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1,3-Diphenyl-2-thiourea (DPTU) and 1-phenyl-3-(2-pyridyl)-2-thiourea (PPTU) were selected as the researched subject for investigating the effect of heteroatoms on the low carbon steel corrosion inhibition ability. Results from the potentiodynamic polarization measurements (PPM) indicate that the addition of a nitrogen atom in the benzene ring increases the corrosion inhibition efficiency of PPTU (97.2%), being higher than that of DPTU (93.1%) at the same condition of 2.0 × 10–4 M at 30 °C. The Nyquist diagrams show that increasing the concentrations of both DPTU and PPTU will enhance the charge-transfer resistance and reduce the double-layer capacitance. The obtained data based on PPM and electrochemical impedance spectroscopy methods are in accordance to the analysis based on the scanning electrochemical microscopy images. Besides, results from quantum chemical calculations prove that the heteroatoms in the inhibitor molecules are the adsorption centers, and the benzene rings increase the electrostatic interaction between the inhibitor molecules and the steel surface. Results from Monte Carlo and molecular dynamics simulation have clarified the adsorption mechanism of DPTU and PPTU on the steel surface. Adsorption energies confirm that PPTU displays the higher inhibition ability as compared with DPTU.

The Duyen Hai Seaport covering more than 427 hectares of water surface is part of a Duyen Hai thermal power plant complex. In the last years, port operations can lead to impact on air, water, land, and the ecosystem. To evaluate the ecological risk caused by heavy metals at the Duyen Hai Seaport, 17 surficial sediment samples were collected along the ship flow from shoreline to the material submerged zone in April 2019. The total concentrations of some heavy metals including lead, cadmium, arsenic, copper, zinc, and mercury were analyzed by using atomic absorption spectrophotometry. The experimental results indicated that there were significant and positive correlations between various heavy metals studied. The geo-accumulation index (Igeo), the potential ecological risk index (RI), and the degree of contamination (Cd) were calculated for evaluating the risks of heavy metal in sediment samples. The Igeo values showed that the Duyen Hai Seaport is slightly contaminated by heavy metals, especially by Cd. Generally, the low potential risk of heavy metal was observed from the values of RI. The potential ecological risk index of heavy metals was found in the order ER (Hg)>ER (Cd)>ER (As)>ER (Pb)>ER (Zn)>ER (Cu), which revealed that Cd was the most important factor leading to the risk. These findings might be useful for making appropriate management strategies to prevent or decrease pollution by heavy metal at the Duyen Hai Seaport.

Dielectric phenomena at phase transition temperature for nanoparticles of triglycine sulfate (TGS) and Sodium Nitrite (NaNO2) embedded into the pores of bacterial nanocrystalline cellulose Acetobacter Xylinum have been investigated. It was shown that the phase transition temperature of these ferroelectrics at nanoscale level strongly changes as compared to those of the massif ferroelectrics: for hydrogen-containing triglycine sulfate nanoparticles the phase transition temperature was shifted to higher temperatures and for non-hydrogen-containing Sodium Nitrite nanoparticles – lower temperatures. The obtained results are explained by knowledge of size effects and the interaction between the matrix and ferroelectric inclusions through hydrogen-bond system as well as dipole-dipole interaction between TGS nanoparticles using a mathematical expansion based on Landau-Ginzburg-Devonshire theory.

The aim of this work is to clarify dielectric relaxation phenomena in paraelectric phase of composites based on nanocrystalline cellulose and triglycine sulfate. Although the dielectric properties of this material were almost thoroughly investigated, but there has been no study devoted to relaxation anomalies in paraelectric phase. The results showed the presence of Debye-like relaxation at the entire studied frequency range 103 – 106 Hz under a weak electric field of 1 V.m-1 from phase transition temperature in the composite (54 ˚C) to 90 ˚C. In addition, the phenomena were observed at lower frequencies as compared to those of triglycine sulfate single crystals. The results were explained by the assumption based on critical slowing down occurred in the nanoparticles in the composite.

The heavy metal pollution of sediment in the Nhue River, which receives wastewater from the To Lich and Kim Nguu River system, was investigated together with the effects of use of this water for irrigation of the surrounding farmland. Eighty soil samples and 40 sediment samples were collected from six locations in the Nhue River and two locations in the To Lich River for chemical and physical analyses. The results showed that the sediments in the Nhue River are heavily polluted by metals (71–420 mg/kg for Cu, 77–433 mg/kg for Pb, 150–350 mg/kg for Zn, 0.7–8.7 mg/kg for Cd, 80– 583 mg/kg for Cr, and 32–70 mg/kg for Ni). There were positive correlations between heavy metal concentration and both clay and organic matter contents in the sediment samples. The concentrations of all metals in soil samples were much higher than the background levels in the farmland, Cd, Cu, and Pb, exceeding Vietnamese standards for agricultural grounds.

There are two rivers in Hanoi City, Vietnam, the To Lich and Kim Nguu rivers, which are the main sources of irrigation water for suburban agricultural land and feed water sources for fish farming ponds. Industrial wastewater that has been discharged into the rivers has degraded the quality of sediments in the river system. The present study showed that sediments in the To Lich and Kim Nguu rivers are heavily polluted with heavy metals. Metal concentrations in sediments appear to be closely related to the type of manufacturing plants located along the rivers. The heavy metals were bound with sediment particles in fractions such as the exchangeable, carbonate, oxide, organic matter and residual fraction. Total heavy metal concentration in the sediment was correlated with organic matter content for copper, lead and nickel while no correlation was found for cadmium, zinc and chromium. Ethylene diamine tetra-acetic acid caused high heavy metal leachability in comparison with water, acetic acid and nitric acid. Average potential leachability decreased in the order: cadmium > nickel > chromium > copper = zinc > lead. The leachability exhibited a tendency of decreasing with increasing organic matter for heavy metals other than chromium and zinc. To reduce the pollutants discharged from plants, countermeasures by the government and the technological improvement of wastewater treatment in manufacturing processes are needed.

The To Lich and Kim Nguu Rivers, laden with untreated waste from industrial sources, serve as sources of water for irrigating vegetable farms. The purposes of this study were to identify the impact of wastewater irrigation on the level of heavy metals in the soils and vegetables and to predict their potential mobility and bioavailability. Soil samples were collected from different distances from the canal. The average concentrations of the heavy metals in the soil were in the order zinc (Zn; 204 mg kg−1) > copper (Cu; 196 mg kg−1) > chromium (Cr; 175 mg kg−1) > lead (Pb; 131 mg kg−1) > nickel (Ni; 60 mg kg−1) > cadmium (Cd; 4 mg kg−1). The concentrations of all heavy metals in the study site were much greater than the background level in that area and exceeded the permissible levels of the Vietnamese standards for Cd, Cu, and Pb. The concentrations of Zn, Ni, and Pb in the surface soil decreased with distance from the canal. The results of selective sequential extraction indicated that dominant fractions ...

The To Lich and Kim Nguu Rivers in Hanoi City are the main sources of irrigation water for suburban agricultural land and fish farm. Wastewater from the industrial plants located along these rivers has been discharged, and has degraded the water quality of the rivers. This study describes the chemical properties of water from the rivers, focusing on heavy metal pollution and the suitability of water quality for irrigation water. Water from the rivers was heavily polluted with organic matter and heavy metals such as Pb, Cu, Zn, Cr, Cd and Ni. Dissolved oxygen, chemical oxygen deman, and total suspended solids, and the concentrations of all heavy metals exceeded the Vietnamese standard for surface water quality in all investigated sites. The concentrations of some heavy metals such as Cu, Cd, Cr and Ni were above the internationally recommended WHO maximum level for irrigation water. A wide variation in the heavy metal concentration of water due to metal types is the result of wastewater discharged from different industrial sources.