A new indicator of ionic polymeric flocculants for the removal of heavy metals anions: Specific charge density

Abstract

Ionic polymeric flocculants, as useful and widely used technology, have been applied for heavy metal pollution control. However, although molecular weight is an important indicator, it is not a comprehensive indicator for evaluating flocculation efficiencies of ionic flocculants. Herein, specific charge density (SCD), defined as charge density of unit molecular weight, is a new indicator to evaluate the performance of ionic polymer flocculants. Polydiallyldimethylammonium chloride (PDADMAC) as coagulant aid is investigated to flocculate different anionic pollutants. The results indicate that PDADMAC with a high SCD value could benefit to the flocculation efficiency of anionic pollutants. According to statistical analysis, the average pollutants residual could decrease to 8.64%–32.27% by that with high SCD value, especially for high valence pollutants with a decrease from 58.97%–60.40% to 27.35%–32.27%. The indicator of SCD values not only could characterize the performance of polymer flocculants but also provide a new sight of the flocculation mechanism of polymeric flocculants. Practitioner points Specific Charge Density (SCD) is defined as charge density of unit molecularweight. SCD as a new indicator to evaluate comprehensively the performance of flocculants. Removal efficiencies by flocculation increase with SCD value of PDADMAC increase. Effect of SCD of PDADMAC on removal of pollutant with high valence is significant. SCD of PDADMAC is less indicative for removal of pollutant with low valence.

Dynamic floc characteristics of flocculated coal slime water under different agent conditions using particle vision and measurement

“…In most research on flocculation and its mechanism in most researches, the flocculation size, fractal dimension, sedimentation velocity, and turbidity of the supernatant are conventionally characterized by sampling either during or at the end of the flocculation process (Lee et al, ). In this process, a laser particle size analyzer, optical microscope (Huang et al, ), or scanning electron microscope (SEM) (Hou, Zhao, Cao, & Ning, ) is commonly used to determine the size and structure of the flocs. Because the measurements are taken after sample handling, any disturbance to the floc structures by sampling should be considered.…”