Adsorptive removal of dyes from aqueous solution onto carbon nanotubes: a review.

Adsorption of methylene blue by a high-efficiency adsorbent (polydopamine microspheres): Kinetics, isotherm, thermodynamics and mechanism analysis

Adsorption of methylene blue from aqueous solution by graphene.

An alkali-acitvated method was explored to synthesize activated carbon nanotubes (CNTs-A) with a high specific surface area (SSA), and a large number of mesopores. The resulting CNTs-A were used as an adsorbent material for removal of anionic and cationic dyes in aqueous solutions. Experimental results indicated that CNTs-A have excellent adsorption capacity for methyl orange (149 mg/g) and methylene blue (399 mg/g). Alkali-activation treatment of CNTs increased the SSA and pore volume (PV), and introduced oxygen-containing functional groups on the surface of CNTs-A, which would be beneficial to improving the adsorption affinity of CNTs-A for removal of dyes. Kinetic regression results shown that the adsorption kinetic was more accurately represented by a pseudo second-order model. The overall adsorption process was jointly controlled by external mass transfer and intra-particle diffusion, and intra-particle diffusion played a dominant role. Freundlich isotherm model showed a better fit with adsorption da...

Enhanced Adsorptive Removal of Methyl Orange and Methylene Blue from Aqueous Solution by Alkali-Activated Multiwalled Carbon Nanotubes

Graphene oxide (GO) is a highly effective absorbent of methylene blue (MB) and can be used to remove MB from aqueous solution. A huge absorption capacity of 714 mg/g is observed. At initial MB concentrations lower than 250 mg/L, the removal efficiency is higher than 99% and the solution can be decolorized to nearly colorless. The removal process is fast and more efficient at lower temperatures and higher pH values. The increase of ionic strength and the presence of dissolved organic matter would further enhance the removal process when MB concentration is high. The results indicate that GO can be applied in treating industrial effluent and contaminated natural water. The implications to graphene-based environmental technologies are discussed.

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Removal of methylene blue from aqueous solution by graphene oxide.

Adsorption behavior of methylene blue on carbon nanotubes.

This study examined the feasibility of removing methyl violet (MV) and methylene blue (MB) from aqueous solutions using carbon nanotubes (CNTs). The effects of dye concentration, CNTs dosage, pH and contact time on adsorption of direct dyes by CNTs were also evaluated. The amount adsorbed increased with the dose of CNTs; however, the adsorption capacity dropped as the CNTs dosage increased. Cationic dyes adsorbed increased with pH due to the electrostatic attraction between the negatively charged CNTs adsorbent surface and the positively charged cationic dyes. The correlation coefficients for the Pseudo second-order kinetics model (R2) are greater than 0.99, indicating the applicability of this kinetic equation and the second order nature of the adsorption process of MB and MV onto CNTs. Additionally, the fact that the Langmuir isotherm fits the experimental data very well may be due to the homogeneous distribution of active sites onto CNTs surface.

Adsorption of cationic methyl violet and methylene blue dyes onto carbon nanotubes

Adsorption of as-produced and purified multiwalled carbon nanotubes (MWNTs) to heavy metal using Cu(II) as a model was investigated and characterized by many techniques. The results show that the oxygenous functional groups can be formed on MWNTs after MWNTs were purified. The oxygenous functional groups play an important role in Cu(II) adsorption to form chemical complex adsorption. The adsorption capacity of Cu (II) on as-produced and purified MWNTs increased with the pH in the pH range of 2–7. The Cu (II) species adsorbed on purified MWNTs mainly aggregate on the ends and at the defects sites on the purified MWNTs. The experimental data for metal ions adsorption onto MWNTs were analyzed using the Langmuir and Freundlich models to describe the equilibrium adsorption. The linear correlation coefficients of Langmuir isotherms were obtained and the results revealed that the Langmuir isotherm fitted the experimental results.

Zhongxiao Xu

Papers

Adsorption behavior of methylene blue on carbon nanotubes.

Adsorption of cationic methyl violet and methylene blue dyes onto carbon nanotubes

Studies of the equilibrium of the adsorption of Cu(II) onto as-produced and purified carbon nanotubes