Department of Mining Engineering and Natural Resources, Politechnical University of Catalunya, Bases de Manresa 61-73, Manresa 08242, Catalonia, Spain.
J Hazard Mater. 2012 Apr 30;213-214:7-18. doi: 10.1016/j.jhazmat.2012.01.027. Epub 2012 Jan 28.
Apatite II™ is a biogenic hydroxyapatite (expressed as Ca(5)(PO(4))OH) derived from fish bone. Using grains of Apatite II™ with a fraction size between 250 and 500 μm, batch and flow-through experiments were carried out to (1) determine the solubility constant for the dissolution reaction Ca(5)(PO(4))(3)(OH) ⇔ 5Ca(2+) + 3PO(4)(3-) + OH(-), (2) obtain steady-state dissolution rates over the pH range between 2.22 and 7.14, and (3) study the Apatite II™'s mechanisms to remove Pb(2+), Zn(2+), Mn(2+), and Cu(2+) from metal polluted water as it dissolves. The logK(S) value obtained was -50.8±0.82 at 25 °C. Far-from-equilibrium fish-bone hydroxyapatite dissolution rates decrease by increasing pH. Assuming that the dissolution reaction is controlled by fast adsorption of a proton on a specific surface site that dominates through the pH range studied, probably ≡PO(-), followed by a slow hydrolysis step, the dissolution rate dependence is expressed in mol m(-2) s(-1) as where Rate(25 °C) = -8.9 × 10(-10) × [9.96 × 10(5) × a(H+)]/[1 + 9.96 × 10(5) × a(H+)] where a(H+) is the proton activity in solution. Removal of Pb(2+), Zn(2+), Mn(2+) and Cu(2+) was by formation of phosphate-metal compounds on the Apatite II™ substrate, whereas removal of Cd(2+) was by surface adsorption. Increase in pH enhanced the removal of aqueous heavy metals. Using the kinetic parameters obtained (e.g., dissolution rate and pH-rate dependence law), reactive transport simulations reproduced the experimental variation of pH and concentrations of Ca, P and toxic divalent metal in a column experiment filled with Apatite II™ that was designed to simulate the Apatite II™-metal polluted water interaction.
Apatite II™ 是一种生物源羟磷灰石（表示为 Ca(5)(PO(4))OH），来源于鱼骨。使用粒径在 250 至 500μm 之间的 Apatite II™ 颗粒，进行了分批和流动实验，以（1）确定溶解反应 Ca(5)(PO(4))(3)(OH) ⇔ 5Ca(2+) + 3PO(4)(3-) + OH(-) 的溶解度常数，（2）在 pH 值 2.22 至 7.14 之间获得稳定的溶解速率，以及（3）研究 Apatite II™ 在溶解过程中从金属污染水中去除 Pb(2+)、Zn(2+)、Mn(2+)和 Cu(2+)的机制。在 25°C 下获得的 logK(S) 值为-50.8±0.82。远离平衡的鱼骨羟磷灰石溶解速率随 pH 值的升高而降低。假设溶解反应受快速质子吸附控制，在研究的 pH 范围内，质子优先吸附在特定的表面位点上，可能是 ≡PO(-)，随后是缓慢的水解步骤，溶解速率的依赖关系以 mol m(-2) s(-1)表示为：其中 Rate(25°C) = -8.9 × 10(-10) × [9.96 × 10(5) × a(H+)]/[1 + 9.96 × 10(5) × a(H+)]，其中 a(H+) 是溶液中的质子活度。Pb(2+)、Zn(2+)、Mn(2+)和 Cu(2+)的去除是通过在 Apatite II™ 基质上形成磷酸盐-金属化合物实现的，而 Cd(2+)的去除是通过表面吸附实现的。pH 值的升高增强了对水中重金属的去除。利用获得的动力学参数（例如，溶解速率和 pH 值速率依赖律），反应性传输模拟再现了在充满 Apatite II™ 的柱实验中 pH 值和 Ca、P 和毒性二价金属浓度的实验变化，该柱实验旨在模拟 Apatite II™-金属污染水的相互作用。
