The global demand for safe and healthy food with minimal synthetic preservatives is continuously increasing. Some natural food antimicrobials with strong antimicrobial activity and low toxicity have been considered as alternatives for current commercial food preservatives. Nonetheless, these natural food antimicrobials are hardly applied directly to food products due to issues such as food flavor or bioavailability. Recent advances in microencapsulation technology have the potential to provide stable systems for these natural antibacterials, which can then be used directly in food matrices. In this review, we focus on the application of encapsulated natural antimicrobial agents, such as essential oils, plant extracts, bacteriocins, etc., as potential food preservatives to extend the shelf-life of food products. The advantages and drawbacks of the mainly used encapsulation methods, such as molecular inclusion, spray drying, coacervation, emulsification, supercritical antisolvent precipitation and liposome and alginate microbeads, are discussed. Meanwhile, the main current applications of encapsulated antimicrobials in various food products, such as meat, dairy and cereal products for controlling microbial growth, are presented.

Cd(II) adsorption onto Fe(II) modified Layered double hydroxide–graphene oxide (LDH–GO@Fe(II)) was investigated using batch experiments. With the modification of Fe(II), LDH–GO maintained its structure, while Fe(II) species formed non-crystalline iron oxide clusters on the surface of the LDH/GO. A kinetics study indicated that adsorption obeyed a pseudo-second-order rate law. The equilibrium data were fitted well with the Langmuir isotherm model. The maximum adsorption capacity of LDH–GO@Fe(II)₁₀ was 28.98 mg g⁻¹, higher those that of pure LDH–GO and LDH–GO@Fe(II)₅₀. The increased sorption capacities could be explained by the increased specific surface area. Modification with Fe(II) would lead to the generation of amorphous Fe oxides and Fe could occupy the binding sites for Cd(II), thus excess Fe in the structure will restrain the adsorption of Cd(II). The XRD and XPS patterns revealed the formation of Cd(OH)₂ after adsorption. Batch experiments indicated that precipitation and surface complexation were the main pathways for Cd(II) removal.

Two novel adsorbents (LDH@GO-NH₂ and LDH@GO-SH) were successfully synthesized by grafting thiol- or amino-functionalized GO onto LDH and their adsorption capacities for heavy metal ions (Cu(II) and Cd(II)) were significantly enhanced. Characterization experiments illustrated that the thiol group (–SH) or amino group (–NH₂) was grafted onto LDH@GO-NH₂ or LDH@GO-SH. Adsorption isotherms were satisfactorily fitted by both Langmuir and Freundlich models. The maximum adsorption capacity of Cd(II) on LDH@GO-SH at 308 K was 102.77 mg/g, which was about triple that of LDH@GO-NH₂. The enhancement in adsorption capacity of LDH@GO-SH was due to the cooperative effect of LDH and GO-SH. The kinetic experimental data for LDH@GO-NH₂ and LDH@GO-SH were found to be in good agreement with the pseudo-second-order model. The thermodynamic parameters calculated from the temperature-dependent adsorption isotherms indicated that the adsorption was spontaneous and an endothermic process. The possible adsorption mechanisms comprising formation of precipitation, isomorphic substitution of Mg(II), and formation of complexation with amino groups or thiol groups were proposed. Desorption experiments put into evidence that LDH@GO-NH₂ and LDH@GO-SH may be promising suitable candidates for the remediation of metal ions from aqueous solutions in real work in the near future.

The competitive adsorption of phosphate and nitrate from aqueous solution on calcined Mg-Al layered double hydroxides (Mg-Al CLDHs) were investigated. Experiments were carried out as a function of adsorbent dosage, contact time, initial pH and temperature. The adsorption processes of phosphate and nitrate were followed by the pseudo second-order and pseudo first-order kinetics, respectively. The X-ray diffraction patterns (XRD) showed structural reconstruction during sorption, the unchanged d-spacing d₀₀₃ indicated phosphate and nitrate were mainly adsorbed on the surface and the near-edge interlayer. The results of Fourier transformed infrared spectroscopy (FTIR) verified nitrate and phosphate adsorbed onto the CLDHs. Desorption behaviors indicated that nitrate can be more easily desorbed from loaded CLDHs than phosphate. The possible mechanism of phosphate adsorption was controlled by chemisorption, while nitrate adsorption was governed by physisorption. The results showed that the Mg-Al CLDHs can be used to simultaneously remove phosphate and nitrate from aqueous solution.