通过插层聚合磷酸盐而不是正磷酸盐来提高层状双氢氧化物肥料的磷含量：可行性研究。
Enhancing the phosphorus content of layered double hydroxide fertilizers by intercalating polymeric phosphate instead of orthophosphate: A feasibility study.
机构信息
Division of Soil and Water Management, Department of Earth and Environmental Science, KU Leuven, Kasteelpark Arenberg 20, B-3001 Heverlee, Belgium.
School of Agriculture, Food and Wine, The University of Adelaide, PMB 1, Waite Campus, Glen Osmond, SA 5064, Australia.
出版信息
J Colloid Interface Sci. 2022 Dec 15;628(Pt A):519-529. doi: 10.1016/j.jcis.2022.07.149. Epub 2022 Jul 27.
HYPOTHESIS
Layered double hydroxide (LDH) loaded with orthophosphate (PO) are suggested as slow-release P fertilizers. However, PO-LDHs have a low maximal P content, related to high charge HPO/PO anions occupying the anion exchange capacity (AEC) of LDHs. We postulate that the P content of LDHs can be enhanced by exchanging them with polymeric-P (i.e. trimetaphosphate, PO), which has a lower molar charge/P ratio than its monomer.
EXPERIMENTS
Adsorption capacities were compared between PO and PO for as-synthesized and calcined MgAl LDHs with Mg/Al ratio of 2, 3, or 4; the P-LDHs were characterized (XRD, FTIR). Dialysis and soil incubation experiments were performed with POLDHs, POLDHs, and corresponding soluble fertilizers to compare their P release and P solubility (CaCl extract).
FINDINGS
The P adsorption capacities were 1.25-1.60 fold larger for PO compared to PO, yet the high theoretical P contents with PO were not achieved (incomplete loading, PO depolymerization). PO-MgAl released polymeric-P whereas PO-MgAl released depolymerized PO, and P release from PO-LDHs was slower than that of PO-LDHs. With soil incubation, soluble P from PO-LDH was initially lower but later converged to that of PO-LDH as result of continued hydrolysis, yet did not exceed that of the soluble PO and PO fertilizers.
假设
层状双氢氧化物（LDH）负载正磷酸盐（PO）被认为是缓慢释放的 P 肥料。然而，PO-LDH 的最大 P 含量较低，这与高电荷 HPO/PO 阴离子占据 LDH 的阴离子交换容量（AEC）有关。我们假设通过用聚合-P（即三偏磷酸盐，PO）交换 LDH 可以提高 P 含量，因为聚合-P 的摩尔电荷/P 比低于其单体。
实验
比较了合成和煅烧的 MgAl LDH 与 Mg/Al 比为 2、3 或 4 时，PO 和 PO 之间的吸附能力；用 XRD、FTIR 对 P-LDHs 进行了表征。用 POLDHs、POLDHs 和相应的可溶性肥料进行了透析和土壤培养实验，以比较它们的 P 释放和 P 溶解度（CaCl 提取物）。
结果
与 PO 相比，PO 的 P 吸附能力提高了 1.25-1.60 倍，但 PO 的理论 P 含量并没有达到（不完全负载，PO 解聚）。PO-MgAl 释放出聚合-P，而 PO-MgAl 释放出解聚的 PO，PO-LDHs 的 P 释放速度比 PO-LDHs 慢。随着土壤培养，PO-LDH 中的可溶性 P 最初较低，但由于持续水解，后来与 PO-LDH 的可溶性 P 趋同，但仍未超过可溶性 PO 和 PO 肥料的 P 释放量。
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