Performance And Mechanism Of Polyferric-epichlorohydrin-dimethylamine Composite Flocculants

In this paper, a series of composite inorganic-organic coagulant was prepared by polyferric chloride (PFC) and epichlorohydrin-dimethylamine (EPI-DMA) with different basicity (B) of PFC, different mass fraction (w(E)) and intrinsic viscosity (η) of EPI-DMA. The advantage of PFC-EPI-DMA over PFC and successive addition of PFC and EPI-DMA in coagulation efficiency and the difference of them in coagulation mechanism were revealed. The effect of B value, w(E),ηvalue and aging period on coagulation efficiency, Fe(Ⅲ) species distribution and floc aggregation process were studied by a variety of methods and technology, such as jar test, zeta potential measurement, Fe-Ferron method and photometric dispersion analyzer. The main conclusions are as follows:(1) Fe-Ferron method was used to examine Fe (Ⅲ) species distribution of PFC-EPI-DMA. The addition of EPI-DMA significantly affects the Fe (Ⅲ) species distribution of the composite coagulant. When w(E)=3.5%,η=850 mPa·s,B=0.5, the content of Feb was the highest in PFC-EPI-DMA with 1d aging.(2) For the treatment of synthetic reactive red wastewater, PFC-EPI-DMA was more efficient than PFC. Compared with successive addition of PFC and EPI-DMA in two reactive dyes wastewater, PFC-EPI-DMA gave higher color removal efficiency but weaker charge neutralization ability in reactive red wastewater treatment, whereas it gave lower color removal efficiency but stronger charge neutralization ability in reactive blue wastewater treatment. In the middle pH range, PFC-EPI-DMA generally achieved better color removal efficiency at higher w(E) andηvalue, lower B value and aging period.(3) For the treatment of synthetic reactive red wastewater, floc growth velocity (Growth rate), the average floc size (Ratio) and the time-weighted steady state variance (TWV) of PFC-EPI-DMA were larger than those of PFC. However, these three parameters of PFC-EPI-DMA were smaller than those of PFC at lower dosage range when treated synthetic reactive blue wastewater. With the increase of w(E) value, three parameters were all increased in reactive red wastewater treatment. For the treatment of synthetic reactive blue wastewater, PFC-EPI-DMA achieved larger Growth rate and Ratio but lower TWV at lower dosage with increasing w(E) value. However, the orders of three parameters at high dosage were contrary to those at low dosage. In the middle pH range, PFC-EPI-DMA with higherηvalue and lower B value achieved larger Growth rate and Ratio, smaller TWV. The effect of aging time on three parameters was complicated.(4) Compared with PFC, PFC-EPI-DMA achieved worse turbidity and organic matter removal in synthetic natural surface water treatment. Generally speaking, PFC-EPI-DMA with higherηvalue, lower w(E) and B value achieved better coagulation performance.The primary coagulation efficiency, coagulation behavior and coagulation mechanism of PFC-EPI-DMA were confirmed in different synthetic water treatment. These contents will provide the theory for impoldering and applying PFC-EPI-DMA.