Production of N–Mg doped biochars for phosphate adsorption from renewable sources

Authors: MAINALI, KALIDAS - Oak Ridge Institute For Science And Education (ORISE); MOOD, SOHRAB - Washington State University; Mullen, Charles; Sarker, Majher; GARCIA-PEREZ, MANUEL - Washington State University

Submitted to: Biomass and Bioenergy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/10/2024
Publication Date: 4/16/2024
Citation: Mainali, K., Mood, S.H., Mullen, C.A., Sarker, M.I., Garcia-Perez, M. 2024. Production of N–Mg doped biochars for phosphate adsorption from renewable sources. Biomass and Bioenergy. 185:107221. https://doi.org/10.1016/j.biombioe.2024.107221.
DOI: https://doi.org/10.1016/j.biombioe.2024.107221

Interpretive Summary: In this study renewable resources have been used to develop low-cost adsorbents which can be used to remove phosphate (PO43-) from aqueous effluents. The presence of phosphate in effluents causes surface water pollution and algal blooms responsible for affecting freshwater quality, fishing industries and other socioeconomic activities. The scientists designed N-doped chars using two renewable C and N sources (Douglas fir and Chitosan) that were altered with magnesium metal (Mg) for PO43- adsorption. By the impregnation of metal, Mg-N doped tailored char was produced. The reaction parameters were optimized to maximize the phosphate adsorption capacity of the developed biochar. The developed char in this study displayed a 112.4 mg PO4-3/g char phosphate adsorption capacity which was comparable to the best chars described in the literature in terms of their ability to adsorb phosphate. This engineered biochar can potentially minimize water pollution where improved water quality will greatly reduce water treatment operating cost.

Technical Abstract: It is crucial for the environment, the economy, and society to create low-cost adsorbents from renewable resources to remove phosphate (PO43-) from aqueous effluents. Here, the scientists used two renewable C and N sources (Douglas fir and Chitosan) to produce engineered N-doped chars modified with Mg for PO43- adsorption. Mg-N doped engineered chars were prepared using an impregnation-carbonization process. A central composite experimental design was used to select combinations of independent variables to maximize phosphate adsorption capacity. Phosphate adsorption isotherms were fitted with Langmuir and Freundlich isotherms. The biochar produced at 700 C, 12 wt. % MgCl2, and Douglas Fir/Chitosan ratio: 1/1, showing the highest PO43- adsorption capacity, was further studied. Proximate analysis, elemental composition, surface area, pore size distribution, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy (FTIR), and Scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDX) were used to characterize this biochar. This char has an adsorption capacity of 112.4 mg PO43-/g char. Its phosphate adsorption rate was adjusted to a pseudo-second-order kinetic model. The phosphate adsorption capacity of the chars produced was comparable with the most effective chars reported in the literature.