Guaya Diana, Piedra Camilo, Carmona Inmaculada
Department of Chemistry, Universidad Técnica Particular de Loja, Loja 110107, Ecuador.
Chemical Engineering School, Universidad Técnica Particular de Loja, Loja 110107, Ecuador.
Molecules. 2025 Jul 2;30(13):2842. doi: 10.3390/molecules30132842.
Valorizing agro-industrial waste into functional materials for environmental remediation and resource recovery is essential for advancing circular economy models. This study presents a novel closed-loop strategy to convert annatto () seed residues into biochar for phosphate recovery from aqueous solutions and real agro-industrial wastewater. A novel ternary modification with Fe, Zn, and Mn metals was applied to enhance the phosphate adsorption performance of the biochar. Materials were synthesized via pyrolysis at 600 °C and 700 °C, with ABC-M700 exhibiting the highest performance. Comprehensive characterization (FTIR, SEM-EDS, and XRF) confirmed the successful incorporation of metal (oxy)hydroxide functional groups, which facilitated phosphate binding. Adsorption studies revealed that ABC-M700 achieved a maximum phosphate removal capacity of 6.19 mg·g, representing a 955% increase compared to unmodified ABC-N700 (0.59 mg·g), and a 31% increase relative to ABC-M600 (4.73 mg·g). Physicochemical characterization indicated increased surface area, well-developed mesoporosity, and the formation of metal (oxy)hydroxide functionalities. ABC-M700 achieved a maximum adsorption capacity of 73.22 mg·g and rapid kinetics, removing 95% of phosphate within 10 min and reaching equilibrium at 30 min. The material exhibited notable pH flexibility, with optimal performance in the range of pH 6-7. Performance evaluations using real wastewater from the same agro-industry confirmed its high selectivity, achieving 80% phosphate removal efficiency despite the presence of competing ions and organic matter. Phosphate fractionation revealed that 78% of adsorbed phosphate was retained in stable, metal-associated fractions. Although the material showed limited reusability, it holds potential for integration into nutrient recycling strategies as a slow-release fertilizer. These findings demonstrate a low-cost, waste-derived adsorbent with strong implications for circular economy applications and sustainable agro-industrial wastewater treatment. This study establishes a scalable model for agro-industries that not only reduces environmental impact but also addresses phosphorus scarcity and promotes resource-efficient waste management.
将农业工业废弃物转化为用于环境修复和资源回收的功能材料对于推进循环经济模式至关重要。本研究提出了一种新颖的闭环策略，将胭脂树籽残渣转化为生物炭，用于从水溶液和实际农业工业废水中回收磷。采用了一种新型的铁、锌和锰金属三元改性方法来提高生物炭对磷的吸附性能。材料通过在600℃和700℃下热解合成，其中ABC-M700表现出最高的性能。综合表征（傅里叶变换红外光谱、扫描电子显微镜-能谱和X射线荧光光谱）证实了金属（羟基）氧化物官能团的成功引入，这促进了磷的结合。吸附研究表明，ABC-M700的最大磷去除容量为6.19mg·g，与未改性的ABC-N700（0.59mg·g）相比增加了955%，相对于ABC-M600（4.73mg·g）增加了31%。物理化学表征表明其表面积增加、中孔结构发达以及形成了金属（羟基）氧化物官能团。ABC-M700的最大吸附容量为73.22mg·g且动力学迅速，在10分钟内去除了95%的磷，并在30分钟时达到平衡。该材料表现出显著的pH灵活性，在pH 6-7范围内性能最佳。使用来自同一农业工业的实际废水进行的性能评估证实了其高选择性，尽管存在竞争离子和有机物，仍实现了80%的磷去除效率。磷分级显示，78%的吸附磷保留在稳定的、与金属相关的组分中。尽管该材料的可重复使用性有限，但作为缓释肥料，它在整合到养分循环策略方面具有潜力。这些发现证明了一种低成本、源自废弃物的吸附剂，对循环经济应用和可持续农业工业废水处理具有重要意义。本研究为农业工业建立了一个可扩展的模型，该模型不仅减少了环境影响，还解决了磷短缺问题，并促进了资源高效的废物管理。
