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. 2025 Jun 18;30(12):2633.
doi: 10.3390/molecules30122633.

Preparation of Biochars from Different Sources and Study on Their Phosphorus Adsorption Properties

Yinlong Shao  1 , Anqi Hu  2 , Yongcan Jiang  1   3 , Xianbiao Wang  1 , Jingchen Li  4 , Guanglong Liu  2
Affiliations

Preparation of Biochars from Different Sources and Study on Their Phosphorus Adsorption Properties

Yinlong Shao et al. Molecules. .

Abstract

Biochar is a solid product generated through the pyrolysis of biomass materials under anaerobic or hypoxic conditions, and it is characterized by its strong adsorption capacity. To investigate the phosphorus adsorption performance of biochar derived from wheat straw, bamboo, and water hyacinth in wastewater, iron modification treatments were applied to these biochars, and the most effective modified biochar was identified. The physicochemical properties of the modified biochars were characterized using Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and scanning electron microscopy (SEM). The results showed that optimal modification was achieved with an iron-carbon mass ratio of 0.70 for wheat straw biochar (Fe-WBC) and 0.45 for both bamboo biochar (Fe-BBC) and water hyacinth biochar (Fe-HBC). The maximum phosphorus adsorption capacities of the three modified biochars were as follows: 31.76 mg g-1 (Fe-WBC) > 27.14 mg g-1 (Fe-HBC) > 25.31 mg g-1 (Fe-BBC). It was demonstrated that the adsorption behavior of Fe-BBC was predominantly multi-molecular layer adsorption, whereas the adsorption behavior of Fe-WBC and Fe-HBC was primarily monolayer adsorption. All three types of modified biochars reached adsorption equilibrium within 30 min, with Fe-WBC exhibiting the best adsorption performance. Analysis revealed that the modified biochars contained a large number of unsaturated C bonds and aromatic rings, indicating relatively stable structures. The surfaces of the modified biochars were rich in hydroxyl and carbonyl groups, which contributed to their strong adsorption properties. Post-modification analysis indicated that iron in the biochars predominantly existed in forms such as goethite (FeOOH) and hematite (Fe2O3). The iron content in each type of modified biochar constituted approximately 3.08% for Fe-WBC, 5.94% for Fe-BBC, and 5.68% for Fe-HBC relative to their total elemental composition. Overall, the iron-modified biochars employed in this study significantly enhanced the adsorption capacity and efficiency for phosphorus removal in wastewater.

Keywords: adsorption; biochar; iron oxide; modification; phosphorus.

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Conflict of interest statement

Authors Yinlong Shao, Yongcan Jiang and Xianbiao Wang were employed by the company PowerChina Huadong Engineering Corporation Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Comparison of phosphorus adsorption capacity of modified biochar with different iron–carbon ratios.
Figure 2
Figure 2
Langmuir (a) and Freundlich (b) isothermal adsorption lines and pseudo-first-order (c) and pseudo-second-order (d) kinetic fitting curves for phosphorus of three modified biochar.
Figure 3
Figure 3
FTIR and XRD spectra of three kinds of biochar before and after modification.
Figure 4
Figure 4
SEM and EDS spectra of three kinds of biochar before and after modification.
See this image and copyright information in PMC

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