Evaluation of the Interaction between Borate Ions and Nickel-Aluminum Complex Hydroxide for Purification of...

A new mixed metal hydroxide adsorbent (NA11, molar ratio_Ni-Al = 1 : 1) was prepared and its physicochemical properties (specific surface area, amount of hydroxyl group, scanning electron microscopy images, X-ray diffraction analysis, elemental distribution, and binding energy) were studied. In addition, the amount of borate ion adsorbed using several adsorbents, including NA11, was evaluated in this study. The specific surface area of and amount of hydroxyl group in NA11 was greater than those of the other studied adsorbents. The amount of borate ion adsorbed showed similar trends to those of the specific surface area and number of hyrdroxyl groups, which indicated that the adsorption mechanism of borate ion was related to the specific surface area and the amount of hydroxyl group. After adsorption, the binding energy of boron B(1s) peaked, and the sulfur peak intensity S(2s) and S(2p) reduced. These results suggest that ion exchange between borate and sulfate ions was one of the adsorption mechanisms. Equilibrium adsorption was reached within 6 h in the case of NA11. These data were fitted into a pseudo-second-order model (r = 0.813-0.998). The solution pH affected the capacity of NA11 for adsorbing borate ion from aqueous solution. It was found that adsorbance was greatest at pH 10. Adsorption isotherm data were fitted to both the Freundlich (r = 0.986-0.994) and Langmuir (r = 0.997-0.999) isotherm equations. Collectively, it is suggested that NA11 is prospectively useful for the adsorption of borate ion from aqueous solutions.