荧光淬灭法探讨三氯化铁与腐殖酸的混凝机理

Study on Coagulation Mechanism of Ferric Chloride with Humic Acids Using Fluorescence Quenching Method

运用荧光检测和光散射颗粒分析仪(PDA)在线监测技术对FeCl3与腐殖酸的混凝机理进行研究。结果表明,FeCl3投量的增加可使混凝去除腐殖酸的有效pH范围由弱酸性变成中性;在弱酸性条件下,FeCl3的水解产物主要为带正电荷的低、中聚合形态,吸附电中和以及共聚络合作用是FeCl3与腐殖酸的主要混凝机理;在中性条件下,FeCl3的水解离子和腐殖酸的主要官能团之间的络合作用与水解反应存在竞争,因此,FeCl3的水解产物对腐殖酸分子的吸附电中和及络合作用无法有效去除腐殖酸,而是通过氢氧化铁沉淀物对腐殖酸的吸附和网扫作用达到这一目的。

The fluorescence quenching method and photometric dispersion analyzer （PDA） were used to study the coagulation mechanism of humic acids （HAs） with ferric chloride. The results show that when the dosage of ferric chloride increases, the effective pH range for HAs removal changes from weak acid to neutral. At the weak acid pH, the hydrolysate of ferric chloride is mainly low and middle molecular metallic polymer with positive electrical charge, and the coagulation of HAs with ferric chloride is mainly due to adsorption/charge-neutralization and complexation. At the neutral pH, the complexation and the hydrolysis are the two competitive reactions happened between hydroxide ions in ferric chloride solution and the functional groups of HAs. Therefore, the removal of HAs is not caused by complexation between ferric chloride and HAs or adsorbing onto the iron hydroxide resulted from ferric chloride hydrolysis, but through the adsorbing and sweep flocculating onto the precipitated iron hydroxides resulted from ferric chloride hydrolysis.