Synthesis of Polymer Grafted Starches and Their Flocculation Properties in Clay Suspension

Nana Zhao,Yunyin Zhu,Yuming Xu,Hani Al Bitar,Zhiqing Shi

doi:10.3390/min10121054

Nana Zhao, Yunyin Zhu + Show 3 more

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https://doi.org/10.3390/min10121054

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Abstract

Starch-based flocculants have been emerged as a promising alternative to conventional synthetic flocculants in wastewater treatment, especially for the treatment of oil sand tailings, as they are low cost, safe, biodegradable, fairly shear-stable, readily available from reproducible agricultural resources, and do not result in secondary pollution. In this paper, three types of polymer-grafted starches (St-g-Polymer) with different charge properties were synthesized and their molecular structures were controlled by atom transfer radical polymerization (ATRP). The correlations between the charge properties of starch-based flocculants, external environmental parameters, and flocculation performance were systematically investigated by conducting jar tests under various environmental conditions. It was found that the charge properties of the branch chain had a significant impact on flocculation performance. The cationic St-g-Polymer demonstrated the best performance due to the grafting of the cationic monomer to the starch backbone which improved the solubility of the copolymer and aided in the removal of small/water-soluble particles. The results obtained could assist in guiding the selection and design of suitable biodegradable flocculants when treating targeted wastewater.

Highlights

Flocculation is a traditional chemical water treatment technique typically applied to separate suspended solids from water
Three types of polymer grafted starches (St-g-Polymer), were synthesized and their molecular structures were controlled by Atom transfer radical polymerization (ATRP)
Three types of polymer-grafted starches (St-g-polymer) with different charge properties were synthesized and their molecular structures were controlled by ATRP

Summary

Introduction

Flocculation is a traditional chemical water treatment technique typically applied to separate suspended solids from water. In the flocculation process, synthetic polymer flocculants are used to form molecular bridges between the solid particles facilitating impurities to be separated from the water. Starch-based flocculants, as alternatives to synthetic polyacrylamide in wastewater treatment, especially for the treatment of oil sand tailings, are high-performance and low-cost natural polymeric flocculants which have attracted much attention because they are inexpensive, biodegradable, and shear stable [1]. In order to increase the flocculation efficiency, the natural starches were commonly modified to alter their functional groups. Polymer grafted starches (St-g-Polymer) have gained extensive interest because they have properties of both natural and synthetic polymers, and they can significantly improve the flocculation performance for water treatment.

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