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A novel nanocomposite consisting of nanocrystalline cellulose (NCC) and sodium nitrite (NaNO2) was synthesized and its dielectric properties were investigated at the temperature range of 20–170 °C and at the frequency range of 10−3–106 Hz under low electric fields (1 V cm−1). The obtained results manifest a reduction in the phase transition temperature of the synthesized composite (110 °C) compared to those of bulk NaNO2 (164 °C) due to the tilting action of the depolarizing field on the polarization for NaNO2 inclusions resulting from the presence of the bound charges on their surfaces. In addition, a significant dispersion of dielectric permittivity was detected and the explanation for this was based on the Maxwell–Wagner–Sillars relaxation mechanism.

In this study, a novel ferroelectric composite consisting of triglycine sulfate and cellulose nanoparticles at different weight composition ratios was successfully synthesized. A comparative study on structure and electrophysical properties for dried and wet composite samples was carried out. The measurements of electrophysical parameters were performed from 10 to 120 °C under a weak electric field with an amplitude of 1 V cm−1 at low and infra-low frequencies (10−3–103 Hz) under different relative humidities of 0, 30, 60, 80, and 100%. The characterization results showed a significant impact of moisture on crystallinity and features of functional groups in the composite. Besides, phase transition temperature of the composite increased by 3 to 63 °C higher than those for single crystal of triglycine sulfate (+ 49 °C) in dependence on cellulose content in the composite. Along with a significant increase in dielectric constant, dielectric loss, and dielectric dispersion in the composite due to high conductivity caused by moisture, the water molecules on sample surface led to the appearance of addition peaks in temperature dependences of dielectric constant and dielectric loss tangent in the initial stage of heating. All the anomalies can be explained by the strong interaction through hydrogen bonds between triglycine sulfate and cellulose components as well as between these components and water molecules in the composite.

In this study, a novel magnetic hydroxyapatite/chitosan composite (HA/Fe3O4/CS) prepared from steel slag, shrimp shells, and bovine bones, and then cross-linked with a green tea extract was used as an adsorbent for Ni(II) ion removal from aqueous solution. Various techniques (SEM, FTIR, XRD, VSM) were used to characterize the adsorbent. Batch experiments were conducted to investigate the adsorption properties of Ni(II) ions on HA/Fe3O4/CS. The optimum conditions for the adsorption process were studied in detail. The adsorption isotherm, mechanism, kinetics, and thermodynamics were further discussed. Besides, the desorption and reusability of the adsorbent were evaluated for further applications. The results indicated that the HA/Fe3O4/CS composite has the potential application for removal of Ni(II) ions from aqueous solution with a maximum adsorption capacity of 112.36 mg/g at optimal conditions (pH of 6, contact time of 60 min, room temperature, and adsorbent dose of 3 g/L). The adsorption process of Ni(II) on HA/Fe3O4/CS was feasible, spontaneous, exothermic, and more favorable at lower temperature. Adsorption isotherm and kinetics were suitable to be described by the Langmuir model and pseudo-second-order kinetic equation, respectively. Recycling results confirmed that the HA/Fe3O4/CS composite maintains a great reusability potential for five consecutive cycles with Ni(II) removal efficiency of greater than 85%. The adsorbent can be easily regenerated by using HCl and EDTA solutions. The overall study revealed that the magnetic hydroxyapatite/chitosan composite can be applied as a low cost, environmental friendly, and highly efficient adsorbent for removal of Ni(II) ions from wastewater because of its high adsorption capacity, easy recovery, and good reusability.