The occurrence of nine phthalic acid esters (PAEs) were determined in indoor dust samples collected from vehicle repair shops, waste processing workshops, and homes in Vietnam. Concentrations of ...total PAEs ranged from 585 to 153,000 (median 33,400 ng/g), which fall in the lower end of global range. The PAE levels in workplace dust (median 49,100; range 9210–153,000 ng/g) were significantly higher than those in house dust (median 23,700; range 585–83,700 ng/g), indicating waste processing activities as potential PAE sources. The most predominant compound was di-(2-ethyl)hexyl phthalate (DEHP), accounting for 62 ± 18% of total PAEs. Other major compounds were benzyl butyl phthalate (BzBP) (10 ± 12%), di-
n
-butyl phthalate (DnBP) (9.7 ± 7.7%), di-
n
-octyl phthalate (DnOP) (7.9 ± 8.1%), and diisobutyl phthalate (DiBP) (6.9 ± 5.0%). Proportions of BzBP and DnBP in some workplace dust samples were markedly greater than in common house dust, suggesting specific emission sources. Daily intake doses of selected PAEs (e.g., DnBP, DiBP, BzBP, and DEHP) through dust ingestion were much lower than reference doses, implying acceptable levels of risk.
Full text
Available for:
CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Phytoremediation and advanced oxidation processes are among the most promising techniques for removing organic pollutants from soils. A field trial was performed for six months to evaluate the effect ...of nano-Fe
3
O
4
on the degradation of organochlorine pesticide residues including Lindane,
p
,
p
′-dichlorodiphenyltrichloroethane (DDT),
p
,
p
′-dichlorodiphenyldichloroethylene (DDE), and
p
,
p
′-dichlorodiphenyldichloroethane (DDD) in pesticide-contaminated soils in the presence of vetiver in Bac Giang province, Vietnam. Vetiver was planted in three zones with different nano-Fe
3
O
4
concentrations. Soil samples from each zone were periodically collected to determine the remaining concentrations of selected organochlorine pesticides via gas chromatography–electron capture detector. Results indicated that the total DDT concentrations in the examined soil were 1.9–13 times higher than the permissible threshold level (10 µg g
−1
) established by the national technical regulation on pesticide residues in soil. The (
p
,
p
′-DDE +
p
,
p
′-DDD)/
p
,
p
′-DDT ratios ranged from 13.5 to 114, indicating the absence of recent inputs of technical DDTs at the study area. DDT dechlorination mainly occurred under aerobic pathways to form DDE. Furthermore, DDE degradation in soil was adequately described by the pseudo-first-order kinetics model (
R
2
> 0.892). In the presence of vetiver, the rate constants of DDE degradation were 0.264, 0.350, and 0.434 month
−1
with 0, 25, and 100 mg kg
−1
of added nano-Fe
3
O
4
, respectively, indicating that the degradation of DDE correlated positively with Fe
3
O
4
concentration in the soil. Additionally, the presence of vetiver and nano-Fe
3
O
4
in the soil increased DDT removal rates, which might be linked to the involvement of Fenton/Fenton-like reactions.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Display omitted
•The ErGO was modified on the glassy carbon electrode by electrochemical reduced method.•The characteristics of graphene oxide and reduced graphene oxide were studied by FT-IR, XRD, ...TEM, SEM.•A sensitive and selective ErGO/GCE was fabricated for determination of amaranth.•Analytical conditions and procedure were optimized and validated.•The developed method was applied to analysis amaranth in food samples.
In this study, the manufacturing conditions of glassy carbon electrode modified with electrochemical reduced graphene oxide (ErGO/GCE) were elucidated to determine amaranth in soft drink and candy samples by adsorptive stripping voltammatry. The ErGO/GCE was fabricated through an electrochemical reduction process of graphene oxide in the potential range from 0 V to −1.5 V using cyclic voltammetry method. Characteristics of graphene oxide and reduced graphene oxide were studied by FT-IR, XRD, TEM, SEM. Amaranth is adsorbed on the ErGO/GCE working electrode surface through an irreversible oxidation process. The optimal conditions used to determine amaranth are Britton-Robinson buffer solution of pH 3.0, an adsorption potential at 0 V, an adsorption time of 30 s, at a scan rate of 20 mV/s, a linearity range from 1.0 × 10−7 mol. L−1 to 1.0 × 10−6 mol. L−1, a (LOD) detection limit of 2.8 × 10−8 mol. L−1 and a (LOQ) qualification limit of 9.3 × 10−8 mol. L−1. The proposed method can be applied to determine amaranth dye in food.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Earlier studies have reported the occurrence of cyclic and linear siloxanes in personal care and household products. Nevertheless, there is a lack of information on the occurrence of siloxanes in ...indoor air. In this study, four cyclic and six linear siloxanes were measured in 97 indoor air samples collected from various micro-environments in four cities in northern, Vietnam, during September 2016 to January 2017. The total concentrations of siloxanes (TSi) in particulate and gas phases ranged from 141 to 7220 μg g−1 (mean: 1880) and 23.8–1580 ng m−3 (mean: 321), respectively. The total concentrations of cyclic siloxanes (TCSi), linear siloxanes (TLSi), and TSi in indoor air were 1.91–1500 ng m−3, 21.8–817 ng m−3, and 41.8–1950 ng m−3, respectively. The highest mean concentration of siloxanes was found in indoor air from hair salons in Hanoi. The concentrations of siloxanes in air collected from homes in Hanoi were higher than those from other smaller cities such as Bacninh, Thaibinh, and Tuyenquang. The human exposures to siloxanes through inhalation were estimated for various age groups based on the measured concentrations. The mean inhalation exposure doses to total siloxanes for infants, toddlers, children, teenagers, and adults were 352, 219, 188, 132, and 95.9 ng kg-bw−1 d−1, respectively.
Display omitted
•Siloxanes were found widely in indoor air from Northern in Vietnam.•Mean concentration of cyclic and linear siloxanes was 228 and 469 ng m−3, respectively.•The highest siloxanes concentrations were measured at hair salons.•The significant correlation existed between D4, D5, and D6 in indoor air.•Mean exposure dose to siloxanes through inhalation by infants was 1020 ng kg-bw−1 d−1.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Titanium dioxide/graphitic carbon nitride (TiO2/gC3N4) nanocomposite was successfully synthesized via the mixing of graphitic carbon nitride (gC3N4) with bulk titanium dioxide (TiO2) under ...sonication. The effect of precursor ratio on the morphological structure and photocatalytic hydrogen peroxide (H2O2) production performance was also investigated. According to the results, the TiO2 was successfully embedded and evenly distributed onto the structure of the gC3N4. Moreover, the as-prepared material with the TiO2 content of 20 % with respect to gC3N4 and catalyst dosage of 3 mg also possessed the greatest photocatalytic performance with an H2O2 production capacity of more than 3000 μM·g−1·h−1. Besides, the material also exhibited great recyclability, which remained at 70 % of the original performance after 5 consecutive reusing cycles. Following to the aforementioned results, the TiO2/gC3N4 nanocomposite can be considered a potential material for the photocatalytic production of H2O2.
Display omitted
•Synthesize TiO2/gC3N4 material by ex-situ method with the mixing of gC3N4 with bulk TiO2 under ultrasonication conditions•Investigate the characterization of TiO2/gC3N4•Investigate the condition factors of photocatalytic production of H2O2 of the TiO2/gC3N4 material
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Zinc oxide - doped titanium dioxide/reduced graphene oxide (ZnO-TiO2/rGO) nanocomposite was fabricated by the two-step hydrothermal method and used for adsorption and photodegradation of methylene ...blue in aqueous solution under UV irradiation. The characteristics of the catalyst material were confirmed by Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, scanning electron microscope, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer-Emmett-Teller specific surface area, thermal gravimetric analysis, and UV-vis spectroscopy. The results showed that the presence and uniform distribution of TiO2 and ZnO nanoparticles on the rGO surface with an average diameter of 20 – 30 nm and high specific surface area (182.52 m2/g). The photodegradation was investigated via the pH media. The equilibrium adsorption at pH of 9 achieved the highest adsorption efficiency after 60 min (43.68 %) and 60 min photodegradation (99.84 %). According to the results, the photodegradation using ZnO-TiO2/rGO nanocomposite was stated to be a promising pathway for removing the organic dye from water.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Recycling biomass to cellulose aerogel (Cell-A) provides a promising approach to develop adsorbent materials for spilled-oil recovery. In this work, Cell-A was fabricated from Vietnamese water ...hyacinth via crosslinking methods using PVA as a crosslinker and freeze-drying process. Various cellulose to PVA ratios were investigated to obtain the optimal synthesis condition. The Cell-A was additionally modified by dip-coating in poly(dimethylsiloxane) (PDMS) and pyrolyzing to form PDMS-coated cellulose aerogels (Cell-AP) and carbon aerogels (CA), respectively. Results of the oil adsorption tests show that pyrolysis produced aerogels with greater adsorption capacity with an optimal mass ratio of 15 : 1 cellulose to PVA. Furthermore, the pseudo-second-order model was found to be more accurate than the pseudo-first-order model for the study of oil absorption kinetics. As a result, the modified cellulose aerogel is promising for replacing earth-unfriendly polymer-based oil sorbents due to their high oil absorption capacity.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•The min-cost parallel drone scheduling vehicle routing problem (PDSVRP) is introduced.•A mixed integer linear program and a Ruin and Recreate (R&R) algorithm are proposed.•Extensive experiments are ...carried out to investigate the performance of the methods.•CART method is used to perform a sensitivity analysis on the impact of drone delivery.•R&R dominates other algorithms proposed for the PDSTSP in terms of solution quality.
Adopting unmanned aerial vehicles (UAV), also known as drones, into the last-mile-delivery sector and having them work alongside trucks with the aim of improving service quality and reducing the transportation cost gives rise to a new class of Vehicle Routing Problems (VRPs). In this paper, we introduce a new optimization problem called the min-cost Parallel Drone Scheduling Vehicle Routing Problem (PDSVRP). This problem is a variant of the well-known Parallel Drone Scheduling Traveling Salesman Problem (PDSTSP) recently introduced in the literature in which we allow multiple trucks and consider the objective of minimizing the total transportation costs. We formulate the problem as a Mixed Integer Linear Program and then develop a Ruin and Recreate (R&R) algorithm. Exploiting PDSVRP solution characteristics in an effective manner, our heuristic manages to introduce “sufficient” rooms to a solution via new removal operators during the ruin phase. It is expected to enhance the possibilities for improving solutions later in the recreate phase. Multiple experiments on a new set of randomly generated instances confirm the performance of our approach. To explore the benefits of drone delivery as well as the insight into the impact of related factors on the contribution of drones’ use to operational cost, a sensitivity analysis is conducted. We also adapt the proposed algorithm to solve the PDSTSP and validate it via benchmarks available in the literature. It is shown that our algorithm outperforms state-of-the-art algorithms in terms of solution quality. Out of 90 considered instances, it finds 26 new best known solutions.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
