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BACKGROUND: Simultaneous removal of arsenic and fluoride anions from water by adsorption remains a challenge for environmental remediation practice. To address this issue, four mesoporous bimetallic oxides (MBOs) were prepared via the evaporation‐induced self‐assembly (EISA) method and studied as adsorbents for the co‐uptake of arsenate (As(V)) and fluoride (F−) from synthetic wastewater. Adsorption envelope and equilibrium experiments were performed to investigate the adsorption behaviors and properties. RESULTS: These composites possessed high surface areas (e.g. 200 m2 g−1 for meso‐Ti/Al) and well‐defined mesopores, enabling high adsorption capacities for both As(V) and F−. The maximum adsorption capacities of mesoporous titanium‐lanthanum oxide (meso‐Ti/La) were as high as 81.42 mg g−1 and 44.37 mg g−1 for As(V) and F−, respectively. Surface complexation modeling indicates that As(V) removal mainly involved bidentate surface complexation with surface ≡Me‐OH, while F− was retained by formation of monodentate surface complexes. CONCLUSION: The removal mechanisms were confirmed by X‐ray photoelectron spectroscopy. These MBOs were found to be effective for simultaneous removal of arsenic and fluoride from water. This study also demonstrated that the incorporation of multi‐components and mesoporosity into one composite is an efficient strategy for design and application of high‐efficiency adsorbents for environmental remediation of aqueous contaminants. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In this study, a class F fly ash and palygorskite have been acid-modified and then evaluated for the adsorption of phosphate in aqueous solution via bench-scale batch experiments. XRD, XRF, SEM, and FTIR were employed to characterize the acid-modified fly ash (MFA) and palygorskite (MPal). Both MFA and MPal show enhanced phosphate adsorption after the modification treatment. The effects of pH, adsorbent dosage, and co-ions on phosphate adsorption, as well as adsorption thermodynamics and kinetics, and leaching features of spent (used) adsorbents were also investigated. The isotherms data fit well with the Langmuir model rather than the Freundlich model, giving maximum capacities (298 K) of 13.3 mg P g − 1 for MFA and 10.5 mg P g − 1 for MPal, respectively. Surface complexation modeling of P adsorption data with the nonelectrostatic generalized composite (GC) approach indicates that phosphate were directly bound to the metal centers by ligand exchange to form two monodentate complexes, ≡ SHPO 4 − and ≡ SPO 4 2 − . The GC model appears to be an easy and efficient tool to provide an insight into the mechanism of phosphate adsorption on complex adsorbents with limited model parameters. Leaching test results suggest that the spent adsorbents can be safely disposed or further reused. [ABSTRACT FROM AUTHOR]

In the present work, three metal (oxyhydr)oxides, i.e. 2-line ferrihydrite (FeOOH), bayerite (β-Al(OH)3), and hausmannite (Mn3O4), were prepared and then employed as adsorbents for As(V) in aqueous solution. Both adsorption equilibrium and kinetics of As(V) have been investigated via batch experiments. The adsorption equilibrium results indicated that all adsorption data follow the Langmuir equation with maximum adsorption capacities of 28.57, 14.29, and 1.00 mg g−1for FeOOH, β-Al(OH)3, and Mn3O4, respectively. It was found that the pseudo-second-order kinetic equation is capable of fitting these kinetic data well with correlation coefficients (R2) greater than 0.98. The effects of co-occurring anions, both phosphate () and sulfate (), were shown to reduce As(V) uptake, whereas calcium ion (Ca2+) was found to enhance As(V) adsorption. This work can extend our understanding of equilibrium and kinetic behaviors of As(V) adsorption on typical metal (oxyhydr)oxides. [ABSTRACT FROM PUBLISHER]

Abstract: Iron-bearing minerals have been used as adsorbents for arsenic anions for many decades, but both the small surface area and the poorly defined pore structure limit their performance in removal of arsenic from aqueous systems. Herein, we report a sonochemical layer-by-layer (LBL) loading process for depositing of ferric species onto mesoporous silicas (i.e., MCM-41, SBA-15, and KIT-6). The surface area, pore size and volume, as well as the iron loading of these mesoporous silicas can be tailored and optimized with increasing in loading cycle via a LBL protocol. The surface functioned materials were characterized by X-ray diffraction (XRD), N2 physisorption, transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectrometry and zeta potential measurement. Their performance in As(V) adsorption was also tested. The results indicate that the iron-loaded mesoporous silicas retained their ordered pore structure as well as the large surface area, which enable them a good kinetic performance in uptake of As(V) anions. When iron loading is as much as 10wt.%, two representative iron-loaded silicas Fe10MCM-41 and Fe10KIT-6, exhibited the best performance in trapping the As(V) anions, with an Fe/As molar ratio of about 5.77 and 5.10, respectively. The Fe/As molar ratio implies they belong to the iron-containing adsorbents with the highest adsorption performance for As(V), and therefore could be used as alternative adsorbents for As(V) adsorption. [Copyright &y& Elsevier]

Abstract: Mesostructured ferric oxyhydroxides (MFOs) were synthesized using both cetyltrimethylammonium bromide (CTAB) and sodium dodecylsulfonate (SDS) as templates in the present study. For CTAB-templating route, the effect of pH and fluoride ions on the resulting MFOs has been evaluated, and the active role of fluoride ions in promotion the mesostructural ordering was verified. Besides, the effect of solvents and hydrolysis ratio on the synthetic layered MFOs was examined via SDS-templating route. X-ray diffraction (XRD), transmission electron microscopy (TEM), and nitrogen physisorption were employed to characterize the MFOs before two typical MFOs with surface areas of 144.7 and 88.1m2 g−1, respectively, were evaluated as potential adsorbent for As(V) removal. Both MFOs presented adsorption isotherms well fitting the Freundlich equation. The two MFOs exhibited adsorption capacities of 75.19 and 10.68mgg−1, respectively, and could be adopted as adsorbent for As(V) removal. [Copyright &y& Elsevier]

• Mesoporous core/shell/shell hierarchical structured MgAl-LDH composites were prepared. • The LDH composites display well-defined pore distributions and good magnetic separability. • The LDH composites show higher adsorption capacities for phosphate and fluoride than other LDHs. • The adsorbed phosphate and fluoride could be successfully recovered. • The regenerated LDH composites can be reused for removal or recovery of fluoride or phosphate. Three core/shell/shell MgAl-LDH composites using Fe 3 O 4 microspheres as the core, a SiO 2 matrix as the inner layer and a MgAl-LDH layer as the outer shell have been synthesized for the removal and recovery of phosphate and fluoride from water by a magnetic separation technique. The synthetic mesoporous MgAl-LDH composites show good magnetic separability, well-defined pore distributions, and have specific surface areas of 73 m2 g−1, 168 m2 g−1, and 137 m2 g−1 for Fe 3 O 4 @SiO 2 @LDH350, Fe 3 O 4 @SiO 2 @ m LDH350, and Fe 3 O 4 @ m SiO 2 @ m LDH350, respectively. The adsorption isotherms of both phosphate and fluoride on these MgAl-LDH composites can be well fitted with the Langmuir model. The maximum adsorption capacities of 57.07 mg g−1 and 28.51 mg g−1 were obtained on Fe 3 O 4 @ m SiO 2 @ m LDH350 for phosphate and fluoride, respectively, much higher than those of other LDH-type materials. The adsorbed phosphate and fluoride could be successfully recovered by NaNO 3 -NaOH solution, and the regenerated MgAl-LDH composites could be reused for phosphate and fluoride removal. Owing to their high adsorption capacities of both phosphate and fluoride, easy magnetic separation from solution, and good reusability, the mesoporous MgAl-LDH composites are expected to have potential applications in removal or recovery of fluoride or phosphate from water. [ABSTRACT FROM AUTHOR]

The co-occurrence of arsenic and fluoride in the water environment has led to many health concerns for living beings. Simultaneous removal of such ions is crucial to the safety of water resources, and biochar has been extensively engaged to address this issue. Here four magnetic biochars (mBCs) including pristine magnetic biochar and three aluminum (Al) and/or magnesium (Mg) oxides-anchored magnetic biochar (i.e., Al-mBC, Mg-mBC, and MgAl-mBC) were prepared via a facile pyrolysis method and then comprehensively evaluated as adsorbents for enhanced co-uptake of arsenate (AsV) and fluoride (F−) from synthetic water. The mBC shows a high specific surface area of 205 m2 g−1, which dropped to 116, 80, and 114 m2 g−1 upon the anchoring of Al, Mg, and Mg + Al, respectively. Our results suggest that the adsorption of either AsV or F− is highly pH-dependent, and pH 4–6 is the optimal range for maximum adsorption. The adsorption isotherm data indicate that the MgAl-mBC adsorbent outranks all other mBCs for co-uptake of both AsV and F−. The adsorption capacity maxima of MgAl-mBC are 34.45, and 21.59 mg g−1 for AsV and F−, respectively (pH = 5, T = 10 °C), also highly outstripping other biochars reported in the literature. The magnetic feature of these mBCs enables us to fast reclaim and regenerate the exhausted adsorbents by an external magnet and dilute NaOH. The Al- and Mg-anchored mBCs are expected to be used as highly efficient adsorbents for environmental remediation of waters contaminated by both AsV and F−. [Display omitted] • Metal-anchored magnetic biochars are prepared via a facile pyrolysis method. • Magnetic biochars exhibit a high adsorption capacity for both AsV and F−. • The spent magnetic biochars can be magnetically recycled and fast regenerated. • MgAl-mBC adsorbent outranks other biochars for simultaneous removal of both AsV and F−. [ABSTRACT FROM AUTHOR]