Purification And Recovery Of Anodizing Baths And Bright Dip Rinse Water

By Paul Pajunen, Eco-Tec Inc.

During 2008, aluminum finshers around the world have been experiencing a perfect storm of chemical supply and demand issues that have resulted in dramatic increases in the cost of manufacturing an anodized product. For example, sulfuric acid prices have risen to over $ 320/ton 93% after being available for as low as $ 90/ton 93% as recently as October, 2007. This price increase can be attributed to a combination of factors including rising sulfur prices, increasing demand for sulfuric acid for the fertilizer markets, and short supply of sulfuric acid.

Sulfuric acid, of course, is used in mining to extract copper, nickel, and uranium. It used in steel production as well as needed to make fertilizers, refine oil, treat wastewater, and to manufacture plastics. The biofuel boom has kicked off a big increase for sulfuric acid demand. In fact, some 60% of the sulfuric acid produced ends up in agriculture. The surge in ethanol production has a dual effect on sulfuric acid usage as corn, for example, needs fertilizer and the ethanol facilities themselves also use sulfuric acid in their own processing. Then, there is the great demand pull from China and India. Traditionally, these two countries produced what they needed. But now their own rapid industrialization has turned the tables in that they have switched from being exporters to importers of sulfuric acid. The boom in metals such as copper and nickel also drives the demand for sulfuric acid. Smelting operations typically throw off sulfuric acid as a byproduct. But even here, metals companies need more than they can produce. Supply is also tight since, as with many commodities, there has been a long period when sulfuric acid prices went nowhere. This subsequently led to a decrease in production facilities.

The situation for phosphoric acid is similar to the story of sulfuric acid. The rise in demand for phosphorous acid, a main component for phosphorous fertilizers, has resulted in a dramatic rise in price as a result of growing population and the driving urge for more food products. Phosphoric aicd prices, what were once in the area of $ 600 /ton 80% in December, 2007, have increased to the level of $ 2,000/ton 80% presently. These prices are expected to be maintained at these levels through the years of 2009/2010.

In light of the above situation, anodizers can and must look at opportunities within their operations that will reduce chemical costs. The most significant areas within an anodizing operation where chemical usage can be impacted involves the purification and recovery of sulfuric acid anodizing solution and, for those anodizers involved with bright dipping of aluminum, the purification and recovery of phosphoric acid bright dip rinsewater.