A chitosan/silver nanoparticles (AgNPs/chitosan) composite has been prepared in situ using natural honey as the reducing and capping agent, and its effectiveness as an inhibitor for St37 steel in 15% HCl solution was assessed using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), dynamic electrochemical impedance spectroscopy (DEIS), and weight loss (WL) methods complemented with surface morphological examination with the aid of energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). AgNPs/chitosan was characterized using Fourier transformed infrared (FTIR), EDS, and SEM. The results obtained show that AgNPs/chitosan is an effective cathodic type inhibitor particularly at higher temperature and protects the metal surface by formation of a protective film. SEM, AFM, and EDS confirm the formation of an adsorbed film. The adsorption followed the Temkin adsorption isotherm; as such, the thermodynamic and kinetic parameters governing the adsorption were calculated and discussed. The values of the free energy of adsorption suggest that a mixed adsorption mechanism characterized the adsorption of AgNPs/chitosan molecules at lower temperature while chemisorption defined the adsorption process at higher temperature.

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Salinity gradient energy is a prominent alternative and maintainable energy source, which has considerable potential. Reverse electrodialysis (RED) is one of the most widely studied methods to extract this energy. Despite the considerable progress in research, optimization of RED process is still ongoing. In this study, effects of the number of membrane pairs, ratio of salinity gradient and feed velocity on power generation via the reverse electrodialysis (RED) system were investigated by using Fujifilm cation exchange membrane (CEM Type 2) and FujiFilm anion exchange membrane (AEM Type 2) ion exchange membranes. In the literature, there is no previous study based on a RED system equipped with Fujifilm AEM Type II and CEM Type II membranes that have homogeneous bulk structure. Using 400 µm of intermembrane distance, maximum obtainable power density by 5 pairs of Fujifilm membranes at 1:45 salinity ratio and with a linear flow rate of 0.833 cm/s was 0.426 W/m2.

This study investigates the influence of co-existing ions on the salinity gradient power generation performance of the reverse electrodialysis (RED) using three different commercial ion exchange membrane pairs. The feed solutions, including the mixture of two different salts, were prepared with 90 wt.% of NaCl and 10 wt.% of LiCl, KCl, CaCl2, MgCl2 or Na2SO4 by keeping the salt ratio between high concentrate solution and low concentrate solution constant as 1:30 (g/g) at various flow velocities (50, 125 and 200 mL/min). It was observed that the divalent ions exhibited a negative impact on the performance of the RED system due to their high valence and low ionic mobility depending on their high hydrated radius and low diffusion coefficients compared to those of the monovalent ions. On the other hand, the effect of the monovalent ions differed according to the properties of ion exchange membranes used in the RED stack. When the power generation performances of ion exchange membrane pairs employed in the RED stack were compared, it was considered that Neosepta AMX and CMX membranes provided the highest power density due to their low membrane thicknesses, low electrical resistances, and relatively high ion exchange capacities compared to other two commercial ion exchange membrane pairs.