Preparation of binder-less activated char briquettes from pyrolysis of sewage sludge for liquid-phase adsorption of methylene blue. (1st December 2021)

• Record Type: Journal Article
• Authors: Hu, Menghao; Deng, Wenyi; Hu, Mingtao; Chen, Guang; Zhou, Piren; Zhou, Yi; Su, Yaxin
• Is Part Of: Journal of environmental management. Volume 299(2021)
• Publication Date: 2021-12-01
• Subjects: Sewage sludge -- Activated char briquette -- Physical activation -- Methylene blue -- Adsorption -- Thermal regeneration; Environmental policy -- Periodicals; Environmental management -- Periodicals; Environment -- Periodicals; Ecology -- Periodicals; 363.705
• DOI: 10.1016/j.jenvman.2021.113601
• Languages: English
• ISSNs: 0301-4797

Abstract

Abstract: Binder-less activated char briquettes from sewage sludge were prepared and used for the liquid-phase adsorption of methylene blue. The properties of sludge char briquettes prepared under the different initial sludge moisture content, compression pressure, and heating rate were systematically investigated through the tests of thermogravimetric analysis (TGA), scanning electron microscopy (SEM), surface and mechanical properties, burn-off rates, methylene blue adsorption kinetics and isotherms. All of the prepared briquettes presented hierarchical structures and microporous/mesoporous characteristics, and the increase of initial sludge moisture content from 10 to 30 wt% resulted in a great increase of surface area ( S BET ), total pore volume ( V T ), apparent density, and a slight decrease of mechanical performance. The decrease of compression pressure markedly enhanced the equilibrium adsorption capacity ( q e, exp ), owing to the decreased diffusion resistance and blockage of diffusion pathways inside briquettes. In consideration of the mechanical performance and adsorption capacity, the optimum preparation condition was obtained at the initial moisture content of 30 wt%, compression pressure of 25 MPa, and heating rate of 10 °C/min, in which the axial compressive strength (ACS) and q e, exp of the prepared briquettes were as high as 22.2 ± 3.1 kg/m 2 and 316.9 mg/g. The results also showed that the equilibrium adsorption data fit well into the pseudo-first order model system, and the adsorption isotherms followed the Langmuir isotherm model, suggesting that the adsorption process was attributed to physical adsorption, and was inclined to happen on the adsorption sites with the same energy level. Finally, the thermal regeneration tests demonstrated that the binder-less briquette had a good regeneration performance and was worthy of reusing for industrial applications. Graphical abstract: Image 1 Highlights: Binder-less sludge briquettes showed a characteristic of hierarchical porous structures. Briquettes prepared with sludge of higher moisture content showed higher S BET . Briquettes prepared with sludge of lower moisture content showed higher mechanical performance. Briquettes maintained 90% of initial adsorption capacity after thermal regeneration for three times.