地聚合物固化重金属Pb^(2+)的研究

Immobilization of Heavy Metal Pb^(2+) with Geopolymer

利用偏高岭土、水玻璃、氢氧化钠和水合成地聚合物,并以地聚合物固化Pb2+.通过固化体的抗压强度和Pb2+浸出浓度来表征固化效果,通过XRD、SEM、FTIR等手段对地聚合物固化体终产物的结构进行分析,并从固化效果、微观结构、矿物结构等方面,将其与水泥固化作对比,分析地聚合物固化重金属和水泥固化重金属在机制上的区别.结果表明,当Pb2+掺加量<3%时,地聚合物对Pb2+的捕集效率达到99.7%以上,固化体抗压强度在40～50 MPa.当Pb2+掺加量相同时,地聚合物固化体的抗压强度明显高于水泥固化体,Pb2+浸出浓度明显低于水泥固化体.分析地聚合物固化Pb2+的机制主要是由于Pb2+参与了地聚合物结构的形成,或被地聚合物骨架中铝离子所吸附,Pb2+被包容在聚合体中.而水泥固化Pb2+主要依靠物理固封或吸附机制.因此无论从固化体的抗压强度、浸出浓度等理化性能,还是从固化体的微观表征及固化反应的机制分析,用地聚合物固化Pb2+比用水泥固化更具优势.

A series of geopolymers were synthesized by mixing metakaolinite,water glass,sodium hydroxide and water,and the lead ion solidification experiments were performed with the geopolymer.Then,the immobilization efficiency was characterized by monitoring the leaching concentration and compressive strength of solidified products.Additionally,the structure and properties of the solidified products were studied by X-ray diffraction（XRD）,scan electron microscopy（SEM） and Fourier transform infrared（FTIR） spectroscopy.Furthermore,based on the analysis of immobilization efficiency,microstructure and mineral structure,the difference between geopolymer and cement on the performance of immobilizing heavy metals was discussed.The results of lead ion immobilization experiments showed that over 99.7% of heavy metal was captured by the geopolymer as the doping concentration of lead ion was less than 3%.Meanwhile,the compressive strength of the solidified product ranged from 40 MPa to 50 MPa.Furthermore,by using the same Pb2＋ concentration,the geopolymer showed higher compressive strength and lower leaching concentration compared to the cement.Because lead ion participated in constitution of structure of geopolymer,or Pb2＋ was adsorbed by the aluminium ions on the geopolymeric skeleton and held in geopolymer.However,cement mainly solidified lead ion by physical encapsulation and adsorption mechanism.Therefore,both from the compressive strength and leaching concentration and from the microstructure characterization as well as the mechanism of the geopolymerization reaction,the geopolymer has more advantages in immobilizing Pb2＋ than the cement.