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Selenium (Se) as an essential nutrient for human beings at trace concentrations, the allowable concentration for the human is only 40 μg/L. Iron sulfide (FeS) nanoparticles have been applied for excessive of selenium (Se) remediation in surface water and groundwater. In this study, FeS nanoparticles were anchored onto biochar (BC) to reduce agglomeration of FeS and prepared into the composite of FeS-BC by pyrolysis to economically and efficiently remove Se(IV) from simulated wastewater based on the excellent performance of FeS and the low cost of BC. Characterizations presented the uniform anchorage of FeS on the BC surface to prevent agglomeration. The results of batch experiments revealed that the removal of Se(IV) by FeS-BC nanomaterials significantly depended on the pH value, with the maximum removal of ∼174.96 mg/g at pH 3.0. A pseudo-second-order kinetic model well reflected the kinetic removal of Se(IV) in pure Se(IV) solution with different concentration, as well as the coexistence of K+, Ca2+, Cl-, and SO 4 2- ions. The presence of K+ ions significantly inhibited the removal of Se(IV) with the increase of K+ ion concentration compared with the effect of the other three ions. SEM-EDS and XPS analyses indicated that the removal process was achieved through adsorption by surface complexation, and reductive precipitation of Se(IV) into Se0 with the electron donor of Fe(II) and S(-II) ions. The FeS-BC nanomaterial exhibited an excellent application prospect in the remediation of Se(IV). • The aggregation issue of FeS nanoparticles was addressed by BC loading. • FeS-BC can effectively remove Se(IV) through surface complexation, ion exchange, and chemical precipitation. • Fe2 + and S2- species simultaneously acted as electron donors to reduce Se(IV) to Se0. • The removal efficiency was affected by K+ ions significantly rather than other ions. [ABSTRACT FROM AUTHOR]

• Porous hexagonal boron nitride (p-BN) was employed for Ni(II) scavenging. • The p-BN displayed a high removal rate to Ni(II). • The p-BN exhibited an adsorption capacity to Ni(II). • Interaction between hydroxyl-O and electron-deficient B is the main mechanism. Intending to remove Ni(II) from wastewater, porous p-BN was employed to recovery Ni(II) by batch and X-ray photoelectron spectroscopy technique. The performances and mechanism of p-BN for Ni(II) sorption had been studied by diverse characterization technologies. The kinetic data was calculated to conform a pseudo-second-order model, and isotherm data fitted to a Freundlich equation. We obtained a high removal rate and a high adsorption capacity. A possible mechanism can be expressed from XPS results. The surface of p-BN is B OH/B NH 2 enriched and exhibits a weak alkalinity. When p-BN contact with Ni(II) solution, the hydroxide ions releases from the surface while there is a formation of B O⋯Ni; the small group of B O⋯Ni is acting with hydroxide ions, thereby forming B O⋯Ni(OH) 2 and continuously adsorbs Ni(II) to form B O⋯Ni(OH)ONi(OH) like as precipitated nucleus. Then, due to the interaction of hydroxyl-O with electron-deficient B, the veil-like Ni(OH) 2 generated from precipitated nucleus evenly attaches to p-BN. The bonding state of Ni(II) on p-BN by XPS spectra revealed that the process of adsorbing Ni(II) onto p-BN was chemisorption through the formation of Ni(OH) 2 and the interaction between hydroxyl-O and electron-deficient B. The analyses implied that p-BN is a promising candidate for recovery of Ni(II) from wastewater. [ABSTRACT FROM AUTHOR]

• Novel composite material of g-C 3 N 4 decorated FeS was designed and prepared. • The adsorption capacity for U(VI) was 917.1 mg/g at pH = 6.0. • The adsorption isotherm for U(VI) was described by the Freundlich model. In this study, a novel graphitic carbon nitride decorated nanoscale FeS composite (g-C 3 N 4 /FeS) was prepared and performed for the removal of U(VI) in aqueous system. Results revealed that g-C 3 N 4 /FeS had excellent adsorbability, which can reach 917.1 mg/g at 303 K. In addition, the effects of pH, adsorbent dose, contact time and initial U(VI) concentration were investigated by batch experiments. Experimental results indicated the removal of U(VI) on g-C 3 N 4 /FeS was strongly dependent on pH, and the adsorption capacity reached the maximum at pH = 6.0. Kinetics studies under different conditions indicated the removal of U(VI) on g-C 3 N 4 /FeS fitted the pseudo-second-order model well. Furthermore, the adsorption isotherms of U(VI) on g-C 3 N 4 /FeS fitted with Freundlich models well. These results demonstrated that g-C 3 N 4 /FeS could be the promising alternative material for environmental remediation. [ABSTRACT FROM AUTHOR]

In order to investigate scavenging mechanism of rare earth metal ions in water by graphene oxide (GO), effects of ion concentration and adsorption time on the adsorption of the metal ions, such as La(III) and Nd(II), were surveyed systematically. The molecular structure, surface functional groups and morphology of the GO before and after adsorbing the rare earth metal ions were characterized by Raman spectroscopy, FITR, and XPS. To shed more light on the sorption mechanism, static density functional theory (DFT) calculation was introduced to portray the molecular-scale interaction between GO and the rare earth metal ions. The results indicated that the GO showed high adsorbing capacities of 105.5 mg/g for La(III) and 99.1 mg/g for Nd(II) at 20 °C and pH 5.5, respectively. The adsorption reached equilibriums within 120 min and the adsorption kinetics of La(III) and Nd(II) followed the pseudo-first-order kinetic model well. The Freundlich and Langmuir models were used to simulate the adsorption isotherms of the rare earth metal ions, demonstrating that the adsorption fitted well with Langmuir model. Experimental results of this work demonstrated that GO was a promising economical material for the removal of La(III) and Nd(II) from aqueous solutions. Unlabelled Image • GO has good removal ability for La(III) and Nd(II) from water. • The adsorption processes of La(III) and Nd(II) on GO are both fitted well by pseudo-first-order kinetic model. • The adsorption of La(III) and Nd(II) on GO both fit well with Langmuir model. [ABSTRACT FROM AUTHOR]