Page 197 - AJWEP-22-4

Bombax ceiba-based carbons for dye removal

2. Materials and methods corresponding to the decomposition of hemicellulose,
cellulose, and partially degraded lignin components.
1,11
2.1. Materials and reagents Based on this thermal behavior, 400°C was selected
All chemicals used in this study were of analytical as the carbonization temperature, offering a favorable
reagent grade and employed without further purification. compromise between carbon yield, thermal stability,
H PO (85%) was obtained from Fisher Scientific (India), and porosity development for effective activation.
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3
while potassium KOH (pellets) and Na CO (anhydrous)
3
2
were procured from Merck (Merck Specialties Pvt. Ltd., 2.2.3. Chemical activation and carbonization
India). These three chemicals served as activating agents ACs were prepared using three different chemical
for the synthesis of biomass-derived AC. activating agents – an acid (H PO ), a base (KOH),
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3
RhB (≥98%), used as the model dye pollutant, was and a salt (Na CO ) – to produce samples designated
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3
purchased from Alfa Aesar (product code: A13572; as Bc-H, Bc-K, and Bc-Na, respectively. A 1:1 weight
Haverhill, USA). Aqueous ammonia (30%) from Baker ratio of dried B. ceiba wood powder to the activating
(J.T. Baker, USA) was used to adjust the solution pH agent was maintained. The biomass was impregnated
during adsorption studies. All aqueous solutions were by soaking in the respective chemical solution for
prepared using double-distilled water to minimize approximately 12 h to allow thorough interaction, after
interference from residual ions or impurities. which the samples were subsequently oven-dried at
The raw biomass precursor, B. ceiba wood dust 110°C to remove residual moisture.
(locally known as “Simal” in Nepal), was collected The dried, impregnated material was then subjected
as waste from a sawmill in Kathmandu, Nepal. This to carbonization in a horizontal tubular furnace at the
lignocellulosic byproduct, selected for its abundance optimized temperature of 400°C (as determined by
and underutilization, was first washed thoroughly with TGA/DSC), with a heating rate of 10°C/min. The final
distilled water to remove surface contaminants, then temperature was maintained for 3 h under a continuous
sun-dried and sieved to achieve a uniform particle size flow of nitrogen gas (100 mL/min) to ensure an inert
suitable for activation and carbonization. atmosphere throughout the process.
This one-step chemical activation and carbonization
2.2. Preparation of ACs method facilitated the formation of porous carbon
2.2.1. Pre-treatment of biomass structures with distinct physicochemical properties,
The B. ceiba wood dust was first washed with distilled largely influenced by the type of activating agent
water to remove surface dust, debris, and water-soluble used. 2,12
impurities. The cleaned material was then sun-dried
for 2 – 3 days and subsequently oven-dried at 110°C 2.2.4. Post-treatment
for 24 h to eliminate residual moisture and volatiles. Following carbonization, the resulting black solids
After drying, the biomass was finely ground and sieved were allowed to cool naturally under a continuous
through a 150 µm mesh to obtain a uniform particle nitrogen flow. Each sample – Bc-H, Bc-K, and Bc-Na
size, ensuring consistency during chemical activation – was thoroughly washed with double-distilled water
and carbonization. until the filtrate reached neutral pH (~7.0), ensuring
The impregnation ratio of biomass to activating the removal of residual activating agents and soluble
agent was fixed at 1:1, based on prior optimization byproducts. The cleaned materials were then oven-dried
trials in which ratios such as 1:2, 2:1, 1:0.5, and 0.5:1 at 110°C, finely ground into a fine powder, and stored
were evaluated. Among these, the 1:1 ratio consistently in airtight containers for subsequent characterization
yielded the most favorable balance between surface and adsorption experiments. Table 1 summarizes the
area development and RhB adsorption efficiency across preparation parameters for the chemically AC samples
different activating agents. synthesized from B. ceiba wood dust.

2.2.2. Thermogravimetric (TG) and DSC analysis for 2.3. Adsorption experiments
carbonization optimization Batch adsorption experiments were conducted to
To determine the optimal carbonization temperature, evaluate the efficiency of AC samples – Bc-H, Bc-K,
TGA coupled with DSC was performed on raw B. ceiba and Bc-Na – in removing RhB from aqueous solutions.
wood powder. The thermal degradation profile revealed A 20 ppm stock solution of RhB was prepared by
significant mass loss between 200°C and 400°C, dissolving 20 mg of the dye in 1 L of double-distilled

Volume 22 Issue 4 (2025) 189 doi: 10.36922/AJWEP025240191