Decadmiation of Natural Phosphates by Heat Treatment and Hydrochloric Acid

摘要

Natural phosphate is the product resulting from the exploitation of minerals containing phosphorus. In addition to the mineral containing phosphorus, phosphate rock contains several impurities including cadmium often with amounts above acceptable levels. The phosphate ore industry generally strives to improve product quality by eliminating this toxic element to avoid contamination of the soil after application of phosphate fertilizers in the long term. Therefore, it is better to use phosphate with a low concentration of cadmium. Currently there is no commercial way to remove the metal completely during the manufacturing process of phosphate fertilizers. The only way to reduce the contents of cadmium in fertilizer products is to use phosphates with a low concentration of this element. This study focuses on the elimination of cadmium from phosphate ore (decadmiation), by heat treatment using reagents such as chlorinating agents. The analysis was based on the amount of cadmium extracted and P2O5 losses. The results by ICP-AES analysis of the treated samples show the extraction between 90 and 98 % of cadmium at temperatures that vary from 750 to 900 °C, with consideration of the influence parameters such as the heat treatment time, the volume of the added acid and the temperature.