Adsorption and Reduction Transformation Behaviors of Cr(VI) on Mesoporous Polydopamine/Titanium Dioxide Composite Nanospheres

Abstract

Mesoporous polydopamine/titanium dioxide (PDA/TiO2) composite nanospheres with different polydopamine content were successfully synthesized by a facile organic–inorganic self-assembly method. The synthesized composite materials were characterized by N2 adsorption–desorption isotherm, X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy (TEM), energy dispersive spectrometry, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, ζ--potential, and cyclic voltammetry. The results showed that the composite material with the most exposure active site exhibits a spherical morphology. The composite material could also be used as a reducing agent, and spheres of the composite material were used as adsorbents for removing hexavalent chromium from aqueous solutions by reducing Cr­(VI) to Cr­(III). The influence of factors, including the initial solution pH, contact time, initial ion concentration, temperature, coexisting ions, and dose of adsorbent, was also studied. The hexavalent chromium adsorption data fit well to a Langmuir isotherm model, and the maximum adsorption capacity was shown to be 244.5 mg/g. The kinetics data follow a pseudo-second-order kinetic model. The study of thermodynamics indicated that the adsorption on the composite nanospheres was a spontaneous and endothermic process. Moreover, a mechanism of adsorption and reduction on the composite spheres was proposed.

Polyaniline coated tungsten trioxide as an effective adsorbent for the removal of orange G dye from aqueous media

“…However, when the PANI@WO 3 dose increased, the capacity of adsorption decreased from 154.85 to 48.68 mg g −1 , indicating that the PANI@WO 3 quantity had to be checked through the OG removal process. 44 …”

“…However, when the PANI@WO 3 dose increased, the capacity of adsorption decreased from 154.85 to 48.68 mg g À1 , indicating that the PANI@WO 3 quantity had to be checked through the OG removal process. 44 To some extent, the removal efficiency of OG dye could be enhanced as the number of active sites augmented, and the dose optimum of adsorbent was 0.5 g L À1 . Aer this optimal adsorbent dose, it was found that the efficiency of removal did not improve as more adsorbent was added.…”

Facile preparation of hierarchical porous polydopamine microspheres for rapid removal of chromate from the wastewater

“…A worldwide agreement has been reached aiming at reducing or eliminating the thread of Cr(VI). In China, the sewage discharge standards mandate that the maximum Cr(VI) concentration of the discharged effluent should be below 0.5 mg/L [4]; and the World Health Organization (WHO) put forwards even much stricter limits of 0.05 mg/L for drinking water [5]. Tremendous efforts have been put into the treatment of Cr(VI) polluted wastewaters, including electrochemical precipitation [6], membrane separation [7], photocatalysis [8,9], ion exchange [10], and bioremediation [11].…”

Design of a Smart Self-Healing Coating with Multiple-Responsive Superhydrophobicity and Its Application in Antibiofouling and Antibacterial Abilities

“…Stimuli-responsive mesoporous polydopamine (MPDA) microspheres with pH/NIR stimuli-responsive performances have been proved to be an excellent type of intelligent responsive material in metal-ion adsorption, photodynamic therapy, and other applications, − and our previous work has exhibited the application of MPDA microspheres with great stimuli-responsive performance in smart self-healing coating . Herein, a novel waterborne smart self-healing coating with superhydrophobicity was gained through blending UV/NIR/acid/base stimuli-responsive ZnO-encapsulated MPDA microspheres (ASO@MPDA/ZnO microspheres) and hydrophobic-modified SiO 2 and ZnO nanoparticles with silicone latex.…”