This study evaluated the efficiency of tannin removal from vinasse using sugarcane bagasse as a biosorbent before and after citric acid modification. A central composite design optimized the modification process, considering bagasse mass, citric acid concentration, and reaction time as independent variables. The FTIR intensity ratio at 1,730/3,400 cm-1 (I1730/I3400) was the response variable, where an increase indicated greater carbonyl incorporation, with 1,730 and 3,400 cm-1 assigned to C=O and O–H stretching, respectively. We optimized the biosorption conditions using the same statistical design, with pH, bagasse mass, and vinasse concentration as the factors and tannin removal efficiency as the response. Both raw and modified bagasse samples were characterized by FTIR, SEM, pHpzc, and surface functional group analysis; the spent adsorbent was analyzed by FTIR and confocal microscopy. Optimal modification was achieved with 10% w/v citric acid, 1.0 g bagasse, and a 20-minute reaction, yielding an FTIR I1730/I3400 ratio of 1.458, indicating successful esterification. The optimal biosorption contact time was set at 120 minutes based on kinetic data showing rapid adsorption during the initial 30 minutes. Under these conditions, citric acid-modified bagasse outperformed raw bagasse in terms of both removal efficiency and pH independence. The kinetic data conformed to a pseudo-second-order model, indicating that intraparticle diffusion was not the sole adsorption mechanism. The equilibrium data fit the Freundlich isotherm, and the experimental adsorption capacity reached 64.84 mg g-1 under optimal conditions. Evidence suggests that tannin adsorption onto citric acid-modified bagasse occurs via a mixed mechanism involving both physical and specific surface interactions. Confocal microscopy confirmed the presence of phenolic compounds on the bagasse surface. These results highlight the potential of citric acid-modified bagasse for treating tannin-rich effluents. Further research should address surface area, regeneration, and performance of diverse adsorbates to fully realize the potential of these sustainable materials.
Understanding the effects of temperature variations on pollutant dynamics is crucial for enhancing the accuracy of simulations of contaminant transport under climate change scenarios and groundwater protection. This study examines how temperature influences the migration of ammonium (NH4+) through silty sandy soils at an unsanitary landfill. Laboratory tests were used to measure the adsorption, diffusion, and permeability coefficients of these soils at four temperatures: 10 °C, 20 °C, 40 °C, and 50 °C. The results indicated that the apparent distribution coefficient (Kad) peaked at 20 °C but decreased at lower (10 °C) and higher (40–50 °C) temperatures. Diffusion analysis revealed that the diffusion coefficient increased from 5.0 × 10⁻10 m2 s-1 at 10 °C to 2.0 × 10⁻9 m2 s-1 at 50 °C, indicating that the ammonium diffusivity increases rapidly with temperature. Moreover, the hydraulic conductivity of the sand increased with both temperature and ammonium concentration, with the permeability increasing slightly from 1.46 × 10⁻6 m s-1 at 10 °C to 1.63 × 10⁻6 m s-1 at 50 °C. The simulations confirmed that the relationship between temperature and break-through behavior is nonmonotonic, reflecting coupled physicochemical transport and the competing influences of advection, diffusion, and adsorption processes. These findings highlight the urgent need for technical and management solutions to minimize environmental risks.
Coastal regions are increasingly under compounded pressures from climate change and rapid socioeconomic development, and integrated approaches to sustainability assessment are needed. This study assesses coastal sustainability in Ho Chi Minh City by developing a composite sustainability index (CSI) structured around three key dimensions: socioeconomic, ecoenvironmental, and institutional management. An integrated coastal zone management (ICZM) framework was adopted to reorganize the index system, enhancing cross-dimensional linkages while explicitly clarifying the predominant role of the environmental dimension and the coordinating function of management. The CSI was quantified and spatially represented through the integration of multicriteria decision-making (MCDM), geographic information systems (GIS), and remote sensing. The results indicated that the CSI values ranged from 0.378 to 0.630, with half of the subareas falling within low to moderate levels, reflecting significant imbalances among the three dimensions. Although the eco-environmental component remained predominant (49%), the findings revealed clear trade-offs between economic growth and environmental quality. Overall, ecosystem degradation emerged as the primary driver of reduced sustainability, highlighting the need to prioritize mangrove conservation and restoration alongside strengthened environmental monitoring within an ICZM-based planning approach. Beyond the case study, the proposed CSI provides a transferable, spatially explicit ICZM-based framework to support sustainability assessment and evidence-based decision-making across coastal regions.
Forest fires are recurrent dry-season hazards in northern and western Thailand, yet their short-term spatial dynamics remain insufficiently understood. In this study, weekly spatiotemporal dynamics of forest fire hotspots in Tak Province, Thailand, were examined using Visible Infrared Imaging Radiometer Suite (VIIRS) active-fire data and GIS-based directional analysis. Hotspots from five fire seasons (2021–2025) were grouped into 24 weekly intervals beginning on 1 December. The analysis integrated weekly hotspot counts, forest-type compositions, mean-center trajectories, standard deviational ellipses, temporal changes in topographic characteristics, and fishnet-based hotspot persistence mapping. The results revealed that fire activity was highly concentrated during the middle of the fire season, with 20,957 hotspots or 89.45% of all detections occurring during weeks 8–16. Dry dipterocarp forest and mixed deciduous forest together accounted for more than 96% of all the hotspots. Directional analysis indicated that hotspot activity was not distributed randomly but became most spatially organized during the middle phase, when centroid movement was more consistent and hotspot distributions showed a stable northwest–southeast directional alignment. Weekly hotspot occurrence also shifted toward higher elevations, deeper forest interiors, steeper slopes, and more rugged terrain as the fire season progressed. Persistence analysis further revealed that high- and very high-persistence cells represented only 5.81% of the grid system but formed recurrent fire-prone cores concentrated in deciduous mountain forests. These findings demonstrate that forest fire activity in Tak Province is characterized by seasonal concentration, directional organization, temporal changes in topographic characteristics, and spatial persistence. The GIS-based directional framework provides an operational basis for identifying priority periods and locations for targeted fire monitoring and prevention.
In recent decades, the decrease in rice cultivation areas in Vietnam, particularly in the Mekong River Delta, caused by climate change and soil salinization, has posed serious challenges for sustainable development. In addition to irrigation and agronomic practices, fertilizers that sustain rice growth under saline conditions play a crucial role in improving crop productivity. Amorphous silica has been reported to increase plant tolerance to drought, salinity, and heavy metal stress. In this study, nanosilica-coated urea (UCS) fertilizers were synthesized by coating urea granules with 1–5 wt% amorphous silica. The products were characterized by SEM, XRD, FTIR, TG‒DSC, and EDX to confirm their structural and chemical features. Laboratory-scale experiments on saline soils revealed that UCS reduced total dissolved salt (TDS) content by up to 40% after 30 days, increased soil organic nitrogen and silicon contents by more than 15%, and promoted stable rice growth. After 30 days, the height of the rice treated with UCS1 reached 42–44 cm, which was 124% greater on average than that with conventional urea (18–30 cm), and higher survival rates were maintained (up to 90% vs. 40%). The growth stages of rice under mild to moderate salinity conditions were evaluated throughout a 120-day cultivation period. These results highlight the strong potential of urea‒silica fertilizers for sustainable rice cultivation in saline soils (0.5%–1% NaCl).
