氧化物组成对煤气化渣-污泥基地聚物力学性能和微观结构的影响

Effect of Oxide Composition on Mechanical Properties and Microstructure of Coal Gasification Slag-sludge Based Geopolymers

以煤气化渣和污泥为原料,通过水玻璃和氢氧化钠为复合碱激发剂制备地聚物,研究了氧化物组分摩尔比(n(H_(2)O)/n(Na_(2)O)、n(Na_(2)O)/n(Al_(2)O_(3))和n(SiO_(2))/n(Al_(2)O_(3)))对地聚物抗压强度和微观结构的影响,利用扫描电子显微镜(SEM)和比表面吸附仪(BET)对地聚物的表观形貌和孔结构进行了观察和分析,结合X射线衍射仪(XRD)和傅里叶变换红外光谱仪(FT-IR)对地聚物的化学结构分析,初步探索了氧化物组分摩尔比对地聚物抗压强度和微观结构的影响机制。结果表明:高n(H_(2)O)/n(Na_(2)O)在一定程度上有助于原料中硅铝活性成分的溶解,但同时也会引起体系碱性降低,阻碍地聚合反应,过多水量还将增加样品内部孔隙率;高n(Na2O)/n(Al_(2)O_(3))能促进反应进行,但也会造成凝胶物质包裹未溶解的煤气化渣-污泥灰颗粒,并加重碳化反应;n(SiO_(2))/n(Al_(2)O_(3))的增加能促进生成硅酸盐寡聚物,有利于地聚物强度的发展。试验得出最佳配比为n(H_(2)O)/n(Na_(2)O)=12,n(Na_(2)O)/n(Al2O3)=0.8,n(SiO_(2))/n(Al_(2)O_(3))=3.0,所制得的地聚物1 d、3 d、7 d和28 d抗压强度分别达到58.1MPa、62.9 MPa、70.1 MPa和73.0 MPa。研究结果可为煤气化渣和污泥等大宗固废的循环利用拓展新途径。

The geopolymer is prepared from coal gasification slag and sludge as raw materials and sodium silicate and sodium hydroxide as complex alkali activators.The effects of the molar ratio of oxide components including n(H_(2)O)/n(Na_(2)O)、n(Na_(2)O)/n(Al_(2)O_(3))和n(SiO_(2))/n(Al_(2)O_(3))on the compressive strength and microstructure of geopolymers are investigated.The apparent morphology and porosity of geopolymer are observed and analyzed using scanning electron microscopy(SEM)and specific surface adsorption instrument(BET).Combined with the chemical structure analysis of the geopolymers by Fourier transform infrared spectrometer(FT-IR)and X-ray diffraction(XRD),the influence mechanism is initially explored.The results show that high n(H_(2)O)/n(Na_(2)O)is conducive to dissolve the active components of Si and Al in the raw material to a certain extent.But it also causes the polymerization reaction to decrease the alkalinity of the system,and the excess wa-ter will increase the internal porosity of the geopolymer.High n(Na_(2)O)/n(Al_(2)O_(3))can promote the reaction,while it also causes the gel to cover the undissolved coal gasification slag and sludge ash particles,and aggra-vates the carbonization reaction.The increase of n(SiO_(2))/n(Al_(2)O_(3))is helpful to the formation of silicate oligo-mers,which is conducive to the development of compressive strength.The optimum ratios are n(H_(2)O)/n(Na_(2)O)=12,n(Na_(2)O)/n(Al_(2)O_(3))=0.8 and n(SiO_(2))/n(Al_(2)O_(3))=3.0.The compressive strength of 1 d,3 d,7 d and 28 d geopolymers reaches 58.1 MPa,62.9 MPa,70.1 MPa and 73.0 MPa,respectively.This study can develop a new way for the recycling of solid waste such as coal gasification slag and sludge.