Nickel and cobalt adsorption on hydroxyapatite: a study for the de-metalation of electronic industrial wastewaters

Abstract

In the present study, the Ni(II) and Co(II) adsorption efficiency and selectivity, as well adsorption mechanisms on a stoichiometric hydroxyapatite (HAP) surface have been investigated. Characterization studies (N2 adsorption/desorption and X-ray powder diffraction (XRPD) analyses) and adsorption tests under various operative conditions provided detailed information about the use of HAP in the de-metalation of wastewaters containing Ni and Co as polluted metal species. The sorption capacity of HAP has been evaluated by static batch adsorption tests varying initial concentration of Ni(II) and Co(II) species (from ca. 0.25 to 4.3 mM), contact time (from 15 min to 24 h), and pH (from 4 and 9) operative parameters. Proposed mechanisms of adsorption of Ni(II) and Co(II) on HAP surface are ion-exchange and surface complexation; a partial contribution of chemical precipitation from bulk solution should be considered at pH 9. In addition, adsorption isotherms of Ni(II) and Co(II) on HAP have been collected at 30°C and pH 4 and modeled by employing different equations. The maximum sorption capacities have been quantified as 0.317 mmol g-1 HAP (18.6 mg g-1 HAP) and 0.382 mmol g-1 HAP (22.5 mg g-1 HAP) for Ni(II) and Co(II), respectively. Selectivity to Co and Ni in the adsorption process on HAP has also been investigated; HAP has higher affinity towards Co than Ni species (Co:Ni=2.5:1, molar ratio).

Noble-metal-free hydroxyapatite activated by facile mechanochemical treatment towards highly-efficient catalytic oxidation of volatile organic compound

“…Hydroxyapatite (HAp, Ca 10 (PO 4 ) 6 (OH) 2 ), as one of the most well-known calcium phosphate materials, has attracted worldwide interests in variable applications as bio-ceramics for artificial bone tissue crafting, adsorbents of proteins and ion-exchanging fillers for heavy-metal ions 22 – 24 . With the discovering of active radical generated via reaction between adsorbed O 2 molecular with trapped electron induced through thermal dehydration of surface hydroxyl group, we previously reported the complete catalytic decomposition of VOC on HAp and initially derived the catalytic reaction mechanism which also emphasizes the important role of the co-existed acidic/basic sites in HAp 25 – 27 .…”

Novel Hydroxyapatite Beads for the Adsorption of Radionuclides from Decommissioned Nuclear Power Plant Sites

“…It is believed that this heterogeneity was caused by the distinct binding sites present on the HdA surface, i.e., positively charged calcium ions and negatively charged hydroxyl, together with phosphate groups [1,20,44]. Consequently, different possible adsorption mechanisms can take place during the adsorption process, i.e., ion exchange and dissolution-precipitation according to Equations (2)-(4) [6,20]. Ca 10 (PO 4 ) 6 (OH) 2 + 2Co 2+ → Ca 8 Co 2 (PO 4 ) 6 (OH) 2 + 2Ca 2+ ,…”

“…The feasibility of hydroxyapatite (HdA) nanoparticles as effective adsorbents is well documented for the adsorption of various multi-valent metal ions, such as lead, cobalt, nickel, copper, zinc, cadmium, strontium, and uranium [1,[17][18][19]. Indeed, the HdA has a versatile structure, which allows foreign ions to substitute Ca-ions on the framework without any distortion [20]. Nevertheless, the use of HdA nanoparticles in the industrial field is limited due to their difficulties in separating them from effluent and the possibility of causing secondary pollution [12].…”

Combination of interfacial reduction of hexavalent chromium and trivalent chromium immobilization on tin-functionalized hydroxyapatite materials

“…Because of the unique properties of bioavailability, biocompatibility, low cost, thermal stability, and water insolubility (K ps ≈ 10 −59 at room temperature), HAP represents a cheap and eco-friendly material which can found multiple applications in the field of environmental protection [37]. In particular, thanks to its functionalized surface (phosphate and hydroxyl groups, in particular) and the ion exchangeproperties, HAP can act as sorbent towards several heavy metal ions [38][39][40].…”