Sulphuric acid (H₂SO₄) was utilized as an activator for the preparation of activated carbon from a biomass solid waste, coconut leaves. The sulphuric acid-treated activated carbon (SAC) was used as low-cost adsorbent for the removal of methylene blue (MB) cationic dye from aqueous solution. Adsorption of MB using SAC from aqueous solution under equilibrium and kinetic conditions in batch mode was evaluated by varying adsorbent dose (0.2–2.5 g/L), solution pH (3–11), initial dye concentration (30–400 mg/L), contact time (0–180 min) and temperature (303–323 K). The Langmuir isotherm model showed better fit to the equilibrium data than the Freundlich model. The adsorption capacity (q_m) of SAC increased with temperature where q_m varied as follows: 126.9 (303 K), 137.0 (313 K) and 149.3 mg/g (323 K). The kinetic uptake results were well described by the pseudo-second-order (PSO) kinetic for each temperatures. The thermodynamic adsorption parameters (∆G°, ∆H° and ∆S°) were driven by favourable entropic factors, in accordance with the low activation energy (29.70 kJ/mol) of the system. This study reveals that SAC is an effective and low-cost adsorbent for the removal of MB from aqueous solution.

Mesoporous-activated carbon was prepared from fallen coconut (Cocos nucifera) leaf, an agricultural waste through a microwave-induced H₃PO₄ activation process. The characterization of the coconut leaf–activated carbon (CAC) was evaluated through the iodine number, ash content, bulk density, and moisture content. Fourier transform infrared spectroscopy, scanning electron microscope, Brunauer–Emmett–Teller (BET) surface area, X-ray diffraction, and pH_PZC. CAC has a mesopore content of 84% with an average pore size of 36.5 Å and a large BET surface area of 632 m²/g. The uptake properties of the CAC with methylene blue was evaluated at different CAC dosage levels (0.2–10 g/L), initial pH (3–10), methylene blue concentration (50–350 mg/L), and time (0–360 min) using batch mode operation. The kinetic profiles were described by the pseudo-second-order kinetics. The equilibrium data were well fitted to the Langmuir model with a maximum monolayer adsorption capacity of 250 mg/g at 30°C. Thermodynamic functions indicate a spontaneous and exothermic nature of the adsorption process. This study indicates that coconut leaves are a promising renewable precursor that can be utilized to develop an efficient mesoporous-activated carbon.

Fallen coconut leaves (CLs) are agricultural wastes largely available in Malaysia.In this\ud 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\ud achieved by simultaneous interactions between adsorbent dosage with pH, adsorbent dosage\ud 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\ud CL surface was 112.35 mg/g at 27 ± 2˚C

In this paper, fallen coconut (Cocos nucifera) leaves were used as precursors to prepare activated carbon by thermal carbonization using KOH-activation method. The physical properties of the prepared coconut leaves-activated carbon (KAC) were calculated through the bulk density, ash content, moisture content, and iodine number. The surface characterization of KAC was undertaken using Scanning Electron Microscopy, Fourier Transform Infrared, and point of zero charge (pH_PZC) method. Batch mode experiments were performed to assess the influence of the adsorbent dose (0.02–0.25 g), initial pH (3–11), initial dye concentration (30–400 mg/L), contact time (5–300 min), and temperature (303–323 K) on the adsorption of the methylene blue (MB). The kinetic uptake profiles are well described by the pseudo-second-order model, while the Langmuir model describes the adsorption behavior at equilibrium. The adsorption capacity (q_m) of KAC increased with temperature where q_m varied as follows; 147.1 (303 K), 151.5 (313 K), and 151.5 mg/g (323 K). Thermodynamic parameters such as standard enthalpy (∆H°), standard entropy (∆S°), and standard free energy (∆G°) showed that the adsorption of MB onto KAC was spontaneous and endothermic in nature under examined conditions. The results showed the potential use of activated carbon developed from waste coconut leaves for the removal of cationic dye (MB).