In the present article, the optimization of removal of Cu²⁺, Ni²⁺, and Pb²⁺ using sugarcane-based activated carbon was studied. The activated carbon synthesized from low-cost sugarcane bagasse via ZnCl₂ activation process was found to possess surprisingly high surface area (>1500 m²/g). In adsorption study, the individual and interactive effects of three critical parameters including initial concentration, pH of solution, and activated carbon dosage on removal efficiency of Cu²⁺, Ni²⁺, and Pb²⁺ were assessed by applying the response surface methodology combined with central composite design. The established second-order polynomial regression models provided an excellent interpretation of experimental data with acceptable coefficients of determination ( R²) and analysis of variance demonstrated statistical significance of the model terms. In the examined region, the predicted maximum removal efficiency and adsorption capacity were found in the order: Ni²⁺ (66.4%, 2.99 mg/g) < Cu²⁺ (90%, 13.24 mg/g) < Pb²⁺ (99.9%, 19.3 mg/g), which were also confirmed in the verification experiments.

Mixed Ni/Fe-base metal-organic framework (Ni/Fe-MOF) with different molar ratios of Ni²⁺/Fe³⁺ have been successfully produced using an appropriate solvothermal router. Physicochemical properties of all samples were characterized using X-ray diffraction (XRD), Raman, field emission scanning electron microscopes (FE-SEM), fourier-transform infrared spectroscopy (FT-IR), N₂ adsorption-desorption analysis, X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS), and photoluminescence spectra (PL). The photocatalytic degradation performances of the photocatalysts were evaluated in the decomposition of rhodamine B (RhB) under a compact fluorescent daylight lamp. From XRD, IR, XPS, and Raman results, with the presence of mixed ion Fe³⁺ and Ni²⁺, MIL-88B (MIL standing for Materials of Institut Lavoisier) crystals based on the mixed metal Fe₂NiO cluster were formed, while MIL-53(Fe) was formed with the presence of single ion Fe³⁺. From UV-Vis DRS results, Ni/Fe-MOF samples exhibited the absorption spectrum up to the visible region, and then they showed the high photocatalytic activity under visible light irradiation. A Ni/Fe-MOF sample with a Ni²⁺/Fe³⁺ molar ratio of 0.3 showed the highest photocatalytic degradation capacity of RhB, superior to that of the MIL-53(Fe) sample. The obtained result could be explained as a consequence of the large surface area with large pore volumes and pore size by the Ni²⁺ incorporating into the MOF’s structure. In addition, a mixed metal Fe/Ni-based framework consisted of mixed-metal cluster Fe₂NiO with an electron transfer effect and may enhance the photocatalytic performance.

The present study focused on the application of response surface methodology to optimize the fabrication of activated carbon (AC) from sugarcane bagasse for adsorption of Cu²⁺ ion. The AC was synthesized via chemical activation with ZnCl₂ as the activating agent. The central composite design based experiments were performed to assess the individual and interactive effect of influential parameters, including activation temperature, ZnCl₂ impregnation ratio and activation time on the AC yield and removal of Cu²⁺ ion from the aqueous environment. The statistically significant, well-fitting quadratic regression models were successfully developed as confirmed by high F- and low P-values (<0.0001), high correlation coefficients and lack-of-fit tests. Accordingly, the optimum AC yield and removal efficiency of Cu²⁺ were predicted, respectively, as 48.8% and 92.7% which were approximate to the actual values. By applying the predicted optimal parameters, the AC shows a surprisingly high surface area of around 1,500 m²/g accompanied by large pore volume and narrow micropore size at low fabrication temperature.

In this study, we investigated sulfate-modified BiVO₄ with the high photocatalytic activity synthesized by a sol-gel method in the presence of thiourea, followed by the annealing process at different temperatures. Its structure was characterized by thermal gravimetric analysis (TGA), powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM/EDS), X-ray photoelectron spectroscopy (XPS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). The BiVO₄ synthesized in the presence of thiourea and calcined at 600 °C (T-BVO-600) exhibited the highest photocatalytic degradation efficiency of methylene blue (MB) in water; 98.53% MB removal was achieved within 240 min. The reaction mechanisms that affect MB photocatalytic degradation on the T-BVO-600 were investigated via an indirect chemical probe method, using chemical agents to capture the active species produced during the early stages of photocatalysis, including 1,4-benzoquinone (scavenger for O₂⁻), ethylenediaminetetraacetic acid disodium salt (scavenger for h⁺), and tert-butanol (scavenger for HO^•). The results show that holes (h⁺) and hydroxyl radicals (HO^•) are the dominant species of MB decomposition. Photoluminescence (PL) measurement results of terephthalic acid solutions in the presence of BiVO₄ samples and BiVO₄ powders confirm the involvement of hydroxyl radicals and the separation efficiency of electron-hole pairs in MB photocatalytic degradation. Besides, the T-BVO-600 exhibits good recyclability for MB removal, achieving a removal rate of above 83% after five cycles. The T-BVO-600 has the features of high efficiency and good recyclability for MB photocatalytic degradation. These results provide new insight into the purpose of improving the photocatalytic activity of BiVO₄ catalyst.

In the present study, we reported the codetermination of highly bioactive compounds, namely, hydroxychavicol, eugenol, and gallic acid in the Piper betle Linn. leaf extract by high‐performance liquid chromatography method. These compounds are of great interest in the pharmaceutical field and also in other food‐related applications owing to their impressive biological and pharmaceutical properties. Moreover, antibacterial and antioxidant activities of the extracts produced by different extracting solvents were also investigated in detail. The methanol extract was found to contain the highest amounts of hydroxychavicol and gallic acid thus offering the strongest antioxidant activity in 1,2‐diphenyl‐2‐picrylhydrazyl free radical scavenging assay. All the three compounds were found at low levels in the hexane extract. However, the solvent type did not affect significantly on the concentration of extracted eugenol. The ethanol, methanol, and ethyl acetate extracts exhibited strong inhibitory effects against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Salmonella typhimurium whereas the hexane extract showed negligible antibacterial activity. These findings suggest that ethyl acetate is a good choice to produce a highly antibacterial extract but methanol and ethanol are more suitable when the antioxidant activity of the extract is more concerned.

Recently, organic contaminants from textile and dye industry have adversely affected on human’s health and living things. Hence, the development of effective contaminated water treatment is one of the most crucial tasks. Expanded Graphite (EG) has been considered as efficient platforms to remove of organic dyes from aqueous solution due to its excellent performance. The main objective of the present work is to investigate adsorption behavior of methylene blue (MB) and Congo Red (CO) on exfoliated graphite fabricated using flake graphite from Yen Bai province. The exfoliation of graphite was carried out using potassium permanganate and perchloric acid as oxidant agent and anhydride acetic as intercalating agent via microwave-assisted technique. The properties of EG were characterized by X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy and nitrogen adsorption/desorption analysis. In batch adsorption experiments, various factors including initial dye concentration (50–600 ppm), adsorbent dosage (0.5–3 g/L), contact time (10–120 min) and pH of solution (4–10) were also studied. It is found that as-prepared EG provided high removal efficiency and fast adsorption rate for MB and CO. The maximum adsorption capacity of EG for CO and MB was found at 201.21 and 47.62 mg/g, respectively. These results demonstrate that the as-synthesized EG appears as an efficient and low-cost platform for remediation of colored effluents via adsorption route.