Removal of propranolol by membranes fabricated with nanocellulose/proanthocyanidin/modified tannic acid: The influence of chemical and morphologic features and mechanism study

Polymer-based membranes containing nanocellulose and natural macromolecules have potential to treat water, however few works have associate the changes in chemical and morphological membrane's features with their performance as adsorbent. Herein, a new green composite based on nanocellulose (NC) and alkylated tannic acid (ATA) and cross-linked with proanthocyanidin was produced and incorporated into polyacrylonitrile (PAN) membranes to eliminate propranolol (PRO) from water. Characterizations revealed that the increasing of NC-ATA content reduced the pore size of the membrane's upper surface and made the finger like structure of the sublayer disappear, due to the formation of hydrophilic domains of NC/ATA which speeds up the external solidification step. The presence of NC-ATA reduced the hydrophilicity, from a water contact angle of 3.65° to 16.51°, the membrane roughness, from 223.5 to 52.0 nm, and the zeta potential from −25.35 to −55.20 mV, improving its features to be a suitable adsorbent of organic molecules. The membranes proved to be excellent green adsorbent, tridimensional, and easy to remove after use, and qmax for PRO was 303 mg·g−1. The adsorption mechanism indicates that H-bonds, ion exchange, and π-π play important role in adsorption. NC-ATA@PAN kept high removal efficiencies after four cycles, evidencing the potential for water purification.