Low-temperature fabrication of low-cost ceramic membranes using spent coffee grounds: microstructure, hydraulic performance, and methylene blue removal

Abstract This study investigates a low-temperature route for producing low-cost ceramic membranes using Chocobofe clay, kaolin, and spent coffee grounds as a biomass-derived pore-forming agent for methylene blue removal. Raw materials were structurally, chemically, and thermally characterized prior to membrane fabrication by uniaxial pressing, followed by sintering at 650 °C. Structural analyses confirmed that the aluminosilicate matrix formed by clay and kaolin ensured membrane integrity, while thermal decomposition of spent coffee grounds promoted pore generation without inducing secondary crystalline phases. Increasing the residue content from 0 to 10 wt% progressively increased apparent porosity from 39.40 to 45.68% and enlarged the average pore diameter from 0.368 to 0.836 µm. These microstructural changes significantly improved hydraulic performance, raising pure water flux from 243.84 to 1529.31 L·m⁻2·h⁻1, corresponding to an increase of approximately 527%. However, enhanced permeability was accompanied by reduced selectivity, with methylene blue rejection decreasing from 86.9 to 32.0%, reflecting the typical permeability–selectivity trade-off of porous ceramic membranes. A preliminary economic analysis estimated an average production cost of 211.51 USD·m⁻2, indicating competitive manufacturing potential. The developed membranes are particularly promising for high-throughput filtration applications requiring moderate solute retention under reduced energy demand.