Application of Granulated Nickel-Aluminum-Zirconium Complex Hydroxide in the Flow Method for Recovery of Chromium(VI) Ions.

A colloidal silicate granulated nickel-aluminum-zirconium (CSG-NAZ) was prepared, and the chromium(VI) (Cr(VI)) ions recovery capacity was evaluated using a sodium sulfate solution in a column experiment. The amount adsorbed and breakthrough time were enhanced by decreasing the flow rate (flow rate is in the order of 3.0 > 2.0 > 0.5 mL). The breakthrough curves and model parameters were estimated using the Thomas and Yoon-Nelson models. The obtained data confirmed to fit both the Yoon-Nelson model (0.858-0.906) and the Thomas model (0.813-0.906). Additionally, Cr(VI) ions that adsorbed onto CSG-NAZ could be desorbed using a sodium sulfate solution in a column experiment. The total recovery percentage of Cr(VI) ions was 80.9% after six repetitions of adsorption/desorption. Finally, the obtained results revealed that CSG-NAZ was a candidate adsorbent for the recovery of Cr(VI) ions owing to its applicability toward a continuous system.

Recovery of Chromium(VI) Ions Using a Nickel-Aluminum-Zirconium Complex Hydroxide Based on Adsorption and Desorption Treatment.

In this study, we evaluate the desorption or recovery capacity of chromium(VI) ions using desorption solutions containing sodium hydroxide (NaOH) or sodium sulfate (Na2SO4). A complex hydroxide of nickel-aluminum-zirconium (NAZ) was prepared as the adsorbent for the removal of chromium(VI) ions. The results from repeated adsorption/desorption experiments on chromium(VI) ions using NAZ complex hydroxide were evaluated. The desorption percentage of chromium(VI) ions increased with the increase in the concentration of NaOH or Na2SO4 in the desorption solution. The determined optimal concentration of NaOH or Na2SO4 in the desorption solution was 10 mmol/L under the used experimental conditions. After three adsorption-desorption cycles, the recovery percentages of chromium(VI) ions using NaOH and Na2SO4 were 60% (total amounts adsorbed and desorbed were 102 and 61 mg/g, respectively) and 75% (total amounts adsorbed and desorbed were 96 and 72 mg/g, respectively), respectively. Additionally, we confirmed the existence of chromium on the surface of the NAZ complex hydroxide. After three adsorption/desorption cycles, the crystal structure of the NAZ complex hydroxide was maintained. These results indicated the potential of the NAZ complex hydroxide using a desorption solution containing NaOH or Na2SO4 for the recovery of chromium(VI) ions.

Granulation of Nickel-Aluminum-Zirconium Complex Hydroxide Using Colloidal Silica for Adsorption of Chromium(VI) Ions from the Liquid Phase.

We combined a nickel-aluminum-zirconium complex hydroxide (NAZ) with colloidal silica as a binder to prepare a granulated agent for adsorbing heavy metals from aqueous media. Three samples with different particle diameters were prepared to evaluate the effects on the properties: small (NAZ-S), medium (NAZ-M), and large (NAZ-L). We confirmed the granulation of the prepared samples at a binder content of 25%. NAZ-S had the largest specific surface area and number of hydroxyl groups, followed by NAZ-M and then NAZ-L. Regarding the adsorption capacity, NAZ-S adsorbed the most chromium(VI) ions followed by NAZ-M and then NAZ-L. The binding energy of Cr(2p) at 575-577 eV was detected after adsorption, and the effects of the temperature, contact time, and pH on the adsorption of chromium(VI) ions were evaluated. We identified the following adsorption mechanism: ion exchange with sulfate ions in the interlayer region of the NAZ samples. Finally, the chromium(VI) ions adsorbed by the NAZ samples were easily desorbed using a desorption solution. The results showed that NAZ offers great potential for the removal of chromium(VI) ions from aqueous solutions.

Exploiting the Different Parameters on the Adsorption of Phosphate Ions and Its Subsequent Recovery Using Complex Nickel-Aluminum-Zirconium Hydroxide.

In this study, the effect of contact time, temperature, pH, and coexistences on the adsorption of phosphate ions using the complex nickel-aluminum-zirconium hydroxide (NAZ) was evaluated. Moreover, the recovery of adsorbed phosphate ions from NAZ using desorption solution with different concentrations was demonstrated. The results showed that the quantity of phosphate ions adsorbed gradually increased with time, and the adsorption equilibrium was achieved within 24 h after adsorption. This kinetic data could be well described by the pseudo-second-order model with the correlation coefficient in the value of 0.997. Additionally, the quantity of phosphate which was adsorbed increased as temperature increased, and these results corresponded well with both the Langmuir, the correlation coefficient ranged from 0.920-0.949, and Freundlich models, the correlation coefficient ranged from 0.863-0.995. These results showed that the adsorption of phosphate ion was monolayer adsorption onto the NAZ surface. The optimal pH for removal of phosphate ions from aqueous media was during 4-8. In addition, chloride, nitrate, and sulfate ions did not significantly affect to the adsorption capability of phosphate ions in the complex solution system. Finally, the phosphate ions which were adsorbed onto NAZ could be recovered using sodium sulfate solution (recovery percentage: approx. 50% using sodium sulfate solution at 1000 mmol/L). These results highlight the potential of using NAZ as the cost-effectiveness adsorbent for phosphate ions removal from aqueous media.

Adsorption Performance on As(III) from Aqueous Solution Using the Complex Nickel-Aluminum Hydroxides.

In this study, complex nickel-aluminum hydroxides were prepared at different molar ratios (NA12, NA11, NA21, NA31, and NA41), and their adsorption capability on arsenic ions (As(III)) from aqueous media was assessed. The physicochemical properties such as morphology, X-ray diffraction pattern, specific surface area, numbers of hydroxyl groups, and surface pH were investigated. In addition, the effect of contact time, temperature, and pH on the adsorption capability on As(III) was also evaluated. NA41 exerted the highest adsorption capability on As(III) comparable to other prepared adsorbents. However, the specific surface area and numbers of hydroxyl groups did not significantly affect the adsorption capability on As(III). The equilibrium adsorption of As(III) using NA41 was achieved within 24 h, and the obtained results corresponded to a pseudo-second-order model with correlation coefficient value of 0.980. Additionally, the adsorption isotherms were well described by both the Langmuir and Freundlich equations. The optimal pH condition for removal of As(III) using NA41 was found to be approximately 6-8. Finally, the adsorption mechanism of As(III) was assessed by analyzing the binding energy and elemental distribution, which indicated that the electrostatic interaction and ion exchange influenced the adsorption of As(III) under experimental conditions. These results demonstrated the potential candidate of NA41 as an effective adsorbent on As(III) removal from aqueous media.

Characterization and Phosphate Adsorption Capability of Novel Nickel-Aluminum-Zirconium Complex Hydroxide.

In this study, the adsorption capability of phosphate ion using a novel tri-metals complex hydroxide was evaluated for preventing the eutrophication in water environment. A nickel-aluminum-zirconium complex hydroxide (NAZ) was synthesized using each inorganic sulfate mixing ratio of 0.9 : 1.0 : 0.1 and was calcined at different temperatures. The characteristics of the NAZ were analyzed by scanning electron microscopy images, X-ray diffraction analysis, elemental distribution, and binding energy. Moreover, the amount adsorbed of phosphate ion onto uncalcined and calcined NAZ was measured. That of phosphate ions onto the uncalcined was the largest of all. These results suggested that the adsorption of phosphate ions tends to depend on the physicochemical properties (e.g., amount of hydroxyl groups, pore volumes, and pH) of the adsorbents. Moreover, the adsorption mechanism of phosphate ions was evaluated on the basis of binding energy and elemental analysis. After adsorption, the binding energy of phosphorus P (2s and 2p) peaked and the sulfur peak intensity S(2s) reduced. This result indicated that the adsorption mechanism of phosphate would be exchanged with sulfate ions.

Evaluation of Nickel-Aluminium Complex Hydroxide for Adsorption of Chromium(VI) Ion.

In this study, nickel-aluminium complex hydroxides at different molar ratios (nickel-aluminium = 1 : 2, 1 : 1, 2 : 1, 3 : 1, and 4 : 1, referred to as NA12, NA11, NA21, NA31, and NA41) were prepared, and their adsorption capability for chromium(VI) ion was investigated. Firstly, physicochemical characteristics (SEM images, X-ray diffraction (XRD) patterns, specific surface area, amount of hydroxyl groups, and surface pH) of nickel-aluminum complex hydroxide were evaluated. The amount of chromium(VI) ion adsorbed onto NA11 (15.3 mg/g) was greater than that adsorbed onto the other adsorbents. This research elucidated that the amount of chromium(VI) ion adsorbed using nickel-aluminium complex hydroxide was related to the adsorbent surface properties (r = 0.818-0.875). Subsequently, the adsorbent (NA11) surface before and after adsorption of chromium(VI) ion was evaluated, and chromium energy (577 and 586 eV) detected after adsorption onto the NA11 surface. These results revealed that the NA11 surface properties were very important for the removal of chromium(VI) ion from aqueous solution. In addition, the effects of pH, contact time, and temperature on the adsorption of chromium(VI) ion were evaluated. We confirmed a high recovery percentage of chromium(VI) ion when using sodium hydroxide solution at 10-1000 mmol/L (approximately greater than 80%) in this experimental condition. Thus, NA11 is a promising adsorbent for the removal of chromium(VI) ion from aqueous solution.

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

A new mixed metal hydroxide adsorbent (NA11, molar ratioNi-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.

Evaluation of phosphate ion adsorption from aqueous solution by nickel-aluminum complex hydroxides.

We prepared a variety of nickel-aluminum complex hydroxides, investigated their physicochemical properties, and evaluated their ability to adsorb phosphate ions (the molar ratios of nickel to aluminum, 1:2, 1:1, 2:1, 3:1, and 4:1, are referred to as NA12, NA11, NA21, NA31, and NA41). NA12 and NA11 have amorphous structures; their specific surface areas and the concentration of associated hydroxyl groups were greater than those of other adsorbents. The number of phosphate ions adsorbed onto NA12 and NA11 was greater than that onto other adsorbents. These results indicated that the phosphate ion adsorption is related to the specific surface area and the amount of hydroxyl groups. The adsorption isotherm data, and the effects of contact time and pH on the adsorption were investigated; our results implied that both the Freundlich equation model and the pseudo-second-order kinetic model describe the adsorption of phosphate ions by NA11. We showed that phosphate ions adsorbed onto NA11 can be desorbed by sodium hydroxide solution at different concentrations and that NA11 could be reused for at least three repeated cycles of phosphate ion adsorption and desorption. This study illustrates that NA11 has the potential for practical application as an adsorbent for phosphate ions from wastewater.

Adsorption of phosphate ions from an aqueous solution by calcined nickel-cobalt binary hydroxide.

Different molar ratios of a Ni/Co binary hydroxide (NiCo82, NiCo91, and Ni100) were prepared and calcined at 270 °C (NiCo82-270, NiCo91-270, and Ni100-270). The properties of the adsorbents and the amount of adsorbed phosphate ions were evaluated. The adsorbents calcined at 270 °C had a nickel oxide structure. The amount of adsorbed phosphate ions, the amount of hydroxyl groups, and the specific surface area of the calcined adsorbents at 270 °C were greater than those of the uncalcined adsorbents. The amount of adsorbed phosphate ions was related to the amount of hydroxyl groups and the specific surface area; the correlation coefficients were 0.966 and 0.953, respectively. The adsorption isotherm data for NiCo91 and NiCo91-270 were fit to both the Freundlich and Langmuir equations. The amount of adsorbed phosphate ions increased with increasing temperature. The experimental data fit the pseudo-second-order model better than the pseudo-first-order model. A neutral pH was optimal for phosphate ion adsorption. In addition, the phosphate ions that were adsorbed onto NiCo91-270 could be recovered using sodium hydroxide, and the adsorbent was useful for the repetitive adsorption/desorption of phosphate ions. Collectively, these results suggest that NiCo91-270 is prospectively useful for the adsorption of phosphate ions from aqueous solutions.