A novel adsorbent of magnetic goethite was prepared by neutralisation hydrolysis and employed for Cr(VI) adsorption from aqueous solution. The magnetic goethite adsorbent was characterised by using scanning electron microscopy (SEM), X‐ray diffractometer (XRD), vibrating sample magnetometer (VSM), fourier transform infrared (FTIR), brunauer‐Emmett‐Teller (BET) and X‐ray photoelectron spectroscopy (XPS) method. VSM showed that the prepared adsorbents are super‐paramagnetic iron hydroxide. FTIR spectra revealed that magnetic goethite have ‐OH and other functional groups. The effects of various factors, including pH, adsorbent dosage, initial concentration, and ion concentration, were evaluated. Under the conditions of pH 3, 4 g/L magnetic goethite, 20 mg/L Cr(VI) concentration, and 0.01 mol/L NaNO3, the removal efficiency of Cr (VI) reached 88.2% and the adsorption capacity of the adsorbent reached 4.32 mg/g. The adsorption kinetic tests showed that the adsorption of Cr(VI) on the adsorbent matched well with pseudo‐second‐order kinetics, indicating the occurrence of chemisorption. The fitting of the Langmuir isotherm model showed that the adsorption of Cr(VI) on magnetic goethite was monolayer adsorption. On the other hand, thermodynamic studies conjectured that the adsorption processes of magnetic goethite for Cr(VI) was endothermic and spontaneous. These results suggest that magnetic goethite has great potential for the removal of heavy metals from wastewater.
Lithium-sulfur batteries have attracted attention because of their high energy density. However, the “shuttle effect” caused by the dissolving of polysulfide in the electrolyte has greatly hindered the widespread commercial use of lithium-sulfur batteries. In this paper, a novel two-dimensional TiS2/graphene heterostructure is theoretically designed as the anchoring material for lithium-sulfur batteries to suppress the shuttle effect. This heterostructure formed by the stacking of graphene and TiS2 monolayer is the van der Waals type, which retains the intrinsic metallic electronic structure of graphene and TiS2 monolayer. Graphene improves the electronic conductivity of the sulfur cathode, and the transferred electrons from graphene enhance the polarity of the TiS2 monolayer. Simulations of the polysulfide adsorption show that the TiS2/graphene heterostructure can maintain good metallic properties and the appropriate adsorption energies of 0.98–3.72 eV, which can effectively anchor polysulfides. Charge transfer analysis suggests that further enhancement of polarity is beneficial to reduce the high proportion of van der Waals (vdW) force in the adsorption energy, thereby further enhancing the anchoring ability. Low Li2S decomposition barrier and Li-ion migration barrier imply that the heterostructure has the ability to catalyze fast electrochemical kinetic processes. Therefore, TiS2/graphene heterostructure could be an important candidate for ideal anchoring materials of lithium-sulfur batteries.
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