Nianwu Li

Facile preparation of magnetic separable powdered-activated-carbon/Ni adsorbent and its application in removal of perfluorooctane sulfonate (PFOS) from aqueous solution

The main aim of this study was to synthesize magnetic separable Nickel/powdered activated carbon (Ni/PAC) and its application as an adsorbent for removal of PFOS from aqueous solution. In this work, the synthesized adsorbent using simple method was characterized by using X-ray diffractionometer (XRD), surface area and pore size analyzer, vibrating sample magnetometer (VSM), and high resolution transmission electron microscope (HRTEM). The surface area, pore volume and pore size of synthesized PAC was 1521.8 m2g−1, 0.96 cm3g−1, 2.54 nm, respectively. Different kinetic models: the pseudo–first-order model, the pseudo–second-order model, and three adsorption isotherms—Langmuir, Freundlich and Temkin—were applied to study the sorption kinetics and isothermal behavior of PFOS onto the surface of an as-prepared adsorbent. The rate constant using the pseudo–second-order model for removal of 150 ppm PFOS was estimated as 8.82×10−5 and 1.64×10−4 for PAC and 40% Ni/PAC, respectively. Our results demonstrated that the composite adsorbents exhibited a clear magnetic hysteretic behavior, indicating the potential practical application in magnetic separation of adsorbents from aqueous solution phase as well.

Improving lithium–sulfur battery performance via a carbon-coating layer derived from the hydrothermal carbonization of glucose

Sulfur possesses a high specific capacity as a rechargeable lithium battery cathode. However, the commercial applications of sulfur cathodes are limited by the poor electronic/ionic conductivity of elemental sulfur and polysulfides, volume expansion of sulfur during the discharge process, and the high solubility of long-chain lithium polysulfides (Li2Sn, 4 ≤ n ≤ 8). Herein, we design a core–shell structure composed of active carbon (AC) and an amorphous carbon-coating layer to encapsulate the sulfur in the carbon matrix. The carbon-coating layer obtained from the hydrothermal carbonization of glucose can effectively entrap the polysulfides. Furthermore, the composite matrix provides a conducting framework serving as an electrochemical reaction chamber for the sulfur cathode. After wrapping AC–S with an amorphous carbon layer, the obtained composite cathode can effectively confine the polysulfides and buffer the volume change. Consequently, the resulting composite cathode possesses a high specific capacity, good rate capability, and stable cycling performance. At 0.2 A g−1 current density, the as-prepared carbon-coated AC–S composite cathode shows a high specific discharge capacity of 1103 mA h g−1. At a current density of 0.8 A g−1 and 1.6 A g−1, the composite cathode exhibits 75% capacity retention over 150 cycles. The Coulombic efficiency of the cell remains at approximately 95%.