Solid waste from aluminum recycling process: characterization and reuse of its economically valuable constituents.

Due to economic advantages, many companies in Brazil recover Al from the process of crushing and water-leaching of secondary aluminum dross. Wastes from this process (non-metallic products and salts) are usually landfilled or disposed without treatment, causing many environmental damages. The purpose of this work is to investigate, in a recycling company sited in Sao Paulo metropolitan area (Brazil), the potential use of the non-metallic product (NMP) in the production of concrete blocks and to evaluate the presence of important chemical compounds that may be useful for other applications. Chemical and mineralogical analyses revealed that NMP is composed of refractory and abrasive oxides (alpha-Al2O3, MgAl2O4, SiO2) and an important source of transition alumina: alpha-Al(OH)3. Concrete blocks were made by adding two parts of NMP to one part of cement and four parts of sand. The blocks were tested according to the Brazilian standard (NBR7173/1982) and they passed dimension, humidity and absorption tests but not compressive strength tests. However, particular NMP constituents have accelerated the strength rate development of the blocks, thus decreasing working time. The commercial use of NMP can reduce the amount of discarded wastes contributing to environmental preservation.