Search

To reduce the limitations of the chemical washing method due to soil texture, the freezing technique has been used to enhance the mass transfer efficiency between the eluent and heavy metal contaminants. With the optimized water supplement and cooling conditions, a large-scale model experiment was conducted. Results show that the optimized method is prone to enhancing the eluent intake of clayey soil, leading to an increase in the amount of soil frost heave, which has a feedback effect by breaking the soil structure and enhancing the eluent intake. The synergistic effect of the two is responsible for the improvement of washing efficiency. In addition, after four freeze-thaw and washing cycles, the total removal rates of the metallic elements Pb and Cd reach 58.73% and 69.04%, respectively, satisfying the soil environmental quality standard. The soil bioavailability is effectively reduced by alternating the eluent with ethylenediaminetetraacetic acid (EDTA) and water, thereby reducing the bioavailability of Pb and Cd by 66.01% and 74.18%, respectively. This remediation strategy for heavy metals in clayey soils utilizes alternate freezing and thawing (natural cold energy) in seasonally frozen regions, which is beneficial for constructing an ecological civilization and protecting the environment. • WSL-GC-CS method for remediation of heavy metal in contaminated clayey soil was proposed. • The new method can solve the problem of poor efficiency for clayey soil in field remediation. • The method can reduce energy consumption and promote sustainable economic development. [ABSTRACT FROM AUTHOR]

With the needs of lightweight and sustainable development, the structure-function integration of natural fibers through multiscale surface modification has attracted much attention. Jute fibers (JFs) stand out from other natural alternatives because of their unique hierarchical structure, lower production cost and better mechanical properties. In this work, a facile and effective strategy for preparing ZnO nanorods (NRs) @JFs was proposed by an in-situ method. The introduction of ZnO NRs not only reinforces the fiber, but also endows additional functionalities. The components and morphologies of ZnO@JFs were characterized. The structurally optimized ZnO@JFs exhibit a significant increase in surface energy, tensile strength, elongation at break, thermal stability with 150.0%, 16.8%, 8.5%, 216.9%, respectively, as well as remarkable enhancement in microwave absorption with 40.0%. These homogeneous and aligned ZnO NRs@JFs that integrate reinforced structure and additional functions have great application potential in the fields of automotive industry, building construction and aerospace. • Homogeneous and aligned ZnO NRs are fabricated on JFs by in-situ deposition. • Growth and regulation mechanisms of ZnO NRs@JFs were revealed. • Mechanical, thermal and absorbing properties of JFs are enhanced by introduce of ZnO. [ABSTRACT FROM AUTHOR]

Jack-up platforms will generally behave as highly dynamic systems because of the structure flexibility. The environmental forces acting on these jack-ups will therefore induce significant dynamic response. In this paper, based on ANSYS, the three-dimensional model of a truss leg jack-up was built. With interaction of fluid–structure–soil being considered, a series of static analysis, modal analysis, and transient analysis were performed for the model with different dimensional or load parameters; and the dynamic magnification factors were calculated. Sensitivity of these parameters on the dynamic response of jack-ups were discussed in detail. [ABSTRACT FROM AUTHOR]

The fractured surfaces include a lot of useful information that can help investigate the reasons that caused metal materials to break. For example, the details on the processes that lead to failure can be determined from these surfaces, making it useful to investigate their morphology. The principle of the fracture-surface topography analysis (FRASTA) was used in this research and some progresses have been made on quantitative reverse deduction of metal fracture surfaces. In FRASTA, the fracture surfaces are scanned by laser microscope and the elevation data is recorded for analysis. The crack-tip opening angle (CTOA) was firstly determined by the cross-sectional plots. Simple bar hypothesis was then proposed. As for the hypothesis, the fracture surfaces can be assumed to be composed of independent rectangular bars. After dividing the plastic deformation left on the fracture surfaces into such single bars, the original lengths of these bars were calculated and then the global strains of these bars during the course of failure were calculated, and finally the J-integral was calculated. Then, the relationship between J-integral and crack opening displacement (COD), and the relationship between J-integral and fracture surface average profile for plain strain were deduced. Furthermore, according to the relationship between true stress and true strain for the material, the normal stress on the cross section of each single bar was determined. Summing up all the loads on all bars provided the total applied load of the specimen. Some experiments have been performed and the proposed methods have been verified to some extent. At the same time, software, namely fracture surface analyst (FSA) was developed as per the proposed methods and was used for analysis successfully. [ABSTRACT FROM AUTHOR]

• BW has strong acid resistance (pH ≥ 1). • BW selectively separates lead from complex heavy metal solutions. • The selective immobilization is due to its specific composite structure. The development of bio-adsorbents with highly selective immobilization properties for specific heavy metals is a great challenge, but has important application value. Biogenic whewellite (BW) with high selectivity for Pb(II) was synthesized by mineral microbial transformation. The selective immobilization properties and mechanism of BW for Pb(II) were analyzed by combining mineral characterization technology and batch adsorption research methods. The results indicated that BW can efficiently and selectively immobilize Pb(II) in single or composite heavy metal adsorption solutions, and the immobilized Pb(II) is difficult to desorb. BW undergoes monolayer adsorption on Pb(II), Q max ≈ 1073.17 mg/g. The immobilization of Pb(II) by BW is a physico-chemical adsorption process with spontaneous heat absorption and an accompanying increase in entropy. In addition, the sequestration of Pb(II) by BW remains around 756.99 mg/g even at pH = 1. The excellent selective immobilization properties of BW for Pb(II) are closely related to its smaller K sp , electrostatic repulsion effect, organic-inorganic composite structure, acid resistance and the formation of Pb(II) oxalate. This study provides beneficial information about the recycling of lead in acidic lead-containing wastewater and composite heavy metal contaminated water bodies. [Display omitted] [ABSTRACT FROM AUTHOR]

For the improved washing efficiency of clayey soil, utilized magnetization technology was used in this study to enhance the physicochemical properties (e.g., viscosity, surface tension, and contact angle) of the eluent. Lead- and cadmium-contaminated clayey soil was used as the research subject in an experimental study aimed to enhance the heavy metal removal efficiency through a magnetized modified eluent and freezing-thawing effect by using EDTA as the eluent. The magnetization test results indicate that the EDTA solution's viscosity, surface tension, and contact angle decrease after magnetization, thus improving the wettability, enhancing the eluent's full contact with heavy metal pollutants, and consequently increasing the removal rate. The results of the freezing–thawing and washing column test show that magnetization reduced the viscosity of eluent, decreased soil seepage or migration resistance, and increased moisture migration during freezing. After three cycles of freezing-thawing and washing, the removal rates for Cd and Pb were 79.35% and 70.38%, respectively. The technology of magnetized eluent is facile to operate and serves as an efficient, cost-effective, and eco-friendly auxiliary method for increasing the efficiency of freezing–thawing–washing processes, offering a novel approach for soil remediation. • The combined magnetization technology and soil washing method for remediation of heavy metal contaminated clay soils is proposed. • Based on enhance the physicochemical properties of the eluent to improve removal efficiency. • To provide basis for remediating heavy metal by magnetization technology. [ABSTRACT FROM AUTHOR]

The strong alkalinity of red mud is a key reason that threatens the environment and restricts the secondary use of red mud. Freeze-thaw (FT)-acid washing (AW) is proposed to remove alkali to improve the dealkalization efficiency of red mud. FT-AW tests were performed using red mud with oxalic acid (OA) and citric acid (CA) to examine the effect of FT cycles and eluent concentration on the dealkalization efficiency. Results showed that the FT-AW method significantly increased the dealkalization efficiency under the synergy of FT and AW. After 5 times of FT-AW, the alkali removal efficiencies of red mud with OA and CA as eluents reached 97.5% and 95.5%, which were 27.3% and 18.9% higher than those of the control group, respectively. The effect of OA on dealkalization was more sensitive than that of CA. The results of SEM-EDS and XRD showed that FT cycles destroyed the crystal structure of red mud and released part of the bonded alkali. The FT-AW method provides a novel idea for future large-scale red mud dealkalization by using FT alternation in seasonally frozen soil areas. • FT-AW had been proposed to improve the dealkalization efficiency of red mud. • The removal efficiencies with OA and CA reached to 97.5% and 95.5%, respectively. • FT cycle destroyed crystal structure of red mud and released part of bonded alkali. [ABSTRACT FROM AUTHOR]

To improve the interfacial combination of jute fiber reinforced polymer composites, sol-gel method was used to deposit nano-SiO 2 layer on the surface of jute fibers. The macroscopic evaluations and molecular dynamics (MD) simulation were carried out to characterize the deposition effect of nano-SiO 2 layer on jute fibers. In addition, the multiscale modeling of nano-SiO 2 deposited on jute fibers was established. The results showed that the deposition effect could be affected by the morphologies of nano-SiO 2 layer including gel, array and aggregated particles. Compared with nano-SiO 2 gel and aggregated nano-SiO 2 particles, nano-SiO 2 array may fill up the surface flaws of jute fibers efficiently, which would eliminate the stress concentration and lotus leaf effect on the jute fibers. The surface energy and tensile strength of jute fibers coated with nano-SiO 2 array were increased by 9.79% and 16.47%, respectively. Additionally, MD simulation confirmed that non-bonding and C–O–Si chemical bonding interactions guaranteed the interfacial combination between the jute fiber and nano-SiO 2 layer. C–O–Si chemical bond could provide with the strong interfacial strength between the jute fiber and nano-SiO 2 layer. [ABSTRACT FROM AUTHOR]