Water-Soluble Starch-Based Copolymers Synthesized by Electron Beam Irradiation: Physicochemical and Functional Characterization

Abstract

Modification of natural polymers for applications in the treatment of waste and surface waters is a continuous concern of researchers and technologists in close relation to the advantages they provide as related to classical polymeric flocculants. In this work, copolymers of starch-graft-polyacrylamide (St-g-PAM) were synthesized by electron beam irradiation used as the free radical initiator by applying different irradiation doses and dose rates. St-g-PAM loaded with ex situ prepared silver nanoparticles was also synthesized by using an accelerated electron beam. The graft copolymers were characterized by chemical analysis, rheology, and differential scanning calorimetry (DSC). The results showed that the level of grafting (monomer conversion coefficient and residual monomer concentration), intrinsic viscosity and thermal behavior (thermodynamic parameters) were influenced by the irradiation dose, dose rate and presence of silver nanoparticles. The flocculation performances of the synthesized copolymers were also tested on water from the meat industry in experiments at the laboratory level. In the coagulation-flocculation process, the copolymer aqueous solutions showed good efficiency to improve different water quality indicators.

Keywords: flocculant; grafting copolymerization; intrinsic viscosity; polysaccharide; radiation; thermal behavior.

Scheme 1

Synthesis of graft copolymers by using electron beam irradiation.

Scheme 2

Mechanism of starch grafting by using electron beam irradiation.

Figure 1

DSC curves of St, pAMD, and graft copolymers synthesized: (a) with the same $\dot{D}$ and different $D$ (Batch 1), (b) with the same $D$ and different $\dot{D}$ (Batch 2), and (c) with and without AgNPs (Batch 3).

Figure 2

Results of the flocculation study at laboratory level: (a) total suspended solids (TSS), (b) organic matters (FM), (c) chemical oxygen demand (COD), and (d) biochemical oxygen demand (BOD₅). The coagulation–flocculation experiments involved inorganic coagulants (CaCO₃ and Al₂(SO₄)₃–blue color) and aqueous solution flocculant (graft copolymer).