Qiaohong Su,Adnan Ali Khan,Zhi Su,Chen Tian,Xiaoqin Li,Jiahua Gu,Ting Zhang,Rashid Ahmad,Xintai Su,Zhang Lin
Adsorbents with excellent redox or adsorption properties are beneficial for the efficient removal of heavy metals. In this work, a novel nitrogen-doped KFeS2/C composite (NSC-1.3) was first prepared by a simple one-step pyrolysis method and used to effectively remove Cr(VI) from aqueous solutions. The kinetics and adsorption isotherms of Cr(VI) were in accordance with pseudo-second-order kinetic and Langmuir models, respectively. The maximum adsorption capacity of NSC-1.3 was 575.68 mg g−1 at 318 K and 326.8 mg g−1 at 298 K. The removal mechanism of Cr(VI) by NSC-1.3 was first discussed by X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) simulation. The XPS analysis showed that nitrogen or carbon functional groups provide abundant active sites for Cr(VI) adsorption, and Sn2− or S8 in NSC-1.3 reduces highly toxic Cr(VI) to less toxic Cr(III). The XPS analysis showed that the removal mechanism of Cr(VI) was through adsorption and redox reaction, but the dominant one was the redox reaction. DFT simulations showed that N atoms doping was feasible and thermodynamically stable. In addition, H2CrO4 makes stronger intermolecular hydrogen bonds and larger adsorption energies with the N-doped KFeS2 layer during the adsorption process, indicating that the N-doped system has a higher adsorption capacity for Cr(VI). This study confirms the importance of the adsorption and redox reaction mechanism of this new composite material, and has promising potential for the removal of highly toxic Cr(VI) from aqueous solutions.
Can Wang,Kailin Li,Qing Sun,Shijin Zhu,Chenzhi Zhang,Yunhao Zhang,Zhongyi Shi,Youzhong Hu,Yuxin Zhang
Bifunctional materials possess remarkable properties that allow them to store and convert electrical energy easily. In this paper, diatomite-like potassium iron disulfide (KFeS2) was synthesized by a multistep sacrificial template method, and its morphological, electrochemical, and oxygen evolution reaction (OER) properties were investigated. KFeS2was found to be porous, hollow, and cake-like, which suggests a high specific surface area (SSA) and abundant electrochemically active sites. A very high specific capacitance of 651 F g−1at 1.0 A g−1was also obtained due to the substance’s unique structure and high porosity. Additionally, the diatomite-like KFeS2possessed a very low overpotential ƞ10of 254 mV at a current density of 10 mA cm−2and a small Tafel slope of about 48.4 mV dec−1. Thus, the diatomite-like KFeS2demonstrates broad application prospects for both energy storage and conversion.Keywords:KFeS2;diatomite;hydrothermal synthesis;supercapacitors;oxygen evolution reaction
Herein, a KFeS2 whisker was formed in mass production at a low temperature, with waste cold-rolling sludge as Fe source, which exhibited good performance in the removal of Zn/Ni from real electroplating effluent. At laboratory scale, KFeS2 was generated at 80 °C by the hydrothermal method, and KFeS2 whisker grew radially with the extension of the reaction time. This method was applied at pilot scale, where a similar KFeS2 whisker was also produced with waste cold-rolling sludge as Fe source, and a residual brownish supernatant was observed after the reaction and then completely recycled in the next round for KFeS2 synthesis. After recycling five times, the produced KFeS2 whisker did not change. The drying and storage of KFeS2 have also been verified. Freeze drying and vacuum drying were applicable, whereas air drying was not profitable. Moreover, the efficiency of Zn/Ni removal using undried KFeS2 was similar to that of dried KFeS2. The efficiencies of Zn/Ni removal using KFeS2 were apparently higher those of common reagents for wastewater treatment.
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