Zeolite imidazolate frameworks (ZIFs) are a novel kind of zeolite materials with regular porous network structures, belonging to mental-organic frameworks (MOFs). Thanks to their high porosity and ...large specific surface area, ZIFs could have potential applications in the field of photocatalysis. In this paper, visible light responsive photocatalyst of ZIF-67 was synthesized by a one-step hydrothermal method under a mild condition. We explored three organic dyes in aqueous solutions were degraded under visible light irradiation. And corresponding photocatalytic performances of ZIF-67 with controllable synthetic conditions were evaluated systematically. It was found that ZIF-67(9 h) had the highest degradation efficiency. Besides, the ZIF-67(9 h) were heated in Ar can maintain their crystal structure and microporous form, but exposed more sites to improve photocatalytic activity with partial bond breakage. More than 75% methyl orange (MO), 85% methyl blue (MB) and 54% Rhodamine B (RhB) can be degraded with a 0.5 g L−1 ZIF-67(9 h)(Ar) under visible light irradiation. Moreover, the ZIF-67(9 h)(Ar) demonstrates a strong pH changing tolerance in both acid and alkaline aqueous solutions, the degradations can be well performed in a wide pH range from 3.0 to 11.0.
ZIF-67 was synthesized by a low temperature hydrothermal method, and with the post Ar annealing treatment, about 75% MO, 85% MB and 54% RhB can be successfully degraded in 1 h under a simulated visible light irradiation. Moreover, the ZIF-67(9 h)(Ar) can also work efficiently in a wide pH range (pH = 3.0–11.0), which is highly demanded in practical water pollution control. Display omitted
This paper presents the preparation of platinum on a reduced graphene oxide matrix (PtrGO) using the microwave-assisted method with three different pH solutions. The platinum concentration determined ...by energy-dispersive X-ray analysis (EDX) was 4.32 (weight%), 2.16 (weight %) and 5.70 (weight%), corresponding to pH 3.3, 11.7 and 7.2, respectively. Pt functionalization of reduced graphene oxide (rGO) decreased the rGO specific surface, as shown by Brunauer, Emmett and Teller (BET) analysis. An XRD spectrum of platinum-decorated reduced graphene oxide (rGO) showed the presence of the associated phases of rGO and centered cubic platinum peaks. An oxygen reduction reaction (ORR) electrochemical characterization performed using the rotating disk electrode (RDE) method showed that in PtGO1 synthetized in an acidic environment, with 4.32 Pt (weight%) determined by EDX, platinum is much more dispersed, which explains its better electrochemical oxygen reduction reaction performance. Koutecky-Levich (K-L) plots calculated at different potentials prove a good linear relationship. Electron transfer numbers (
) determined from the K-L plots are between 3.1 and 3.8, which confirms that the ORR for all the samples can be regarded as first-order reaction kinetics of O
concentration formed on the Pt surface during ORR.
Due to low efficiency and the material choice limitations of traditional evaporation systems to treat acid wastewater, humidification and dehumidification (HDH) as the core process was applied in the ...treatment and reduction of wastewater with organic acid pollutant concentrations. The forecasting of pH changes and COD reduction is important for the system’s design. Therefore, a study of the pollutant removal efficiency with different parameters, such as the reaction temperature, air quantity, and flow rate was conducted with ASPEN modeling. In this article, ASPEN modeling was used to simulate the water and acid material transformation in HDH system. The process was composed of blocks, such as RadFrac, heater and split. The analysis was taken with different air quantities, tower diameters, heat loads and flow rates. The analysis indicated that the pH of the maleic acid wastewater changed from 3.0 to 5.7. The relationship between inlet quantity, air quantity, inlet heat and the clean water yield was also shown in the modeling results. Based on these studies, we determined that the model can help engineers solve the key problems of HDH systems, such as heat balance calculation, equipment selection, and the prediction of incoming and outgoing evaporation materials.
Influence of the dissolution medium on the in vitro theophylline release profiles from matrices based on starch–methyl methacrylate copolymers. Tablets are compacted at a crushing force of 90–100N ...and tested in a pH-changing medium (1.2–7.5) at a basket rotation speed of 50r.p.m. Theo-Dur® and Theolair® are included as reference products. The type of copolymer, the tablet crushing force and the agitation rate affected the drug release kinetics.
Direct-compressed matrix tablets were obtained from a variety of potato starch–methyl methacrylate copolymers11OD-HSMMA, oven-dried hydroxypropylstarch methyl methacrylate; FD-HSMMA, freeze-dried hydroxypropylstarch methyl methacrylate; OD-CSMMA, oven-dried carboxymethylstarch methyl methacrylate; FD-CSMMA, freeze-dried carboxymethylstarch methyl methacrylate. as sustained-release agents, using anhydrous theophylline as a model drug. The aim of this work was to investigate the influence of the copolymer type, the tablet crushing force and dissolution variables such as the pH of the dissolution medium and the agitation intensity on the in vitro drug release behaviour of such matrices. Commercial sustained-release theophylline products (Theo-Dur® 100mg, Theolair® 175mg) were used as standards. Test formulations were compacted into tablets at three different crushing force ranges (70–80, 90–100 and 110–120N) to examine the effect of this factor on the porous network and drug release kinetics. In vitro release experiments were conducted in a pH-changing medium (1.2–7.5) with basket rotation speeds in the range 25–100r.p.m. to simulate the physiological conditions of the gastrointestinal tract. The release rate of theophylline was practically not affected by pH in the case of Theo-Dur® and HSMMA matrices. In contrast, Theolair® and CSMMA tablets demonstrated a biphasic drug release pattern, which appeared to be sensitive to the pH of the dissolution medium. An increase in the crushing force of the copolymer matrices was accompanied by a reduction of the matrix porosity, although the porous network depends markedly on the type of copolymer, having a strong influence on the drug release kinetics. Mathematical modelling of release data shows a Fickian diffusion or anomalous transport mechanism. Based on the similarity factor f2, FD-HSMMA, OD-CSMMA and FD-CSMMA at 90–100N were selected for agitation studies. In general, all formulations showed an agitation speed-dependent release, with Theo-Dur® and FD-CSMMA matrices being the less susceptible to this factor.
The pH of reaction solutions played a vital role and determines the nature of the final product formed. According to our experimental findings, we were able to control energy band gap, size and ...configuration of cobalt selenide thin films from aqueous solutions by suitable control of last solution pH. We present a simple solution processed synthesis route for cobalt selenide nanostructure thin films using chemical bath deposition method. The films were characterized by X-ray diffraction, UV–visible spectroscopy for energy band gap estimation and scanning electron microscopy to surface morphology investigation. In this work, the size of the nanosphers and other nanoparticles are relatively easy to control by pH controlling.
