Effective adsorption of Direct Red 23 by sludge biochar-based adsorbent: adsorption kinetics, thermodynamics and mechanisms study

• Published in: Water science and technology Vol. 83; no. 10; pp. 2424 - 2436
• Main Authors: Jiang, Ruqing, Yu, Guangwei, Ndagijimana, Pamphile, Wang, Yu, You, Futian, Xing, Zhenjiao, Wang, Yin
• Format: Journal Article
• Language: English
• Published: London IWA Publishing 15.05.2021
• Subjects: Adsorbents; Adsorption; adsorption kinetics; Charcoal; Chemical oxygen demand; direct red 23; Dyes; Energy consumption; Hydrothermal treatment; Kinetics; mechanism; Pollutant removal; Pollutants; Pyrolysis; Sludge; sludge biochar-based adsorbent; Textile industry; thermodynamic; Wastewater; Water pollution; Water treatment; United States > US
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2021.126

Abstract Using solid adsorbents, such as biochar, has been a potential practice to remove the pollutants from water bodies to render the water safer for potential usage. A potential application of sludge biochar-based adsorbent (SBA), obtained by pyrolysis with hydrothermal treatment, was developed to adsorb Direct Red 23 (DR23) from wastewater. The results showed that for the synthesized SBA (0.5 g/L) in the adsorption of DR23 at low concentration (<20 mg/L), the DR23 was totally removed from the aqueous solution. pH had a limited effect on the adsorption, while an increase in temperature was shown to have a large enhancing effect. The adsorption kinetics were best fitted by the pseudo-second-order kinetic model, while the equilibrium data were best fitted by the Langmuir isotherm. A maximum saturation adsorption capacity of SBA of 111.98 mg/g was achieved. SBA could then be regenerated by pyrolysis, and after three cycles, SBA still retained good adsorption ability for DR23, a removal rate exceeding 97% was achieved. Functional groups, pores, π-π bond, and electrostatic interactions are the key to the adsorption mechanisms. The results proved that SBA would be a promising material in the application of removing dyes in printing and dyeing wastewater.