Preparation of a cationic polyacrylamide (CPAM) and its flocculation performance in the environmental estrogen removal and separation

In this study, a new cationic polyacrylamide (CPAM) with different cationic degree was developed for the 17β-estradiol (E2) environmental estrogen removal. This new flocculant (PAA) was copolymerized byacrylamide (AM) and acryloyloxyethyl dimethylbenzyl ammonium chloride (AOD- BAC) using ultrasonic-initiated polymerization technique. The structure, morphology and thermal decomposition property of the prepared copolymer were analyzed through instrumental analyses such as Fourier transform infrared spectroscopy (FT-IR), 1 H nuclear magnetic resonance spectroscopy ( 1 HNMR), scanning electron microscopy (SEM) and thermogravimetry/differential scanning calorimetry (TG/DSC). The results showed that PAA was successfully synthesized. Meanwhile, it was demonstrated that PAA had a rough surface area with many holes and a favorable thermal stability. The E2 flocculation results demonstrated that the optimal flocculation conditions was at a cationic degree of 40%, pH = 7, stirring speed of 120 rpm, stirring time of 10 min, sedimentation time of 30 min and E2 initial concentration of 0.6 mg/L. In this condition, an excellent E2 flocculation performance (E2 removal rate: 92.3%, floc size: 22.1 μm) was obtained for PAA-3. During the E2 flocculation process, the charge neutralization was the main effect in both neutral (pH = 7) and acidic (pH = 4) conditions, but the adsorption was the dominant effect in alkaline (pH = 10) condition.