Search

A new hopan-type triterpenoic peracid, tinctoride A (1), together with three known compounds, zeorin (2), 6β,22-dihydroxyhopane (3), and ergosterol peroxide (4), was isolated from Parmotrema tinctorum (Despr. ex Nyl.) Hale. Their chemical structures were identified by extensive 1D and 2D NMR analysis and high-resolution mass spectroscopy and compared with those reported in the literature. The enzyme inhibitory potential of compounds 1–3 against α-glucosidase was investigated, exhibiting nil to weak inhibitory activity.

Untreated or inadequately treated domestic wastewater has adversely affected the aquatic environment and public health in many cities in Vietnam. A conventional anaerobic–anoxic–oxic (AAO) process is recognized as an easy-to-handle approach that constrains chemical use during the procedure. Herein, we improve an AAO system by adding more oxic orders in association with a biological membrane in order to increase the hydraulic retention time (HRT) of the oxic zone in the system. The investigated system was applied to the treatment of real domestic wastewater during 168 days of operation. The performance of the system reached a stable state after 60 days of operation. The removal efficiency of total nitrogen (TN), total phosphorus (TP), total suspended solids (TSS), biological oxygen demand (BOD5), and chemical oxygen demand (COD) was found to be 93.6 ± 3.0%, 91.9 ± 3.5%, 88.6 ± 1.2%, 82.6 ± 1.4%, and 71.8 ± 0.7%, respectively. After the operation process, the TN, TP, and TSS contents in the wastewater effluents met the A level in accordance with the QCVN 14-MT:2015/BTNMT regulation, and the effluents of COD and BOD5 almost satisfied the requirement, with only some points being slightly higher than the limit values. The obtained data revealed that the AAO/O system was capable of treating domestic wastewater in small and medium-sized domestic wastewater treatment facilities.

In this study, macadamia nutshell residue, a prevalent leftover and green agricultural waste in Vietnam, was utilized to prepare a magnetic activated carbon adsorbent. The obtained material was characterized by its surface functionalities, elemental composition, crystalline structure, and magnetic properties. The characterization results revealed that the composite comprised Fe3O4 nanoparticles attached to the carbon matrix. The saturation magnetization (Ms) of the composite was found to be 38.2 emu g−1, indicating a convenient separation of the solid adsorbent from aqueous media using an external magnetic field. The feasibility of removing zinc (II) ion from an aqueous solution of the activated carbon/Fe3O4 (AC/Fe3O4) composite was examined. The adsorption kinetics were best explained by the Elovich model and the pseudo-second-order model. The adsorption capacity at equilibrium and the initial rate of Zn2+ adsorption determined by the pseudo-second-order model were 22.73 mg g−1 and 4.18 mg g−1 min−1, respectively. The implications of this study are that a low-cost, green, and magnetically separable material prepared by a large-scale available solid waste can be a promising adsorbent for the elimination of heavy metals.

Plant-derived coagulants have exhibited a good potential in wastewater treatment due to their “green” characteristics, high coagulating-flocculating activity, cost-effectiveness, and biodegradability. Nevertheless, research studies have focused mainly on bench-scale experiments; pilot-scale and full-scale simulations are still limited. Herein, we firstly report a pilot-scale study of real domestic textile wastewater treatment using Cassia fistula coagulant. The material characterizations using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and dynamic light scattering (DLS) revealed that the natural gum extracted from C. fistula seed possessed a rough and irregular surface containing a high molecular weight galactomannan. The bench-scale investigation was initially conducted to determine the optimal pollutant concentration, initial pH, and coagulant dosage in the coagulation-flocculation process. The pilot-scale study revealed that C. fistula coagulant is an effective material for real textile wastewater treatment, showing percentage removal of 93.83% at a volume of 30 L and a coagulant dosage of 1.17 mg·L−1. Coagulation-flocculation using C. fistula seed gum could be an efficient primary wastewater treatment prior to membrane or biological methods to meet Vietnamese environmental standards. The main mechanisms of textile wastewater treatment involve adsorption/bridging interactions via hydrogen bonding and electrostatic attraction between negatively charged carboxylate groups of the coagulant and positively charged pollutants.

Coagulants derived from plants have shown great potential in wastewater treatment, with good coagulation–flocculation performance, economic benefits and high environmental friendliness. Therefore, the coagulation–flocculation processes conducted by coagulants prepared from Cassia fistula and tamarind seeds were studied for the removal of Cu2+ ions. Fourier-transform infrared spectra, scanning electron microscopy images and nitrogen adsorption–desorption analysis of the synthesized coagulants indicated the presence of many important functional groups along with preferable surface characteristics for the removal of heavy metal ions. The effects of different variables, including initial solution pH and coagulant dosage, were also estimated to reveal the optimal conditions for Cu2+ removal as pH 5.0 and a dosage of 0.6 g/L of C. fistula seed-derived coagulant and 1.5 g/L of tamarind seed-derived coagulant. A further pilot-scale study at a volume of 30 L revealed the great efficiency of C. fistula coagulant for removing Cu2+ ions from real wastewater, with 89.45% removal at a dosage of 0.884 g/L. The obtained results have proved the great potential of these bio-coagulants. [ABSTRACT FROM AUTHOR]

Conventional optimal power flow studies neglect the effect of temperature on resistance for simple calculation. However, the branch resistance changes with the change of temperature. Thus, the optimal power flow (OPF) should consider the temperature effect for accurate calculation. Moreover, contingency cases should be considered to ensure system security. Accordingly, the security-constrained temperature-dependent optimal power flow (SC-TDOPF) emerges as a critical and practical issue in power systems. To deal with the SC-TDOPF problem, this study suggests a hybrid method, namely pseudo-gradient based particle swarm optimization and differential evolution method (PGPSO-DE). The suggested PGPSO-DE method is applied to the standard IEEE 30 bus system under normal condition as well as contingency condition. The findings have shown that the PGPSO-DE method provides better solution quality than other studied optimization methods. Consequently, the PGPSO-DE method proves its effectiveness in solving the complex SC-TDOPF problem. [ABSTRACT FROM AUTHOR]