Determination of the adsorption density of high molecular weight polymers on ultrafine sub-micron particles

This paper reports the high molecular weight polyacrylic acid (PAA) adsorption density on ultrafine particles was measured by three different methods, total organic carbon (TOC), attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR) and elemental analyzer. The results show that the TOC is not an appropriate method to quantify the high-molecular-weight polyacrylic acid (PAA) adsorption density on ultrafine particles. However, the other two direct methods are appropriate methods to measure the PAA adsorption density on the ultrafine particles with the larger surface area. The R-2 of the three techniques calibration curve is large than 0.99. However, it is difficult to separate the ultrafine particles and PAA with high-molecular-weight using the filtrate and centrifuge methods when the particle is ultrafine and the radius of gyration is larger, which is limit TOC method to usage. Comparing with the solid-free supernatant, it is easier to collect the flocs, which can present all the particles adsorption density identifying by the Fe3O4. Elemental analyzer and ATR-FTIR methods can directly determine the PAA adsorption density. The ultrafine particles have a big surface area, i.e., it has strong adsorption capacity, so elemental analyzer and ATR-FTIR technique are appropriate methods to quantify the high-molecular-weight PAA adsorption capacity.

Automated summary

This study measured the adsorption density of high molecular weight polyacrylic acid (PAA) on ultrafine particles using three different methods (total organic carbon, attenuated total reflectance fourier transform infrared spectroscopy, and elemental analyzer). The results showed that total organic carbon is not suitable for quantifying the PAA adsorption density, while the other two direct methods are appropriate. However, the difficulty of separating ultrafine particles and high molecular weight PAA using filtration and centrifugation methods limits the usage of total organic carbon. Comparatively, it is easier to collect the flocs and determine the PAA adsorption density using elemental analyzer and attenuated total reflectance fourier transform infrared spectroscopy. The strong adsorption capacity of ultrafine particles makes these two techniques suitable for quantifying the adsorption capacity of high molecular weight PAA.