Exploring the Potential of Biochar as Desiccant: Comparison of Sodium Hydroxide and Sulfuric Acid Impregnation Effect on Moisture Uptake
DOI:
https://doi.org/10.48048/tis.2026.12201Keywords:
Biochar, Desiccant, NaOH, H2SO4, Water vapor adsorption, Moisture, DesorptionAbstract
The development of sustainable and low-cost desiccants is imperative for advancing moisture control technologies. The present study investigated the effect of NaOH and H2SO4 impregnation at various concentrations and impregnation times on rice husk char (RHC) and coconut shell char (CSC). The samples were characterized using SEM-EDX, BET-BJH, and FTIR analyses, and their water vapor uptake was evaluated through adsorption–desorption experiments. NaOH impregnation, particularly at 6.0 N for 8 h, markedly enhanced adsorption by promoting pore development and introducing polar oxygenated groups. RHC exhibited the highest capacity of 0.515 g/g, while CSC demonstrated moderate improvement primarily through surface functionalization. In contrast, H2SO4 treatment generated oxygenated and sulfur-containing groups but suppressed pore formation, thereby lowering performance, particularly in CSC. Both adsorption and desorption kinetics followed the pseudo-second-order (PSO) model, while the sorption isotherms were best described by the Henderson model. Desorption analysis revealed activation energies for NaOH-impregnated RHC and CSC (123.8 and 94.9 kJ/mol). Overall, NaOH-treated RHC demonstrated superior adsorption and structural properties, indicating its potential as a renewable desiccant material requiring optimized regeneration efficiency.
HIGHLIGHTS
- NaOH impregnation (6.0 N, 8 h) markedly improved water vapor uptake of rice husk char (0.515 g/g) by promoting pore development and introducing polar oxygenated groups.
- H2SO4 impregnation functionalized the surface with oxygenated and sulphur groups but suppressed pore formation, resulting in lower adsorption capacity, especially in CSC.
- Adsorption-desorption kinetics followed the pseudo-second-order (PSO) model.
- Desorption analysis revealed high activation energies (123.8 kJ/mol for RHC, 94.9 kJ/mol for CSC).
GRAPHICAL ABSTRACT
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