Sorption of Antimony onto Hydroxyapatite

Abstract

We prepared synthetic hydroxyapatite [HAP; Ca5(PO4)(3-x)(CO3)x(OH)(1+x) (x = 0.3)] and then investigated this material's ability to remove trivalent antimony [Sb(III)] from water. The HAP was characterized by X-ray diffraction analysis, scanning electron microscopy, X-ray energy dispersive spectroscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. The sorption of Sb(III) to HAP was measured over an Sb(III) concentration range of 0.05-50 mg L(-1), at constant ionic strength (I = 0.01 mol dm(-3)) in equilibrated aqueous suspensions (34 g dm(-3)) for 5 < pH < 8 in vessels that were closed to the atmosphere. Under these conditions, we found that HAP particles were enriched in Ca after incongruent dissolution of the solid. More than 95% of the Sb(III) in solution adsorbed to the solid-phase HAP in <30 min. The equilibrium distribution of Sb(III) (solid vs liquid phase) was characterized by a Langmuir model with gamma(max) = 6.7 +/- 0.1 x 10(-8) mol m(-2) (1.4 +/- 0.2 x 10(-4) mol dm(-3) g(-1)) and K(ads) = 1.5 +/- 0.2 x 10(3) dm3 mol(-1). As Sb adsorption occurred, the pH of the isoelectric point (pH(iep)) of the HAP suspensions declined from 7.7 to 6.9. This finding supports the idea that the negative surface potential of the HAP increased due to the adsorption of Sb as a charged species. The decline in pH(iep) during Sb adsorption plus the thermodynamic description of the Sb(III)-HAP-H2O system suggest likely surface reactions for the interaction of Sb with HAP. We discuss the efficiency of Sb removal from water by HAP in the context of phosphate enrichment.

Synthesis of Ce(III)-doped Fe3O4 magnetic particles for efficient removal of antimony from aqueous solution

“…Among these techniques, the adsorption is considered as an attractive technique with some significant advantages such as simplicity, low-cost, and eco-friendly [13]. Recently, varieties of adsorbents have been developed for the removal of antimony from aqueous solution [8,[14][15][16]. Nevertheless, the disadvantages of these conventional adsorbents should be addressed, such as greater difficulty of adsorbing Sb(V), which is the principal form of antimony in the aqueous environments, as compared to Sb(III) [17] and difficult to separate from the aquatic system when they are saturated.…”

Efficiency of Iron-Based Oxy-Hydroxides in Removing Antimony from Groundwater to Levels below the Drinking Water Regulation Limits

“…The reaction setup was pumped with a 40 g/L FeSO 4 ·H 2 O solution at a 10 L/h rate, whereas redox potential and pH were regulated by the addition of drops of H 2 O 2 (50% w/w) and NaOH (30% w/w), respectively. Particularly, in each synthesis, the pH was set at a constant value (4,7,9) and for this condition the redox potential was controlled to the corresponding maximum point, before oxygen bubbles appear, i.e., from +410 to +170 mV for the specific pH range. Formed solids were collected from the outflow of the system and thickened using an Imhoff tank.…”

“…Nevertheless, particular attention has not been dedicated to the understanding of Sb aqueous chemistry, as well as to the development of respective methods for its efficient removal to levels below the regulation limits. This can be attributed to the lower frequency of the presence of Sb in aquatic systems, which is a consequence of its limited solubility, when compared to aquatic species of other elements of the same group in the Periodic Table, such as arsenic and phosphorus [4]. Still, high concentrations of Sb were reported in water sources near hot springs, in areas with specific industrial activities such as the production of flame retardants, batteries, chemicals, ceramics, etc., as well as in certain mining fields.…”

“…Among the available treatment processes, the application of adsorbents in the column bed filter configuration is considered as a more advantageous setup due to its simplicity and almost unattended operation. Iron-based oxy-hydroxides (FeOOHs) are the main class of adsorbents studied so far for Sb uptake, while other solid phases or inorganic composites, including zero valent iron [12], graphene oxide [13,14], activated alumina [15], aerobic bio-granules [16], hydroxyapatite [4] and zeolites [17], were also reported as alternative active adsorption materials.…”

Adsorption of Cu(II) from aqueous solutions by tannins immobilized on collagen

“…Although all of these techniques are capable of removing heavy metals to some extent, adsorption by solid substrates is preferred because of its high efficiency, easy handling and cost-effectiveness, as well as the availability of adsorbents. Activated carbon has long been used as an adsorbent for adsorption of heavy metal ions in situations involving duing relatively low metal contents 1,2 also mineral materials, 3 -5 polymer resins, 6 synthetic hydroxyapatite 7 and zirconium phosphates 8,9 have been utilized successfully for the removal of heavy metal ions such as Pb(II), Zn(II), Cd(II) and U(VI).…”