Optimization of Zinc Removal Process in Sodium Aluminate Solution Based on Orthogonal Experiment

Zinc is one of several impurities in alumina products. To reduce zinc in Bayer liquor, a novel method using organic additives was proposed. An orthogonal experiment methodology was applied to explore the interactions between different impacts. L9 (33) orthogonal experiments were designed to optimize the process parameters such as temperature, retention time, and dezinc agent (species and dosage). The results show that the optimum experimental conditions are: temperature 80 degrees C, retention time 2 h, and dezinc agent dosage 0.4 gpl. Based on the experimental results and in line with theory, it is concluded that the temperature has the main influence, followed by dezinc agent dosage, and then retention time. The impact of organic additive on the content of organics in the Bayer liquor was also investigated. Results show that the organic additives had little effect on the organic content in Bayer liquor, which implies that these additives have great application potential in alumina refineries for impurity control.