Poly(vinylidene fluoride) derived fluorine-doped magnetic carbon nanoadsorbents for enhanced chromium removal

Newly designed fluorine-doped magnetic carbon (F-MC) was synthesized in situ though a facile one-step pyrolysis-carbonization method. Poly(vinylidene fluoride) (PVDF) served as the precursor for both carbon and fluorine. 2.5% F content with core-shell structure was obtained over F-MC, which was used as a adsorbent for the Cr(VI) removal. To our best knowledge, this is the first time to report that the fluorine doped material was applied for the Cr(VI) removal, demonstrating very high removal capacity (1423.4 mg g−1), higher than most reported adsorbents. The unexpected performance of F-MC can be attributed to the configuration of F dopants on the surface. The observed pseudo-second-order kinetic study indicated the dominance of chemical adsorption for this process. High stability of F-MC after 5 recycling test for the Cr(VI) removal was also observed, indicating that F-MC could be used as an excellent adsorbent for the toxic heavy metal removal from the wastewater

One-pot melamine derived nitrogen doped magnetic carbon nanoadsorbents with enhanced chromium removal

Novel nitrogen doped magnetic carbons (NMC), in-situ synthesized through facile pyrolysis-carbonization processes using Fe(NO3)3 and melamine as precursors, were demonstrated as excellent nanoadsorbents to remove Cr(VI) effectively. The achieved removal capacity in both neutral and acidic solution was 29.4 and 2001.4 mg g−1 respectively, much higher than the reported adsorbents so far. The unprecedented high adsorption performance can be attributed to the incorporation of the nitrogen dopant, which increased the negative charge density on the surface of adsorbent and thereby enhanced the interaction between the adsorbents and Cr(VI) ions. The density functional theory (DFT) calculation demonstrated that the nitrogen dopants can decrease the adsorption energy between the Cr(VI) ions and NMC (−3.456 kJ mol−1), lower than the undoped sample (−3.344 kJ mol−1), which boosted the adsorption behavior. Chemical rather than physical adsorption was followed for these magnetic nanoadsorbents as revealed from the pseudo-second-order kinetic study. Furthermore, the NMC showed high stability with recycling tests for the Cr(VI) removal

Upgrading a regional groundwater level monitoring network for Beijing Plain, China

Monitoring of regional groundwater levels provides important information for quantifying groundwater depletion and assessing impacts on the environment. Historically, groundwater level monitoring wells in Beijing Plain, China, were installed for assessing groundwater resources and for monitoring the cone of depression. Monitoring wells are clustered around well fields and urban areas. There is urgent need to upgrade the existing monitoring wells to a regional groundwater level monitoring network to acquire information for integrated water resources management. A new method was proposed for designing a regional groundwater level monitoring network. The method is based on groundwater regime zone mapping. Groundwater regime zone map delineates distinct areas of possible different groundwater level variations and is useful for locating groundwater monitoring wells. This method was applied to Beijing Plain to upgrade a regional groundwater level monitoring network

Hydrogel-based composites beyond the porous architectures for electromagnetic interference shielding

With the rapid development of the electronic industry and wireless communication technology, electromagnetic interference (EMI) or pollution has been increasingly serious. This not only severely endangers the normal operation of electronic equipment but also threatens human health. Therefore, it is urgent to develop high-performance EMI shielding materials. The advent of hydrogel-based materials has given EMI shields a novel option. Hydrogels combined with conductive functional materials have good mechanical flexibility, fatigue durability, and even high stretchability, which are beneficial for a wide range of applications, especially in EMI shielding and some flexible functional devices. Herein, the current progress of hydrogel-based EMI shields was reviewed, in the meanwhile, some novel studies about pore structure design that we believe will help advance the development of hydrogel-based EMI shielding materials were also included. In the outlook, we suggested some promising development directions for the hydrogel-based EMI shields, by which we hope to provide a reference for designing hydrogels with excellent EMI shielding performance and multifunctionalities.ISSN:1998-0000ISSN:1998-012

Modal identification of a high-rise building subjected to a landfall typhoon via both deterministic and Bayesian methods

Modal identification involves primarily the determination of natural frequencies, damping ratios, mode shapes of a dynamic system, etc. It is usually regarded as an essential task in a wide branch of structural dynamics and civil engineering, such as structural vibration control and damage identification of buildings or bridges. There are many modal identification techniques. Basically, these techniques can be categorized into two groups: deterministic methods and Bayesian approaches. The first group can be used to provide deterministic (or optimal) estimations of modal parameters, but they are unable to quantify the estimation uncertainties. The second group is based on a usage of the Bayesian framework. Compared to the first group, the second group of methods has a typical merit of being able to offer uncertainty information of identified parameters, which is of great interests, or even necessary, for some follow-up studies. In this paper, both a deterministic method, i.e., a combination of spectral analysis, filtering and Random Decrement Technique (RDT), and a Bayesian method, i.e., Bayesian Spectral Density Approach (BSDA), are exploited to experimentally identify the modal parameters of a 303 m high-rise building that was subjected to a landfall typhoon. The validity and efficiency of each method is verified by comparing the two kinds of results. Meanwhile, the identified modal parameters are used for the serviceability assessment of this high-rise building against some frequency-specific criteria

Nanocellulose-assisted preparation of electromagnetic interference shielding materials with diversified microstructure

Sustainable and renewable nanocellulose attracts more and more attention in various fields due to its high strength-to-weight ratio, small diameter, large aspect ratio, and abundant functional groups. The excellent properties and structural characteristics enabled a great potential of nanocellulose for efficient interactions with functional nanomaterials such as carbon nanotube, graphene, transition metal carbides/nitrides (MXenes), and metal nanoparticles, which is beneficial for preparing high-performance electromagnetic interference (EMI) shields. We review the advances in the nanocellulose-assisted preparation of composite films and aerogels for EMI shielding application. The nanocellulose-based composites are evaluated in terms of their EMI shielding performance and the shielding mechanisms, including conduction, polarization, and multiple reflections are summarized. In addition to the constituent structure and contents, we highlight the significance of the microstructure design in enhancing the EMI shielding performance of the nanocellulose-based EMI shields. Finally, the current challenges and outlook for these fascinating nanocellulose-based EMI shielding composites are discussed.ISSN:2688-819XISSN:2766-852