Cross-scale mechanism of hematite flocculation and sedimentation regulated by different ionic PAMs

KANG Zhangke; CUI Baoyu; SHEN Yanbai; LIU Wengang; GAO Shuling; ZHAO Qiang; DU Haoyu

doi:10.13247/j.cnki.jcumt.20250172

Abstract：The flocculation and settling behavior of—30μm ultrafine hematite particles regula-ted by polyacrylamides(PAMs)of different ionic types was studied.A cross-scale response model of"interfacial adsorption-floc structure-settling performance"was established to reveal the multiscale mechanism by which molecular-level adsorption characteristics affect macroscop-ic settling behavior.Four types of PAMs-nonionic(NPAM),anionic(APAM),cationic(CPAM),and amphoteric(AmPAM)were evaluated.Zeta potential and adsorption density tests,Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS),molecular dynamics simulation,and extended Derjaguin-Landau-Verwey-Overbeek(DLVO)theory were used to analyze differences in interfacial behavior,including adsorption energy and hydrogen bond formation.The results show that APAM has the strongest chain extension,most stable interfacial interaction,lowest adsorption energy,and the highest num-ber of hydrogen bonds.Based on focused beam reflectance measurement(FBRM),scanning e-lectron microscopy(SEM),fractal dimension,and porosity analyses,APAM-induced flocs ex-hibit an average chord length of 519.5 μm,a fractal dimension of 1.82,and a porosity of 38.9％,indicating the highest structural compactness.During settling,the APAM system shows a flocculation reaction time of 1.01 s,supernatant turbidity of 331 NTU,and floc con-centration of 51.9％,significantly outperforming the other systems.This study quantitatively clarifies the synergistic regulation mechanism of PAM ionic structures on hematite flocculation across molecular,mesoscopic,and macroscopic scales,providing theoretical support for floc-culant selection and process optimization in fine-particle slurry treatment.