Effect of Oxycations in Clay Mineral on Adsorption—Vanadyl Exchange Bentonites and Their Ability for Amiloride Removal

Abstract

The presence of drugs in aquatic bodies is a prevailing issue, and their removal by adsorption is an effective treatment. Among the adsorbents, those based clay minerals have been proposed. Bentonite is a clay mineral that is widely studied as an adsorbent due to its unique physicochemical properties, such as cation exchange capacity (CEC), intercalation, and adsorption. The properties of bentonites can be improved through chemical modifications, such as the incorporation of organic and/or inorganic compounds. These modifications allow for the efficient removal of different contaminants, including pharmaceutical compounds. In this work, raw sodium bentonite (Na+-Bent) and vanadyl bentonites were prepared using 100 (BentV1), 300 (BentV3), and 500% (BentV5) of the cationic exchange capacity of the Na+-Bent and further used for amiloride removal from aqueous solution. Analysis of X-ray fluorescence and Na+ in solution after interaction indicated that the principal mechanism of interaction between bentonite and ions was the ion exchange between sodium of the matrix and vanadyl in solution. Infrared spectroscopy suggested the contribution of coordination of the interlayer water with the vanadyl ions and hydrogen bonding between vanadyl and structural OH. X-ray diffraction analysis indicated that vanadyl ions were incorporated onto Na+-Bent. Amiloride adsorption was better at pH 5.8, using a solid dosage of 75 mg of Na+-Bent, 25 mg of BentV1 and BentV5, and 50 mg of BentV3. The adsorption occurred briefly until 20 min, and maximum removal values were 457.08, 374.64, 102.56, and 25.63 mg·g−1 for Na+-Bent, BentV1, BentV3, and BentV5, respectively. At lower drug concentrations (48.78 and 91.24 mg·g−1 for Na+-Bent and BentV3), the best performance was obtained for the BentV3 sample.