Superb Adsorption Capacity Research Articles

Adsorption characteristics of Direct Red 23 azo dye onto powdered tourmaline

The high electric field on the surface of tourmaline particles has a potential of enhancing electrostatic reactions during adsorption. However, information concerning the adsorption characteristics of dyes onto tourmaline is currently unavailable. In the present study, the behavior and efficiency of powdered tourmaline (PT) in removing the diazo Direct Red 23 (DR23) dye from aqueous solution were investigated. The observations from batch adsorption experiments indicated that the adsorption was more favorable under low adsorbate surface loading, low pH, high temperature, and low ionic strength conditions. A homogeneous particle diffusion model (HPDM) was used to characterize the process, and the rate of adsorption was found to be controlled by intra-particle diffusion. An activation energy of 4.54kcal/mol was calculated, suggesting that the adsorption proceeded with a low energy barrier and that a physisorption was involved. The functional groups binding anionic DR23 on the PT particles were also identified. A maximum adsorption capacity of 153mg/g was determined according to the Langmuir isotherm. The PT was subjected to a total of 5 regeneration runs without losing much of its dye-adsorption capacities. Due to its low price, abundant availability, and superb adsorption capacity, PT has a great potential for use as an effective adsorbent in removing DR23 from aqueous solutions.

Removal of Mercury(II) from Aqueous Solutions by Adsorption on Poly(1-amino-5-chloroanthraquinone) Nanofibrils: Equilibrium, Kinetics, and Mechanism Studies

Poly(1-amino-5-chloroanthraquinone) (PACA) nanofibrils were applied as novel nanoadsorbents for highly toxic mercury removal from aqueous solutions. A series of batch adsorption experiments were conducted to study the effect of adsorbent dose, pH, contact time, and metal concentration on Hg(II) uptake by PACA nanofibrils. Kinetic data indicated that the adsorption process of PACA nanofibrils for Hg(II) achieved equilibrium within 2 h following a pseudo-second-order rate equation. The adsorption mechanism of PACA nanofibrils for Hg(II) was investigated by Fourier transform-infrared (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS) analyses. The adsorption isotherm of Hg(II) fitted well the Langmuir model, exhibiting superb adsorption capacity of 3.846 mmol of metal per gram of adsorbent. Lastly, we found out that the as-synthesized PACA nanofibrils are efficient in Hg(II) removal from real wastewater. Furthermore, five consecutive adsorption-desorption cycles demonstrated that the PACA nanofibrils were suitable for repeated use without considerable changes in the adsorption capacity.

Superior adsorption capacity of hierarchical iron oxide@magnesium silicate magnetic nanorods for fast removal of organic pollutants from aqueous solution

Novel hierarchical core–shell iron oxide@magnesium silicate magnetic nanorods (HIO@MgSi) were fabricated via a versatile sol–gel process through hydrothermal reaction. They contain magnetic iron oxide (Fe3O4) cores and hierarchical shells (MgSi) made of ultrathin nanosheets (ca. 5 nm). Using methylene blue as a model compound, the HIO@MgSi nanorods showed fast adsorption kinetics and a superb adsorption capacity. 99.3% of methylene blue was adsorbed onto the surface of the HIO@MgSi nanorods in 40 min contact time. A maximum adsorption capacity of 2020.20 mg g−1 was achieved after 4 h. This study indicated that HIO@MgSi nanorods can be used as a potential super adsorbent to remove cationic organic pollutants effectively and rapidly from large volumes of industrial wastewater or drinking water.

Superb Adsorption Capacity and Mechanism of Flowerlike Magnesium Oxide Nanostructures for Lead and Cadmium Ions

A facile method based on microwave-assisted solvothermal process has been developed to synthesize flowerlike MgO precursors, which were then transformed to MgO by simple calcinations. All the chemicals used (magnesium nitrate, urea, and ethanol) were low cost and environmentally benign. The products were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution TEM, and N(2) adsorption-desorption methods. These flowerlike MgO nanostructures had high surface area and showed superb adsorption properties for Pb(II) and Cd(II), with maximum capacities of 1980 mg/g and 1500 mg/g, respectively. All these values are significantly higher than those reported on other nanomaterials. A new adsorption mechanism involving solid-liquid interfacial cation exchange between magnesium and lead or cadmium cations was proposed and confirmed.

Emulsion template synthesis of all conducting polymer aerogels with superb adsorption capacity and enhanced electrochemical capacitance

4-(2,3-Dihydrothieno[3,4-b][1,4]dioxin-2-yl)-methoxybutane-1-sulfonate (EDOT-S) as a reactive surfactant was used to disperse 3,4-ethylenedioxythiophene (EDOT) to make a PEDOT-S/PEDOT hydrogel by emulsion polymerization. The corresponding all conducting polymer aerogels have been obtained by supercritical drying or freeze drying of the as-synthesized PEDOT-S/PEDOT hydrogels. The stability of the EDOT-S stabilized EDOT emulsion has been investigated by zeta potential and size tests. The mechanical property and gelation mechanism of the resulting PEDOT-S/PEDOT hydrogels have been studied by rheological experiments, X-ray powder diffraction and X-ray photoelectron spectroscopy. The molecular structure of the resulting PEDOT-S/PEDOT aerogels has been revealed by infra-red and Raman spectroscopy, and the porous attribute of the as-synthesized PEDOT-S/PEDOT aerogels has been investigated by scanning electron microscopy, transmission electron microscopy and nitrogen sorption tests. It has been found that molar ratios of EDOT-S to EDOT have played a significant role in determining the stability of the resulting emulsion, the mechanical properties of the resulting hydrogel, and the porous properties of the resulting aerogels. The electrical, electrochemical and adsorption properties have also been disclosed in this manuscript. The results show that the as-prepared all conducting polymer aerogels have high conductivity with the level of 101 S m−1, enhanced electrochemical capacitance with good rate capability and excellent cycling stability, and superb adsorption capacity to dyestuff and heavy metals ions.