Adsorption of arsenic ions on Brazilian sepiolite: Effect of contact time, pH, concentration, and calorimetric investigation

The original sepiolite clay mineral has been collected from Amazon region, Brazil. The compound 2-aminomethylpyridine (AMP) was anchored onto Amazon sepiolite surface by heterogeneous route. The natural (SPT) and modified (SPTAMP) sepiolite samples were characterized by elemental analysis, SEM, N2 adsorption, and nuclear magnetic nuclei of 29Si and 13C. The well-defined peaks obtained in the 13C NMR spectrum in the 0–160 ppm region confirmed the attachment of organic functional groups as pendant chains bonded into the porous clay. The ability of these materials to remove As(V) from aqueous solution was followed by a series of adsorption isotherms at room temperature and pH 4.0. The maximum number of moles adsorbed was determined to be 7.26 × 10−2 and 11.70 × 10−2 mmol g−1 for SPT and SPTAMP, respectively. In order to evaluate the clay samples as adsorbents in dynamic system, a glass column was fulfilled with clay samples (1.0 g) and it was fed with 2.0 × 10−2 mmol dm−3 As(V) at pH 4.0. The energetic effects caused by metal cations adsorption were determined through calorimetric titrations. Thermodynamics indicated the existence of favorable conditions for such As(V)–nitrogen interactions.

Graphical abstractThis investigation reports the use of original and modified sepiolite as alternative absorbents. The compound 2-aminomethylpyridine was anchored onto Amazon sepiolite surface by heterogeneous route.Figure optionsDownload full-size imageDownload high-quality image (61 K)Download as PowerPoint slide