REMOVAL OF TOXIC Pb²⁺ IONS BY SYNTHETIC HYDROXYAPATITES

REACTION OF Ca-DEFICIENT HYDROXYAPATITE WITH HEAVY METAL IONS ALONG WITH METAL SUBSTITUTION

“…On the other hand, no band for internal OH was observed in HAP-400-Fe, but broaden bands for adsorbed H 2 O (OH) and PO 4 was observed. Thereby, it was reconfirmed that HAP-400-Fe is constituted of disrupted apatic structure and amorphous hydrated In comparison of ionization tendency (standard oxidative-reductive potential) 15 of metals employed in the present study, Ca has the highest tendency.…”

“…13 This is the reason for the efficient reactivity of HAP-400 with Pb (II) as well as the sharper XRD peaks of HAP-400-Pb. FIGURE 1c and 2c, which are concerned with Fe (III)-bearing hydroxyapatites, reveal disruption of apatic structure, or transformation into amorphous 14 Suzuki et al 6 reported that stoichiometric hydroxyapatite is subjected to attack of Fe 3+ to the apatic lattice to produce amorphous FePO 4 •mH 2 O (m=1~9), which indicates no degradability in acidic solution even at pH 3 or below. This report at least supports that the present HAP-300-Fe has FePO 4 structure.…”

“…Stoichiometric hydroxyapatite, Ca 10 (PO 4 ) 6 (OH) 2 , has substitution ability with cations such as sodium 1,2 and heavy metal [3][4][5][6][7][8][9] ions as well as anions such as sulfonate 1,2 and halogen 10,11 ions. It is supposed that Ca-deficient hydroxyapatite, 12 denoted as Ca 10-x (HPO 4 ) x (PO 4 ) 6-x (OH) 2-x , exhibits ion substitution ability different from stoichiometric hydroxyapatite since Ca-deficient apatite has a crystal structure with many Ca-deficient sites.…”

“…Similarly to HAP-400, HAP-400-Pb indicated bands for surface and internal OH, adsorbed H 2 O (OH), and PO 4 .…”

Study of the mechanisms of heavy metal sorption by mineral apatite: the feasibility of soil and ground water remediation

“…Sa druge strane, molski odnos sorbovanog Pb 2+ i otpuštenog Ca 2+ bi bio približno jednak jedinici i u slučaju mehanizma rastvaranja HAP-a i taloženja hidroksipiromorfita (HPM). Po ovom mehanizmu reakcija rastvorenog olova sa hidroksiapatitom može se prikazati sledećim jednačinama : Suzuki i saradnici (1982;1985) ponudili kao dokaz teorije da je izmena jona osnovni mehanizam reakcije je molski odnos uklonjeno Pb/ otpušteni Ca, bio približno jednak 1 u njihovim eksperimentima. Međutim, reakcije (13)-(16) takođe mogu da objasne činjenicu da je molski odnos uklonjeno Pb/otpušteni Ca približno jednak jedinici.…”