Abstract Phosphorus is an essential plant nutrient required by all living organisms and global phosphate resources, being finite, are expected to last another 125 years. This study investigated a sustainable approach to retrieving phosphates from aqueous media using a composite of commonly available biological and mineral sources. Two composites were synthesized using (i) feldspar, alginate, and agar cross-linked by ferric and calcium ions (FAA), and (ii) feldspar, fly ash, and alginate crosslinked with copper ions (FFA). Adsorption parameters were determined using a synthetic phosphate solution. The FAA composite adsorbed 69% of the phosphates within 4 hours; 81% was adsorbed after equilibrium was reached in 9.5 h (pH 4–10). The FFA composite adsorbed 82% of the phosphate reaching equilibrium after 5.5 h (pH 3–7). Characterization of the composite by scanning electron microscopy and Fourier Transform Infrared spectroscopy showed the presence of inorganic and organic functional groups in the agar and alginate that could adsorb phosphate ions. The kinetic and isotherm data suggest that the phosphate ions migrate to the composite boundary and are precipitated by the Ca2+, Fe3+, and Cu2+ in the composite matrix. Once the outer composite is saturated, the rest of the phosphate ions are entrapped by the biopolymers through H and covalent bonding. These two biopolymer composites can be easily synthesized and scaled up for phosphate adsorption. Recovery of the adsorbed phosphates, in future studies, can be used for plant nutrition to complete the open-ended cycle of phosphates leaching into water bodies.

中文翻译：

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两种聚合物-硅酸盐复合材料从水中吸附磷酸盐

摘要 磷是所有生物体所必需的植物营养素，全球磷酸盐资源是有限的，预计还能再使用 125 年。这项研究调查了一种可持续的方法，使用常见的生物和矿物来源的复合材料从水性介质中回收磷酸盐。使用 (i) 铁和钙离子 (FAA) 交联的长石、藻酸盐和琼脂，以及 (ii) 铜离子 (FFA) 交联的长石、粉煤灰和藻酸盐合成了两种复合材料。使用合成磷酸盐溶液确定吸附参数。FAA 复合材料在 4 小时内吸附了 69% 的磷酸盐；在 9.5 小时（pH 4-10）内达到平衡后，81% 被吸附。FFA 复合材料吸附了 82% 的磷酸盐，在 5.5 小时（pH 3-7）后达到平衡。通过扫描电子显微镜和傅里叶变换红外光谱对复合材料的表征表明琼脂和藻酸盐中存在可吸附磷酸根离子的无机和有机官能团。动力学和等温线数据表明磷酸根离子迁移到复合边界并被复合基体中的 Ca2+、Fe3+ 和 Cu2+ 沉淀。一旦外部复合材料饱和，其余的磷酸根离子就会通过 H 和共价键被生物聚合物捕获。这两种生物聚合物复合材料可以很容易地合成并放大用于磷酸盐吸附。在未来的研究中，吸附磷酸盐的回收可用于植物营养，以完成磷酸盐浸入水体的开放式循环。