Treatment and reuse of hypo-salinity wastewater using a novel starch-based flocculant with ultra salt-sensitive...

Chemical residues in reclaimed wastewater after water treatment hinder the reutilization of saline wastewater and achievement of net-zero emissions. The development of water treatment chemicals with self-cleaning abilities is envisioned as a viable strategy for the sustainable use of saline wastewater. Herein, a novel ultra salt-sensitive starch-based flocculant (USSF) is synthesized by grafting allyl glycidyl ether and 2-chloro-4,6-amino-[1,3,5]-triazine onto starch skeleton through simple etherification reaction. USSF can detect ultra-low salinity (0.5 g/L Na₂SO₄) and respond with salting-out sedimentation, with flocculant residuals as low as 7.9 %. Inorganic salt can promote the salting out of USSF to improve the anti-restabilization ability. Even when the dosage exceeds four times the optimal dose, USSF still maintains excellent color removal effect. Most importantly, USSF demonstrates excellent self-cleaning properties, maintaining a flocculant residual as low as 7.9 % in hypo-salinity wastewater. In addition, the dyeing experiment showed that color fixation rate (73.7 %) and color strength (9.1) of reuse water are comparable to the value of fresh water. This work develops a new starch-based ultra salt-responsive flocculant with enhanced efficacy in dye wastewater remediation, in this way, reuse of salinity wastewater can be implemented in exhaust dyeing with reactive dye.