Abstract
The presence of dyes in wastewater effluents made from the textile industry is a major environmental problem due to their complex structure and poor biodegradability. In this study, a cationic lignin polymer was synthesized via the free radical polymerization of lignin with [2-(methacryloyloxy) ethyl] trimethyl ammonium chloride (METAC) and used to remove anionic azo-dyes (reactive black 5, RB5, and reactive orange 16, RO16) from simulated wastewater. The effects of pH, salt, and concentration of dyes, as well as the charge density and molecular weight of lignin-METAC polymer on dye removal were examined. Results demonstrated that lignin-METAC was an effective flocculant for the removal of dye via charge neutralization and bridging mechanisms. The dye removal efficiency of lignin-METAC polymer was independent of pH. The dosage of the lignin polymer required for reaching the maximum removal had a linear relationship with the dye concentration. The presence of inorganic salts including NaCl, NaNO3, and Na2SO4 had a marginal effect on the dye removal. Under the optimized conditions, greater than 98% of RB5 and 94% of RO16 were removed at lignin-METAC concentrations of 120 mg/L and 105 mg/L in the dye solutions, respectively.
Highlights
Dyes are readily found in wastewater effluents of various industries including: dye manufacturing, textile, cosmetic, pharmaceuticals, food, rubber, leather, printing, and pulp & paper
Lignin-METAC was prepared in an aqueous heterogeneous reaction by the free radical polymerization of kraft lignin and METAC under mild acidic condition initiated by K2 S2 O8
Increasing the charge density and molecular weight of the lignin-METAC polymer improved the efficiency of lignin-METAC polymer for the dye removal
Summary
Dyes are readily found in wastewater effluents of various industries including: dye manufacturing, textile, cosmetic, pharmaceuticals, food, rubber, leather, printing, and pulp & paper. There are approximately 8000 dyes and 10,000 commercial dye-based products in the market [3,4]. 60–70% of commercially used dyes in the world [5,6]. They are generally used for coloring plant fibers including cotton, hemp and linen, wool fibers, as well as inorganic particles (e.g., clay) [5,6]. Not all of the dye is adsorbed onto the end-use products, and as a result, some remain in the process effluents (i.e., wastewater), which must be treated [7]. The identification of an effective chemical treatment for the removal of dyes from wastewater is currently needed
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