Photocatalytic nanotechnology is one of the techniques that brings many new breakthroughs since it possesses high potential for the supply of clean energy and the degradation of persistent organic pollutants in the environment. The drawback of photocatalytic materials such as TiO2, ZnO, V2O5 is the activation only under ultraviolet light. To extend the applicability of photocatalytic nanomaterials to a visible light region, recent research has focused on the modification of semiconducting photocatalysts. In this study, V2O5-MgO/TiO2 mixed oxide nanocomposites were synthesised via a sol-gel method by using polyvinyl alcohol as a gelling agent. The basic structural characteristics of nanocomposites were determined by analytical techniques such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET, energy dispersive x-ray (EDX), x-ray diffraction (XRD), infrared (IR) and ultraviolet-visible (UV–vis) spectroscopy. The results obtained from EDX and XRD analyses indicate that V2O5 and MgO particles with a size between 14.5 and 21.3 nm were formed and uniformly dispersed in TiO2 phases. Moreover, the effects of oxide weight ratios, illuminating conditions and reaction time on the photocatalytic activity of the nanocomposites were investigated via CO conversion with the input CO concentrations of 8000 ppm. Significantly, the V2O5-MgO/TiO2 nanocomposites were used for treating CO in motorcycle exhaust fumes. The efficiency of the process reached 82% for 10 min, indicating the potential applicability of the V2O5-MgO/TiO2 nanocomposites for the CO treatment of industrial emissions.

Marine debris assessment gives information about their quantity, type, and composition, which provides data to help with their management and control. The authors conducted two surveys at three beaches at Sam Son, Hai Tien, Hai Hoa) in Thanh Hoa province in March 2020 and July 2020, respectively, during an inactive and active tourism period. A total of 3,803 waste units were collected for assessment, of which plastic waste accounts for more than 98%. The density of marine debris at the idle time of tourism ranged from 0.25–1.21 items/m2. But the active tourist season recorded from 0.52–1.4 items/m2. According to the Clean Coast Index (CCI), the cleanliness of beaches was grade from average clean (i.e., Hai Tien) to filthy (i.e., Hai Hoa). The plastic debris present at these beaches was mainly porous waste derived from fishing boats and food preservation foam boxes. The results also showed that the marine debris was composed of 77% polystyrene (PS), 17% polypropylene (PP) and 6% high-density polyethylene (HDPE). The water parameters were lower than the critical values during the study period according to the QCVN 10-MT:2015/BTNMT for both periods, which indicated the coastal water quality was still suitable for recreational activities.

Photocatalytic technology has many new applications and great potential in providing clean energy and decomposing organic pollutants in the environment. Among them, TiO2 is a good photochemical catalyst, but has a limitation that is only shown in ultraviolet light. To expand the application of photocatalytic materials using solar radiation in visible light, this research focuses on the semiconductor photochemical transformation process. In this study, TiO2-Eu2O3 nanomaterial was synthesised by the sol-gel method with polyvinyl alcohol used as gelling agent. The effects of the contents of TiO2, Eu2O3 and the sintering temperature of the gel were investigated. The obtained material samples were analysed for characteristics and properties by the surface analysis techniques SEM, EDX, TEM, XRD, the infrared spectrum and the UV–vis molecular absorption spectrum. Analysis of modified TiO2 according to EDX, XRD showed the formation of crystalline and evenly dispersed Eu2O3 particles in TiO2 phases with an average particle size of 20–50 nm. The photocatalytic activity of TiO2-Eu2O3 nanoparticles was determined by the phenol decomposition efficiency in the hypothetical water sample and the actual wastewater samples with a concentration of 10 ppm under ultraviolet light and visible light. The resulting phenol decomposition was more than 90% efficient after about 150 min.

This paper presents the results of a study on the impacts of the interaction of tide and river flow on water quality at the Hai Phong coastal water, outside the Nam Trieu estuary and Lach Huyen, drawn from field observation from October 14, 2022, to October 17, 2022. During the field observation, the dissolved oxygen concentration was measured, and water samples were taken at the surface, mid-depth, and bottom of 8 observational points at 1:00, 7:00, 13:00, and 19:00 h. Five sewage wastewater samples at Do Son coast and 6 coastal and river water samples were also taken. The collected seawater samples were laboratory analyzed to determine the concentration of BOD5, COD, TN, and TP. Additionally, the concentration of ions NH4+, NO2-, NO3-, and PO43- are determined by analyzing collected coastal, river, and sewage water samples and seawater samples at mid-depth at all observational points in a laboratory. It was found that the concentration of essential nutrients and other environmental components in wastewater samples generally does not exceed those specified in Vietnam regulations. The discharge of wastewater during the field observation was minimal. Thus it could be expected that the wastewater would not have a notable influence on seawater quality in the marine study area. Consequently, the study area’s primary source of nutrient pollutants was rivers. Time variation of the concentration of environmental components reveals that the nutrient concentration in the marine study area strongly influences by the interaction of the tide and river flow. The concentration of dissolved oxygen and major nutrient components in seawater at 8 points was within the limit of Vietnam standard for coastal water. However, significant nutrient concentration exceeds thresholds for eutrophication.