Surface chemical characteristics of acid-thermal modified sepiolites and the adsorption performance of tannin

With tannin as target pollutant, the effects of such factors as the initial concentration pH, adsorption time, and adsorbent dosage on the adsorption of acid-thermal modified sepiolite are analyzed. At the same time, the chemical properties of the natural sepiolite, acid-thermal modified sepiolite and adsorption of tannic sepiolite were investigated using surface charge, X-ray powder diffraction and infrared spectroscopy. The removal rate of tannin adsorbed increased from 35.0% to 74.8% for acid-thermal modified sepiolite as the pH increased from 2 to 10. At the same time, the amount of tannin adsorbed increased from 7.0 to 15.0 mg/g. As the adsorbent dosage increased, so did the removal rate. When the adsorption time was 6h, the removal rate was 71.0% and the amount of tannin adsorbed was 14.2 mg/g. Then the removal and adsorption capacity of tannin basically remained unchanged. The pHZPC of the natural sepiolite and acid-thermal sepiolite were 7.32±0.1 and 6.44±0.1, respectively. This suggested that acid and thermal treatment increased the surface acidity of sepiolite and the surface available sites for adsorption. The acid and thermal treatment improved the adsorption capacity and purity of sepiolite. After the acid-thermal modified sepiolite absorbed tannin, the changes in the IR absorption bands of the sample were noted at 2975, 2919, and 1629 cm ^-1. This shows that the adsorption of tannin was well on acid-thermal modified sepiolite.