New lotus leaf biochar shows promise for cleaning toxic beryllium from mining wastewater

Beryllium is valued for its light weight, strength, and heat resistance, making it important in aerospace, alloys, optics, and other advanced industries. But when beryllium enters wastewater during mining and processing, it can pose serious risks to ecosystems and human health. Long-term exposure to beryllium can damage the lungs and other organs, while beryllium-containing waste may threaten soil and water environments.

Researchers have developed a new biochar material made from lotus leaves that can efficiently remove beryllium from simulated mining wastewater. The study, published in Biochar, reports that the material, called modified lotus leaf biochar, or MLLB, combines a porous carbon structure with phosphate and ammonium functional groups that strongly attract and immobilize beryllium.

“Beryllium mining wastewater is difficult to treat because it contains many other ions that can interfere with removal,” said corresponding author Fang Hu. “Our goal was to design a biochar that is not only efficient, but also selective for beryllium under realistic wastewater conditions.”

Lotus leaves are widely available agricultural waste in China. In this study, the team used lotus leaf powder as the starting material, treated it with dilute ammonia, added phosphoric acid and calcium hydroxide, and then heated the mixture to produce a porous biochar. This modification introduced multiple active groups, including phosphate, ammonium, and hydroxyl groups, onto the biochar surface.

Tests showed that the material removed beryllium rapidly and effectively. Under optimized conditions, MLLB achieved a beryllium adsorption capacity of 40.38 g kg−1 at 35 °C and pH 5.5. The adsorption process reached equilibrium within about two hours, with removal efficiency as high as 99%. The process was spontaneous and endothermic, meaning that beryllium was naturally favored to bind to the material and that higher temperatures promoted adsorption.

A key challenge in mining wastewater treatment is selectivity. Wastewater often contains other ions, including zinc, manganese, uranium, magnesium, calcium, and potassium, which may compete for adsorption sites. In simulated wastewater containing these ions, MLLB still maintained 97 to 99% beryllium removal. Its distribution coefficient for beryllium reached 2.6 × 10⁴ mL g−1, higher than those of the competing ions, indicating strong selective adsorption.

“Selectivity is especially important for practical wastewater treatment,” Hu said. “The material must still work when other metal ions are present. Our results show that the phosphate and ammonium groups help MLLB capture beryllium preferentially.”

The researchers also investigated how the material works. Scanning electron microscopy showed that the modified biochar had many pores, providing more surface area for adsorption. X-ray diffraction, Fourier-transform infrared spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy confirmed that beryllium was fixed mainly through surface complexation and precipitation. The captured beryllium formed products such as Be(OH)₂ and Be(NH₄)PO₄ on the biochar surface.

The material also showed potential for reuse. When sodium hydroxide was used as the eluent, MLLB maintained more than 80% adsorption efficiency after five adsorption and desorption cycles, while desorption efficiency remained around 90%.

Although further testing with real wastewater and scale-up studies will be needed, the findings suggest that agricultural waste-derived biochar could offer an effective and recyclable tool for controlling beryllium pollution.

“This work turns lotus leaf waste into a functional material for environmental protection,” Hu said. “It provides a promising route for reducing beryllium exposure during mining and improving the sustainability of wastewater treatment.”

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Journal Reference: Zhao, X., Wang, Q., Sun, Y. et al. Beryllium adsorption from beryllium mining wastewater with novel porous lotus leaf biochar modified with PO₄³⁻/NH₄⁺ multifunctional groups (MLLB). Biochar 6, 89 (2024).   

https://doi.org/10.1007/s42773-024-00385-4  

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About Biochar

Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field. 

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