Flocculation of kaolin and anion dye by cationic cellulose-based flocculant: RSM-optimized synthesis and experimental study

An efficient cellulose-based flocculant, CMA, was synthesized using a free radical initiation method in a NaOH/Urea aqueous solution. The optimal synthesis conditions were determined through single-factor and RSM experiments: a molar ratio of MCC to AA of 1:3.6, MCC to CTA of 1:8.2, and a reaction temperature of 45.8 °C. CMA was characterized using FTIR, SEM, XRD, DLS, XPS, and TG and applied successfully to the flocculation treatments of kaolin, simulated dyes, and actual dye wastewater. It exhibited low pH sensitivity, achieving over 90% removal efficiency at pH 3–12, with a maximum of 98.3%. In simulated dye wastewater, the removal efficiency of various dyes was greater than 95%, with a maximum of 97%. After CMA flocculation and ozone aeration, 86.5% of COD and 93.6% of turbidity were removed from the actual dye wastewater. CMA carried out the flocculated dye removal process via charge neutralization, double layer compression, and bridging adsorption, as revealed by various instrument characterization and analysis. A polysaccharide-based flocculant, CMA exhibits environmentally friendly properties, low pH sensitivity, and high efficiency in removing wastewater pollutants, making it a promising flocculant for highly turbid wastewater and anionic dye wastewater.