In this study, the biosorption mechanisms of methylene blue (MB) and Cr(III) onto pomelo peel collected from our local fruits are investigated by combining experimental analysis with ab initio simulations. Factors that affect the adsorption such as pH, adsorption time, adsorbent dosage and initial adsorbate concentration, are fully considered. Five isotherm models—Langmuir, Freundlich, Sips, Temkin, and Dubinin–Radushkevich—are employed to estimate the capacity of pomelo peel adsorption, whereas four kinetic models—pseudo-first-order, pseudo-second-order, Elovich and intra-diffusion models—are also used to investigate the mechanisms of the uptake of MB and Cr(III) onto the pomelo fruit peel. The maximum biosorption capacities calculated from the Langmuir models for MB and Cr(III) at 303 K are, 218.5 mg g⁻¹ and 11.3 mg g⁻¹, respectively. In particular, by combining, for the first time, the experimental FT-IR spectra with those obtained from ab initio calculations, we are able to demonstrate that the primary adsorption mechanisms of the uptake of MB onto pomelo fruit peel are electrostatic attraction and hydrogen-bond formations, whereas the adsorption mechanisms for Cr(III) are electrostatic attraction and n–d interactions.

Lanthanum (La)-doped zinc oxide nanoparticles were synthesized with different La concentrations by employing a gel combustion method using poly(vinyl alcohol) (PVA). The as-synthesized photocatalysts were characterized using various techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX), photoluminescence (PL) spectroscopy, and UV–visible absorption spectroscopy. The average size of ZnO nanoparticles decreased from 34.3 to 10.3 nm with increasing concentrations of La, and the band gap, as evaluated by linear fitting, decreased from 3.10 to 2.78 eV. Additionally, it was found that the photocatalytic activity of doped samples, as investigated by using methyl orange dye under visible lights, improved in response to the increase in La concentration. The decomposition of methyl orange reached 85.86% after 150 min in visible light using La0.1Zn0.9O as the photocatalyst.

Basil plant is a common source for linalool and estragole. However, it has been showed that the chemical composition of basil varies considerably depending on many factors including method of extraction, cultivar of the plant or geographical location. In this study, we attempted to extract essential oil from Vietnamese basil and analyze the chemical composition of the obtained oil using gas chromatography–mass spectrometry (GC-MS). The extraction method of choice was microwave-assisted hydro-distillation (MAHD) and the process was optimized with Response Surface Methodology (RSM) with regard to four experimental parameters including raw material size, raw material to water ratio, extraction time and microwave power. The results showed that ground basil leaves, when extracted with optimal conditions of water-to-material ratio of 3.2:1, extraction time of 97 (min) and microwave power of 430 (W), gave the actual essential oil yield of 0.6%. Regarding ANOVA results of the quadratic model, high determination coefficient (R² = 0.9077), significant F-value of 10.92 and the p-value of less than 0.05 indicate that this model is significant between experimental and predicted variables, and should be fixed. In addition, GC-MS analysis revealed that major components of Vietnamese Basil were Estragole (87.869%), α-Bergamotene (2.922%), τ-Cadinol (2.770%), and Linalool (1.347%).