Controlled Release of Phosphate from Layered Double Hydroxide Structures: Dynamics in Soil and Application as Smart Fertilizer

A route is proposed to produce a hydrotalcite-like layered double hydroxide structure ([Mg-Al]-LDH) for phosphate fertilization. The mechanism of controlled phosphate release from the structure was investigated. The preparation strategy resulted in a phosphorus content of around 40 mg·g^–1 LDH, which was higher than previously reported for related fertilizers. The release of phosphate into water from [Mg-Al-PO₄]-LDH continued over a 10-fold longer period, compared to release from KH₂PO₄. Analysis using ³¹P NMR elucidated the nature of the interactions of phosphate with the LDH matrix. In soil experiments, the main interaction of P was with Fe³⁺, while the Al³⁺ content of LDH had no effect on immobilization of the nutrient. Assays of wheat (<i>Triticum aestivum</i>) growth showed that [Mg-Al-PO₄]-LDH was able to provide the same level of phosphate nutrition as other typical sources during short periods, while maintaining higher availability of phosphate over longer periods. These characteristics confirmed the potential of this preparation route for producing controlled release fertilizers, and also revealed fundamental aspects concerning the interactions of phosphate within these structures

Sustainable Production and <i>In vitro</i> Biodegradability of Edible Films from Yellow Passion Fruit Coproducts via Continuous Casting

Edible films made up of yellow passion fruit (YPF) rind and pectin as a matrix-forming agent are proposed as a means of valorizing passion fruit processing wastes. YPF films were produced at pilot-scale using continuous casting from aqueous formulations covering pectin/rind and water/pulp mass ratios of 100/0–0/100. YPF films were successfully obtained with systematic, tunable yellowish coloration and were achieved at an optimal temperature of 120 °C, leading to a drying time of 7 min and productivity of 0.03 m² film min^–1. YPF pulp is found to plasticize the pectin matrix of the films and thus can replace glycerol or other synthetic plasticizers. Films with the largest rind content (50 wt %) showed mechanical strength comparable to that of PVC cling film (9 vs 5 MPa). The biodegradable, renewable character of YPF films was demonstrated upon exposure to <i>Escherichia coli</i>, <i>Staphylococcus aureus,</i>, and <i>Bradyrhizobium diazoefficiens</i>, a nitrogen-fixing symbiotic bacterium