Aluminum extraction from a metallurgical industry sludge and its application as adsorbent

Abstract

The aluminum industry produces a high number of wastes that are concentrated in the sludge of their water treatment plants. This sludge is rich in aluminum, which could be extracted and purified. In this work, three extraction methods have been evaluated to recover the aluminum from the sludge samples provided by a metallurgical industry from Medellín, Colombia. The sludge has been characterized to confirm its high aluminum content. The Bayer extraction method has been carried out, using 1:10, 1:15 and 1:20 sludge/solution mass ratios, and HCl extraction, by using 1:15 and 1:20 ratios. The extraction with isopropanol has also been evaluated. The amounts of Al, Fe, Cu, and Ni present in the aqueous phase have been measured to determine the recovery of the metals, as well as the selectivity of the extraction method. The highest metal recovery (99.3%) is achieved by HCl extraction for a sludge/solution ratio of 1:20, while the Bayer method (1:15 ratio) has shown the best selectivity. On the other hand, the extraction with isopropanol has not been successful for any of the ratios evaluated. The extracted material has been tested as an adsorbent for the removal of chlorpyrifos (200 mg l−1), where the removal percentages have been higher than 95% for all the weight ratios studied. Hence, this Al-enriched material shows good prospects to be used as an adsorbent in the treatment of polluted water.