Evaluation of physical - mechanical separation techniques for polycotton textile waste

The rising volume of textile waste, particularly blended fabrics, presents significant challenges for recycling and waste management. Polyester-cotton blends compose a macromolecule complex and thus traditional recycling methods prove to be insufficient and therefore novel mechanical separation technologies are required to recover polyester from cotton. The present study investigates two separations methods, froth flotation and density separation, to maximize fiber recovery and their potential for large-scale textile recycling. Tests were evaluated under systematically control conditions, such as fiber size (1 mm and 2 mm), pH (4, 7, and 9), surfactant (tergitol) concentration. In the froth flotation approach the difference in hydrophobicity between polyester and cotton was exploited wherein polyester floated selectively and cotton would go to the sink fraction. Maximum separation efficiency was observed at pH 7 with 1 mm fiber size at one step experiment, in which 90% polyester fibers were recovered in the floated fraction and 90% cotton were retained in the sediment. A pH-dependence of flotation efficiency was found by observed diminished selectivity at acidic (pH 4) and alkaline (pH 9) conditions. A three-stage gradual flotation process was further experimented with to improve the quality of the separation, but this also caused the selectivity of the fiber to decrease in the second and third runs, resulting in entanglement and contamination of the material. Density separation experiments A controlled density gradient for separation of fibers was generated using NaCl solutions (density gradient of solute in g/cm3). At a fiber size of 2 mm, a density separation could be obtained that allowed polyester recovery of about 80% and cotton recovery of about 75%.The froth flotation process had lower energy consumption than density separation and thus is favored for development and large scale commercialization. Although flotation is an effective method for fiber separation, surfactant concentration, processing time, and filtration steps still need to be optimized in order to improve fiber purity and reduce chemical usage. These results present vital data on the enhanced recycling of waste textiles through mechanical separation, confirming the feasibility of possible industrial applications. Further research is needed to refine chemical formulations, develop more selective separation mechanisms, and explore alternative surfactants with reduced environmental impact. This further advance in these approaches can allow the textile industry to move in a more sustainable and energy efficient direction reflecting effective and more circular recycling solutions, reducing the environmental burden of blended fabric waste.