Multi-walled carbon nanotubes (MWCNTs) were used successfully for the removal of heavy metals from aqueous solution. Characterization techniques showed the carbon as nanotubes with an average diameter between 40 and 60 nm and a specific surface area of 61.5 m 2 g À1 . The effect of carbon nanotubes mass, contact time, metal ions concentration, solution pH, and ionic strength on the adsorption of Cu(II), Pb(II), Cd(II) and Zn(II) by MWCNTs were studied and optimized. The adsorption of the heavy metals from aqueous solution by MWCNTs was studied kinetically using different kinetic models. A pseudo-second order model and the Elovich model were found to be in good agreement with the experimental data. The mechanism of adsorption was studied by the intra-particle diffusion model, and the results showed that intra-particle diffusion was not the slowest of the rate processes that determined the overall order. This model also revealed that the interaction of the metal ions with the MWCNTs surface might have been the most significant rate process. There was a competition among the metal ions for binding of the active sites present on the MWCNTs surface with affinity in the following order: Cu(II) > Zn(II) > Pb(II) > Cd(II).
The Suzuki cross‐coupling reaction has developed as one of the foremost effectual approaches for the synthesis of biaryls or substituted aromatic moieties from aryl halides and arylboronic acids with a palladium‐catalyst in the past two eras. In this study, Pd‐free layered double hydroxides (LDHs) nickel‐containing catalysts were prepared by a coprecipitation method under ultrasonic irradiation and N2 atmosphere with different molar ratios of Ni:Mg:Al and coded as (1NiLDHs−Dr), (1.5NiLDHs−Dr) and (2NiLDHs−Dr). A series of reduced catalysts under 5% H2/N2 at 200 °C were coded as 1NiLDHs−R200, 1.5NiLDHs−R200 and 2NiLDHs−R200. Deep investigation of all catalysts was done using different techniques such as inductively coupled plasma optical emission spectroscopy (ICP‐OES), X‐ray photoelectron spectroscopy (XPS), powder X‐ray diffraction (XRD), thermogravimetric analyses (TGA), Fourier transfer infrared (FTIR), scanning electron microscopy (SEM) connected with energy dispersive X‐ray (EDX), transmission electron microscopy (TEM) and N2‐physisorption at –196 °C. The results attained verified that ɑ‐Ni(OH)2 was fashioned for a 2NiLDHs−Dr catalyst and that the enclosure of nickel ions in the cationic sheet of the layered structure was responsible for the fascinating catalytic efficacy rather than the basic nature of material. The Ni‐containing LDHs catalysts encourage forthcoming studies in Pd‐free catalyzed C−C coupling reactions.
Herein, we report the synthesis of nickel‐layered double hydroxide amalgamated Y‐zeolite (NiLDH@YZ) hybrids and the evaluation of the synergistic effect of various NiLDH@YZ catalysts and mechanochemical agitation on Glaser homocoupling reactions. Nitrogen adsorption‐desorption experiments were carried out to estimate the surface area and porosity of NiLDH@YZ hybrids. The basicity and acidity of these hybrids were determined by CO2‐TPD and NH3‐TPD experiments respectively and this portrayed good acid‐base bifunctional feature of the catalysts. The NiLDH@YZ‐catalyzed mechanochemical Glaser coupling reaction achieved best yield of 83 % for the 0.5NiLDH@0.5YZ hybrid after 60 min of agitation, which revealed the highest acid‐base bifunctional feature compared to all the investigated catalysts. The developed catalyst has proven itself as a robust and effective candidate that can successfully be employed up to four catalytic cycles without significant loss in catalytic activity, under optimized reaction conditions. This work demonstrated a new strategy for C−C bond formation enabled by the synergy between mechanochemistry and heterogeneous catalysis.
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