Improvement of Lignite Flocculation by Ultrasound Pre-Treatment and Performance Optimization Using Box-Behnken Design

Abstract

There were two objectives of this study. The first was to investigate the influence of ultrasound treatment on coal flocculation in the presence of polymers. In this context, it was observed that the flocculation success increased by using ultrasound as a pre-treatment, but flocculation did not occur with its application in the flocculation phase (ultrasound-induced flocculation only). Also, the short-term application of ultrasound pre-treatment at high power created a more positive effect. In the flocculation process with polymers, the use of ultrasound treatment as a pre-treatment for the suspension enhanced the aggregation of coal particles. In addition, the ultrasound pre-treatment reduced the magnitude of the zeta potential of coal with anionic polymer, which also supported the flocculation. The second objective of the study was to determine the influence of variables related to stirring speed, flocculation time, polymer concentration, and pH on flocculation efficiency by using Box- Behnken design. With the Box-Behnken design, it was found that the optimal conditions for flocculation efficiency were a stirring speed of 300 rpm, a flocculation time of 4 min, a polymer concentration of 1 mg/L, and pH-7, and these values were consistent with experimental results.