Adsorption investigation of polyacrylic acid on sub-micron titanium dioxide surface and associated effects on flocculation.

Sun, Xianfeng; Zheng, Shenke; Cai, Zhonghao; Wang, Dong; Zhou, Boxin; Chen, Chubin; Wang, Daowei

This work investigated the flocculation of sub-micron titanium dioxide (TiO2) by polyacrylic acids (PAAs), with a focus on studying the correlation between the PAAs adsorption conformation and the flocculation efficiency/floc property. The adsorption analysis of PAAs on the TiO2 surface was studied by attenuated total reflection Fourier transform infrared, Raman, X-ray photoelectron spectroscopy, CHNS elemental analyzer coupled with quartz crystal microbalance with dissipation monitoring. Adsorption densities were fitted using Langmuir and Freundlich isotherm models. The flocculation process of TiO2 by PAAs of different molecular weights (MWs) was monitored in real-time by a photometric dispersion analyser, and the floc structure was studied by scanning electron microscope. The results showed that the adsorption of PAAs followed the Langmuir isotherm, and formed monolayer adsorption on the TiO2 surface regardless of MWs through hydrogen and bidentate chelating chemical bonds. The thickness of adsorption layer increased with increasing MW, which could promote floc size by providing molecular "bridges"; but impeded the flocculation rate. For sub-micron particles, polyacrylic acid with a medium MW (512 kDa) was the optimum polymer owing to obtaining the fastest flocculation rate and relatively dense flocs in this work. PAA with high MW resulted in larger flocs with greater porosity, whereas the low MW PAA can only generate smaller flocs with a slower flocculation rate.

TITANIUM dioxide surfaces; ATTENUATED total reflectance; QUARTZ crystal microbalances; CHEMICAL bonds; X-ray photoelectron spectroscopy; FLOCCULATION

Journal of Polymer Research, 2024, Vol 31, Issue 8, p1

1022-9760

Academic Journal

10.1007/s10965-024-04058-5