Optimization of photocatalytic decolorization of lignin in water matrix using immobilized nano-TIO2 catalyst by Box-Behnken design of experiment

• Main Authors: Belmonte, Beatriz Avellana, Estrellan, Carl Renan
• Format: text
• Published: Animo Repository 2012
• Subjects: Lignin; Photocatalysis; Water—Purification—Photocatalysis; Chemical Engineering
• Online Access: https://animorepository.dlsu.edu.ph/faculty_research/5097
• Institution: De La Salle University

Wood in paper manufacturing consists of lignin which is hard to biodegrade and responsible for the intense brown color of the wastewater. The objective of the study is to optimize the operational parameters which would result in the highest photocatalytic efficiency for the decolorization of lignin in water using nano-titania catalyst immobilized on microscopy glass plates. Three-variable and three level Box-Behnken design was the optimization technique that was employed. The different parameters investigated and used as independent variables were initial Ph of the solution (3, 5, 7), initial lignin concentration (60, 80, 100 ppm) and oxygen flowrate (20, 50, 80 mL/min). The response was the photocatalytic efficiency which was expressed as the amount of lignin decolorized per unit weight of catalyst per unit time (ppm/mg cat-hr). The catalyst loading and irradiation time were fixed at 0.13g/L and 6 hours respectively. The design-expert 7.1.5 software was used to determine the optimum conditions of the variables which would result in the most desirable response value. The optimum values of the parameters were found to be 3 for initial pH, 100 PPM for initial lignin concentration and 80 mL/min for oxygen flowrate. The response was 0.116 ppm/mg cat-hr. The experimental data obtained were analyzed by the response surface regression procedure with the aid of design-expert software and a fitted linear model that represents the relationship between the response and the input variables was generated. When the optimum values of the parameters were applied to actual lignin-containing wastewater from the partner recycling paper mill, the values of the experimental and predicted response were in good agreement. Furthermore, the port characterization of the catalyst in terms of surface morphology, element composition, crystallite phase and size, and surface area revealed that the good properties of the immobilized nano-titania catalyst were preserved after its utilization to the photocatalytic treatment of lignin in actual wastewater.