For a number of years I took students in my graduate course Aqueous Geochemistry to tour the DuPont Plant in New Johnsonville, TN, about two hours west of Nashville. The plant manufactures Titanium Dioxide TiO2 by mining the mineral ilmenite FeTiO3 and reacting it Hydrochloric acid HCl as follows: FeTiO3 + 2HCl = FeCl2 (aq) + TiO2 + H2O. The Titanium dioxide is a pigment that gives Kilz paint, Oreos, and many types of toothpaste their brilliant white color. There are two problems with this process. One is that the product solution is still very acidic. The other problem is that ilmenite contains many toxic heavy metals that are soluble in the acidic solution. In the 1960’s when people didn’t know better, DuPont was allowed to dispose of hundreds of thousands of gallons of this toxic acid solution directly into the Tennessee River, which of course killed all fish and bottom feeders downstream. Later they switched to the more environmentally friendly but more expensive process of deep-well injection. They drilled wells between 1000-2000 feet deep and then pumped the acidic waste into a confined, deep limestone layer. The thinking was that the limestone (which contains calcite CaCO3 and dolomite CaMg(CO3)2) would neutralize the acid: CaCO3 + 2H+ = Ca2+ + H2O + CO2. The confining (impermeable) layer above would keep the waste isolated from shallow aquifers that supplied drinking water. Once again, there were two problems with this plan, which my class would remind the DuPont engineers of every year, and every year they would claim ignorance. First, the acidic solution dissolves the limestone, which results in the formation of large caves deep underground. Eventually the weight of the overlying rock layers causes them to collapse, breaking into pieces, falling, and filling the caves. This shatters the confining layer and makes it permeable, so that the wastes can rise up into the aquifers. The other problem is that, as shown in the reaction, limestone dissolution produces CO2 gas, and the pressure of that gas can build until it shatters the overlying rock and escapes. Either way, it seemed likely that the confining layer would eventually be compromised. So, to their credit, DuPont came up with a new solution that was even more environmentally friendly but (they claimed) even more expensive. Since around the year 2000 DuPont has been reacting the ilmenite with sodium carbonate, and according to the DuPont engineers the only by-product is harmless FeCO3 (the mineral siderite), which is used to make bricks for construction. However, recently it was learned that this process produces dioxin as a by-product. Pure Dioxin is the strongest poison known to man (it is the neurotoxin in Agent Orange), and the New Johnsonville Plant is the fourth-largest producer of dioxin in the U.S..
This case study illustrates many different points. First, it is difficult to anticipate all of the potential outcomes of a complex industrial process. That is why ecologists advocate the precautionary principle. Second, industrial chemistry sorely needs to be “greened”. Green chemistry is a field just now coming into its own, and it has the potential to reduce greatly the environmental impact of the chemical industry. Third, despite repeated attempts at trying to “green” the chemical process, the production of Titanium Dioxide still causes serious environmental problems. DuPont is being sued by numerous plaintiffs who live near or work at their Titanium Dioxide plant in DeLisle, Mississippi, who claim that dioxin has seriously damaged their health or caused the death of loved ones (http://video.google.com/videoplay?docid=-7693391300780002092). At New Johnsonville, TN, many citizens are afraid to talk about the health risks posed by the DuPont plant because they work for the plant, their livelihood depends on its success, and they fear retaliation (http://www.dupontsafetyrevealed.org/newjohnsonville.htm). This raises many questions: Should we allow chemical companies to manufacture goods like Titanium Dioxide that are nonessential (it is simply used for aesthetic reasons) but that cause great harm to human health and the environment? Or should we close the plants, even if it meant that thousands of people would lose their jobs? The plants in New Johnsonville DeLisle are by far the largest local employers, so closing them would be an economic disaster for those communities. In fact, years ago when DuPont reapplied to the State of Tennessee for a permit for deep well injection, a representative of the Tennessee Environmental Council asked me if I would testify against the application. I refused, saying that deep well injection seemed to be the best of the alternatives known at the time, and that I couldn’t bear the thought of helping to put all of those people in New Johnsonville out of work. Yes, I am pro-environment, so I believe we should always be looking for ways to protect the environment, but the overall benefits of change have to outweigh the overall negatives, and in this case, the economic vitality of New Johnsonville seemed to me to outweigh the potential risks of deep-well injection.