Removal of microplastics from wastewater with aluminosilicate filter media and their surfactant-modified products: Performance, mechanism and utilization

Abstract

• Cationic surfactant-modified zeolite had a significant removal (>96%) for PE and PA. • Three retention mechanisms of modified zeolites for microplastics were proposed • Entanglement improved microplastic removal in water treatment by modified zeolite. • Modified materials provided a range of potential for immobilization of microplastics. • This performance could be further utilized to improve microplastic removal in WWTPs. Effluent discharge from wastewater treatment plants (WWTPs) is an important source of microplastics, which has attracted worldwide attention. Tertiary sewage treatment of microplastics in WWTPs has also been implemented. In this paper, microplastic removal by aluminosilicate filter media and their cationic surfactant modified products as the potential low-cost integrated material was studied. The role of modified aluminosilicate filter media in the removal of microplastics from WWTPs has not been focused on in the previous studies. The concentration of microplastics with particle size<10 μm in wastewater was not clear due to the exclusion in many studies and the difficulty in quantification. The granular polyethylene microplastic (PE, 10 μm) and fibrous polyamide microplastic (PA, 100 μm) were selected based on their frequent detection in sewage samples. According to a series of column test and further analysis, the immobilization and removal mechanisms of microplastics by filter were explored. Current results demonstrated that aluminosilicate filter media modified by cationic surfactant had a significant removal (>96%) and fixation capacity for PE and PA, which is much greater than that of rapid sand filter (63%). The obtained scanning electron microscopy (SEM) images showed three morphological retention mechanisms: captured, trapped and entangled. The negatively charged microplastics can also be directly electrostatically bonded with the positively charged HDPB head base. The entangled fixation mechanisms provided a higher removal efficiency of microplastics in wastewater for the modified aluminosilicate filter media than the rapid sand filter. The modified materials provided a wide range of potential for the immobilization of microplastic in wastewater treatment process. In principle, this performance can be further studied and utilized to improve the removal efficiency of microplastics in WWTPs.