Layered double hydroxides and layered hydroxide salts have generated enormous excitement in the inorganic field due to their potential to act as versatile host materials in fabricating novel host–guest layered materials. The ability of the layered hydroxide anion exchanger to be incorporated with a wide range of guest ions enable them to be exploited in various applications related to pesticides. This review sums up the different methods of preparing layered hydroxide anion exchanger, summarises the types of anion intercalated into these layered hydroxide anion exchanger based on their respective systems, and elucidates their potential applications in pesticide-related fields.

Oleic acid modified magnetic iron oxide nanoparticles (OA-MIONs) was prepared for removal of Cu²⁺ ion from aqueous solution. OA-MIONs was prepared by W/O microemulsion template which composed of mixed non-ionic surfactants and 1-hexanol as emulsifier. The effect of weight ratio of the constituent of microemulsion template on the physical and chemical properties of OA-MIONs was studied by characterization using Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) analysis. FT-IR spectra showed that all templates shared similar chemical structure with slight difference in the peak intensity. Scanning electron micrograph illustrated that the OA-MIONs synthesized via template with the lowest weight ratio of emulsifier to heptane had a more regular spherical shape and was well-distributed. XRD had confirmed that the identity of synthesized OA-MIONs was Fe₃O₄. Based on the characterization result, the template with lowest weight ratio of emulsifier to heptane was chosen for the heavy metal adsorption study. The adsorption capacity OA-MIONs as a function of pH, contact time and adsorbent dosage were studied. The adsorption process reached equilibrium for 90 minutes and successfully adsorbed 43% of Cu²⁺ ion from aqueous solution. The adsorption behavior was well described by Langmuir isotherm. The maximum adsorption capacity was determined and found to be 555.56 mg/g. The value of Langmuir equilibrium parameter, R_L was found between 0 and 1, suggested that a favorable monolayer adsorption process had taken out.