Environmental condition effects on radionuclide 64Cu(II) sequestration to a novel composite: polyaniline grafted multiwalled carbon nanotubes

Removal of U(vi) from aqueous solutions by an effective bio-adsorbent from walnut shell and cellulose composite-stabilized iron sulfide nanoparticles

FeS nanoparticles were easily aggregated and oxidized in the natural environment. It was important to stabilize the iron sulfide nanoparticle composite with a stabilizer. Biochar could be used as an effective carrier to inhibit the agglomeration and oxidization of FeS nanoparticles. An efficient and novel bio-adsorbent (CFeS-WS) from walnut shell (WS) and cellulose composites-stabilized iron sulfide nanoparticle was synthesized by the modified method. The removal of U(vi) ions from an aqueous solution by CFeS-WS was carried out. The experimental results indicated that numerous functional groups were observed on the surface of CFeS-WS. In addition, the biochar was loaded successfully with cellulose and FeS nanoparticle composites. The cellulose and biochar effectively prevented the agglomeration of FeS nanoparticles. The adsorption process of U(vi) ions by CFeS-WS was more consistent with the pseudo second-order kinetic model and Langmuir isotherm model. The adsorption process of U(vi) ions was an endothermic and chemical reaction process. The proposed reaction mechanism of the U(vi) ion removal by CFeS-WS mainly consisted of the ion exchange reaction, reduction reaction, hydrogen bonding and functional group, and pore of the adsorbent filling. According to the results of the recycle experiment, it indicated that the chemical stability of CFeS-WS was good.

Iron-loaded carbon nanotube-microfibrous composite for catalytic wet peroxide oxidation of m-cresol in a fixed bed reactor

A kind of novel iron-loaded carbon nanotube-microfibrous composite (Fe₂O₃-CNT-MF) catalyst is prepared and tested for fixed bed m-cresol catalytic wet peroxide oxidation (CWPO) reaction. Results show that the Fe₂O₃-CNT-MF can significantly decline the pressure drop of the fixed bed. Higher temperature, lower feed flow rate, higher catalyst bed height, and higher H₂O₂ dosage are beneficial to m-cresol degradation. Lower pH can also improve m-cresol degradation, but it will cause severe iron leaching. The highest m-cresol removal (over 99.5%) and total organic carbon (TOC) removal (53.6%) can be observed under condition of 2 cm bed height, flow rate of 2 mL/min, reaction temperature of 70 °C, 6 g/L H₂O₂, and initial pH = 1. Meanwhile, the Fe₂O₃-CNT-MF catalyst shows good stability with less than 10% decrease in m-cresol conversion and 7% decrease in TOC conversion after 24-h reaction and less than 2 mg/L iron leaching is observed in all conditions except for strong acid condition. Two probable pathways of m-cresol degradation process are presented. Under most conditions, m-cresol will first be turned into methylhydroquinone, followed by oxidation to p-toluquinone. In basic condition, some m-cresol will first be changed into 4-methylpyrocatechol. These aromatic intermediates will then be oxidized into some small molecular acids and finally be mineralized to CO₂ and H₂O.

The effect of MWCNT treatment by H2O2 and/or UV on fulvic acids sorption

The carbon nanotubes (CNT) present in the wastewater subjected to treatment will possess altered physico-chemical properties. The changed properties will result in the unknown behavior of CNT in the environment after disposal; and it is expected to differ from their pristine analogues. In the present paper the effect of sorption of dissolved organic matter with fulvic acids (FA) as representatives onto UV and/or H₂O₂ treated CNT was tested. Both kinetics and mechanism of sorption was estimated. The chemical adsorption was a rate limiting step and a pseudo-second order kinetics described the sorption of FA onto UV and/or H₂O₂ treated CNT. The treating increased affinity towards FA and treating by UV and H₂O₂ simultaneously possessed greater impact on k₂ than UV and H₂O₂ separately. The greatest effect on CNT sorption capacity revealed H₂O₂. The sorption mechanism was described by Temkin (CNT-H₂O₂) and Dubinin-Radushkevich model. The increase in CNT surface disorder caused by UV and/or H₂O₂ treatment favored sorption of FA via π-π interactions (exfoliated surface and disordered CNT walls). FA sorption occurred between aromatic rings of FA and CNT and hydrogen bonds formed with the oxygen functional groups. The results indicate that UV and/or H₂O₂ treatment affected the sorption capacity and affinity of CNT towards FA.

Diglycolamic acid-functionalized multiwalled carbon nanotubes as a highly efficient sorbent for f-block elements: experimental and theoretical investigations

Diglycolamic acid-functionalized carbon nanotubes were employed for the efficient and selective separation of Pu⁴⁺, PuO₂²⁺ and Am³⁺.

Sorption of indium (III) onto carbon nanotubes

Indium has numerous applications in different industrial sectors and is not an abundant element. Therefore appropriate technology to recover this element from various process wastes is needed. This research reports high adsorption capacity of multiwalled carbon nanotubes (MWCNT) for In(III). The effects of pH, kinetics, isotherms and adsorption mechanism of MWCNT on In(III) adsorption were investigated and discussed in detail. The pH increases improves the adsorption capacity for In(III). The Langmuir adsorption model is the best fit with the experimental data. For the kinetic study, the adsorption onto MWCNT could be fitted to pseudo second-order. The adsorption of indium(III) can be described to a mechanism which consists of a film diffusion controlled process. Metal desorption can be achieved with acidic solutions.

J, Boda A, Ali SM. An amide functionalized task specific carbon nanotube for the sorption of tetra and hexa valent actinides: experimental and theoretical insight

An amide functionalized multiwalled carbon nanotube (CNT-DHA) was used for efficient and selective solid phase separation of tetravalent (Th⁴⁺) and hexavalent (UO₂²⁺) actinides.

Sorption behaviour of Pu4+ and PuO22+ on amido amine-functionalized carbon nanotubes: experimental and computational study

Amido amine-functionalized multi-walled carbon nanotubes (MWCNT-AA) were used for efficient and selective solid phase separation of plutonium(iv) and plutonium(vi).

Impact of particle size, temperature and humic acid on sorption of uranium in agricultural soils of Punjab

Batch experiments were conducted to study the sorption of uranium (U) onto soil in deionised water as a function of its dosage, temperature and humic acid (HA). Furthermore, soils were characterized for particle sizes in the form of sand (>63 µm), silt (>2-<63 µm) and clay (<2 µm). The textural analysis revealed that soils were admixture of mainly sand and silt along with a small abundance of clay. X-ray diffraction analysis indicates that clay factions ranging from 2.8 to 5% dominated by quartz and montmorillonite. Experimental results indicated that soil with high abundance of clays and low sand content has relatively high U sorption which could be due to availability of high exchange surfaces for metal ions. However, at low concentration of HA, sorption of U was maximum and thereby decreased as the HA concentration increased. The maximum sorption may be due to increase in the negative active surface sites on HA and further decrease could be attributed to saturation of sorption site and surface precipitation. Conversely, the thermodynamic data suggested that the sorption is spontaneous and enhanced at higher temperature.

Colloidal diatomite, radionickel, and humic substance interaction: a combined batch, XPS, and EXAFS investigation

This work determined the influence of humic acid (HA) and fulvic acid (FA) on the interaction mechanism and microstructure of Ni(II) onto diatomite by using batch experiments, X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure (EXAFS) methods. Macroscopic and spectroscopic experiments have been combined to see the evolution of the interaction mechanism and microstructure of Ni(II) in the presence of HA/FA as compared with that in the absence of HA/FA. The results indicated that the interaction of Ni(II) with diatomite presents the expected solution pH edge at 7.0, which is modified by addition of HA/FA. In the presence of HA/FA, the interaction of Ni(II) with diatomite increased below solution pH 7.0, while Ni(II) interaction decreased above solution pH 7.0. XPS analysis suggested that the enrichment of Ni(II) onto diatomite may be due to the formation of (≡SO)2Ni. EXAFS results showed that binary surface complexes and ternary surface complexes of Ni(II) can be simultaneously formed in the presence of HA/FA, whereas only binary surface complexes of Ni(II) are formed in the absence of HA/FA, which contribute to the enhanced Ni(II) uptake at low pH values. The results observed in this work are important for the evaluation of Ni(II) and related radionuclide physicochemical behavior in the natural soil and water environment.