Page 198 - AJWEP-22-4

Shrestha

Table 1. Summary of preparation parameters for This systematic approach enabled the optimization
chemically activated carbons of adsorption parameters and provided a comparative

Parameter Condition evaluation of the dye removal performance of the ACs
Biomass precursor Bombax ceiba (Simal) synthesized with different chemical agents.
wood dust
Particle size 100 µm 2.4. Characterization techniques of AC samples
characterization
physicochemical
Comprehensive
Activating agents Phosphoric acid (Bc-H), was conducted to evaluate their thermal behavior,
potassium hydroxide morphology, crystallinity, functional groups, structural
(Bc-K), and sodium
carbonate (Bc-Na) disorder, and surface textural properties of the raw
Impregnation ratio 1:1 (w/w) biomass and synthesized AC samples, all of which are
critical for understanding their adsorption performance.
Impregnation time Overnight (~12 h)
Pre-drying temperature 110°C 2.4.1. Thermal analysis
Carbonization temperature 400°C TGA and DSC were performed using an SDT Q600
Carbonization duration Three hours V20.9 Build 20 system (TA Instruments, USA) to
Atmosphere Nitrogen gas (inert) analyze the pyrolytic behavior of sieved wood powder
Final drying 110°C of (raw) B. ceiba wood dust and to determine the optimal
carbonization temperature.

water. To optimize experimental parameters, 2.4.2. Morphological characterization
preliminary tests were carried out at varying initial dye The surface morphology and porosity of the AC
concentrations (above and below 20 ppm) and at pH samples were examined using SEM (Nanoeyes
values of 3.5, 6.5, 8.5, and 10.5. Based on these trials, SEM, South Korea) to observe surface texture, pore
20 ppm dye concentration and pH 8.5 were found to development, and particle structure.
yield the highest removal efficiency and were selected
for subsequent kinetic and comparative studies. 2.4.3. Phase analysis
For each batch adsorption test, 100 mL of the dye The structural order of the carbon samples was assessed
solution was transferred to a 250 mL Erlenmeyer flask, through XRD using a Rigaku RINT 2000 Diffractometer
followed by the addition of 0.02 g of AC. The mixture (Rigaku Corporation, Japan). Broad diffraction peaks
was stirred at 400 rpm for 10 min using a magnetic were analyzed to distinguish amorphous features and
stirrer, under ambient conditions, at the optimized pH. crystalline tendencies.
During adsorption, 3 mL aliquots were withdrawn at
2-min intervals (0, 2, 4, 6, 8, and 10 min), transferred 2.4.4. Functional group identification
to microcentrifuge tubes, and centrifuged for 5 min to Fourier transform infrared spectroscopy was carried out
separate the carbon particles. The supernatants were using a Bruker Vertex 70 (Bruker, Germany) to identify
analyzed using an ultraviolet-Vis spectrophotometer surface functional groups. Spectra were recorded
(SCINCO Mega-2100, double beam, SCINCO, in the 4,000 – 400 cm range with a resolution of
−1
South Korea) to measure the residual RhB concentration. 4 cm , highlighting oxygenated functionalities such as
−1
To investigate the effect of adsorbent dosage, the hydroxyl, carboxyl, phosphate, and ether groups.
experiment was repeated using different carbon masses
(0.02 g, 0.025 g, 0.03 g, and 0.035 g). The influence of 2.4.5. Structural disorder evaluation
solution pH on adsorption efficiency was also assessed Raman spectroscopy (LabRAM HR800, Jobin Yvon,
by conducting tests at the same pH values used in the Jobin Yvon, France), with a 532 nm excitation laser, was
preliminary trials. The percentage of dye removed was used to evaluate structural disorganization in the carbon
calculated using the following formula in Equation I: samples. The intensity ratio of the D and G bands was
% Removal = (Co−Ce)/Co × 100% (I) used to quantify graphitic defects and amorphous content.

where Co is the initial dye concentration (mg/L), and 2.4.6. Textural properties
Ce is the equilibrium dye concentration after adsorption The BET method was employed using a Micromeritics
(mg/L). ASAP 2020 system (Micromeritics Instrument

Volume 22 Issue 4 (2025) 190 doi: 10.36922/AJWEP025240191