Development of Methods for Leaching and Recovering Heavy Metal Ions from Fly Ash

1.利用X射线荧光光谱仪对飞灰进行了X射线荧光分析，并对飞灰中金属的浸出进行了分析。飞灰中的主要元素为钙、钾、钠、氯、硅，锌的含量约为0.5摩尔%。铜和铅的含量均小于0.05mol%。以HCl、HNO3和CH3COOH水溶液为淋洗剂，采用间歇淋洗和渗滤两种工艺，研究了重金属铜、锌、铅的浸出行为。0.25M和0.5M的HCl和0.25M的HNO_3对铅有较好的萃取效果，而0.5M的HNO_3和CH_3COOH对铅的萃取效果较差。用水溶性螯合聚合物和中空纤维回收金属离子，在循环模式下测定了金属离子(Cu(II)和La(III))的回收率，其中水溶性螯合聚合物(聚丙烯酸)的水溶液流入浸泡在金属离子溶液中的中空纤维的管腔侧。考察了聚合物溶液的流速和金属离子溶液的搅拌速度对回收率的影响，测得Cu(II)和La(III)在膜壁上的有效扩散系数分别为3.3×10~(-9)/m^2/S和2.8×10~(-9)m~(-2)/S。3.固定化金属离子磷酸氢盐(Na_2HPO_4、K_2HPO_4、MgHPO_4、CaHPO_4)能很好地去除水溶液中的铅(II)、镉(II)、钴(II)和铜(II)。羟基磷灰石钙对钛(IV)和锆(IV)具有良好的固定化作用。

1.XRF analysis of fly ashes and leaching of metals from fly ashElemental compositions of fly ash were measured with a X-ray fluorescence spectrometer. The major elements in the fly ash were Ca > K, Na, Cl, Si, and the content of Zn was about 0.5 mol %. Cu and Pb were contained less than 0.05 mol %. Leaching behaviors of the hazardous heavy metals of Cu, Zn and Pb were investigated using aqueous solutions of HCl, HNO_3 and CH_3COOH as eluents in batch and percolation processes.In both processes, Zn was effectively extracted with every eluent used. While, Pb was well extracted with HCl (0.25 M and 0.5 M) and 0.25 M HNO_3 but slightly with 0.5 M HNO_3 and CH_3COOH. Cu was effectively extracted with HNO_3 and CH_3COOH rather than HCl.2.Recovery of metal ions using a water-soluble chelating polymer and a hollow fiberRecovering rate of metal ions (Cu(II) and La(III)) was measured in a circulating mode, where the aqueous solution of water-soluble chelating polymer (polyacrylic acid) flowed in the lumen side of the hollow fiber which was immersed in metal ion solution. Effects of flow rate of the polymer solution and stirring rate of metal ion solution on the recovery rate were examined, and the effective diffusion coefficients of Cu(II) and La(III) trough the membrane wall were determined to be 3.3×10^<-9> m^2/s and 2.8×10^<-9> m^2/s, respectively.3.Immobilization of metal ionsHydrogen phosphates (Na_2HPO_4, K_2HPO_4, MgHPO_4, CaHPO_4) could favorably remove Pb(II), Cd(II), Co(II) and Cu(II) from aqueous solutions. Calcium hydroxyapatite was shown to be useful to immobilize Ti(IV) and Zr(IV).