Journal of Water and Wastewater; Ab va Fazilab (in persian)

Journal of Water and Wastewater; Ab va Fazilab (in persian)

Comparative Study of the Adsorption Efficiency of Carbon Nanotubes and Biochar in the Removal of Crystal Violet Dye from Aqueous Solution

Articles in Press

Document Type : Research Paper

Authors
Shahriar Mahdavi 1
Mohammad Taghi Mohajer 2
Masome Naseri Tekyeh 3
1 Assoc. Prof., Dept. of Soil Science and Engineering, Faculty of Agriculture, Malayer University, Malayer, Iran
2 MSc. Student, Dept. of Soil Science and Engineering, Faculty of Agriculture, Malayer University, Malayer, Iran
3 Postdoctoral Researcher, Dept. of Soil Science and Engineering, Faculty of Agriculture, Malayer University, Malayer, Iran
10.22093/wwj.2026.550885.3517
Abstract
Organic dyes such as Crystal Violet represent persistent and toxic pollutants in industrial wastewaters, underscoring the urgent need for efficient removal methods. This study investigates the performance of two adsorbents-carbon nanotubes and biochar-in removing Crystal Violet dye. FESEM and EDS analyses were employed to identify the morphology and chemical composition of the adsorbents. The average particle size was determined to be 26.32 nm for carbon nanotubes and 72.09 nm for high-purity biochar. Adsorption experiments were conducted under various conditions of adsorbent dosage, contact time, and temperature, and the optimum adsorbent dose and equilibrium time were determined to be 1 g/L and 90 min, respectively. Increasing the adsorbent dosage resulted in a decrease in specific adsorption capacity due to a reduced ratio of dye molecules to available active sites and particle agglomeration. Adsorption isotherm analysis revealed that the Freundlich model for carbon nanotubes and the Temkin model for biochar provided the best fit to the experimental data, and the extracted qmax values confirmed the high adsorption capability of both adsorbents, while pH showed no significant influence on the adsorption process. Kinetic and thermodynamic investigations indicated that adsorption was mainly governed by intraparticle diffusion, was spontaneous and endothermic in nature, and involved an increase in surface randomness, which was further supported by FESEM images and EDS analysis confirming effective dye attachment on the adsorbent surfaces. The findings of this study demonstrate that both carbon nanotubes and biochar exhibit high potential for the removal of organic dyes, with the intraparticle diffusion mechanism playing a key role in the adsorption process. Moreover, the good agreement of the Freundlich and Temkin models with the experimental data indicates the heterogeneous nature of the adsorbent surfaces.
Keywords
Carbon nanotubes
biochar
Crystal Violet
Adsorption
Kinetic model
Adsorption isotherm
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Journal of Water and Wastewater; Ab va Fazilab (in persian)

Articles in Press, Accepted Manuscript
Available Online from 11 August 2025