•The Hummers treatment exfoliated the bulk g-C3N4 nanosheets into nanorods.•The bandgap increased from 2.72 eV to 2.85 eV due to the Hummers treatment.•The photocatalytic activities of g-C3N4 are improved to 96.61%.In this study, graphitic C3N4 (g-C3N4) with high photocatalytic properties to methylene blue (MB) was synthesized by treating the bulk g-C3N4 using the Hummers method. The bulk g-C3N4 was obtained by calcining dicyandiamide. The g-C3N4 treated by the Hummers method (E-g-C3N4) was characterized and utilized for the photocatalytic removal of MB. The results showed that the Hummers treatment exfoliated the nanosheets bulk g-C3N4 into nanorods and improved the dispersion of E-g-C3N4 in an aqueous solution. It also distinctly enhanced the photocatalytic activity of g-C3N4 to MB, i.e., the removal efficiency increased from 38.45% for the bulk g-C3N4 to 96.61% for the E-g-C3N4.Figure optionsDownload full-size imageDownload high-quality image (273 K)Download as PowerPoint slide

•MgO was synthesized via hydrothermal and calcination method without surfactant.•MgO nanosheets exhibited high removal abilities toward Ni(Ⅱ) (885 mg/g).•The removal efficiencies of MgO reached 99.99% in 15 min.The mesoporous MgO nanosheets were obtained using Mg(NO3)2·6H2O and urea as the raw materials without any surfactant via hydrothermal and calcination method. The effect of annealing temperature on the nanostructures and the adsorption performance were reported. The MgO annealed at 600 °C were mesoporous nanosheets with surface area of 45 m2/g. More interestingly, it exhibited high-rate adsorption property of Ni (Ⅱ) with a removal efficiency up to 99.99% in 15 min and a maximum adsorption capacity of 885 mg/g.

•Mg(OH)2 film on AZ91 was prepared by an in-situ hydrothermal method.•Mg(OH)2 films are composed of circular nano-flakes.•The growth process of Mg(OH)2 film was analyzed and illustrated.•The Mg(OH)2 film showed strong adhesion and good corrosion resistance.Mg(OH)2 films have been fabricated on magnesium alloy AZ91 substrates by an in-situ hydrothermal method. AZ91 alloy substrates act as both the source of Mg2+ ion and the support for the Mg(OH)2 film in synthetic process. The effect of pH value and hydrothermal treatment time on the morphologies and corrosion resisting properties of Mg(OH)2 film is studied. The obtained Mg(OH)2 films are uniform and compact. The adhesion between the films and the substrate is strong due to the in-situ growth process, which enhances their potential for practical applications. Potentiodynamic polarization measurements showed that the Mg(OH)2 films obtained at pH 10, 3 h exhibits the highest increase in corrosion potential at −0.7097 V and lowest icorr, which suggests that it is the best effective film in improving the corrosion resistance of AZ91in all obtained films.A simple and green hydrothermal route was employed to fabrication nontoxic Mg(OH)2 films on AZ91 substrate. In the reaction, the source of Mg2+ in Mg(OH)2 all came directly form AZ91 substrate resulting strong adhere to the substrate, only OT (Sodium dioctyl sulfosuccinate) and NaOH solution are employed promising a green process. The as grown Mg(OH)2 film inhibited corrosion of the underlying metal.

Porous spinel ferrites Mn1−xZnxFe2O4 (0 ⩽ x ⩽ 0.8) are synthesized by a simple sol–gel method with egg white. All samples exhibit porous morphologies and large BET surface area (SBET). The substitution of Zn2+ affects the magnetic properties of ferrites and the adsorption properties of methylene blue (MB) on ferrites, obviously. The saturation magnetization (Ms) of Mn1−xZnxFe2O4 increases before x = 0.4, and decreases with further increase of Zn2+ substitution. This can be ascribed to the changes of the cationic distribution and the variation of spin arrangement in A-site and B-site of spinel structure. All samples show high adsorption capacity and the removal efficiencies of MB reach up to >90% within 3 h. The Zn2+ substitution accelerates the adsorption rate and capacity of MB on Mn1−xZnxFe2O4. The quickest adsorption occurred at x = 0.2 and the largest adsorption capacity occurred at x = 0.8.Graphical abstractPorous ferrites Mn1−xZnxFe2O4 (0 ⩽ x ⩽ 0.8) show high speed adsorptive properties of methylene blue (MB) and can be separated conveniently by a magnet for their ferromagnetic properties. Research highlights► All samples of Mn1−xZnxFe2O4 synthesized by sol–gel method are porous shapes and Zn2+ addition can affect their morphologies. ► The porous of Zn2+ doped ferrite Mn1−xZnxFe2O4 show both ferromagnetic and adsorption properties, which realize the effective adsorption and convenient magnetic separation. ► Moreover, the addition of Zn2+ accelerate the adsorptive speed obviously, the quickest adsorption.

Three dimensions (3D) porous NiFe2O4 is synthesized by a sol–gel method using egg white. The obtained NiFe2O4 shows both good ferromagnetic properties and high adsorption capacity. The porous NiFe2O4 shows good adsorption properties for organic dyes (Methylene Blue (138.50 mg/g), Fuchsine Red (14.61 mg/g), Methyl Violet (19.06 mg/g)) and heavy metal ions (Cu (II) (55.83 mg/g), Cr (VI) (36.95 mg/g) and Ni (II) (37.02 mg/g)) due to its 3D interconnected porous structure. The maximum adsorption of Methylene Blue (MB) fit the pseudo-second-order model and Langmuir isotherm equation well. More interestingly, the ferromagnetic NiFe2O4 can be separated under a magnetic field conveniently and keeps high removal efficiency (>97%) during seven reusable cycles. These results suggest that the porous NiFe2O4 is a promising favorable and reusable adsorbent.Graphical abstract3D porous NiFe2O4 was synthesized by sol–gel method. It showed excellent adsorption properties for organic dye and could be magnetic separated easily.Highlights► Porous NiFe2O4 was synthesized by a simple sol–gel method using egg white. ► The pore structure forming process was studied. ► Porous NiFe2O4 shows large adsorption capacity for organic dye and heavy metal ions. ► The ferromagnetic property of NiFe2O4 resulting in excellent magnetic separation.

Spongelike porous MnFe2O4 (SPM) was synthesized by a sol–gel method with egg white. The obtained SPM was characterized and applied for the removal of methylene blue (MB) from aqueous solution in the batch system. The morphologies of SPM were spongelike porous bulks and the pore size could be controlled by the dosage of egg white. SPM showed good magnetic property at room temperature. In addition, SPM was suitable for adsorption due to its porous structure and high BET surface areas. The pseudo-second-order model described the adsorption kinetics well. FT-IR analysis suggested that –N+(CH3)2 of MB cations and the Fe–O bond of SPM were responsible for good adsorption. The adsorption equilibrium data fit Langmuir isotherm equation well with a maximum MB adsorption capacity of 20.67 mg/g. Moreover, SPM could be separated conveniently under a magnetic field (recovery ratio >98%) and reused seven cycles keeping a high activity (>96%). MB removal efficiencies of the last three cycles (99.5%) were even higher than that of the first four cycles. The results suggested that the SPM was a promising reusable adsorbent to remove MB form wastewater.