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我们以蒙脱石为对照,测定了以水合氧化物型表面为主的试样四个方面的表面性质:电荷零点(ZPC)、滴定曲线、羟基释放量及不同pH条件下对NH_4~+和Cl~-的吸附。结果表明,在pH 4—9范围内,氧化物型表面提供可变正电荷1—8 meq/100g,提供可变负电荷3—15meq/100g;三二氧化物使土壤的ZPC升高,而永久负电荷和有机质使土壤的ZPC降低。作为粘土酸,氧化物表面的酸性较弱,其表面质子逐步解离,使滴定曲线不出现突跃。氧化物表面的羟基和水合基密度很高,增加了土壤对离子的专性吸附能力。土壤中常见的氧化物型表面主要来自Fe,Al氧化物及非品质矿物,就它们的化学式而言,主要有Si—OH、Fe—OH及Al—OH,它们可存在于同一土壤中,在土壤常见的pH范围内,具有低ZPC的Si—OH亚表面提供可变负电荷,具有高ZPC的Fe—OH和Al—OH亚表面提供可变正电荷。
We use montmorillonite as a control and determine the surface properties of the hydrate oxide-based samples in four aspects: the charge zero (ZPC), the titration curve, the amount of hydroxyl release and the effect of pH on NH 4 + and Cl ~ - adsorption. The results show that the oxide type surface provides a variable positive charge of 1-8 meq / 100 g at pH 4-9 providing a variable negative charge of 3-15 meq / 100 g; the trioxide increases the soil ZPC while Permanent negative charge and organic matter decreased soil ZPC. As a clay acid, the acidity of the oxide surface is weak, and the surface protons are gradually dissociated, so that the titration curve does not jump suddenly. The hydroxyl and hydrated groups at the oxide surface have high densities and increase the soil’s specific adsorption capacity for ions. Common oxide-type surfaces in soils are mainly Fe, Al oxides and non-qualifying minerals. For their chemical formulas, there are mainly Si-OH, Fe-OH and Al-OH, which can exist in the same soil, The Si-OH sub-surface with low ZPC provides a variable negative charge in the soil’s common pH range, while the Fe-OH and Al-OH sub-surfaces with high ZPC provide a variable positive charge.