ABSTRACT
In this paper, a carbon dot hydrogel composite (CDs-Hy) capable of efficiently removing Pb(II) was prepared by hydrogen bonding self-assembly in combination with carbon dots and a hydrogel. CDs-Hy was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS), and the effect of the adsorption conditions on the adsorption efficiency of CDs-Hy was studied. The results of the study showed that the incorporation of carbon dots, on the one hand, significantly increased the adsorption capacity of the material. On the other hand, it can increase the stability of hydrogels in aqueous solution. The possible adsorption mechanisms were further verified as ion exchange and coordination. CDs-Hy is a novel adsorbent material capable of removing Pb2+ efficiently, which can be reused several times with high stability.
ABSTRACT
In this study, hydrophobic quaternary ammonium intermediate was synthesized by epichlorohydrin (ECH) and oleamide propyl dimethyl tertiary amine (PKO). Sodium carboxymethylcellulose (CMC) was chemically modified by introducing a large number of hydrophobic quaternary ammonium branched chains to improve CMC's salt resistance, thickening ability, and solubility. The quaternary ammonium salt structure can partially offset the compression double-layer effect of linear polymers in a low-price salt ion solution, which makes CMC more stretchable and helps it obtain a higher viscosity and greater drag-reduction performance. The experiment was mainly divided into three parts: Firstly, we performed an epichlorohydrin and oleic acid PKO reaction, generating an oleic acid chain quaternary ammonium chlorine atom intermediate. Secondly, the etherification reaction between intermediate -Cl and -OH groups of CMC was completed. Finally, the modified CMC was characterized by IR, SEM, and XPS, and the viscosity and the drag-reduction rate were evaluated. After CMC and the intermediate were reacted at a mass ratio of 9:1.8 at 80 °C for 5 h, the new CMC with enhanced thickening ability, salt resistance, and drag-reduction performance was obtained. We found that the apparent viscosity increased by 11%, the drag reduction rate increased by 3% on average, and the dissolution rate was also significantly accelerated, which was ascribed to the introduction of quaternary ammonium cation. Moreover, the oleic acid amide chain increased the repulsive force of the CMC chain to low-priced metal cations in solution and intermolecular repulsive force, which is beneficial to increase the viscosity, salt resistance, and drag-reduction performance.
ABSTRACT
The dynamics of energetic particles and tearing modes and the interactions between them are of great significance for magnetically confined fusion plasmas. In this review, we focus on these issues in the context of tokamak plasmas. The interaction between energetic particles and tearing modes is considered from two perspectives: (i) the influence of energetic particles on tearing modes and (ii) the transport of energetic particles by tearing modes. The influence of energetic particles on tearing modes is described on the basis of a general dispersion relation for tearing modes. The effects of energetic particles are considered separately in the outer region and the island region of a tearing mode. The physics mainly results from the modification of the perturbed parallel current by energetic particles without wave-particle resonance. In addition, the resonance between energetic particles and tearing modes is also reviewed. For the transport of energetic particles, transport of both circulating and trapped energetic particles by tearing mode is reviewed. Our descriptions of physical phenomena here are based on an analytical approach, while the experiments and simulations are used to illustrate and confirm our results. Finally, a number of open issues are discussed.
ABSTRACT
In contrast with the stability effects of trapped energetic ions on tearing modes, the effects of circulating energetic ions (CEI) on tearing modes depend on the toroidal circulating direction, and are closely related to the momentum of energetic ions. CEI provide an additional source or sink of momentum to affect tearing modes. For co-CEI, tearing modes can be stabilized if the momentum of energetic ions is large enough. On the other hand, the growth of tearing modes can be enhanced by counter-CEI. Further, a possibility to suppress the island growth of neoclassical tearing modes by co-CEI is pointed out.
