Removal of Fine Particles from Water Using Plant-based Microfoams

The persistent challenge of removing fine particles from wastewater necessitates the development of environmentally sustainable and efficient treatment technologies. This study explores the application of micro-foam bubbles, also known as Colloidal Gas Aphrons (CGAs), made from plant-based surfactants on fine particle separation from wastewater. The performance of plant-based surfactants (Soapnut and Shikakai) was compared with that of a synthetic surfactant (Sodium Dodecyl Sulphate) in terms of flotation efficiency, foam stability, and water quality improvement. A series of experiments assessed the influence of the surfactant type, foam-to-feed ratio, solution pH, and column height on CGAs' performance. The results showed that SDS produced the highest average removal efficiency across all particle types (49.59%), followed by Soapnut (48.95%) and Shikakai (43.64%). However, Shikakai displayed superior removal performance for specific contaminants such as kaolinite and algae under certain conditions. The optimal foam-to-feed ratio was found to be 1.0 for SDS (60.59% removal), 0.5 for Shikakai (38.61%), and 0.1 for Soapnut (32.06%). Foam stability, a critical factor in flotation efficiency, varied significantly with the pH and surfactant type. Quantitative analysis revealed a strong negative correlation between foam stability and removal efficiency for Soapnut (r = -0.79) and Shikakai (r = -0.76), as well as a moderate positive correlation for SDS (r = 0.47). Additionally, the effect of column height on flotation efficiency confirmed that moderate sampling port heights (45–60 cm) provided optimal removal efficiencies due to enhanced contact time. This study demonstrates the potential of sustainable use of plant-based surfactants in CGA-based flotation and provides insights into optimising flotation parameters, thereby contributing towards greener water treatment processes.