Rational design of cationic starch with high purification performance and insight into the working mechanism

The utilization of starch to treat sewage that received widespread attention has become one of the promising ways to purify water due to the advantages of low cost and biodegradability. However, the poor purification capacity for wastewater and difficult liquid phase dispersion of natural starch severely hindered its application in wastewater treatment and limited the development of starch materials. Hence, a series of cationic starches with different particle sizes were fabricated by controlling the acidification time and combining starch with N-2,3-epoxy-propyl trimethyl ammonium chloride to improve the dispersion and purification effect of starch in water. Acid hydrolysis could destroy the spatial structure of starch, which improved the etherification property to enhance the purification property of starch to different pollutants and the dispersed stable state in water. The maximum adsorption capacities of the optimal functional agents were 43.2 mg/g (methyl orange), and 236.8 mg/g (acid black) and the optimal penetration rate of the treated kaolin solution was 94.6%. The working behavior of cationic starch could be composed of rapid, stable, and equilibrium stages, and the working process of HS-g-GTA conformed to the pseudo-second-order dynamic model. This work provides a simple and low-energy pretreatment method for preparing cationic starch, which has important application value in removing anionic substances from wastewater.