Optimizing Hyperbranched Polyglycerol on Plant Polyphenolic Composite Membranes for Robust Boron Removal and Desalination

Grafting hyperbranched polymers on polymer membrane surfaces offers a promising route to desalination and boron removal. However, the functional modulation of hyperbranched polymers is still not fully realized, and the specific selective synthesis of terminal hydroxyl groups still needs further exploration. Here, we report a method to prepare high-performance adsorption membranes using hyperbranched polyglycerol (HPG) that can optimize the dendritic distribution of the terminal hydroxyl groups. Poly(caffeic acid) (PCA) was rapidly deposited on the surface of the poly(ether sulfone) (PES) membrane assisted by copper sulfate (CuSO4) and hydrogen peroxide (H2O2), and subsequently, HPG was grafted onto PCA coatings via a covalent bond. The prepared functional modified membrane exhibited excellent performance on salt and boron removal; especially, the maximum boron uptake was 1.661 mmol g–1 at an initial boron concentration of 5.0 mmol L–1, better than most of the traditional adsorption membranes reported. The boron adsorption on the membranes was fitted well with the pseudo-first-order adsorption kinetic model and Langmuir isothermal model. Strikingly, the regeneration efficiency could be recovered to 97% after 10 cycles of acid rinsing and desorption. The functional membrane had good application potential and research value in seawater desalination and boron removal.