DECOLORIZATION OF LIGNIN IN WASTEWATER BY CATALYTIC OZONATION USING ZINC OXIDE-COATED RIVER GRAVEL
DOI:
https://doi.org/10.55766/sujst11561Keywords:
Lignin, Zinc oxide, Catalytic ozonation, Continuous flowAbstract
This study investigated the efficiency of catalytic ozonation for decolorizing lignin in synthetic wastewater using a heterogeneous catalyst - zinc oxide (ZnO) coated on river gravel - in a continuous flow reactor. The effects of three independent variables were examined: initial lignin concentration, solution pH, and ZnO catalyst dosage. Ozonation without a catalyst achieved a maximum lignin removal efficiency of 43.38% at an initial concentration of 100 mg L-1, pH 3, and a hydraulic retention time of 60 min. The reaction followed first - order kinetics with rate constants of 0.0117 min-¹ at pH 3 and 0.899 min-¹ at pH 11. Increasing the pH to 11 enhanced lignin removal to 51.75%. When ZnO/gravel catalyst was introduced at 3 g L-1 and pH of 11, the lignin removal efficiency significantly improved to 94.90%, with a reaction rate constant of 2.168 min-¹. Across the tested pH range (3 - 11), catalytic ozonation using ZnO/gravel demonstrated consistently high decolorization efficiency, ranging from 68.25% to 94.90%.
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