Statistical analysis and optimisation of coagulation-flocculation process for recovery of kaolinite and calcium carbonate from suspensions using xanthan gum

This paper explores the efficiency of xanthan gum, a natural polymer and food additive as a flocculant in the recovery of fine kaolinite particles from a suspension. Xanthan gum was benchmarked against alum for kaolinite recovery. Its efficiency was tested for the removal of calcium carbonate (CaCO3) particles from suspension. Statistical optimisation using Box-Behnken Design (BBD) revealed that at pH 6, 8 mg/L of alum and 6 mg/L of xanthan gum would result in 100% turbidity removal. However, an experimental run using these predicted values recorded 96.58% of turbidity removal efficiency. Additionally, 73.20% of fine kaolinite and 70.00% of fine CaCO3 particles were successfully recovered using simple filtration. These results suggest that for recovering commonly used minerals in food industry, such as kaolinite and CaCO3, xanthan gum can be used to substitute synthetic polyacrylamide (PAC) in conventional coagulation and flocculation method in the effluent treatment system. Xanthan gum being a food grade material, offers the scope for recovering and reusing such fines, saving cost and protecting environment.