CIEPQPF, Department of Chemical Engineering, Faculty of Sciences and Technology, University of Coimbra, Pólo II, Rua Sílvio Lima, 3030-790, Coimbra, Portugal.
CIEPQPF, Department of Chemical Engineering, Faculty of Sciences and Technology, University of Coimbra, Pólo II, Rua Sílvio Lima, 3030-790, Coimbra, Portugal; UNIPAMPA, Federal University of Pampa, Campus Bagé, RS, Brazil.
J Environ Manage. 2019 May 15;238:451-459. doi: 10.1016/j.jenvman.2019.03.015. Epub 2019 Mar 13.
Phosphorus scarcity has become a significant issue in the European Union (EU) during 21st Century, due to its relevance as an irreplaceable macronutrient for life, and because of the total dependency of EU regarding imports. This work aims to evaluate the phosphorus recovery by adsorption in batch and fixed-bed column, using a thermally modified eggshell as an adsorbent. The screening phase revealed that calcined eggshell at 700 °C (CES700) is the most suitable material compared with the other thermally modified eggshells tested. Thus, CES700 was characterized regarding the specific surface area, pore volume, zero-point charge pH, total dissolved solids and organic matter. The influence of pH and adsorbent dosage was investigated in batch conditions. Langmuir-Freundlich model described the equilibrium data and the maximum adsorption capacity was about 39 mg P-PO/g. The kinetics follows a pseudo-first order model, with constants between 0.063 and 0.224 min. Fixed-bed studies indicated that increasing fluid superficial velocity and feed concentration led to an early saturation of the adsorbent. Yoon-Nelson, Thomas and Bohard-Adams empirical models properly adjusted the breakthrough curves with R ≥ 0.98. Germination tests using CES700 loaded with phosphate revealed a germination index of 120 and 124% to 48 and 72 h, respectively. CES700 is statically better than the other tested materials, which opens the possibility of its use as fertilizer. This study showed that the developed material, CES700, can be applied in batch or fixed-bed processes to recover phosphate ions from liquid effluents, and the loaded adsorbent has potential to be further used as fertilizer.
磷的匮乏在 21 世纪已成为欧盟的一个重大问题，这是因为磷作为一种不可或缺的生命所需的大量营养元素，以及欧盟对进口的完全依赖。本工作旨在评估通过吸附作用从间歇和固定床柱中回收磷，使用经热改性的蛋壳作为吸附剂。筛选阶段表明，与测试的其他热改性蛋壳相比，700°C 煅烧蛋壳（CES700）是最合适的材料。因此，对 CES700 的比表面积、孔体积、零电荷 pH 值、总溶解固体和有机物进行了表征。在间歇条件下考察了 pH 值和吸附剂用量的影响。Langmuir-Freundlich 模型描述了平衡数据，最大吸附容量约为 39mg P-PO/g。动力学遵循伪一级模型，常数在 0.063 和 0.224 min 之间。固定床研究表明，增加流体表面速度和进料浓度会导致吸附剂早期饱和。Yoon-Nelson、Thomas 和 Bohard-Adams 经验模型适当地调整了穿透曲线，R²≥0.98。用磷酸盐负载的 CES700 进行的发芽试验显示，发芽指数分别为 120%和 124%，分别为 48 和 72 h。CES700 在静态方面优于其他测试材料，这为其作为肥料的应用开辟了可能性。本研究表明，开发的 CES700 材料可用于间歇或固定床工艺从液体废水中回收磷酸根离子，负载的吸附剂有可能进一步用作肥料。
