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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.

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

a b s t r a c tA sequence of organized precipitation test was conducted based on the Taguchi robust design so as to evaluate the best conditions for the preparation of Gd 2 (CO 3 ) 3 nano-particles in the absence of common additives like surfactants, templates or catalysts, indicating that the dimensions of the product nanoparticles can be manipulated merely through altering the parameters affecting the reaction. These parameters include the concentrations of Gd(III) and carbonate ions as well as the reactor temperature. The optimal reaction conditions led to the production of Gd 2 (CO 3 ) 3 nano-particles of 36 nm in average diameter, which were evaluated by scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FT-IR), thermogravimetric-differential thermal analysis, and UV-Vis spectrophotometry. Gd 2 (CO 3 ) 3 was further calcinated at 700°C to decompose into spherical Gd 2 O 3 nano-particles with average diameters below 25 nm, the formation of which was established by SEM, X-ray diffraction (XRD), and FT-IR techniques. In order to obtain the band gap energies of the fabricated carbonate and oxide nano-products, they were characterized by UV-Vis diffuse reflectance spectroscopy (DRS). Besides, the photocatalytic behaviors of the nano-products in degradation of methyl orange as a pollution of water were explored, and the results exhibited the efficacy of both products in eliminating of the organic pollutant.

a b s t r a c tIn this work, the potential of biomass waste, pomegranate (Punica granatum) peel (PP) as low cost adsorbent for adsorption of methylene blue (MB) from aqueous solution was studied. The physicochemical properties of PP were characterized using instrumental analyses such as CHNS-O analyzer, Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and point of zero charge (pH pzc ) analysis. Batch mode adsorption studies were conducted by varying operational parameters such as adsorbent dosage (0.02-0.16 g), solution pH 3-11, initial MB concentrations (50-300 mg/L), and contact time (0-390 min). The equilibrium data was found to better fit with Langmuir isotherm model compare to Freundlich model. The maximum adsorption capacity, q max of PP for MB was 200 mg/g at 303 K. The kinetic study revealed that the present system obeyed pseudo-second-order (PSO) model. The thermodynamic adsorption parameters, standard enthalpy (ΔH°), standard entropy (ΔS°), and standard free energy (ΔG°) showed that the adsorption of MB onto PP surface exothermic and spontaneous under the experimented conditions. All results mentioned above indicate that the PP can feasibly employ for the elimination of MB from aqueous solution.

In this study, coconut leaves were used as a starting material for the production of activated carbon by thermal carbonization using FeCl 3 -activation method. Dalam kajian ini, daun kelapa telah dipilih sebagai bahan pemula bagi penghasilan karbon teraktif melalui penkarbonan haba dengan menggunakan FeCl 3 sebagai agen pengaktif. Pencirian karbon teraktif (FAC) dianalisis dengan menggunakan mikroskop elektron imbasan (SEM), transformasi Fourier inframerah (FTIR) dan analisis elemen (CHNS-O). Beberapa parameter yang mempengaruhi penyahwarnaan metilena biru pada suhu 303 K seperti dos bahan penjerap (0.02-0.25 g), pH awal (3-11), kepekatan (30-350 mg/L) dan masa (0-180 min) telah dikaji dan dioptimumkan dengan menggunakan

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