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In this study, the potassium adsorption for the purification of crude ammonium perrhenate solutions in the presence of various cheap and available ion exchange resins is reported for the first time. After the resin screening test, the optimum resin (Purolite® C100 resin as a strong acid cation ion exchange resin in the sodium form) was selected for morphological analysis using field emission scanning electron microscopy, which was further examined by energy-dispersive spectroscopy. Moreover, X-ray elemental mapping of the surface of C100 resin revealed homogeneous potassium adsorption. BET and TGA tests confirmed the adsorbed potassium on the C100 resin. Among the isotherm models, the Langmuir isotherm provided the best fit according to the correlation coefficients. The adsorption parameters have been scrutinized, including contact time, initial potassium concentration, temperature, and competitive binary potassium and sodium adsorption. The result of the binary system exhibited a decrease in the potassium adsorption capacity of the resin in the presence of secondary ions due to competition for adsorption sites. Kinetic characteristics of the potassium adsorption process were investigated by pseudo-first-order and pseudo-second-order, intraparticle diffusion, and Elovich models. The adsorption process has been found to match the pseudo-first-order reaction. The continuous/extended experiments and the elution test were also evaluated. [ABSTRACT FROM AUTHOR]

In a new approach, we considered the special affinity between Ni and poly-histidine tags of recombinant urate oxidase to utilize Ni-MOF for immobilizing the enzyme. In this study, a carbon paste electrode (CPE) was modified by histidine-tailed urate oxidase (H-UOX) and nickel-metal–organic framework (Ni-MOF) to construct H-UOX/Ni-MOF/CPE, which is a rapid, sensitive, and simple electrochemical biosensor for UA detection. The use of carboxy-terminal histidine-tailed urate oxidase in the construction of the electrode allows the urate oxidase enzyme to be positioned correctly in the electrode. This, in turn, enhances the efficiency of the biosensor. Characterization was carried out by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), Brunauer–Emmett–Teller (BET), and field emission scanning electron microscopy (FE-SEM). At optimum conditions, the biosensor provided a short response time, linear response within 0.3–10 µM and 10–140 µM for UA with a detection limit of 0.084 µM, repeatability of 3.06%, and reproducibility of 4.9%. Furthermore, the biosensor revealed acceptable stability and selectivity of UA detection in the presence of the commonly coexisted ascorbic acid, dopamine, L-cysteine, urea, and glucose. The detection potential was at 0.4 V vs. Ag/AgCl. [ABSTRACT FROM AUTHOR]

In the present work, 2D monolayers of WS 2 and g-C 3 N 4 were synthesized for the preparation of WS 2 /g-C 3 N 4 nanostructure through a two-step process. 1D graphene oxide nanoribbons (GONRs) were synthesized via unzipping of multi-walled carbon nanotubes (MWCNTs) and applied for the preparation of three-component g-C 3 N 4 /WS 2 @rGONR (x) (x = 1, 2, and 5 wt%) nanocomposites. The synthesized nanocomposites were evaluated via Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), high-resolution transmission electron microscopy (HRTEM), and diffuse reflectance spectroscopy (DRS). The photocatalytic performance of the nanostructures was investigated in the hydrogen evolution reaction (HER) using the Fluorine-doped tin oxide (FTO) as the electrode. Subsequently, a possible photocatalytic mechanism was estimated. According to the results, the g-C 3 N 4 /WS 2 @rGONR (x) modified FTO has the lowest Tafel slope (60 mV dec−1), and overpotential (150 mV), the highest current density (47 mA cm−2) and also the maximum stability (19 mA for 3000s). Therefore, g-C 3 N 4 /WS 2 @rGONR (2) photocatalyst can be a novel and efficient candidate for hydrogen production as a clean fuel. • g-C 3 N 4 /WS 2 naosheets were prepared and placed on the graphene oxide nanoribbons. • Heterojunction g-C 3 N 4 /WS 2 @rGONR (x) nanocomposites were used in water splitting process. • rGONR act as an effective bridge for improving the photocatalytic properties of g-C 3 N 4 /WS 2. • g-C 3 N 4 /WS 2 @rGONR (2) photocatalyst showed promising performance for H 2 production. [ABSTRACT FROM AUTHOR]