Methylene Blue Adsorption Mechanism onto Palm Kernel Shell-derived Activated Carbon: From Particle Diffusion to Site Adsorption

The mechanism of methylene blue adsorption was investigated for palm kernel shell-derived activated carbon from the bulk solution to active sites. For different initial dye concentrations, 100 ppm methylene blue led to approximately 10 mg/g adsorption capacity while experiencing a decreasing trend at lower initial dye concentrations as follows: 50 ppm (approximately 5 mg/g) > 20 ppm (approximately 2 mg/g) > 5 ppm (approximately 0.5 mg/g). Based on the Boyd external diffusion model, the mechanism of methylene blue adsorption started with its diffusion from the bulk solution via the bounding film encapsulating the activated carbon. The adsorbed species occupied more than one class of active site with an adsorption rate of 0.54 mg/g.min, while the adsorption capacity accounted for 14.7 mg/g. The information about methylene blue offers useful insights into describing the steps of dye adsorption onto palm kernel shell-activated carbon.

Automated summary

The mechanism of methylene blue adsorption on palm kernel shell-derived activated carbon was investigated. The adsorption capacity of methylene blue decreased with lower initial dye concentrations, with 100 ppm leading to approximately 10 mg/g and 50 ppm, 20 ppm, and 5 ppm resulting in lower adsorption capacities. The adsorption process involved diffusion from the bulk solution to the activated carbon via a bounding film, occupying multiple classes of active sites.