Nanofiltration membranes composed of carbonized giant cane and Pongamia meal binder for ion sieving in water and molecular sieving in organic solvents

Abstract

Climate change and other environmental problems necessitate the use of renewable resources and the development of sustainable technologies. Thus, giant cane, which is naturally abundant, and a plant-based binder extracted from Millettia pinnata seeds were used to fabricate carbon-based composite membranes. A continuous and uniform layer of a carbonized giant cane was formed on a porous support using a simple filtration method. The hardness of the membranes increased with the carbon content. The increase in the carbon content in the membrane yielded a looser and more selective nanofiltration membrane; the water permeance increased from 13 to 19 L m−2 h−1 bar−1 and the NaCl/MgSO4 selectivity doubled from 10 to 20. Similarly, the rejection of five different salts and seven organic molecules decreased in water and acetone, respectively. The acetone permeance and molecular weight cutoff increased from 7 to 12 L m−2 h−1 bar−1 and from 577 to 795 g mol−1, respectively. The long-term performance tests on the membranes indicated a stable rejection of higher than 99% for rose bengal and a stable steady-state flux over a week of continuous filtration. The membranes exhibited good stability and high permeance in different organic solvents, including a harsh polar aprotic solvent, i.e., N,N-dimethylformamide. The toxicity of the giant cane carbon and the binder was examined via a cytotoxicity assay using NIH 3T3 cells. No toxicity was observed for either material. This study proposes a sustainable route for preparing aqueous and organic solvent nanofiltration membranes using natural nontoxic resources.