摘要
用Pb(II)参与钙矾石的合成试验表明,在SO42-存在时,钙矾石把少量的Pb(II)包容在其晶格内,造成化学俘获,但在无SO42-时,Pb(OH)3-不能替代SO42-进入钙矾石晶格;另一种水泥水化物CSH在碱性条件下对溶解态Pb(II)的吸附很强。监测水泥浆液中溶解态Pb(II)、SO42-的浓度和pH值的变化过程可知,PbSO4和Pb(OH)2的沉淀作用能把绝大多数的溶解态Pb(II)予以固化。采用TCLP检测法检测表明,采用复合型水泥固化Pb2+的效果良好,尤其是不掺石膏的复合水泥。虽然搅拌水中Pb2+的浓度达到4g/L,但其28d龄期的胶砂粉碎样滤取Pb2+的浓度已低至0.0002g/L。由于形成的Pb(OH)2沉淀物阻止水泥水化使得掺Pb(NO3)2后砂浆试件早期的抗压强度有所降低。因此,复合水泥对铅固化的机理主要是Pb(II)在水泥浆中发生的沉淀作用、水化物对Pb(II)的化学俘获和混凝土中微孔隙对含Pb微粒的裹限作用。
The synthesis of lead - containing ettringite indicate that ettringite can accommodate a little of Pb （Ⅱ） in its lattice when sulfate is present, thus giving rise to chemical entrapment. But when the synthetic solution is free of sufate, Pb（OH）3^- can＇ t accommodated by ettringite as the replacement of sulfate. C - S - H has high capacity to adsorb lead at higher pH values. According to the chemical changes in lead - containing cement slurry, the precipitations of lead hydroxide and sulfate make great contribution to solidification of lead by the cement. TCLP shows that Pb^2＋ is strongly solidified in the composite cement, especially in P · C without gypsum. Although the concentration of Pb^2＋ in the mix water was as high as 4g/L, it could be lowered to 0.002g/L in the filtrate from 28d old pastes in TCLP test. Since the precipitation of Pb （OH）2 stifles cement further hydration, the compressive strength of the test hard mortar - cubes at early stage reduced after blending with Pb^2＋. Overall the mechanisms of lead solidified in composite cement include precipitations of lead compounds, the chemical entrapment of lead by the cement hydrates and encapsulation of lead - containing particles in the concrete.
出处
《硅酸盐通报》
CAS
CSCD
北大核心
2005年第4期10-15,共6页
Bulletin of the Chinese Ceramic Society
基金
国家自然科学基金资助重点项目(49832005)
