Low pressure nano-composite biopolymer membranes for the removal of herbicides from water under ultrafiltration conditions

This study demonstrates the capability of nano-composite membranes composed of biopolymers to effectively reject a range of herbicides from water. The nano assembly consists of humic acid (HA) and chitosan (CHI) constructed on a positively charged nylon microfiltration (MF) membrane using the layer by layer (LbL) technique. The resulting nano-composite biopolymer membranes were analyzed and characterized through scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), spectroscopic ellipsometry, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and UV–vis spectroscopy. Under ultrafiltration conditions (20 psi pressure and 500 rpm at 30 °C), this engineered system was employed to extract four particular herbicides from water at concentrations of 10–4 mol L−1, namely 2,4-D, 2,4,5-T, buturon, and diphenamid. It was shown that the membrane's efficiency in eliminating pesticides improved with the increase in the number of nano-bilayers. The 9 bilayer HA/CHI nano-composite biopolymer membrane system demonstrated the best performance available. Among the herbicides that the membrane rejected, 2,4-D had the highest rejection rate (~ 99%), followed by buturon (~ 97%), 2,4,5-T (~ 85%), and diphenamid (~ 33%). The functionality of the nano-composite biopolymer membrane was subsequently examined through experimentation in various settings.