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[Display omitted] • Zr-doped Fe-MOFs/GO nanocomposites were successfully fabricated by an in-situ growth approach. • FeZr-MOFs/GO nanocomposites delivered an excellent adsorption capacity of up to 91.69 mg·g−1. • Appropriate doping of Zr(IV) led to a substantially improved water stability of MIL-101(Fe)/GO. • Adsorption mechanism of As(V) on FeZr-MOFs/GO was ascribed to chemical complexation and hydrogen bonding. Eliminating arsenic contaminants has become an imperative issue due to its persistent and serious harm to the environment and human health. Herein, a novel FeZr-MOFs/GO nanocomposite for effectively removing As(V) was fabricated by growing Fe-based metal–organic frameworks (Fe-MOFs) of MIL-101(Fe) on the graphene oxide (GO) surface with the addition of Zr(IV) dopants. The presence of GO, the doping amount of Zr ions, and the functional groups of the ligands were found to have an impact on the adsorption performance of Fe-MOFs. Notably, doping an appropriate amount of Zr(IV) resulted in a significant increase in water stability of MIL-101(Fe) and MIL-101(Fe)/GO nanocomposites. This improvement, along with chemical complexation and hydrogen bonding, played a pivotal role in the adsorption of As(V). The optimized FeZr-MOFs-0.2/GO (0.2 represented the molar ratio between Zr and Fe) nanocomposites demonstrated superior As(V) adsorption performance with an adsorption capacity of up to 91.69 mg·g−1. Moreover, this system proven effective across a wide range of pH (2–10) and environmental matrices. This study not only provides attractive MOF nanocomposites for broadening the application of aqueous solutions, but also opens up a novel avenue for the rational design and development of nanocomposites with exceptional properties and stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Magnetic Fe 3 O 4 /GO nanocomposites were synthesized using solvothermal and pyrolysis methods. • Fe 3 O 4 /GO nanocomposite exhibited a fully-formed MOF morphology and crystal structure. • Fe 3 O 4 /GO nanocomposite delivered a remarkable adsorption capacity of 49.88 mg/g at 298.15 K. • Fe 3 O 4 /GO nanocomposite displayed excellent resistance to ionic interference and wide pH applicability. • The adsorption mechanism of As(V) was ascribed to both chemical complexation and electrostatic interaction. The urgent need to remove arsenic from groundwater stems from the irreversible damage it causes to aquatic systems and biological health. In this study, unique magnetic Fe 3 O 4 /graphene oxide (GO) nanocomposites derived from MIL-100(Fe)/GO precursor were rationally and precisely developed by combination of solvothermal synthesis and pyrolysis methods. The optimized MIL-100(Fe)/1%GO-400 magnetic nanocomposite (where 1% and 400 represent the mass ratio of GO to MIL-100(Fe) and pyrolysis temperature, respectively) exhibited exceptional adsorption capacity for As(V) and possessed magnetic separation properties. The novel nanocomposite had complete MOF morphology and crystal structure, as well as good resistance to interference from ions and could be used effectively over a wide pH range (2–9) for adsorption of As(V). The As(V) adsorption on the nanocomposite was found to follow the pseudo-second-order (PSO) kinetic model and Temkin adsorption isotherm model, as well as a spontaneous endothermic process dominated by chemisorption. The incorporation of GO and pyrolysis of the Fe-MOFs was proven to enhance the adsorption capacity of nanocomposite, water stability, and magnetic recovery ability. The adsorption mechanism was attributed to the synergistic effect of chemical complexation, hydrogen binding and electrostatic interaction. This work not only presents a feasible strategy for the development of Fe-MOFs-based derivatives, but also offers a promising approach to expanding the application of functional Fe-MOFs-based derivatives in arsenic-contaminated wastewater treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • ECSs are reused as an adsorbent for Cr(VI) from wastewater. • The maximum experimental removal capacity of ECSs for Cr(VI) was 110.50 mg/g. • Removal mechanisms include redox, electrostatic adsorption, and flocculation. Exhausted copper slags (ECSs) are secondary slags produced in the reusing process of copper smelting fly ashes and have the potential to synthesize adsorbent for the elimination of toxic elements. This study focuses on the potential of the original ESCs for the detoxication and removal of Cr(VI) from aqueous solutions. Batch adsorption experiments showed that ESCs present an excellent performance on Cr(VI) eliminate, and the maximum adsorption capacity is 110.50 mg∙g−1 at acid solutions (pH = 2) with a mild temperature condition (308 K). Furthermore, the adsorption efficiency of Cr was barely effected by the comment co-existing elements, such as NO 3 – and SO 4 2-, indicating its specific adsorption capacity for Cr. The elimination of Cr onto ESCs fits well with the Langmuir adsorption model, indicating that the adsorption process was controlled by monolayer adsorption. Moreover, Cr(VI) adsorption onto ESCs also followed the Pseudo-second-order kinetics with the adsorption rate constant k at 2.65 × 10-3 g·mg−1·min−1. Mechanistic analysis indicated that ECSs eliminated Cr(VI) by electrostatic adsorption and flocculation precipitation, and reduced Cr(III) by Fe2+, Mo2+, S2-, and SO 3 2-. The environmental risks during its adsorption implication process were also accessed and the toxic elements, such as Cu, As, and Pb in the materials were barely detected in the residue solutions. Thus, ECSs could be used as a facile and cost-effective adsorbent for Cr(VI) removal, even without any further pre-treatment process, which is meaningful to the disposal of this typical industrial waste. [ABSTRACT FROM AUTHOR]

[Display omitted] • PPy/NP were synthesized via an in situ chemical polymerization technique. • The maximum adsorption capacity of Cr(VI) on PPy/NP was 261.78–395.26 mg/g. • PPy/NP showed an excellent performance for adsorption and reduction of Cr(VI). • Cr(VI) removal was attributed to ion exchange, adsorption and reduction. • PPy/NP could be a promising material for efficient removal of Cr(VI). Easily agglomeration of polypyrrole (PPy) significantly limits its practical applications. In this study, natural pyrite (NP) was applied to disperse PPy and overcome this agglomeration; a novel composite of PPy/NP was synthesized and applied for the efficient removal of hexavalent chromium [Cr(VI)] from aqueous solutions. Results showed that the PPy/NP composites exhibited better Cr(VI) removal performance than PPy alone. This enhanced removal capacity is attributed to the addition of NP, which prevents PPy agglomeration and reduces Cr(VI) to trivalent chromium[Cr(III)]; Cr(VI) removal was significantly dependent on the solution's pH. The sorption kinetics of Cr(VI) with PPy/NP was described by the pseudo-second-order model and Elovich models, which highlight the chemicalsorption process. The sorption isotherm was well simulated by Langmuir model and the maximum adsorption capacity of Cr(VI) on PPy/NP was 261.78–395.26 mg/g at 303 – 323 K, which is significantly higher than that of PPy alone (124.84–194.17 mg/g). Thermodynamic analyses confirmed that this adsorption process was spontaneous and endothermic. PPy/NP composites could be used as a recyclable absorbents for four Cr(VI) reduction cycles without any evident loss in adsorption performance. The mechanism Cr(VI) removal by PPy/NP composites is attributed to ion exchange (9.47 %), adsorption (31.03 %), and reduction (59.50 %). [ABSTRACT FROM AUTHOR]