Oxide modified aluminum for removal of methyl orange and methyl blue in aqueous solution

In this work, pristine aluminum (Al) powder was soaked in deionized water for a time period and then it was dried and heat-treated at 400 °C such that a layer of fine Al₂O₃ grains covered the Al particle surfaces, forming oxide modified Al powder (OM-Al). It was found that OM-Al greatly enhanced the efficiency in removing methyl orange (M-orange) and methyl blue (M-blue) in aqueous solution. The time to completely degrade M-orange and M-blue by OM-Al is about one third of that by pristine Al powder, and decreases with increasing dosage of OM-Al. The enhancement in dye removal rate by oxide modification is much better than that with ultrasonic assistance, especially for M-blue. LC/MS spectrum analyses revealed that large dye molecules are broken into small biodegradable organic molecules after reaction with OM-Al. It is deduced that the promotion of fine Al₂O₃ on the hydration process of Al surface passive oxide film is the main mechanism responsible for the enhancement of dye removal by OM-Al. Furthermore, OM-Al has a good recyclability and 80% of M-orange and M-blue can be removed even when it was reused for up to three cycles. These results indicate that oxide modification is an effective way to activate Al for the removal of organic dyes.