Spectroscopic Studies on Interaction of Congo Red with Ferric Chloride in Aqueous Medium for Wastewater Treatment

In situ utilization of biomass pretreatment liquor as a novel flocculant for anion dyes removal: Performance and mechanism

In this work, it was first found biomass pretreatment liquor (PL) produced from rice straw (RS) pretreatment with FeCl₃ and polyethylene glycol 400 co-solvent can be used in situ as a new flocculant to remove anionic dyes from wastewater. The removal performance of nine dyes was investigated using various PL doses at different pH values. The experiment indicated that the PL had different flocculation effects on these dyes (color removal efficiency: 42.58-99.84%). Positive color removal results for the dyes were unachievable with six commercial coagulants. Among the nine dyes treated by PL flocculation, the best removal efficiencies for color, turbidity and suspended matter were obtained for Congo red. In the flocculation process, Fe³⁺ plays a role in charge neutralization, lignin nanoparticles (LNP) relies on hydroxyl groups to react instantaneously with the amino groups on the dye, and are bridged together by π-π interactions to promote the formation of floc clusters until they completely settle. Utilization of PL as a flocculant helps pave the way to simultaneously treat waste biomass, waste treatment liquor and dye wastewater. This research is of great significance for future water environment remediation and material development.