A novel hydrophobic chitosan-polyaluminum chloride composite flocculant for effectively simultaneous removal of microplastic and antibiotics composite pollution

Composite pollution of emerging pollutants such as microplastics (MPs) with small size and antibiotics has brought a great challenge in the fields of water and wastewater treatment. Up to now, the simultaneous removal of MPs and antibiotics by traditional coagulation is still not satisfied. Herein, a novel composite flocculant named hydrophobic chitosan-polyaluminum chloride (Hmcs-PAC) was designed and prepared for efficiently simultaneous removal of polyethylene terephthalate (PET, 10 μm) and tetracycline (TC) from water. Under the optimal preparation conditions (i.e. Basicity = 1 and the weight ratio of Hmcs:Al = 0.5), the Hmcs-PAC exhibited better removal of both PET and TC than PAC and Hmcs under the same dosage, with the maximum removal efficiency of 99.9 % for PET, and 91.5 % for TC, respectively. The PAC was successfully grafted on the Hmcs via Al-N bond, confirmed by FTIR and 27Al NMR. More importantly, the removal of TC in composite PET + TC system was significantly enhanced by above 10 % compared with that in single TC system, which was mainly attributed to the complexes formation of Hmcs-PAC-PET-TC via the PET bridging effect based on 2D Fourier transform infrared correlation spectroscopy (2D-FTIR-COS) and scanning electron microscopy (SEM) analysis. In contrast, the removal of PET in composite system was slightly lower than that in PET single system, possibly due to the competition of TC for the active sites of hydrolysates of Hmcs-PAC. Furthermore, the presence of co-existing ions except CO32− and cationic surfactant had adverse effect on the coagulation removal, especially for TC. While the increase in temperature, humic acid and anionic surfactant content showed a promotion effect on the removal of PET and TC. Finally, the prepared Hmcs-PAC exhibited a potential removal of composite pollutants from urban sewage. This study can provide a promising flocculant for the effective co-removal of MPs and antibiotics from water and wastewater.