Flocculation of Coal Waste Slurry Using Bioflocculant Produced by Azotobacter chroococcum

摘要

The flocculation technique is the most common sedimentation method for the dewatering of coal waste slurry, which is fine grained and has high ash content. Bioflocculants are flocculants which are vital to accelerating the settling of coal waste slurry via the flocculation technique. In this work, the bioflocculation of coal waste slurry was studied using a biofloccuant produced by Azotobacter chroococcum. Quartz and clay minerals were used for comparison. Flocculation tests showed that the bioflocculant effectively flocculated coal waste slurry. Approximately 83% of the flocculation rate was achieved at a bioflocculant dosage of 80 mg/L when the coal waste slurry concentration was 30 g/L. The maximum flocculation of coal waste slurry occurred around pH 2. The flocculation of clay minerals and quartz under the same conditions indicated that the bioflocculant flocculated clay minerals effectively and efficiently, but "quartz was scarcely flocculated. zeta-Potential measurements showed that the surface charges of demineralized coal, clay minerals, and quartz became more negative after interaction with the bioflocculant. Adsorption tests and FTIR analysis results suggested that the bioflocculant shows a higher affinity to the demineralized coal, kaolinite, and illite than to quartz. Quartz had a negative impact on coal waste slurry flocculation with the bioflocculant.