Smart flocculant with temperature and pH response derived from starch

Abstract

Temperature and pH responsive starches (TPRS) were prepared by etherification of starch with varying degrees of substitution with butyl glycidyl ether (BGE) and 2,4-bis(dimethylamino)-6-chloro-[1,3,5]-triazine (BDAT). Their structure was confirmed by FTIR spectroscopy and their substitution degrees by both BGE and BDAT were determined by means of ¹H NMR and elemental analysis. TPRS were demonstrated to be effective flocculants for anionic dye Avitera Red SE with the maximum color removal of 100% and a saturated flocculation capacity of 882 mg g⁻¹. Adjustments in the temperature and pH induced phase transitions that facilitated easy regeneration and subsequent separation of the flocculant from the dye contaminant. The obtained starch flocculants with temperature and pH dual response can be readily recycled from the solution, and then reused many times while retaining high flocculation capacity, promising significant potential in real dye recovery from wastewater.