Novel Magnetic Fly Ash/Poly(acrylic acid) Composite Microgel for Selective Adsorption of Pb(II) Ion: Synthesis and Evaluation

Preparation and Characterization of a Novel Amidoxime-Modified Polyacrylonitrile/Fly Ash Composite Adsorbent and Its Application to Metal Wastewater Treatment

The polyacrylonitrile/fly ash composite was synthesized through solution polymerization and was modified with NH2OH·HCl. The amidoxime-modified polyacrylonitrile/fly ash composite demonstrated excellent adsorption capacity for Zn2+ in an aqueous medium. Fourier transform-Infrared spectroscopy, thermogravimetric analysis, nitrogen adsorption, X-ray diffraction, and scanning electron microscopy were used to characterize the prepared materials. The results showed that the resulting amidoxime-modified polyacrylonitrile/fly ash composite was able to effectively remove Zn2+ at pH 4-6. Adsorption of Zn2+ was hindered by the coexisting cations. The adsorption kinetics of Zn2+ by Zn2+ followed the pseudo-second order kinetic model. The adsorption process also satisfactorily fit the Langmuir model, and the adsorption process was mainly single layer. The Gibbs free energy ΔG0, ΔH0, and ΔS0 were negative, indicating the adsorption was a spontaneous, exothermic, and high degree of order in solution system.

Synthesis, parameters, properties and applications of responsive molecularly imprinted microgels: a review

Responsive molecularly imprinted microgels (MIGs) have gained a lot of interest due to their responsive specificity and selectivity for target compounds. Study on MIGs is rapidly increasing due to their quick responsive behavior in various stimuli like pH and temperature. MIGs show unique property of morphology control on in-situ synthesis of nanoparticles in response of variation in reactant concentration. Literature related to synthesis, parameters, characterization, applications and prospects of MIGs are critically reviewed here. Range of templates, monomers, initiators and crosslinkers are summarized for designing of desired MIGs. This review article describes effect of variation in reactants combination and composition on morphology, imprinting factor and percentage yield of MIGs. Hydrolysis of similar templates using MIGs is also described. Relation between percentage hydrolysis and hydrolysis time of targets at different temperatures and template:monomer ratio is also analyzed. Possible imprinting modes of ionic/non-ionic templates and its series are also generalized on the basis of previous literature. MIGs are investigated as efficient anchoring vehicles for adsorption, catalysis, bio-sensing, drug delivery, inhibition and detection.

Microgels as efficient adsorbents for the removal of pollutants from aqueous medium

Due to their responsive behavior, high stability, and reusability, microgels have gained importance as adsorbents for the removal of aqueous pollutants such as heavy metals, nitroarenes, organic matter, and toxic dyes. However, there are few challenges that need to be addressed to make microgels as potential adsorbents for the removal of aqueous pollutants. This review article encircles the recent developments in the field of microgel usage as adsorbents for the extraction of aqueous pollutants. Many factors that influence the adsorption of pollutants such as pH, temperature of the medium, agitation time, pollutant concentration, microgel dose, and feed contents of microgels have been discussed in detail. Different adsorption isotherms as well as the kinetic and thermodynamic aspects of the adsorption process have also been enlightened to interpret the insight of the adsorption process. Microgel recovery from the reaction mixture as well as reusability is discussed from the financial point of view. The biodegradability of microgels induced due to the incorporation of specific biomacromolecules is also discussed.

A functionalized metal-organic framework decorated with O- groups showing excellent performance for lead(ii) removal from aqueous solution

A novel MOF decorated with O^– groups was elaborately constructed and showed excellent performance for Pb²⁺ removal.

Heavy metal ions are highly toxic and widely spread as environmental pollutants. New strategies are being developed to efficiently remove these toxic ions. Herein, we use the intrinsic advantages of metal–organic frameworks (MOFs) and develop a porous Zn(ii)-based MOF decorated with O^– groups for the removal of Pb²⁺. Benefiting from its multiple porosity, sufficient adsorption sites and strong affinity, the activated MOF material exhibits an ultrahigh Pb²⁺ uptake capacity (616.64 mg g^–1), surpassing all those of reported MOF adsorbents. Moreover, it can selectively capture Pb²⁺ with high efficiency (>99.27%) against background ions. Even in the presence of a high concentration of competitive ions, such as Ca²⁺ or Mg²⁺, effective removal (>99.21%) can also be achieved in a short time. The excellent removal performance demonstrates the strong electrostatic attraction and coordination interaction between the highly accessible O^– groups and Pb²⁺. The possible adsorption mechanism was systematically verified by zeta potential, FT-IR and XPS studies. Our work reveals the enormous potential of functionalized MOFs as an appealing platform to construct sorbent materials.

Large-scale synthesis and characterization of magnetic poly(acrylic acid) nanogels via miniemulsion polymerization

A facile method for the large-scale preparation of poly(acrylic acid) (PAA) nanogels was reported by miniemulsion polymerization. After the encapsulation of magnetic nanoparticles, magnetic PAA nanogels were fabricated successfully.