Synthesis And Properties Of Layered Double Hydroxides/Microemulsion Based Pesticide Delivery System

This paper aims at the preparation and properties of the pesticide-LDHs nanohybrid/pesticide-microemulsion, plan to develop a new kind of pesticide formulation.Nowadays in china, the second biggest country of pesticide producing, preparations forms are mainly powder, oil concentrate and suspension concentrate, which are irrational and large application. Pesticide as brought many ignorant effects such as air pollutions, environmental destroy, food safety and so on, which has baffled agricultural sustainable development. Now the hit research trends of pesticide forms in the world are water-based, controlled release and multifunctional. Microemulsion has become one of the most popular research topics in the last decades because of its special advantages, such as efficient, environment-friendly, high stability.Layered double hydroxides (LDHs), also called Hydrotalcite-like compounds (HTlc), consisting of divalent and trivalent metal ions and with the same layered crystal structure as Hydrotalcite, are a class of layered materials which has been paid a great of attention in recent years. The interlayer region of LDHs may be considered as a microvessle, some pesticide and drug molecules may be intercalated into the gallery of LDHs to form pesticide/drug-LDHs nanohybrids. The nanohybrids may evidently inhibit the release of molecules in the interlayer because of the hydrogen bond, van deel waals force and steric hindrance in LDHs gallery. LDHs can be potentially used in pesticide/drug delivery and controlled-release. But rare work has been done on pesticide-LDHs nanohybrid both in home and aboard. Many problems needed to be solve eagerly, such as dispersibility, suspension property, adhesive capacity and so on.Microemulsion is a new type of pesticide delivery system. It has been widely researched in the last decade because the high stability, adherence and efficiency. The disadvantage of microemulsion is: (1) high pesticide selectivity; (2) low pesticide content; (3) difficult to control the release process.In order to cover the shortage of the two formulations, this paper brings forward a new direction that the research of the LDH-SFME pesticide delivery compound system, which is a complementary of advantages of the two formulations.Many works have been done to prepare and character the compound system and verify the feasibility of this direction. Primary works are: (1) preparation and characterization of LDHs and pesticide-LDHs nanohybrid; (2) Preparation and performance study of the pesticide microemulsion, especially the surfactant-free microemulsions (SFMEs); (3) Preparation of pesticide-LDHs/SFME system and its performance analysis as a pesticide formulation. Target to provide a new direction and foundation of novel pesticide formulations.Primary conclusion:1. Mg-Al, Ni-Fe and Mg-Al-Fe-LDHs were synthesised by coprecipitation method. Ferrite spinels with well crystal structure can obtained by calcination of Ni-Fe and Mg-Al-Fe-LDHs at a relative low temperature of 700℃.2. The magnetic properties of Ni-Fe, Mg-Al-Fe-LDHs and their calcinates were studied in detail using a vibrating sample magnetometer(VSM). The Ni-Fe and Mg-Al-Fe-LDH show paramagnetism at normal temperature, the calcined samples of LDHs show super-paramagnetism. The magnetization increases with the higher Fe³⁺ content and is independent of the crystal structure of LDHs. Magnetization of the calcinates of Ni-Fe-LDHs is higher than the Mg-Al-Fe-LDHs.3. Two novel SFME systems were found for the first time, that is furaldehyde/DMF/water and furaldehyde/ethanol/water system. Similar to the traditional microemulsion, SFME has three types of water in oil(W/O), bicontinuous(BC) and oil in water(O/W) microstructure. The phase behavior of the SFME system is independent of the temperature and salt concentration.4. The stability of SFME system is excellent. The stability was examined by the following processes, respectively: (1) heat-storage at 80°C for one week; (2) cold-storage at -10℃for week; (3) freeze (-10℃)-thaw (40℃) cycle for 3 times; and (4) centrifugalized under 100 g for 15 min; (5) storage at room temperature for 24 months. It was found that their stability was not destroyed to the slightest degree and samples remained transparent.5. Avermectin-LDHs(AM-LDHs) nanohybrid were prepared by re-assemble method, the pesticide released behavior is a slow-release process, providing that the LDHs is a novel pesticide slow-release formulation and the potential use as a controlled-release formulation is feasible.6. Avermectin-SFME(AM-SFME) system was prepared and its stability is as good as the SFME system itself. Using SFME as a pesticide delivery system is practicable.7. AM-LDHs/SFME compound system was prepared and characterized. The avermectin content is much higher than the AM-SFME system. The stability of the compound system satisfies the requirement as a pesticide formulation, its application as a pesticide delivery system is practicable.Primary innovations:1. Two novel SFME systems are found fo the first time consisting of furaldehyde/DMF/water and furaldehyde/ethanol/water. Similar to the traditional microemulsion, SFME also has three microstructures: water in oil(W/O), bicontinuous(BC) and oil in water(O/W).2. Avermectin-LDHs(AM-LDHs) nanohybrid were prepared by re-assemble method, the pesticide released behavior is a slow-release process, providing that the LDHs is a novel pesticide slow-release formulation and the potential use as a controlled-release formulation is feasible.3. AM-LDHs/SFME compound system was prepared as a example. The avermectin content is much higher than the AM-SFME system. The stability of the compound system satisfies the requirement as a pesticide formulation, its application as a pesticide delivery system is practicable.