Adsorption of methylene blue from aqueous solution onto multiporous palygorskite modified by ion beam bombardment: Effect of contact time, temperature, pH and ionic strength

• Adsorption of methylene blue onto palygorskite modified by ion beam was investigated.
• The adsorption kinetics was dominated by the pseudo-second-order reaction model.
• The adsorption isotherms fit with both Langmuir and Freundlich isotherm models.
• Thermodynamic analysis indicated the adsorption was spontaneous and exothermic.
• The effect of pH and ion strength on adsorption was interpreted by Zeta potential.

Our previous work has reported that an inorganic nano-network of palygorskite with multiporous structure can be fabricated from rigid nano-rods by ion beam bombardment and has better adsorption capability than nano-rods. Here, this dispersed modified nano adsorbent was characterized by Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscope (SEM). The adsorption property of methylene blue (MB) onto this adsorbent was investigated. It was found that the adsorption capacity increased with contact time, pH, MB initial concentration, respectively, and then reached an equilibrium. Moreover, the effect of pH on the adsorption was strongly determined by zeta potential. The adsorption kinetics of MB was dominated by the pseudo-second-order reaction model, and the adsorption isotherms fit the Freundlich isotherms better than the Langmuir isotherms. Three temperatures (293 K, 303 K, 313 K) were set for describing the thermodynamic parameters (ΔHθ, ΔSθ, and ΔGθ), which indicated that the adsorption was spontaneous and exothermic. Lastly, the mechanism of the influence of ionic strength on the adsorption was discussed.

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