金属氧化物颗粒/水界面上NOM吸附机制的研究

以腐殖酸作为天然有机物(NOM)的代表,研究了腐殖酸分子在金属氧化物(赤铁矿)颗粒/水界面上的吸附特征,分析了pH值和离子强度对界面吸附配位反应的影响,及它们对赤铁矿颗粒表面吸附密度和团聚体粒径的影响.结果表明,吸附密度随pH值的升高而减少,随离子强度的升高而增大;颗粒团聚体粒径随pH值的升高先增大后减小,随离子强度的升高而增大.pH=4时吸附密度最大,为6.22 mg/m2,但此时团聚体粒径最小;pH=5时吸附密度较小,但团聚体粒径较大;pH=8为配位反应等电点,吸附密度和团聚体粒径均较小;pH=10吸附密度最小,为0.50 mg/m2,团聚体粒径也较小.应用SS/SF混合模型初步分析了赤铁矿颗粒/水界面上腐殖酸分子的吸附构型.当pH值较低时,构型多为链状和环状;当pH值较高时,构型多为扫尾状.离子强度越高,链状和扫尾状构型越多;离子强度越低,环状构型越多.

Research on Adsorption Mechanism of NOM on Metal Oxide Particles/Water Interface

The adsorption of humic acid molecules on metal oxide (hematite) particles/water interface was studied, with humic acid used as a representative of natural organic matter. This paper mainly analyzed influences of pH values and ionic strength on the adsorption coordinate reaction, as well as on the adsorption density and the size of aggregating-particles. The adsorption density decreased with pH values increasing and increased as ionic strength increased, while the size of aggregating-particles increased firstly and then decreased with pH value increasing, and increased with the ionic strength increasing. When pH value was 4, the adsorption density was the largest, i.e. 6.22 mg/m², while the size of aggregating-particles was the smallest. When pH value was 5, the adsorption density was smaller, but the size of aggregating-particles was larger. When pH value was 8, it reached the isoelectric point of coordination reactions, therefore the adsorption density and the size of aggregating-particles were all considerably small. When pH value was 10, the adsorption density is the smallest, i.e. 0.50 mg/m², and the size of aggregating-particles is also smaller. Finally, the SS/SF hybrid model was introduced briefly, and used to analyze the adsorption configurations of humic acid molecules on hematite particle/water interface preliminarily. When pH value was low, the configurations were mostly train and loop, when pH value was high, the configurations were mostly tail. The higher the ionic strength was, the more train and tail configurations there were. The lower the ionic strength was, the more loop configurations there were.