Comparative analysis of new natural coagulant extracts for turbidity removal in water systems

Abstract

The ability of two plant materials, lupin beans and rice straw, to serve as sources of coagulation-active components for water treatment was investigated using synthetic turbid water. The functional groups, surficial architecture, and elemental composition of lupin beans and rice straw were determined using FTIR, scanning electron microscope, and X-ray (EDAX). The point of zero charges, zeta potential, and particle size distribution of aqueous extracts were measured. The optimal dosage of 50 mg/L of the lupin bean extract achieved 86.4% turbidity removal at initial turbidity of 500 NTU, pH 7, and 25 °C. Similarly, rice straw extract achieved 63.3% removal under the same conditions. The coagulation efficiency of both extracts improved with higher initial turbidity and temperatures between 20 and 40 °C, and their performance was unaffected by pH variations. Combining natural coagulants with alum reduced alum usage by 25–50%, achieving up to 98.7% turbidity removal. These results suggest that the use of natural coagulants can effectively lower treatment costs and reduce environmental impacts associated with chemical coagulants.