Structure-activity relationships of a novel coarse flocculant for organic carbon capture in municipal wastewater

An innovative kind of coarse flocculant employs captured organics from wastewater as a raw material was proposed in our previous research, which is subsequently utilized to capture organics from wastewater in return. Coarse flocculants with different molecular weight, zeta potential and charge density were produced by adjusting modification condition. They were characterized through various methods, while the flocculation effect and structure-activity relationship of the coarse flocculant was also evaluated. The flocculation performance is primarily determined by the charge properties. The molecular weight significantly influences the adsorption-bridging and catching-sweeping effect, thereby affecting floc size and stability. The charge density has important impact on the colloidal particle instability, which in turn impacts floc size. The flocculation mechanisms were discussed based on the structure-activity relationship. Notably, when zeta potential ranges from 7 ± 0.02–9.5 ± 0.02 mV and charge density exceeds 1.35 ± 0.01 mmol·L −1 , the charge neutralization effect is maximized. Large floc particle helps enhance organic matter capturing. The results help to guide the development of the novel flocculant. • A novel coarse flocculant was made from the hydrothermal liquid of concentrated organic matter. • Six distinct coarse flocculants were produced and evaluated. • Structure-activity relationship of the flocculants was analyzed. • The results help further improve the preparation of coarse flocculant.