Insight into chromium adsorption from contaminated soil using Mg/Al LDH-zeolite.

The study investigated the effectiveness of Mg/Al LDH-zeolite (MALZ) in immobilizing exchangeable Cr (e-Cr) within the soil. The research systematically evaluated various variables affecting the immobilization of e-Cr in contaminated soil (CS), including soil pH levels (ranging from 5.0 to 9.0), different weight ratios of MALZ (1 %, 3 %, and 5 %), durations of differing incubation periods (15, 30 and 45 days), and different SM content levels (30 %, 50 %, and 70 %). The initial concentration of Cr in the CS was maintained at 50 mg/kg. The investigation findings revealed that the optimal conditions for immobilizing the e-Cr were a soil pH of 5.0, an MALZ weight ratio of 3 %, an incubation period of 30 days, and an SM level of 70 %. Under these ideal conditions, the percentage of e-Cr within the CS decreased significantly, from 87.49 % (45.64 mg/kg) in the control treatment (CT) to just 19.82 % (10.08 mg/kg) when incubated with MALZ. The primary mechanisms responsible for immobilizing the e-Cr onto MALZ included pore filling, reduction processes, co-precipitation, organic interactions and electrostatic attractions leading to the formation of carbonate-bound complexes such as Cr(VI)-carbonate, Cr(III)-carbonate, and organic complexes. Surface functional groups on MALZ, housing iron and aluminium oxyhydroxides and silicon and oxygen elements, expedited these procedures. This study provided a valuable understanding of the mitigation of soils contaminated with chromium and contributed to understanding the relations between MALZ and the e-Cr in the soil. The discoveries carry substantial consequences for the advancement of efficient remediation technologies.

Enhancing/Improving Forming Limit Curve and Fracture Height Predictions in the Single-Point Incremental Forming of Al1050 Sheet Material.

Single-point incremental forming (SPIF) has emerged as a cost-effective and rapid manufacturing method, especially suitable for small-batch production due to its minimal reliance on molds, swift production, and affordability. Nonetheless, SPIF's effectiveness is closely tied to the specific characteristics of the employed sheet materials and the intricacies of the desired shapes. Immediate experimentation with SPIF often leads to numerous product defects. Therefore, the pre-emptive use of numerical simulations to predict these defects is of paramount importance. In this study, we focus on the critical role of the forming limit curve (FLC) in SPIF simulations, specifically in anticipating product fractures. To facilitate this, we first construct the forming limit curve for Al1050 sheet material, leveraging the modified maximum force criterion (MMFC). This criterion, well-established in the field, derives FLCs based on the theory of hardening laws in sheet metal yield curves. In conjunction with the MMFC, we introduce a graphical approach that simplifies the prediction of forming limit curves at fracture (FLCF). Within the context of the SPIF method, FLCF is established through both uniaxial tensile deformation (U.T) and simultaneous uniform tensile deformation in bi-axial tensile (B.T). Subsequently, the FLCF predictions are applied in simulations and experiments focused on forming truncated cone parts. Notably, a substantial deviation in fracture height, amounting to 15.97%, is observed between simulated and experimental samples. To enhance FLCF prediction accuracy in SPIF, we propose a novel method based on simulations of truncated cone parts with variable tool radii. A FLCF is then constructed by determining major/minor strains in simulated samples. To ascertain the validity of this enhanced FLCF model, our study includes simulations and tests of truncated cone samples with varying wall angles, revealing a substantial alignment in fracture height between corresponding samples. This research contributes to the advancement of SPIF by enhancing our ability to predict and mitigate product defects, ultimately expanding the applicability of SPIF in diverse industrial contexts.

Microplastics in Asian freshwater ecosystems: Current knowledge and perspectives.

Plastic pollution in freshwater ecosystems, including microplastics (MPs) smaller than 5 mm, has become an emerging global concern. Asia is considered a "hot spot" for plastic pollution due to rapid economic and demographic growth, together with rapid urbanization. Here, we provide an overview of the current knowledge on MP abundance, sources, fate, and transfer in Asian freshwater ecosystems based on publications from January 2014 to May 2021. MP contamination in freshwater compartments, including water, sediment, and biota, was found to vary strongly. In water, it ranged from 0.004 items m-3 in a moderately urbanized region to more than 500,000 items m-3 in a dumping river in a highly populated watershed. In the sediment, MP abundance ranged from 1 to more than 30,000 items kg-1 dry weight. Polyethylene (PE) and polypropylene (PP) were predominant in both water and sediment compartments. MP was detected in biota samples from all the studied species, but their abundance depended on the locations and species studied. Overall, MP characteristics (form, size, color, and polymer type) depended on sources and natural constraints (mainly hydrodynamics). This study also revealed that MP in Asian freshwater ecosystems mainly originated from domestic wastewater/runoff, followed by industrial emissions, fisheries and aquaculture wastewater. Plastic waste is not efficiently recycled or incinerated in Asia, leading to MP transfer and accumulation in the aquatic environment, and, more importantly, to ingestion by low to high trophic level organisms. This work highlights several knowledge gaps to guides future research to improve MP pollution management for the sustainable development of highly populated regions such as Asia.

Enhanced simultaneous adsorption of As(iii), Cd(ii), Pb(ii) and Cr(vi) ions from aqueous solution using cassava root husk-derived biochar loaded with ZnO nanoparticles.

This study presents the modification of cassava root husk-derived biochar (CRHB) with ZnO nanoparticles (ZnO-NPs) for the simultaneous adsorption of As(iii), Cd(ii), Pb(ii) and Cr(vi). By conducting batch-mode experiments, it was concluded that 3% w/w was the best impregnation ratio for the modification of CRHB using ZnO-NPs, and was denoted as CRHB-ZnO3 in this study. The optimal conditions for heavy metal adsorption were obtained at a pH of 6-7, contact time of 60 min, and initial metal concentration of 80 mg L-1. The heavy metal adsorption capacities onto CRHB-ZnO3 showed the following tendency: Pb(ii) > Cd(ii) > As(iii) > Cr(vi). The total optimal adsorption capacity achieved in the adsorption of the 4 abovementioned metals reached 115.11 and 154.21 mg g-1 for CRHB and CRHB-ZnO3, respectively. For each Pb(ii), Cd(ii), As(iii), and Cr(vi) metal, the maximum adsorption capacities of CRHB-ZnO3 were 44.27, 42.05, 39.52, and 28.37 mg g-1, respectively, and those of CRHB were 34.47, 32.33, 26.42 and 21.89 mg g-1, respectively. In terms of kinetics, both the pseudo-first-order and the pseudo-second-order fit well with metal adsorption onto biochars with a high correlation coefficient of R 2, while the best isothermal description followed the Langmuir model. As a result, the adsorption process of heavy metals onto biochars was chemisorption on homogeneous monolayers, which was mainly controlled by cation exchange and surface precipitation mechanisms due to enriched oxygen-containing surface groups with ZnO-NP modification of biochar. The FTIR and EDS analysis data confirmed the important role of oxygen-containing surface groups, which significantly contributed to removal of heavy metals with extremely high adsorption capacities, comparable with other studies. In conclusion, due to very high adsorption capacities for metal cations, the cassava root husk-derived biochar modified with ZnO-NPs can be applied as the alternative, inexpensive, non-toxic and highly effective adsorbent in the removal of various toxic cations.

Enhancement of exchangeable Cd and Pb immobilization in contaminated soil using Mg/Al LDH-zeolite as an effective adsorbent.

In the present study, experiments using zeolite and Mg/Al LDH-zeolite for immobilization of Cd and Pb ions in artificial soil were conducted. The conditions which affect Cd and Pb ion immobilization in soil were evaluated, namely soil pH (5-7), the mass ratio of adsorbents (1%, 3% and 5%), incubation time (15 days, 30 days and 45 days) and soil moisture (30%, 50% and 70%). The results indicated that the optimal soil pH, mass ratio of adsorbents, incubation time and soil moisture for immobilization of Cd and Pb ions by the adsorbent were, respectively, 7.0, 3%, 30 days and 70%. The exchangeable Cd ion content in the contaminated soil dropped from 22.17 mg kg-1 (87.65%) to 11.03 mg kg-1 (43.48%) and 6.47 mg kg-1 (26.36%) on incubation with zeolite and Mg/Al LDH-zeolite, respectively, while the exchangeable Pb content fell from 23.28 mg kg-1 (90.02%) to 14.12 mg kg-1 (54.04%) and 9.47 mg kg-1 (35.24%) using zeolite and Mg/Al LDH-zeolite as absorbents in contaminated soil, respectively. Fe-Mn oxide occluded (F2), carbonate bound (F3) and organically complexed (F4) were the main forms for immobilization of the exchangeable Cd and Pb when the zeolite and Mg/Al LDH-zeolite absorbents were separately cultivated into soil. Precipitation, co-precipitation and electrostatic attraction were the main mechanisms of exchangeable Cd and Pb immobilization onto the Mg/Al LDH-zeolite to form carbonate metals (CdCO3 and PbCO3). This was due to the surface functional groups of the adsorbent and the presence of Fe and Al oxyhydroxides, Mn oxides, and Si and O elements in the Mg/Al LDH-zeolite's constituents. The efficiency of Cd and Pb immobilization by the Mg/Al LDH-zeolite was higher than that by zeolite from 1.5 to 1.6 times. The Mg/Al LDH-zeolite showed an enhanced ability of exchangeable Cd and Pb immobilization in contaminated soil.

Identification of new-onset atrial fibrillation after cardiac surgery in Vietnam. A feasibility study of a novel screening strategy in a limited-resource setting: study protocol.

INTRODUCTION: Atrial fibrillation (AF) developing after cardiac surgery is the most common postoperative complication with an incidence up to 50%. The presence of postoperative AF is associated with significant morbidity, mortality and economic burden. However, in Vietnam, data on AF postcardiac surgery are limited, in part due to a shortage of screening equipment. This project aims to identify the incidence, risk factors and postoperative complications of new-onset postoperative AF after cardiac surgery, and the feasibility of introducing a novel screening strategy using the combination of two portable devices to detect AF. METHODS AND ANALYSIS: This is a feasibility study examining patients who are (1) ≥18 years old; (2) undergoing coronary artery bypass graft and/or valve surgery and (3) in normal sinus rhythm prior to their operation. Patients with congenital heart disease, a prior history of AF or those who require a pacemaker after surgery will be excluded. All patients will be followed up for the duration of their hospitalisation. The screening strategy will include monitoring the continuous ECG tracing in the intensive care unit, and if AF is suspected, a 30 s lead-1 ECG will be recorded using the smartphone-based AliveCor Kardia Mobile. On the postoperative wards, blood pressure will be measured three times daily using a modified blood pressure device (Microlife BP200 Afib): and if AF is suspected a 30 s ECG will be recorded using the AliveCor Kardia Mobile. A 12-lead ECG may be ordered subsequently if clinically indicated. The primary outcome is the incidence of postoperative AF. Secondary outcomes include establishing the risk factors and complications associated with postoperative AF; and the barriers and facilitators of the screening strategy. ETHICS AND DISSEMINATION: Ethics approval was granted by Scientific Board of Cardiovascular Centre, E Hospital on 28 September, 2017. Study results will be disseminated through local and international conferences and peer-reviewed publications.

Bioturbation effects on bioaccumulation of cadmium in the wetland plant Typha latifolia: A nature-based experiment.

The development of efficient bioremediation techniques to reduce aquatic pollutant load in natural sediment is one of the current challenges in ecological engineering. A nature-based solution for metal bioremediation is proposed through a combination of bioturbation and phytoremediation processes in experimental indoor microcosms. The invertebrates Tubifex tubifex (Oligochaeta Tubificidae) was used as an active ecological engineer for bioturbation enhancement. The riparian plant species Typha latifolia was selected for its efficiency in phyto-accumulating pollutants from sediment. Phytoremediation efficiency was estimated by using cadmium as a conservative pollutant known to bio-accumulate in plants, and initially introduced in the overlying water (20µg Cd/L of cadmium nitrate - Cd(NO3)2·4H2O). Biological sediment reworking by invertebrates' activity was quantified using luminophores (inert particulates). Our results showed that bioturbation caused by tubificid worms' activity followed the bio-conveying transport model with a downward vertical velocity (V) of luminophores ranging from 16.7±4.5 to 18.5±3.9cm·year-1. The biotransport changed the granulometric properties of the surface sediments, and this natural process was still efficient under cadmium contamination. The highest value of Cd enrichment coefficient for plant roots was observed in subsurface sediment layer (below 1cm to 5cm depth) with tubificids addition. We demonstrated that biotransport changed the distribution of cadmium across the sediment column as well as it enhanced the pumping of this metal from the surface to the anoxic sediment layers, thereby increasing the bioaccumulation of cadmium in the root system of Typha latifolia. This therefore highlights the potential of bioturbation as a tool to be considered in future as integrated bioremediation strategies of metallic polluted sediment in aquatic ecosystems.