| چکیده انگلیسی مقاله |
Rare earth elements (REEs) have an increasingly wide range of applications in various industries. This study investigates the dissolution of REEs using two methods: direct atmospheric leaching and digestion with sulfuric acid, aiming to compare the efficiency of both approaches. Prior to leaching experiments, magnetic and gravity pre-concentration processes were applied to the sample to enhance the grade of rare earth elements. The total concentrations of REEs, titanium, and iron in the monazite low-grade sample were 0.88%, 3.88%, and 8.25%, respectively. In the direct leaching method, the effects of various parameters, such as temperature, time, acid concentration, and the liquid-to-solid ratio on the recovery of REEs and associated metals were examined. Based on the experiments, the optimal conditions for these parameters were found to be an acid-to-solid ratio of 1.5, a liquid-to-solid ratio of 1.5, a temperature of 125°C, and a duration of 3 hours. Under these optimal conditions, the recovery rates for REEs, titanium, and iron were 80.1%, 89%, and 81.2%, respectively. For the digestion method using sulfuric acid, influential factors, such as digestion temperature, sulfuric acid-to-solid ratio, water leaching time, water leaching-to-solid ratio, water leaching temperature, and water leaching duration were investigated. The optimal conditions for digestion and subsequent leaching were determined to be a sulfuric acid-to-solid ratio of 1.2, a digestion temperature of 220°C, a digestion time of 1 hour, a water-to-solid ratio of 1.5 during leaching, a leaching time of 1 hour, and a leaching temperature of 30°C. Under these optimal conditions, the recovery rates for REEs, titanium, and iron were 91.4%, 88.2%, and 72.4%, respectively. |