چكيده به لاتين
Red mud or bauxite residue is considered as one of the challenges of Bayer process. Being hazardous, red mud should be stored in tailings dams, which occupies a large area of land and can be the cause of water and soil pollution in the environment. Also, maintaining it in the form of mud is one of the other challenges of this industry. On the other hand, this residue contains various metals that can be recovered. In this work, a red mud sample from Iran Alumina Company (Jajarm, North Khorasan Province, Iran) containing 20.32% iron and 9.81% Al was subjected to a hydrometllurgical processing aiming at recovery of the iron content. In order to reduce the alkaline factors in the sample, the red mud first pre-treated in two stages; first by water leaching (70 ℃) and then by hydrochloric acid leaching (1 M, 45 ℃). As a result, the iron content in the remaining mass increased to about 27% by weight. Then, leaching experiments were carried out with the help of oxalic acid and sulfuric acid mixtures. Leaching experiments were designed and carried out using the central composite design (CCD) methodology. The variables were oxalic acid concentration, time, sulfuric acid concentration and temperature, and the dissolution percent of Fe and Al were measured as responses in each experiment. According to these experiments, the highest dissolution recovery of Fe and Al was 82.04% and 80.11%, respectively. From the statistical analysis of the data, a model was fitted to each response, and the conditions for achieving maximum iron recovery in optimal conditions were obtained. In the next step, the PLS containing iron (III) oxalate was exposed to sunlight for 2 days for photocatalytic precipitation. As a result, a yellow precipitate was formed, which contained aqueous Iron (II) oxalate as evidenced by XRD analysis.
