INTRAPARTICLE DIFFUSION

The adsorbate species are most probably transported from the bulk of the solution into the solid phase through an intraparticle diffusion process, which is often the rate-limiting step in many adsorption processes. The possibility of intraparticle diffusion can be explored by using the intraparticle diffusion model:
q_t = K_idt^1/2 + C
where C is the intercept and k_id is the intraparticle diffusion rate constant (mol/g min^1/2).

ADSORPTION ISOTHERMS FOR ORGANIC CONTAMINANTS

Adsorption capacity and removal efficiency of RECAM RE.55 for organic contaminants can be calculated according to the following equations:

Removal % = (C₀ - C_e)100/C₀

q_e = (C₀ - C_e)V/W

where q_e (mg/g) is the amounts of contaminant adsorbed onto RECAM^® at equilibrium, C₀ (mg/L) and C_e (mg/L) are initial and equilibrated contaminant concentrations, respectively; V (L) is the volume of added solution, and W (g) is the mass of the RECAM^® (dry).

Adsorption of organic contaminants on RECAM^® follows the Langmuir isotherm and assumes the monolayer coverage of adsorbate over a homogeneous adsorbent surface.
The adsorption isotherm is based on the assumption that sorption takes place at specific homogeneous sites within the adsorbent. Once an adsorbate molecule occupies a site, no further adsorption takes place at the same site, with no interaction between adsorbed species.
An explanation for the adsorption kinetics can be well described by a pseudo-second-order kinetic model, which means that the adsorption rate is dependent on the unoccupied surface of the nanosheets presents in RECAM^®.