Adsorption of sunset yellow by luffa sponge, modified luffa and activated carbon from luffa sponge

We investigated the adsorption of sunset yellow (SY) in water by luffa sponge (LC)-based materials. Modified luffa sponge (MLC) and luffa sponge activated carbon (LAC) were prepared by chemical modification and H3PO4 activation, respectively, followed by charring. Dried LC adsorbs SY poorly through a physical adsorption process, with an equilibrium adsorption capacity of 14 mg/g at 298 K. MLC and LAC showed substantially improved adsorption of SY. The maximum equilibrium adsorption capacity of MLC for SY reached 137 mg/g -9.78 times that of raw luffa - and this adsorbent had a maximum removal rate of 99.9%. The adsorption capacity of LAC for SY was even higher, with the maximum equilibrium adsorption rate reaching 476.19 mg/g and the maximum removal rate exceeding 99% at 298 K. The kinetics of absorption fit the pseudo-second-order kinetic equations for the three adsorbing agents, which suggests that the main limiting factor for adsorption is the adsorption mechanism. The isotherm curves for the three adsorbents fit the Langmuir isotherm equation with correlation coefficients above 0.99, which indicates the adsorption is monolayer adsorption.