Henan Normal University

About: Henan Normal University is a education organization based out in Xinxiang, China. It is known for research contribution in the topics: Catalysis & Ionic liquid. The organization has 10863 authors who have published 11077 publications receiving 166773 citations.

Adsorption of perfluorooctane sulfonate (PFOS) on corn straw-derived biochar prepared at different pyrolytic temperatures

Abstract: The adsorption behavior of perfluorooctane sulfonate (PFOS) on biochar produced from corn straw at varying pyrolytic temperatures ( i.e ., 250, 400, 550, and 700 °C, BC250–700, respectively) was investigated. High pyrolytic temperatures (>400 °C) resulted in the increase of some fine-pore structures, larger surface area (SA) and higher aromaticity of biochar. The adsorption kinetics of PFOS fitted well to a pseudo-second order model while the adsorption isotherms followed a Langmuir adsorption isotherm model ( R 2 > 0.949). The adsorption capacity increased with the pyrolytic temperature with the highest adsorption capacity ( i.e ., 169.30 mg/g) being obtained on BC 700. The adsorption of PFOS on the biochar samples was mainly governed by hydrophobic and electrostatic interactions. The hydrophobicity enhancement of biochar pyrolyzed at high temperatures is one of the important factors contributing to PFOS adsorption. The capacity of biochar for adsorbing PFOS decreased with the increase of solution pH. The adsorption of PFOS on the biochar samples is a spontaneous and endothermic process.

Thermodynamics and kinetics of Hawking-Page phase transition

Abstract: We study the thermodynamics and the kinetics of the Hawking-Page phase transition in Einstein gravity and in massive gravity based on the underlying free energy landscape. For Einstein gravity, Schwarzschild--anti-de Sitter (AdS) black holes as well as thermal AdS space can be considered as macroscopic emergent states or phases. The stability and phase transition of these states can be determined by free energy landscape topography quantified by the barrier height between the state basins. Due to the thermal fluctuations, a black hole or AdS space has the chance to escape from one phase to another phase. The first passage process describes a system that undergoes such a kinetic process for the first time, and the mean first passage time can typically be used to quantify the kinetic speed. The probabilistic evolution of such a stochastic process can be described by the corresponding Fokker-Planck equation. We derive analytical integral expressions for the mean first passage time and its fluctuations. The results show that the mean first passage time and its fluctuations are closely related to free energy landscape topography through barrier heights and the temperature. The conclusions for the Hawking-Page phase transition in massive gravity are qualitatively similar to those in Einstein gravity. This study provides a systematic way of studying black hole thermodynamics and kinetics of the black holes from free energy landscape topography.