Activated carbon–embedded free-standing glucomannan membrane for efficient dye removal

A free-standing composite membrane was successfully fabricated by embedding activated carbon (AC) into a konjac glucomannan (KGM) matrix, and its performance in removing methylene blue (MB) from aqueous solution was evaluated. The resulting KGM and AC membrane exhibited high mechanical stability and uniform AC dispersion, which was achieved by incorporating polyethylene glycol as a dispersion aid. Adsorption experiments revealed that the membrane retained nearly the full adsorption capacity of raw powdered AC. For membranes with a mass fraction of AC ( MF AC ) of 0.83, the capacity reached up to 280 mg·g -1 , compared to 330 mg·g -1 for raw AC with MF AC equal to 1.0. Although the adsorption rate decreased due to diffusion resistance within the membrane matrix, the equilibrium adsorption capacity remained comparable to that of the raw AC, indicating that the internal adsorption sites were fully accessible. The adsorption behavior followed the Langmuir isotherm, indicating monolayer adsorption, and the maximum capacity increased in proportion to MF AC . Permeation experiments demonstrated that the membranes maintained a stable pure water flux under moderate pressure up to 0.3 MPa, with an estimated pore radius in the range of 10 to 50 nm. Under continuous flow conditions, the membranes achieved high rejection of MB greater than 99% until saturation, although some reduction in capacity was observed due to concentration polarization and internal transport limitations. These findings highlight the potential of KGM-based composite membranes as multifunctional adsorbents that are suitable for integrated adsorption and filtration systems in water purification.