Chemistry dominates a large part of the industrial processes we know, playing a fundamental role in the world economy, an importance that has brought with it a serious consequence: an environmental devastation never before witnessed in history.
The damage caused by the improper disposal of chemical industry waste ranges from soil pollution to the compromise of our water resources. This fact has sparked a gradual interest in improving green chemistry, coming from both the population and the chemical industry, which wishes to remain strong in the economy of the sustainable era.
The interest of chemistry in the environment seems to have emerged in the late 1940s with the Scientific Conference of the United Nations Organization on the Conservation and Utilization of Resources (UNSCCUR) and has been refined to this day. The year 2011 was adopted as the International Year of Chemistry and how will the field of chemistry be aimed at being more sustainable? What areas has so-called green chemistry focused on?
It is known that the concept of green chemistry is based on 12 principles:
1) Prevention: it is better to prevent the formation of waste than to treat it later;
2) Atomic Economy: synthetic methods should be developed to maximize the incorporation of the atoms of the reagents into the desired final products;
3) Synthesis with Less Toxic Reagents: whenever possible, synthetic methodologies should be designed to use and generate substances that have little or no toxicity to human health and the environment;
4) Development of Safe Compounds: chemicals should be developed to have the desired function, presenting the lowest possible toxicity;
5) Reduction of Solvents and Auxiliaries: the use of auxiliary substances (solvents, separation agents, etc.) should be avoided whenever possible, or harmless substances should be used in the process;
6) Energy Efficiency: synthetic methods should be conducted at ambient pressure and temperature whenever possible, reducing their economic and environmental impact;
7) Use of Renewable Raw Materials: whenever possible, technically and economically, use renewable raw materials;
8) Reduction of the use of derivatives: the use of blocking, protection or deprotection reagents, and temporary modifiers should be minimized or avoided whenever possible, as these reaction steps require additional reagents and can consequently produce undesirable by-products;
9) Catalysis: catalytic reagents (as selective as possible) are superior to stoichiometric reagents;
10) Development of Degradable Compounds: chemicals should be developed for the harmless degradation of toxic products, not persisting in the environment;
11) Real-Time Analysis for Pollution Prevention: analytical methodologies need to be developed to allow for real-time monitoring of the process, to control the formation of toxic compounds;
12) Safe Chemistry for Accident Prevention: substances used in chemical processes should be chosen to minimize potential accidents, such as explosions and fires.
According to the article “Twenty Years of Green Chemistry: Achievements and Challenges”, the most discussed topic when it comes to green chemistry is catalytic techniques. This is likely for economic reasons, as more than 80% of chemical products are produced using catalysts, and therefore the cleaner and more efficient this process is, the effects will extend across various areas of chemistry.
Some believe that the catalytic process is an inherently green technique, but the production of catalysts may not be, and therefore research for the development of new ways to produce catalysts is also a focus of research for green chemistry.
Another chemical compound widely used in the industry that is of interest in green chemistry is solvents. Their substitutes would be ionic liquids, which, in addition to being more chemically and thermally stable (and therefore safer), are non-flammable and do not evaporate, thus reducing the risk of fires and explosions. They are also relatively easy to obtain. Despite so many advantages regarding ionic liquids, a study published recently in the journal Green Chemistry (2006, 8, 238-240) questions whether they are indeed that green. The team that developed this study analyzed the acute toxicity of ionic liquids on zebrafish (Danio rerio), effects that depend on the structure of the ionic liquid in question, but which would cause fatal damage to the gills of these tropical fish.
Green chemistry is still not the main area of chemistry but has the immense challenge of pushing everyone out of their comfort zone and leading to the discovery of new reagents, solvents, and technologies to further improve the performance of these compounds without harming ecosystems. In fact, the main challenge of chemistry is to try to make it as a whole greener and not just a specific area dedicated to being less aggressive to the environment, the main demand of today's economy and society.
