Preparation of starch-based adsorbing-flocculating bifunctional material St-A/F and its removal of active, direct and disperse dyes from textile printing and dyeing wastewater

A starch-based adsorbing-flocculating bifunctional material St-A/F is prepared via graft copolymerization with two cationic monomers DMC and DMDAAC, using a safe and clean Fenton initiating system. C-13 NMR, XRD, SEM and BET are used in characterization of chemical construction and physicochemical property for the product. St-A/F has double functions of adsorbing and flocculating; it can remove hydro-soluble reactive and direct dyes, and insoluble disperse dyes simultaneously. In adsorption study, the removal ratio (RR) of direct dye 4BS and reactive dye KE-4B were 92.06 and 94.13%, respectively. The adsorption behaviors have higher fitting degree to pseudo-second-order kinetic and Langmuir isothermal model than pseudo-first-order and Freundlich isothermal model. In flocculation study, the RR of St-A/F was recorded above 93.91% to three disperse dyes. St-A/F has significantly increased Zeta potential and isoelectric point (pI 9.08). St-A/F can cause destabilization and aggregation to negatively charged disperse dye particles, via charge neutralization and bridging effects, using its positively charged graft branched chains. St-A/F can simultaneously remove soluble and insoluble pollutants, so it considered to have great advantage in treatment for practical textile printing and dying wastewater with complicated composition.