Determination of technological parameters of Zn-Al layered double hydroxides, as a matrix for functional anions intercalation, under different synthesis conditions

Abstract

Layered double hydroxides, especially Zn-Al, are valuable bases for intercalating various functional anions: dyes, drugs, food additives, etc. For purposeful development and optimization of the synthesis technology of functional materials based on Zn-Al layered double hydroxides, the technological parameters of Zn-Al nitrate layered double hydroxide samples (Zn:Al=4:1) synthesized at solution flow rates of 0.8 and 1.6 l/h, pH=7, 8, 9, 10 and t=10, 20, 30, 40, 50 and 60 °C were determined. The yield values of the samples were determined by the gravimetric method. The sedimentation rate was studied by measuring the normalized thickness of the precipitate layer (relative to the initial layer thickness) during 30 minutes of settling. It was found that with an increase in the synthesis pH, the yield increased from 74.68 % to 83.54 %. Increasing the flow rate of the solutions led to a decrease in yield. On the yield-synthesis temperature dependence, two sections of 10–20 °C and 30–60 °C were identified, within which an increase in temperature led to a decrease in yield. It is shown that with increasing synthesis pH, as well as the solution flow rate, the sedimentation rate increased significantly. At pH=10, almost complete sedimentation of the sample occurred within the first 5 minutes. The obtained data indicate that the pH of the zero charges of the Zn-Al-NO3 layered double hydroxide particles was close to 10. It was found that increasing the temperature reduced the sedimentation rate. An abnormally low sedimentation rate at a synthesis temperature of 30 °C and an abnormally high sedimentation rate at 50 °C were detected. The obtained data confirm the previously stated hypothesis regarding the change of the mechanism or kinetics of the formation of layered double hydroxides at temperatures of 30 °C and 50 °C

Investigation of the characteristics of Zn-Al layered double hydroxides, intercalated with natural dyes from spices, as a cosmetic pigments

“…The preparation was carried out with continuous stirring, which continued for 30 minutes after the end of the synthesis. This is necessary for the process of crystallization and intercalation to proceed [66,67]. The resulting pigment precipitate was filtered under vacuum from the mother liquor, dried for 24 hours at 80 °C, grinded, soaked in distilled water, filtered, and dried again under the same conditions.…”

Layered Double Hydroxides as the Unique Product of Target Ionic Construction for Energy, Chemical, Foods, Cosmetics, Medicine and Ecology Applications

“…For this, Ukrainian authors select MgÀ Al and ZnÀ Al LDHs as the most promising. [103,104] The following LDH-based pigments have been obtained: ZnÀ Al and Acid Yellow 17, [105] MgÀ Al and o-Methyl Red, [106] NiÀ Fe and o-Methyl Red, [107] ZnÀ Al and Mordant Yellow, [108,109] ZnÀ Al and Acid Yellow 3, [110] ZnÀ Al and bi-anion Acid Green 28. [111] Studies have shown high thermal and photostability of the color of such LDHs, [105,109,111] which is an additional and very significant advantage of such pigments.…”

Development of the retrieving technology of carotenoids from pumpkin (Cucurbita SPP.) pulp using Zn-Al layered double hydroxides

“…It is also necessary to ensure the completeness of the separation of fibers and cake from fresh juice. The technology of the stage of obtaining the carotenoids-LDH composite corresponds to the technology of the synthesis of dye-intercalated pigments [34,41]. The completeness of coagulation of the composite precipitate is experimentally shown (Fig.…”

“…As a result, an excess positive charge is formed in the crystal lattice, which can be compensated by the intercalation of additional anions into the interlayer space. Such anions can be counterions of precursor salts [33,34]. But most often, anions with special functional properties are purposefully intercalated into LDH structures.…”