adsorbate

This is because adsorption is a multistep process, which involves the movement of adsorbate molecules first to the boundary layer on the outer surface of adsorbent followed by its diffusion to adsorbent surface and finally to the internal porous structure through pore diffusion.

AAS was used to measure the concentration of the metal ion remaining in the adsorbate solution.

Another important thermodynamic parameter that provides relevant information about the heat exchanges in the adsorption process is the isosteric adsorption heat ([DELTA][H.sub.x]), defined as the standard adsorption enthalpy change for a constant amount of adsorbate [29].

where: [C.sub.0] and [C.sub.eq] = represent, respectively, the initial and at balance concentrations (mg.[L.sup.-1]); V = the adsorbate volume (L); and m = the adsorbent mass (g).

319.85 g/mol, WINLAB) used as adsorbate in the present study.

The quantity of adsorbate adsorbed in time t, [q.sub.t] (mg.[g.sup.-1]) was calculated using Equation (1).

Because the adsorption process is not at a steady state as the influent flows through the fixed-bed column under predesigned operating conditions, it is not easy to express the dynamic behavior of adsorbate in the column.

Various parameters that influence adsorption including the effect of pH (pH 1 to pH 12), contact time (20-180 min), initial adsorbate concentration (25 to 150 mg/L), and adsorbent dosage (0.63 to 10.63 g/L) were studied.

where [c.sub.e] is equilibrium concentration of adsorbate (mg/L), [Q.sub.o] is adsorption capacity (mg/g), b is constant (L/mg), and [q.sub.e] is the amount adsorbed at equilibrium (mg/g).