Removal of Chromium Species by Adsorption: Fundamental Principles, Newly Developed Adsorbents and Future Perspectives

Emerging chromium (Cr) species have attracted increasing concern. A majority of Cr species, especially hexavalent chromium (Cr(VI)), could lead to lethal effects on human beings, animals, and aquatic lives even at low concentrations. One of the conventional water-treatment methodologies, adsorption, could remove these toxic Cr species efficiently. Additionally, adsorption possesses many advantages, such as being cost-saving, easy to implement, highly efficient and facile to design. Previous research has shown that the application of different adsorbents, such as carbon nanotubes (carbon nanotubes (CNTs) and graphene oxide (GO) and its derivatives), activated carbons (ACs), biochars (BCs), metal-based composites, polymers and others, is being used for Cr species removal from contaminated water and wastewater. The research progress and application of adsorption for Cr removal in recent years are reviewed, the mechanisms of adsorption are also discussed and the development trend of Cr treatment by adsorption is proposed.

Efficient and selective adsorption of Au(iii), Pt(iv), and Pd(ii) by a radiation-crosslinked poly(ionic liquid) gel

A PIL gel was prepared for Au(iii), Pt(iv), and Pd(ii) recovery. The PIL gel exhibited fast adsorption rates and excellent selectivity for target ions. Furthermore, the gel could efficiently separate Au(iii) from gold slag leaching solution.

Recent advances in magnetic carbon nanotubes: synthesis, challenges and highlighted applications

Magnetic carbon nanotubes (MCNTs), consisting of carbon nanotubes (CNTs) and magnetic nanoparticles (MNPs), have enormous exploration and application potentials due to their superior physical and chemical properties, such as unique magnetism and high enrichment performance. This review concentrates on the rapid advances in the synthesis and application of magnetic carbon nanotubes. Great progress has been made in the preparation of MCNTs by developing methods including chemical vapor deposition, pyrolysis procedure, sol-gel process, template-based synthesis, filling process and hydrothermal/solvothermal method. Various applications of MCNTs as a mediator of the adsorbent in magnetic solid-phase extraction, sensors, antibacterial agents, and imaging system contrast agents, and in drug delivery and catalysis are discussed. In order to overcome the drawbacks of MCNTs, such as sidewall damage, lack of convincing quantitative characterization methods, toxicity and environmental impact, and deficiency of extraction performance, researchers proposed some solutions in recent years. We systematically review the latest advances in MCNTs and discuss the direction of future development.

An ionic liquid functionalized polymer for simultaneous removal of four phenolic pollutants in real environmental samples

An ionic liquid functionalized polymer (IL-P) was prepared feasibly and simply by grafting1-butyl-3-vinylimidazolium bromide onto the silica surface. The IL-P was fully characterized, and the results showed that IL-P has a rough surface with a lower specific surface area (205.49 m² g^-1), and the involvement of ionic liquid significantly improved the adsorption performance of IL-P. The pH, initial concentration, adsorption time and temperature were investigated to discuss the adsorption behaviors of IL-P in aqueous solution. The adsorption process of 2,4-dichlorophenol (2,4-DCP), bisphenol A (BPA) and 2,4-dinitrophenol (2,4-DNP) onto IL-P better fitted the pseudo-second-order model, while that of 2-isonaphthol (2-NP) followed the pseudo-first-order model. The adsorption behaviors of IL-P towards 2,4-DCP and 2,4-DNP fitted well with Liu isotherm model, and that of BPA and 2-NP can be described by Langmuir model. The maximum adsorption capacities of 2,4-DCP, BPA, 2,4-DNP and 2-NP bound on IL-P was 239.7, 68.39, 56.86 and 64.28 mg g^-1, respectively, and the adsorption of IL-P is a spontaneous physical process. Comparing with other adsorbent, the as-prepared IL-P showed excellent recognition ability towards the phenolic compounds and can be applied to adsorb and remove trace 2,4-DCP, 2-NP, 2,4-DNP and BPA simultaneously in complicated wastewater and soil samples.

Designing a sulphonic acid functionalized benzimidazolium based poly(ionic liquid) for efficient adsorption of hexavalent chromium

Herein, the facile synthesis of sulphonic acid functioned benzimidazolium based poly(ionic liquid) (SBPIL) is reported for the first time and we investigated its efficacy towards the removal of Cr(vi).

Preparation of neutral red functionalized Fe3O4@SiO2 and its application to the magnetic solid phase extraction of trace Hg(ii) from environmental water samples

Trace level of Hg(ii) was extracted from water by neutral red functionalized Fe₃O₄@SiO₂ based on the electrostatic and coordinate interactions of Hg(ii) with neutral red.

Modified surface-active ionic liquid-coated magnetic graphene oxide as a new magnetic solid phase extraction sorbent for preconcentration of trace nickel

General procedure for preconcentration/recovery of nickel ions using modified surface-active ionic liquid-coated magnetic graphene oxide nanocomposite.

Monolithic magnetic carbonaceous beads for efficient Cr(vi) removal from water

Alginate-derived magnetic monolithic carbonaceous beads were synthesized for the first time, aiming for efficient Cr(vi) removal, easy recovery and reusability.

Heterogenization of an imidazolium ionic liquid based on magnetic carbon nanotubes as a novel organocatalyst for the synthesis of 2-amino-chromenes via a microwave-assisted multicomponent strategy

The microwave-assisted synthesis of the first ionic liquid stabilized CNTs–Fe₃O₄as a novel nanocatalyst for the synthesis of 2-amino-chromenesviaa multicomponent reaction is reported.

The efficient adsorption removal of Cr(vi) by using Fe3O4 nanoparticles hybridized with carbonaceous materials

Carbonaceous materials, such as pinecone and graphene, have been hybridized with Fe₃O₄ to modify its surface properties and enhance its adsorption efficiency for Cr(vi) removal in aqueous solution.

Sodium alginate-based magnetic carbonaceous biosorbents for highly efficient Cr(vi) removal from water

A novel magnetic alginate-based biosorbent, aiming for efficient removal of Cr(vi) from aqueous system, was successfully synthesized.