Activated multi-walled carbon nanotubes decorated with zero valent nickel nanoparticles for arsenic, cadmium and lead adsorption from wastewater in a batch and continuous flow modes.

Nickel nanoparticles (NiNPs) supported on activated multi-walled carbon nanotubes (MWCNTs) were used as an adsorbent applied towards Pb(II), As(V) and Cd(II) remediation from industrial wastewater. The result revealed the hydrophilic surface of MWCNTs-KOH was enhanced with the incorporation of NiNPs enabling higher surface area, functional groups and pore distribution. Comparatively, the removal of Pb(II), As(V) and Cd(II) on the various adsorbents was reported as NiNPs (58.6 ± 4.1, 46.8 ± 3.7 and 40.5 ± 2.5%), MWCNTs-KOH (68.4 ± 5.0, 65.5 ± 4.2 and 50.7 ± 3.4%) and MWCNTs-KOH@NiNPs (91.2 ± 8.7, 88.5 ± 6.5 and 80.6 ± 5.8%). Using MWCNTs-KOH@NiNPs, the maximum adsorption capacities of 481.0, 440.9 and 415.8 mg/g were obtained for Pb(II), As(V) and Cd(II), respectively. The experimental data were best suited to the Langmuir isotherm and pseudo-second order kinetic model. The fitness of experimental data to the kinetic models in a fixed-bed showed better fitness to Thomas model. The mechanism of metal ion adsorption onto MWCNTs-KOH@NiNPs show a proposed electrostatic attraction, surface adsorption, ion exchange, and pore diffusion due to the incorporated NiNPs. The nanocomposite was highly efficient for 8 adsorption cycles. The results of this study indicate that the synthesized nanocomposite is highly active with capacity for extended use in wastewater treatment.

Metal-organic frameworks for pesticidal persistent organic pollutants detection and adsorption - A mini review.

The global population growth demands intensification of anthropogenic processes, thus leading to inter alia pollution of both land and aquatic environments with toxic organic compounds. Particularly harmful synthetic compounds are classified as persistent organic pollutants (POPs). Their relatively high chemical resistance resulted in a worldwide ban or strict control on the use of POPs. The majority of POPs were commonly used as pesticides, and unfortunately, some of them are still utilized as an aid in agricultural practices. Therefore, environmental monitoring in terms of reliable detection and quantification of pesticidal POPs is an ever-increasing need. Chemical sensors and adsorption materials crafted for specific pesticide operate on host-guest interactions should provide selectivity and sensitivity, thus leading to the detection of target molecule down to the nanomolar range. This could be achieved with materials exhibiting a very large active surface area, well-defined structure, and high stability. The novel materials studied in that context are metal-organic frameworks (MOFs). The structure of various MOFs can be functionalized to provide desired host-guest interactions. In this mini-review, we critically discuss the application of MOFs for the detection and adsorption of selected pesticides that are classified as POPs according to the Stockholm Convention.

Correction: Gold-carbonyl group interactions in the electrochemistry of anthraquinone thiols self-assembled on Au(111)-surfaces.

[This corrects the article DOI: 10.1039/C9SC00061E.].

Gold-carbonyl group interactions in the electrochemistry of anthraquinone thiols self-assembled on Au(111)-surfaces.

New anthraquinone derivatives with either a single or two thiol groups (AQ1 and AQ2) were synthesized and immobilized in self-assembled monolayers (SAMs) on Au(111) electrodes via Au-S bonds. The resultant AQ1- and AQ2-SAMs were studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which enabled mapping of the gold-carbonyl group interactions and other dynamics in the Au-S bound molecular framework. Understanding of these interactions is important for research on thiol-coated gold nanoclusters, since (I) anthraquinone derivatives are a major compound family for providing desired redox functionality in multifarious assays or devices, and (II) the gold-carbonyl interactions can strongly affect anthraquinone electrochemistry. Based on equivalent circuit analysis, it was found that there is a significant rise in polarization resistance (related to SAM structural reorganization) at potentials that can be attributed to the quinone/semi-quinone interconversion. The equivalent circuit model was validated by calculation of pseudocapacitance for quinone-to-hydroquinone interconversion, in good agreement with the values derived from CV. The EIS and CV patterns obtained provide consistent evidence for two different ECEC (i.e. proton-controlled ET steps, PCET) pathways in AQ1- and AQ2-SAMs. Notably, it was found that the formal reorganization (free) energies obtained for the elementary PCET steps are unexpectedly small for both SAMs studied. This anomaly suggests high layer rigidity and recumbent molecular orientation on gold surfaces, especially for the AQ2-SAMs. The results strongly indicate that gold-carbonyl group interactions can be controlled by favorable structural organization of anthraquinone-based molecules on gold surfaces.

Lignin Modification for Biopolymer/Conjugated Polymer Hybrids as Renewable Energy Storage Materials.

Lignin derivatives, which arise as waste products from the pulp and paper industry and are mainly used for heating, can be used as charge storage materials. The charge storage function is a result of the quinone groups formed in the lignin derivative. Herein, we modified lignins to enhance the density of such quinone groups by covalently linking monolignols and quinones through phenolation. The extra guaiacyl, syringyl, and hydroquinone groups introduced by phenolation of kraft lignin derivatives were monitored by (31) P nuclear magnetic resonance and size exclusion chromatography. Electropolymerization in ethylene glycol/tetraethylammonium tosylate electrolyte was used to synthesize the kraft lignin/polypyrrole hybrid films. These modifications changed the phenolic content of the kraft lignin with attachment of hydroquinone units yielding the highest specific capacity (around 70 mA h g(-1) ). The modification of softwood and hardwood lignin derivatives yielded 50 % and 23 % higher charge capacity than the original lignin, respectively.