Eco Friendly Fireworks
WHETHER THEY'RE lighting up Roman candles or basking in the glow of a fireworks extravaganza this 5th November, chemists are entitled to feel a certain amount of professional pride along with their patriotism. After all, it's the chemistry that gives a humble rocket its pop and makes a chrysanthemum shell bloom into a crowd-pleasing explosion of coloured sparks.
Even so, when it comes to pyrotechnics, students of chemistry would be wise to bear in mind this old adage from physics: What goes up must come down. The complex brew of oxidizers, propellants, fuels, binders, and colouring agents is what makes each firework's burst brilliant. But it leaves behind a smoky ghost of combustion products and particulate matter, which waft their way into the nearby soil and water.
The same thing happens when real rockets give off their red glare. Military pyrotechnics, which encompasses everything from missile propellants to handheld flares, release a plume of smoke and potentially toxic products that pose a health hazard to the men and women of the armed forces who may breathe them in.
Consequently, chemists have been working to make new pyrotechnic compounds and formulations so that fireworks are safer and eco-friendlier.
Typical pyrotechnics function by burning, so their basic chemical components consist of an oxidant and a fuel. Black powder, the original pyrotechnic, blends potassium nitrate oxidizer with charcoal and sulfur fuel. Set this witch's brew alight, and in a flash the nitrate oxidizes the charcoal and sulfur, producing glowing solids and a vast volume of hot gases. Other components, such as colorants, binders, and propellants, can be added to the mix, depending on the task the pyrotechnic has to perform.
Smoke is essentially the main issue. The black powder used to propel the fireworks skyward left a trail of smoke, as did pyrotechnic combustion products, such as potassium chloride from the potassium perchlorate oxidant, and metal oxides from metallic fuels, such as magnesium.
Disney was able to solve the black powder problem with an engineering solution. The company built a system that uses compressed air to send pyrotechnics aloft, eliminating the need for black powder. The other problem is a chemistry problem, which is eliminating the smoke once it gets up there....continued at Chemical & Engineering News