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Updated: Nov 26, 2025

Physical, Chemical and Biological Characterization of Six Biochars Produced for the Remediation of Contaminated Sites
Published on: November 28, 2014
Environmental-friendly coal gangue-biochar composites reclaiming phosphate from water as a slow-release fertilizer
Bing Wang1, Yuena Ma2, Xinqing Lee3
1College of Resource and Environmental Engineering, Guizhou University, Guiyang 550025, Guizhou, China; Key Laboratory of Karst Environment and Geohazard, Ministry of Natural Resources, Guiyang 550025, Guizhou, China; Guizhou Karst Environmental Ecosystems Observation and Research Station, Ministry of Education, Guiyang, Guizhou 550025, China.
Abstract:
To solve the problem of limited adsorption efficiency of pristine biochar for phosphate, a novel biochar composite was prepared from different feedstocks and coal gangue by one facile-step pyrolysis method. The effects of pyrolysis temperature, adsorbent dosage, pH of the solution, and coexisting ions on phosphate adsorption were analyzed. The adsorption performance and mechanism of phosphate in water were investigated. The application of the phosphorus-laden (P-laden) composite as slow-release fertilizer was evaluated by a germination test. The results showed that the maximum phosphate adsorption capacity of coal gangue modified oilseed rape straw biochar prepared at 700 °C (CG-OR700) was 7.9 mg/g at pH 4.0, which is 4.6 times that of pristine biochar. The adsorption process can be well fitted by the pseudo-second-order kinetic and Langmuir isotherm adsorption model. The mechanism of phosphate adsorption mainly includes surface precipitation, ligand exchange, and electrostatic attraction. The P-laden biochar can be used as a slow-release fertilizer to promote seed germination and growth. This study shows that the coal gangue modified biochar composite can not only be used to remove phosphate from wastewater, but also be used as a slow-release fertilizer, providing a new way for the phosphorus recovery and resource utilization of solid wastes.
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