Adsorption of Lead and Cadmium on Ca-Deficient Hydroxyapatite

Abstract

A Ca-deficient hydroxyapatite(d-HAp) has been used to remove lead and cadmium from their mixed ions solution. The effect of pH, coexistent calcium and magnesium ions, and humic acid on the adsorption efficiency were investigated. The results showed that this d-HAp adsorbed both Cd 2þ and Pb 2þ efficiently within a wide pH range. The existence of humic acid reduced the removal efficiency of Cd 2þ and Pb 2þ . The addition of Ca 2þ and Mg 2þ with a concentration of 500 mg/L only slightly reduced the removal efficiency. The adsorption kinetics was described by pseudo-second-order reaction model and the adsorption isotherm followed the Langmuir model.

Strontium-doped hydroxyapatite as adsorbent effectively to remove lead ions from water

“…After the concentration was 20 mg/L, a further increase in the concentration of HA would not lead to the signi cant change in Pb 2+ adsorption, and the removal rate remained basically constant. The similar phenomenon had been observed in previous studies (Wang et al, 2008;Zhu et al, 2010). Because of the strong a nity between Pb 2+ and Sr-HAP, Sr-HAP always acted faster on Pb 2+ than that of HA.…”

A comprehensive review on Cd(II) removal from aqueous solution

“…Experimental results revealed that adsorption of Cd 2+ on zeolite sands increases with increase in pH, temperature and initial adsorbate concentration. Zhu et al [111] used Ca-deficient hydroxyapatite to remove cadmium and lead from their mixed ion solution at a pH 6 and found that d-Hap adsorbed cadmium efficiently with the highest adsorption capacity of 97.81% at zero concentration of co-existing cations (Ca 2+ and Mg 2+ ). Rouibah et al [112] used olive stones as an adsorbent for the removal of Cd(II) from aqueous solution.…”

Cork-derived hierarchically porous hydroxyapatite with different stoichiometries for biomedical and environmental applications

“…Literature reports heavy metal removal performed with calcium-deficient hydroxyapatite, 45 although only one study was performed comparing directly stoichiometric and nonstoichiometric materials. 46 This investigation showed that calcium-deficient hydroxyapatite can have enhanced performance in the adsorption of metals; the authors explained this behaviour as being due to fact that the calcium deficient material was B-type carbonate HA (carbonate groups substituting phosphate ones), and the presence of carbonate ions favoured the metal immobilisation.…”