The Investigation Of Adsorption Capacity Of Hydroxyapatite For Heavy Metal Ions In WFGD Solution

The wet flue gas desulfurization(WFGD) can effectively remove both the SO2 and heavy metal in the coal-fired flue gas,but the absorbed heavy metal is not stable, the mercury in the desulfurization solution can be converted back to elemental mercury(Hg0) and re-emitted, and the heavy metal in the WFGD gypsum can be transferred to the environment when the WFGD gypsum is utilized. Therefore, the study of desulfurization gypsum slurry and the heavy metal adsorption and stability must be strengthened. Hydroxyapatite-based material can adsorb heavy metals in industrial waste water, but the adsorption capacity and adsorption mechanism of heavy metal in desulfurization slurry remains unclear. Hydroxyapatite adsorption kinetics of heavy metals in desulfurization slurry, the effect of initial concentration, initial pH and the amount of adsorbent for heavy metal adsorption remains unclear. Its in-depth study helps to master the hydroxyapatite-based material on the desulfurization adsorption properties of heavy metals, and provide a theoretical basis for the removal of heavy metals synergy.HAP(HAP) and MNHAP(MNHAP) are Synthesized by chemical precipitation method, and do characterization tests:BET surface area measurement, X-ray diffraction(XRD), X-ray energy dispersive, scanning electron microscopy(SEM) analysis and magnetic. The results showed that: HAP particle structure and MNHAP have porous surface, MNHAP has a high specific surface area(148.5 m2/g), two materials' Ca / P ratio are close to 1.67. Magnetic separation experiment shows MNHAP easily separated from the aqueous solution.Adsorption mechanism of hydroxyapatite sorbent slurry Hg2 + remains unclear. Studied the adsorption and stability of HAP and MNHAP desulfurization slurry Hg2 +, adsorption capacity, adsorption kinetics, we investigated the effects of the initial concentration, initial pH and the amount of adsorbent, and explore the Hg2+ by using experimental methods. The results showed that: HAP and MNHAP to Hg2+ kinetic process are in line with quasi-second order kinetic model, isotherm data followed Langmuir isotherm model. HAP and MNHAP of Hg2+,maximum adsorption capacity was 71.2 mg/g and 88 mg/g, the optimum amount of adsorbent were 4 g/L and 2 g/L. HAP is MNHAP adsorption Hg2+ main active ingredient, adsorbed process these three stages including surface complexation adsorption process, dissolve the precipitate and ion exchange. Ability of MNHAP stable Hg2+ in sulfur gypsum is stronger than HAP.There is currently a lack of MNHAP adsorpt Pb2+, Cd2+, Cr3+, Ni2+ study in desulfurization slurry. Experimentally studied MNHAP desulfurization slurry Pb2+, Cd2+, Cr3+, Ni2+ adsorption kinetics, investigated the effects of the initial concentration, initial pH, and the amount of adsorbent. The results showed that: MNHAP of Pb2+, Cd2+, Cr3+, Ni2+ adsorption kinetic process are in line with the pseudo second dynamic model,isotherm data with Langmuir isotherm model. MNHAP desulfurization slurry Pb2+, Cd2+, Cr3+, Ni2+ maximum adsorption capacity was 348 mg/L, 148 mg/L, 123 mg/L, 135 mg/L, the optimum amount of adsorbent were 0.83 g/L, 1.66 g/L, 0.83 g/L, 0.072 g/L. HAP is MNHAP adsorption Pb2+, Cd2+, Cr3+, Ni2+ main active ingredient. When there is competition between different heavy metal ions adsorption increased Pb2+concentration MNHAP of Cd2+ adsorption capacity significantly reduced, the maximum amount of adsorption by the 93.1 mg/g dropped to 75.2 mg/g. But the ability to change the concentration of Cd2+ and Pb2+ adsorption on MNHAP little effect, indicating MNHAP desulfurization slurry Pb2+ adsorption capacity stronger. The results provides a theoretical basis for the wet desulfurization synergistic removal Hg2+ and other heavy metal(Pb2+, Cd2+, Cr3+, Ni2+) and resource utilization gypsum of wet desulpHurization.