This article studies the enhancement of methyl orange (MO) adsorption by Mongolian montmorillonite (MMt) modified by the intercalation of the Keggin Al₁₃ complex, followed by calcination during the pillaring process. The properties of MMt, Al-intercalated MMt (P-MMt), and Al-pillared MMt (P-MMt-C) were determined using X-ray diffraction (XRD), thermogravimetric analysis (TGA), surface-area analysis, and a field emission scanning electron microscope (FE-SEM). The MO adsorption by modified MMt was subsequently evaluated. The XRD basal distance (d₀₀₁) and the specific surface area (SSA) increased after the modification of MMt. The TGA results revealed that P-MMt and P-MMt-C had better thermal stability than MMt. The Al-pillared MMt obtained after calcination (e.g., P-MMt-C400) showed a larger basal distance and surface area than that without pillaring. The MO adsorption process of P-MMt-C400 was supposed to be dominated by chemisorption and heterogeneous multilayer adsorption, according to the kinetic and isotherm studies. The maximum adsorption capacity of P-MMt-C400 is 6.23 mg/g. The MO adsorption ability of Al-pillared MMt was contributed by the Keggin Al₁₃ complex attracting MO and the increase in the surface area of macro-, meso- and micro-pores (>1.2 nm). The Al-pillared MMt in this study could be applied as an adsorbent in a water purification system to remove MO or other dye elements.

In this research, the lead (Pb(II)) removal rate of montmorillonite (Mt) was studied in aqueous solution. The adsorption conditions (contact time, pH, and temperature) were adjusted to study the effect of those factors on the removal rate of Pb(II) adsorption by Mt. The results indicated that the effect of temperature on the Pb(II) removal rate of Mt was not significant. The Pb(II) removal rate was found to be pH-dependent, improving with increasing pH in the range of 3 to 7. The equilibrium time of adsorption was attained after around 1 hour. The adsorption kinetics were analyzed by fitting to three models (pseudo-first-order (PFO) kinetic model, pseudo-second-order (PSO) kinetic model and intraparticle diffusion model. In comparison, R² value (0.9952) of PSO kinetic model is better than PFO (0.9718), supposing that the adsorption process of Pb(II) onto Mt was chemisorption. The intraparticle diffusion model fitting showed that the Pb(II) adsorption process by Mt was controlled by three steps. Langmuir, Freundlich, Redlich-Peterson and Sips isotherm models were used to describe the adsorption mechanism of Pb(II) adsorbed onto Mt. The experiment results showed the adsorption isotherms are a perfect fit to the Sips model, indicating both homogeneous monolayer adsorption and heterogeneous multilayer adsorption were occurred in the Pb(II) adsorption process by Mt, and the adsorption was mainly controlled by heterogeneous multilayer adsorption.