Sorption properties of polymer-modified bentonite to Pb(Ⅱ) ions

To investigate the heavy metal sorption properties of the polymer-modified bentonite (PMB), the batch sorption tests are conducted. The sorption behaviors of the sodium activated calcium-bentonite (NCB) and PMB to Pb(Ⅱ) ions are investigated using four sorption kinetic models (i.e., pseudo-first-order, pseudo-second-order, intra-particle diffusion, and Elovich models) and four isothermal sorption models (i.e., Langmuir, Freundlich, D-R, and Temkin models). Additionally, the specific surface area and pore size distribution of the bentonites are analyzed the through BET (Brunauer-Emmett-Teller) tests. The results indicate that at solution pH = 1 (strong acidity), the sorption efficiency of the PMB to Pb(Ⅱ) ions is 60%, with an improvement of 33% over the NCB. The sorption kinetics of bentonites to Pb(Ⅱ) ions conformes more closely to the pseudo-second-order model, with the PMB rapidly adsorbing Pb(Ⅱ) ions within the first 5 minutes, achieving the sorption rate of 50%. The Langmuir sorption isotherm model provides a better description of the sorption characteristics of both bentonites to Pb(Ⅱ) ions, and the calculated maximum sorption capacity closely matches the testing results.