Adsorption of Phosphate Ions from Aqueous Solution of Nickel Hydroxides Calcined at Different Temperatures

Abstract

Nickel hydroxide (Ni100) and nickel hydroxide, including cobalt (NiCo91), were calcined at different temperatures. These materials were investigated by analyzing data obtained from X-ray diffraction (XRD), scanning electron microscopy, specific surface area, thermogravimetric-differential thermal (TG-DTA) technique, and electron-probe microanalysis. The XRD and TG-DTA data obtained indicated that calcination at 250-270 • C can promote the conversion of Ni(OH)2 into NiO, and that cobalt hardly affected the structural changes of nickel hydroxide. The specific surface areas of Ni100 and NiCo91 were determined to be in the range 17.9-148.3 and 21.0-145.1 m 2 /g, respectively. The specific surface area increased suddenly at 260 • C. The amount of phosphate adsorbed onto Ni100 and NiCo91 was measured to be in the range 29.2-44.7 and 29.7-54.0 mg/g, respectively. The amount adsorbed onto Ni100 or NiCo91 was greater than that onto another adsorbent previously reported. The correlation coefficient relationships between the specific surface areas of Ni100 and NiCo91 and the saturated amount of the adsorbed phosphate ions were found to be 0.935 and 0.960, respectively. These results suggested that adsorption of phosphate ions with Ni100 or NiCo91 is related to the specific surface area. Our study demonstrated that Ni100 and NiCo91 can be considered as promising materials for the adsorption of phosphate ions from aqueous solutions.

Granulation of Cobalt-containing Nickel Hydroxide with Polyethylene Terephthalate and its Phosphate Ion Adsorption Capability

“…This linear relationship suggests that the phosphate ions were exchanged with the surface hydroxyl groups of the adsorbents. A similar adsorption mechanism for powdered NiCo91-270 was reported previously [28]. Further studies are needed to elucidate the relationship between the amount of adsorbed phosphate ions and the properties of adsorbents.…”

“…The adsorbent (NiCo91-270) consisted of spherical particles of various diameters, while the PET surface was smooth. In addition, our previous study showed that calcination hardly affected the surface morphology of NiCo91 [28], which could be granulated with PET in this study (under the experimental conditions used herein). We could also observe each adsorbent particle on the granulated adsorbent, indicating that the PET binder did not completely mask the NiCo91-270 surface.…”

“…In addition, the amounts of hydroxyl groups on PET20L, PET25L, and PET30L were 0.06, 0.04, and 0.03 mmol/g, respectively. Our previous study showed that the specific surface area and the amount of hydroxyl groups of NiCo91-270 were 125.1 m 2 /g and 1.5 mmol/g [28], respectively, indicating that granulation with the binder affects the adsorbent properties, decreasing the above values under these experimental conditions. Surface pH was not drastically changed by granulation with the PET binder.…”

“…Previous studies reported that NiCo91 had received much attention in recent years for application in alkaline secondary batteries, fuel cells, electrochemical capacitors, electrolyzers, electrosynthetic cells, and electrochromic devices. In addition, previous studies reported that NiCo91 calcined at different temperatures showed a great adsorption capability of phosphate ion from aqueous solution [28,[32][33][34][35][36]. Therefore, we chose NiCo91 as adsorbent for the removal of phosphate ion from aqueous solution in this study.…”

“…For instance, Al-Fe hydroxide, mesoporous Cr-Zr binary oxide nanoadsorbent, hydrous zirconium oxide-based nanocomposites, and Fe-Al-Mn trimetal oxide have been reported as phosphate-ion-removal agents [24][25][26][27]. In addition, we previously reported that nickel hydroxide, cobalt hydroxide, and cobalt-containing nickel hydroxide show sufficient capabilities for phosphate ion adsorption [20,22,28].…”