Determination of flocculation characteristics of red mud suspensions in the presence of different polymers

This study aims to identify alternative natural polymer types for dewatering of red mud residues, commonly using bio-polymers instead of widely used poly-electrolytes. For this purpose, Konya-Eti Alüminyum Inc., the only integrated factory in Turkey that obtains aluminum from bauxite ore, conducted dewatering studies on red mud waste with bio-polymers. Chitosan, lignin, and chitin were utilized as bio-polymers for flocculation experiments. To compare the results, experiments were also conducted with anionic, cationic, and non-ionic polymers. Additionally, experiments were carried out using Poly Aluminum Chloride Hydroxide Sulfate (PACS), which has been commonly used in dewatering in recent years. Optimum concentrations and result turbidities for anionic, cationic, and non-ionic flocculants were determined as follows (for a settling time of 10 minutes): 1,1 mg/L- 9,2 NTU; 9 mg/L- 6,6 NTU; 8 mg/L- 36 NTU, respectively. Among the studied bio-polymers, the most effective result was obtained with chitosan, and the optimum results (for a settling time of 30 minutes) were determined as 10 mg/L- 43,6 NTU (95% efficiency). Dual flocculation experiments were conducted with iron chloride and aluminum sulfate to enhance the effectiveness of chitosan, resulting in a turbidity value of 28,6 NTU with 8 mg/L chitosan + 100 mg/L Al2(SO4)3. Although PACS provided rapid sedimentation, it was observed to lead to the formation of a voluminous and loose sludge. As a result, it was concluded that bio-polymers are not as effective as poly-electrolytes, but they are worth investigating as an alternative approach for sustainable environmental practices.