Tailored ethylenediamine-functionalized graphene oxide membrane on kaolin hollow fibers for pectin concentration

Pectin is a valuable product that can be extracted from waste fruit peels. Here we propose the use of graphene oxide (GO)-based membranes for pectin concentration. The synthesized GO was functionalized with ethylenediamine (EDA) to molecularly design the GO framework. Kaolin hollow fibers with asymmetric pore distribution were used as a porous substrate for GO/EDA deposition. A GO/EDA layer with a thickness of 2.86 ± 0.24 μm was assembled on the substrate by the simple vacuum-assisted deposition method. After GO/EDA depositions, the water permeance of the pristine kaolin hollow fibers reduced from 8.46 ± 0.17 to 0.52 ± 0.03 L h^-1·m^-2·kPa^-1. A pectin aqueous extract from orange peels was filtered at cross-flow mode through the prepared membranes and the steady-state fluxes through pristine and GO/EDA-coated hollow fibers were 56 ± 2 and 20 ± 3 L h^-1 m^-2, respectively. The GO/EDA-coated membrane presented greater pectin selectivity than the pristine hollow fiber. The GO/EDA-coated hollow fiber concentrated the galacturonic acid, phenolic, and methoxyl contents in 19.5, 17.4, and 29.2 %, respectively. Thus, filtration through the GO/EDA-based membrane is a suitable alternative for pectin concentration.