Effect of acid activation of palygorskite on their toluene adsorption behaviors

In this paper, acid-activated palygorskite (APalx) samples were prepared by a facile acid treatment method with different concentrations of HCl (0.5, 1, 3, 5 and 7 mol/L). The dynamic toluene adsorption performances of APalx were evaluated and the relevant adsorption mechanism was discussed. The prepared adsorbents were characterized using X-ray diffraction (XRD), elemental analysis, transmission electron microcopy (TEM), nitrogen adsorption-desorption isotherms and Fourier-transform infrared spectroscopy (FTIR). The results show that the palygorskite has a good resistant ability to acid attack, the structure still remains when the acid concentration is as high as 7 mol/L. Acid activation could significantly enhance the surface area (228, 250, 271, 273, 329 and 308 for Pal, APal0.5, APal1, APal3, APal5 and APal7, respectively) and porosity of palygorskite. APal5 has the best toluene adsorption capacity (90.4 mg/g) due to its highest SBET (329 m(2)/g) and V-micro. (0.055 cm(3)/g). The adsorption performance in terms of dynamic toluene adsorption capacities follows the order of Pal (44.6 mg/g) < APal0.5 (63.5 mg/g) < APal1 (71.3 mg/g) < APa17 (74.2 mg/g) < APal3 (75.1 mg/g) < APal5 (90.4 mg/g). APal5 can be readily regenerated by thermal desorption and has exhibited steady reproducibility after 6 cycles. These results have demonstrated that acid activation is a feasible and effective method for the structure and surface optimizing of palygorskite, enabling the APalx to become a promising candidate for the adsorption of volatile organic compounds in practical applications.