Adsorptive Separation of Lead (Pb2+) from Aqueous Solution Using Tri-n-octylamine Supported Montmorillonite

Divalent lead present in the water stream was removed by using adsorption techniques with montmorillonite clay (Mt) modified with tri-n-octylamine (Mt-TOA). Batch adsorption data at equilibrium were determined with different initial Pb2+ ions concentration (8, 10, 12, 14, and 16 mg.L-1) in the aqueous solution at 298 K, and these results were correlated by using three different isotherm models, for instance, the Langmuir, the Freundlich, and the Temkin. The two-parameter Langmuir model was the best fit to the equilibrium data with a coefficient (R-2) greater than 0.99. The maximum capacities for monolayer adsorption of Mt and Mt-TOA were determined to be 3.37 mg.g(-1) and 33.1 mg.g(-1), respectively, as estimated from Langmuir. Also, experimental values were generated to evaluate the influence of adsorbent amount (w, 0.05-0.3 g for Mt, 0.01-0.06 g for Mt-TOA), starting Pb2+ ion concentration (C-0,8 mg.L-1 to 16 mg.L-1), pH (between 1 and 9), and contact period (t, from 10 to 110 min) on the removal effectiveness and adsorption capability of Mt and Mt-TOA adsorbents. In respect to kinetic studies, the removal efficiency of Pb2+ ion reached to a fixed value of 81.42% with Mt (0.1 g) and 80.67% by Mt-TOA (0.01 g) next 100 and 80 min, respectively. Pseudo-first order, pseudo-second order, and intraparticle diffusion models were studied to obtain the kinetic parameters of the adsorption practice. It is observed that the rate of mass transfer of Pb2+ ions was mainly governed by the intraparticle diffusion mechanism.