In this work, two monomers, acrylamide (AM) and [2-(methacryloyloxy)ethyl]trimethylammonium chloride (DMC) were copolymerized from kraft lignin (KL) in an aqueous suspension initiated by free radical copolymerization in the presence of potassium persulfate. The impact of copolymerization conditions on the charge density and molecular weight of the copolymers was investigated. The molecular weight and mass balance analyses confirmed that the homopolymer [polyDMC (PDMC) and polyAM (PAM)] and undesired copolymer (AM-DMC) productions dominated as time, initiator, and DMC dosage increased more than the optimum values. The activation energy of the polymerization of KL and AM (43.02 kJ mol 21 ), KL and DMC (21.99 kJ mol 21 ), AM (14.54 kJ mol 21 ), DMC (10.34 kJ mol 21 ), and AM and DMC (18.13 kJ mol 21 ) was determined. Proton nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetric analysis, and elemental analysis confirmed the production of KL-AM-DMC copolymer.
Currently, lignin of black liquor is incinerated to generate energy in pulp mills; but it has potential to be valorized through different modification methods. In this work, kraft lignin (KL) was polymerized with 2-[(methacryloyloxy) ethyl] trimethylammonium chloride (DMC) to produce cationic water soluble polymers. After producing five polymers with different molecular weights and charge densities, their flocculation efficiency in kaolin suspensions was investigated. The adsorption, zeta potential and flocculation results confirmed that the polymer with the highest charge density and molecular weight (KLD5) was a more effective flocculant than other polymers. The structure and size of flocs formed from the interaction of kaolin with KLD were determined by a focused beam reflectance measurement (FBRM). The sedimentation studies, conducted under gravitational (by vertical scan analyzer) and centrifugal force (by Lumisizer analytical centrifuge), revealed that KLD5 was very effective in flocculating kaolin particles.
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