Preparation and Application of Efficient Biobased Carbon Adsorbents Prepared from Spruce Bark Residues for Efficient Removal of Reactive Dyes and Colors from Synthetic Effluents

• Main Authors: Glaydson Simões dos Reis, Sylvia H. Larsson, Mikael Thyrel, Tung Ngoc Pham, Eder Claudio Lima, Helinando Pequeno de Oliveira, Guilherme L. Dotto
• Format: Article
• Language: English
• Published: MDPI AG 2021-06-01
• Series: Coatings
• Subjects: biobased carbon materials; meso- and microporous carbons; dye adsorption; chemical adsorption; electrostatic interactions
• Online Access: https://www.mdpi.com/2079-6412/11/7/772

Biobased carbon materials (BBC) obtained from Norway spruce (Picea abies Karst.) bark was produced by single-step chemical activation with ZnCl₂ or KOH, and pyrolysis at 800 °C for one hour. The chemical activation reagent had a significant impact on the properties of the BBCs. KOH-biobased carbon material (KOH-BBC) had a higher specific surface area (S_BET), equal to 1067 m² g⁻¹, larger pore volume (0.558 cm³ g⁻¹), more mesopores, and a more hydrophilic surface than ZnCl₂-BBC. However, the carbon yield for KOH-BBC was 63% lower than for ZnCl₂-BBC. Batch adsorption experiments were performed to evaluate the ability of the two BBCs to remove two dyes, reactive orange 16 (RO-16) and reactive blue 4 (RB-4), and treat synthetic effluents. The general order model was most suitable for modeling the adsorption kinetics of both dyes and BBCs. The equilibrium parameters at 22 °C were calculated using the Liu model. Upon adsorption of RO-16, Q_max was 90.1 mg g⁻¹ for ZnCl₂-BBC and 354.8 mg g⁻¹ for KOH-BBC. With RB-4, Qmax was 332.9 mg g⁻¹ for ZnCl₂-BBC and 582.5 mg g⁻¹ for KOH-BBC. Based on characterization and experimental data, it was suggested that electrostatic interactions and hydrogen bonds between BBCs and RO-16 and RB-4 dyes played the most crucial role in the adsorption process. The biobased carbon materials showed high efficiency for removing RO-16 and RB-4, comparable to the best examples from the literature. Additionally, both the KOH- and ZnCl₂-BBC showed a high ability to purify two synthetic effluents, but the KOH-BBC was superior.