Layered Double Hydroxide (LDH) intercalated with phosphate ions (LDH-phosphate) was synthesized by ionexchange method from a precursor containing nitrate ions between the layers. The materials were characterized by X-ray diffraction (XRD), attenuated total reflectance−Fourier transform infrared spectroscopy (ATR-FTIR), thermogravimetric analysis coupled to differential scanning calorimetry and mass spectrometry (TGA-DSC-MS), specific surface area (BET), scanning electron microscopy (SEM), and elemental analysis. We hypothesized that LDH-phosphate can be used as a slow release fertilizer and help increase phosphate fertilization efficiency in tropical weathered soils. This new fertilizer technology was tested in a kinetic study of P release and a bioassay with controlled conditions of light, humidity, and temperature using maize (Zea mays) as our indicator plant. The bioassay was performed using an adaptation of the Neubauer method, wherein the LDHphosphate was compared to the commercial triple superphosphate (TSP) fertilizer in two different weathered soils: a sandy soil and a clayey soil. Under the bioassay experimental conditions, LDH-phosphate increased plant productivity (mass of dry matter), height, and the content of phosphorus (P) in the dry matter. In addition, LDH-phosphate promoted an increase in the soil pH value, contributing to decrease the P adsorption capacity of the soil, making it more available to the plants.

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The adsorption of textile dyes onto Layered Double Hydroxides (LDH) and their thermally decomposed products is a promising strategy for the treatment of contaminated effluents-combining high removal efficiency with reasonable cost. The main purpose of this paper was to investigate the adsorption of textile azo dye Acid Yellow 42 (AY) onto calcined and uncalcined Mg-Al-CO 3-LDH. A set of analytical techniques was used to characterize the materials, namely X-ray diffraction (XRD), Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), thermogravimetric analyses (TGA), N 2 adsorption-desorption isotherms and Scanning Electron Microscopy (SEM). In the study of azo dye adsorption, the following factors were assessed: kinetics, adsorption capacity, effect of temperature, initial pH value, and recyclability of the adsorbent material. The adsorption capacity of calcined LDH (CLDH) was almost four times greater than that of the LDH precursor: 1266 mg•g −1 (1.669 mmol•g −1) and 330.0 mg•g −1 (0.4350 mmol•g −1), respectively, at pH equal to 7.0 and 25°C. The greater adsorption capacity for CLDH is related to the recovery property of these materials in light of the so called "memory effect", which allows an intercalation process of the anionic dye, as demonstrated by XRD data.

The LDH memory effect is driven by an aggregative nucleation and growth mechanism limited by the adsorption of the anionic dye in on the external surface.

The current research aims to introduce Layered Double Hydroxides (LDH) as nanomaterials to be used in agriculture, with particular reference to its use as storage and slow release matrix of nutrients and agrochemicals for plant growing. Structural characteristics, main properties, synthesis methods and characterization of LDH were covered in this study. Moreover, some literature data have been reported to demonstrate their potential for storage and slow release of nitrate, phosphate, agrochemicals, besides as being used as adsorbent for the wastewater treatment. This research aims to expand, in near future, the investigation field on these materials, with application in agriculture, increasing the interface between chemistry and agronomy.

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