In this work, the kinetics of the photocatalytic decolourization of methylene blue (MB) is investigated using different surface morphologies of multilayer TiO 2 coating onto a glass plate under irradiation from a 55-W household florescent lamp. A simple direct dip-coating technique was used, and the coating properties of TiO 2 powder were improved by adding epoxidized natural rubber (ENR) as an organic binder in the coating formulation. The effects of the fundamental parameters that govern the kinetics of the photocatalytic decolourization of MB, such as the mass of TiO 2 coated onto the glass plate, the pH and the TiO 2 surface morphology, were also studied. The kinetics of the MB decolourization in all cases was found to be pseudo-first-order kinetics and was fitted to the Langmuir-Hinshelwood model. The degraded part of the ENR binder led to generating pores within the surface of the TiO 2 /ENR film and converting it into porous form, as confirmed by SEM analysis. Furthermore, TGA, FTIR and leachability analyses were conducted to further confirm the depletion of the ENR from the TiO 2 /ENR film. The kinetics of the MB decolourization and the efficiency of the MB colour removal indicated that the porous TiO 2 /ENR film becomes approximately twice as fast as the non-porous TiO 2 /ENR film.

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Acid-treated banana peel (ATBP) was developed by H 2 SO 4 activation to be a potential adsorbent for methylene blue (MB) from aqueous solution. Batch mode adsorption studies were conducted by varying adsorbent dosage (0.02-0.30 g), solution pH (3-12), initial MB concentrations (10-300 mg/L) and contact time (0-1440 min). The adsorption data of MB by ATBP were in agreement with Langmuir isotherm, with maximum adsorption capacities of 250 mg/g at 303 K. The pseudo-first-order kinetic model best described the kinetic data. The adsorption of MB onto ATBP surface was endothermic in nature and spontaneous under the experimented conditions. Results supported the potential use of the ATBP as an effective adsorbent for the treatment of cationic dyes such as MB from aqueous solution. ARTICLE HISTORY

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A B S T R A C TFallen coconut leaves (CLs) are agricultural wastes largely available in Malaysia. In this study, we utilized CLs as a low-cost adsorbent for adsorptive removal of methylene blue (MB), a cationic dye from aqueous solution. Response surface methodology was employed to investigate the effects of operational parameters on MB removal efficiency. The investigated variables included adsorbent dosage (0.5-1.5 g/L), initial MB concentration (10-50 mg/L), initial solution pH (4-10), and agitation time (5-45 min). The analysis of variance was incorporated to test the adequacy of the model. The highest MB removal efficiency was achieved by simultaneous interactions between adsorbent dosage with pH, adsorbent dosage with agitation time, and pH with agitation time. Other simultaneous interactions showed lower effects. The optimum adsorbent dosage, initial MB concentration, initial solution pH, and agitation time were 1.26 g/L, 19.01 mg/L, 8.65, and 5.00 min, respectively. Under optimal conditions, high removal efficiency for MB was observed as 86.38%, and the equilibrium adsorption isotherms and kinetics were investigated. The Langmuir, Freundlich, and Temkin models of adsorption were used to analyze the experimental data. Pseudo-first-order and pseudo-second-order models were also employed to analyze the kinetic data obtained at different MB initial concentrations. The adsorption kinetics closely followed the pseudo-secondorder model. Based on the Langmuir model, the maximum adsorption capacity of MB on the CL surface was 112.35 mg/g at 27 ± 2˚C.