Sorption of Coated and Uncoated Nanocrystalline Zinc Oxide from Aqueous Solutions onto Raw and Acetylated Cellulose Sago Hampas: Equilibrium, Kinetic and Thermodynamic Studies

In this study, sorption efficiency of coated (C-) and uncoated (U-) zinc oxide nanoparticles (ZnO-NPs) in aqueous solution onto raw sago hampas (RSH) and acetylated sago hampas (ACSH) was studied. Physical and chemical characteristics of both the sorbate and sorbents were analysed using various characterization techniques. The mechanism of the sorption process was evaluated using equilibrium isotherms, kinetic and thermodynamic studies. From the study, maximum percentage removal of both sorbate ions were achieved at an equilibration time of 100 minutes with an optimum sorbate mass of 2.0 g per 50 ml. The study recorded a maximum % removal of 85.1% & 87.6% for C-and U-ZnO-NPs (< 50 nm) onto RSH and 90.0% & 91.1% onto ACSH. Langmuir isotherm fitted well for the sorption process with the highest efficiency of 0.793 mg/g recorded for C-ZnO-NPs onto RSH. Pseudo-second model best described the sorption process. An exothermic and non-spontaneous sorption process was realised in all the sorption studies except that of U-ZnO-NPs (< 50 nm) onto ACSH which became spontaneous as temperature increased. Based on the findings from the multiple approaches employed, both sorbents could be proposed as viable alternatives to act as a green sorbent in the removal of ZnO-NPs from water and wastewater.

Исследование мемристорного эффекта в нанокристаллических пленках ZnO

The results of experimental investigations into the memristor effect and influence of annealing modes on the electrical properties of nanocrystalline zinc-oxide films fabricated by pulsed laser deposition are presented. The possibility of fabricating a nanocrystalline zinc-oxide film by pulsed laser deposition in a broad range of electrical (resistivity from 1.44 × 10^–5 to 8.06 × 10^–1 Ω cm) and morphological (roughness from 0.43 ± 0.32 to 6.36 ± 0.38 nm) parameters due to the use of post-growth annealing in oxygen (pressure 10^–1 and 10^–3 Torr, temperature 300 and 800°C, and duration from 1 to 10 h) is presented. It is shown that a nanocrystalline zinc-oxide film 58 ± 2 nm in thickness manifests a stable memristor effect slightly dependent on its morphology—applying a voltage of –2.5 and +4 V leads to switching between states with the resistance 3.3 ± 1.1 × 10^9 and 8.1 ± 3.4 × 10^7 Ω, respectively. These results can be used when developing designs and production processes of resistive random-access memory (RRAM) units based on the memristor effect as well as optoelectronics, microelectronics, and nanoelectronics and nanosystem devices.