solubility of CO

2in ionic liquids is substantial, reach-

ing mole fractions as high as 0.6 at just 8 MPa. Yet the twophases do not become completely miscible, so CO

2can be

used to extract compounds from the ionic liquids. Mostimportantly, the composition of the CO

2-rich phase is es-

sentially pure CO2, and there is no measurable cross-cont-

amination of the CO2by the ionic liquid. Moreover, non-

volatile organic solutes (using naphthalene as a prototype)may be quantitatively extracted from the ionic liquid withCO

2, demonstrating the tremendous potential of ionic liq-

uid/CO2biphasic systems as environmentally benign sol-

vents for combined reaction and separation schemes.

Green Analytical Chemistry

Development of analytics and environmental moni-toring leads to better knowledge of the state of the envi-ronment and the processes that take place in it. Due to the

introduction into an analytical practice new methodolo-gies and new measuring techniques for identification anddetermination of trace and micro-trace components insamples with complex compositions have enabled thediscovery of the following important facts:

— acidifying the particular elements of the environ-ment,

— the existence of stratospheric ozone depletion phe-nomenon,

— designation of long term trends in changes of tracecomponents in atmospheric air,

— increase of concentration level of so called persis-tent organic pollutant (POPs), i. e. compounds be-longing to dioxins (PCDD, PCDF), polychlorinat-ed biphenyls (PCBs) and others,

— examination of pollutant bioaccumulation in tis-sues of organisms on different steps of the trophicchain.

This branch of analytical chemists creates many chal-lenges. The most important are as follows:

— low and very low concentration levels of analytes,— the existence of time and space fluctuations of an-

alytes in the investigated media,— a broad range of concentration of analytes belong-

ing to the same group of compounds,— the possibility of the presence of interfering com-

pounds, frequently with similar chemical structureand properties.

The irony is that the analytical methods used to assessthe state of environmental pollution may in fact be thesource of emission of great amount of pollutants nega-tively influencing the environment. This is connectedwith the necessity of using considerable amounts ofchemical compounds in successive steps of applied ana-lytical procedures. Sampling and especially preparationfor their final determination is frequently connected withthe forming of large amounts of pollutants (vapours,wastes of reagents and solvents, solid waste). Therefore,it is necessary to introduce the rules of green chemistryinto chemical laboratories on a large scale. There is anurgent necessity to evaluate the used analytical methodsnot only in respect for the reagent, instrumental costs andanalytical parameters but also on the basis of their nega-tive influence on the environment. A good tool for suchevaluation may be Life Cycle Assessment (LCA). It canbe stated that green analytical chemistry is the essentialelement of green chemistry. The constant developmentof a new solventless technique is a good example of theactivities in this field. The following direct analyticaltechniques (a preparation step is not necessary) may betreated as the typical examples of procedures that aremore friendly for the environment:

— X-ray fluorescence,— surface acoustic wave (SAW) used during deter-

mination of volatile organic compounds (VOCs),— immunoassay.Also, the other techniques in which the amount of

reagents and solvents is limited (calculated per one ana-


lytical cycle) belong to environmentally benign proce-dures, e.g.:

— solid phase extraction (SPE),— accelerated solvent extraction (ASE), — solid phase microextraction (SPME)— liquid-liquid microextraction (MLLE), and other

microextraction techniques,— ultrasonic extraction,— supercritical fluid extraction (SFE),— extraction in automated Soxhlet apparatus,— vacuum distillation of volatile organic com-

pounds,— mass spectrometry with membrane interface

(MIMS).The extraction of pesticides from soil samples using

accelerated solvent extraction is a good example of an an-alytical procedure fulfilling the rules of green chemistry[20]. This procedure is characterized by many advantagesin comparison to classical extraction techniques used forextraction of analytes from complex matrices. The mainadvantages considering green chemistry are as follows:

— reduction of used solvents (up to 95%),— shortening of analysis time (from 16 hours to 10

minutes),— savings of energy (the heating of extraction cell of

ASE instrument to 100°C by 10 minutes in com-parison to 16 hours heating of a plate in Soxhletapparatus),

— decreasing exposure to solvents due to shorteningof extraction time and to smaller amounts of ap-plied solvents),

— similar analytical characteristics (precise and ana-lyte recoveries) for smaller sample (ASE).

This procedure can be treated as an alternative tocommonly used extraction in Soxhlet apparatus.

The ability to rapidly assess or monitor the disposi-tion of environmental contaminants at purported or ex-isting hazardous waste sites is an essential component ofgreen chemistry. Soil samples have to be collected fromsurface to ground water and then shipped off-site foranalysis with waiting periods exceeding months. Soilsamples, which represent approximately half the totalnumber, are extracted with solvents, then further separat-ed using additional solvent to produce chemical-specificfractions. Each fraction is then analyzed by an appropri-ate method. The proposed technology by Professor Al-bert Robbat from Tufts University is aimed at reducingor eliminating solvent usage during the sample collectionand sample analysis process by collecting and detectingorganic pollutants at depth without bringing the actualsoil sample to the surface. A thermal extraction cone pen-etrometry probe coupled to an ultra-fast gas chromatog-raphy/ mass spectrometer (TECP-TDGC/MS) has beendeveloped to collect and analyze subsurface organic con-taminants in situ. The TECP is capable of heating the soilto 300°C, which is sufficient to collect volatile and semi-volatile organics bound to soil, in the presence of soil-water content as high as 30%. Rather than using solvents

to extract organics from soil, the TECP uses heat, thentraps the hot vapor in a Peltier-cooled thermal desorptionGC sample inlet for on-line analysis. In addition, the pro-posed technology reduces solvent usage when deconta-minating sample collection probes and utensils used tohomogenize samples. No other technology exists that iscapable of thermally extracting organics as diverse asPCBs, explosives, or PAHs under these conditions. Whencombined with the ION Fingerprint Detection™ soft-ware, ultra-fast TDGC/MS is capable of analyzing com-plex environmental samples in less than 5 minutes [19].

The next important challenge of green analyticalchemistry is in-process monitoring. Developing andusing the in-line or on-line analyzers allow us to deter-mine analytes in real time, enabling us to detect distur-bances in the course of a process in the initial steps. Suchmeans of analysis gives rapid information and a chancefor proper reaction — stopping the technological processor changing the operational parameters, and improvesoverall efficiency.

The application of green chemistry rules during de-signing greener analytical methods is a key to diminishnegative effects of analytical chemistry on the environ-ment [2, 21]. The same ingeniousness and novelty ap-plied earlier to obtain excellent sensitivity, precision andaccuracy is now used to abate or eliminate the applica-tion of hazardous substances in environmental analytics.

Teaching of Green Chemistry.

The main rule: Teaching must be in harmony with

practice.The question of how to educate the future generation

of chemists possessing the skill and knowledge to prac-tice environmentally friendly chemistry lies in the centerof educational materials related to green chemistry [22].

Education is especially important in the populariza-tion of green chemistry. It is realized both at the level ofacademia and on the level of pro-environmental educa-tion for broad circles of society. Young chemists are cur-rently acquainted with new methods of organic com-pound syntheses instead of traditional methods and withnew analytical chemistry techniques allowing them to as-sess the state of environmental pollution in an increasingnumber of high schools. Different international institu-tions, i.e. the American Chemical Society (ACS) and Pol-ish Chemical Society (PTChem), are active in publishingmaterials that promote the rules and achievements ofgreen chemistry. The green chemistry program shouldlead to sustainability by designing and using the methodsin which natural raw materials will be economicallyprocessed, rational usage of energy sources, eliminationof hazardous gaseous, liquid and solid wastes and by in-troduction of safety products for man. The popularizationof green chemistry in schools, among the workers atplants of chemical industry and distributors of chemicalproducts is also very important. The broad usage of green


chemistry achievements will enable us to balance eco-de-velopment profitable for society, economy and the envi-ronment. The numerous educational materials, availablecurrently on market [23] and on the Internet, are veryuseful in everyday teaching of green chemistry princi-ples, e.g.:Green Chemistry Resources, ACS homepage:www.acs.org/education/greenchemGreen Chemistry Institute:chemistry.org/greenchemistryinstituteEPA Green Chemistry Program: www.epa.gov/greenchemistryGreen Chemistry, a journal of the Royal Society of Chemistry:www.rsc.org/is/journals/current/green/greenpub.htmGreen Chemistry Network:chemsoc.org/networks/gcnChemical Education Foundation: www.chemed.orgChemical Industry Education Centre:www.york.ac.uk/org/ciec

Conclusions

Green chemistry is not a new branch of science. It isa new philosophical approach that through applicationand extension of the principles of green chemistry cancontribute to sustainable development. Presently it iseasy to find in the literature many interesting examplesof the use of green chemistry rules. They are applied notonly in synthesis, processing and using of chemical com-pounds. Many new analytical methodologies are also de-scribed which are realized according to green chemistryrules. They are useful in conducting chemical processesand in evaluation of their effects on the environment. Theapplication of proper sample preparation techniques, (e.g.SPME, SPE, ASE) allows us to obtain precise and accu-rate results of analysis.

Great efforts are still undertaken to design an idealprocess that starts from non-polluting initial materials,leads to no secondary products and requires no solventsto carry out the chemical conversion or to isolate and pu-rify the product. However, more environmentally friend-ly technologies at the research stage do not guarantee thatthey will be implemented on an industrial scale. Adop-tion of environmentally benign methods may be facilitat-ed by higher flexibility in regulations, new programs tofacilitate technology transfer among academic institu-tions, government and industry and tax incentives for im-plementing cleaner technologies.

Furthermore, the success of green chemistry dependson the training and education of a new generation ofchemists. Student at all levels have to be introduced tothe philosophy and practice of green chemistry.

Finally, regarding the role of education in greenchemistry:

THE BIGGEST CHALLENGE OF GREEN

CHEMISTRY IS TO USE ITS RULES IN PRACTICE.

The presented problem is strictly related to the activityof the Centre of Excellence in Environmental Analysis andMonitoring (CEEAM, www.pg.gda.pl/chem/ CEEAM/)sponsored by EU funds in the frame of the 5th Frame Pro-gram.

References

1. ANASTAS P. T., WARNER J. C. Green Chemistry: Theoryand Practise. Oxford University Press, Oxford 1998.

2. NAMIEŒNIK J., WARDENCKI W. Solventless samplepreparation techniques in environmental analysis. J. HighResol. Chromatogr. 23, 297, 2000.

3. SATO K., AOKI M., NOYORI R. A “Green” Route toAdipic Acid: Direct Oxidation of Cyclohexenes with 30percent hydrogen peroxide. Science. 281, 1646, 1998.

4. http:// www.epa.gov/greenchemistry5. BARDLEY D., DYSON P., WELTON T. Room temperature

ionic liquids. Chem. Rev. 9 (5), 18, 2000.6. ROMANO U., GARBASSI F. The environmental issue.

A challenge for new generation polyolefins. Pure Appl.Chem. 72, 1383, 2000.

7. NICOLAS N., BENVEGNU T., PLUSQUELLEC D. Sur-factants from renewable resources. Actualite Chimique 11-

12, 70, 2002.8. STASHENKO E. E., PUERTAS A. M., SALGAR W., DEL-

GADO W., MARTINEZ J. R. Solid-phase microextractionwith on fibre derivatization applied to the analysis of volatilecarbonyl compounds. J. Chromatogr. A. 886, 175, 2000.

9. ACARDI A., BIANCHI G., DI GIUSEPPE S., MARINEL-LI F. Gold catalysis in the reaction of 1,3-dicarbonyls withnucleophiles. Green Chemistry. 5 (1), 64, 2003.

10. SCOTT G. Green polymers. Polym. Degrad. Stab. 68 (1),1, 2000.

11. TUNDO P., SELVA M., MEMOLI S. Dimethylcarbonate asa green reagent. ACS Symp. Ser., 767 (Green ChemicalSynthesses and Processes), 87, 2000.

12. MERRILL M., PARENT K., KIRCHHOFF M. GreenChemistry. Stopping Pollution before it starts. Chem Mat-ters. April, 7, 2003.

13. JESSOP P. G., LEITNER W. Chemical synthesis using su-percritical fluids. Wiley-VCH Weinheim, 1999.

14. SARRADE S., GUIZARD C., RIOS G. M. New applica-tions of supercritical fluids and supercritical fluids process-es in separation. Separation and Purification Technology.32 (1-3), 57, 2003.

15. BRANNEGAN D. R., ASHRAF-KHORASSANI M., TAY-LOR T. L. Supercritical fluid extraction of ethoxyquin froma beef matrix. Chromatographia. 54 (5/6), 399, 2001.

16. WOLSKI T., LUDWICZUK A. Extraction of natural prod-ucts with supercritical gases. Przem. Chem. 80, 286, 2001.

17. SKOWROÑSKI B., MORDECKA Z. Polish installation forsupercritical extraction of hops. Przem. Chem. 80, 521, 2001.

18. http://www.micell.com19. The Presidential Green Chemistry Challenge Awards Pro-

gram. Summary of 2000 Award Entries and Recipients,www.epa.gov/greenchemistry, August 2001.


20. U. S. EPA Method 354521. WARDENCKI W., NAMIEŒNIK J. Some remarks on gas

chromatographic challenges in the context of green analyti-cal chemistry. Pol. J. Envir. Stud., 11, 185, 2002.

22. HJERESEN D. L., SCHUTT D. L., BOESE J. M. Greenchemistry and education. J. Chem. Educ. 12, 1543, 2000.

23. LANCASTER M. Green Chemistry. An Introductory Text.Royal Society of Chemistry, Cambridge, 2002.
