Enhanced adsorption performance, separation, and recyclability of magnetic core-shell Fe3O4@PGMA-g-TETA-CSSNa microspheres for heavy metal removal

Synthesis and Characterization of Innovative Double-Network Hydrogels with Potential as Adsorbent Materials for Wastewater Treatment

Nowadays, large amounts of wastewater arise from various industrial applications. The discharge of wastewater into the environment represents a threat to the aquatic ecosystem and human health. Thus, in the present study, innovative double-network (DN) hydrogels with pH-sensitive features and applicability as adsorbents in the treatment of leather dye wastewater were prepared. The polyelectrolyte, poly(N,N-dimethylaminoethyl methacrylate (PDMAEMA), was obtained via the radical polymerization process, while the supramolecular structure was co-assembled through physical interactions. As a novelty, the double network was obtained through the interpenetration of the supramolecular network in the cross-linked polymeric one. The new hydrogels were physico-chemically and morphologically characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and in terms of thermogravimetric analysis (TGA), swelling degree measurements, and dye adsorption studies. The DN hydrogels present interconnected macropores and high thermal stability. The swelling capacity of the dual network gels highlights a superadsorbent behavior at pH 3. Furthermore, the dye adsorption study highlights the effects of several variables (pH, concentration dose of adsorbent) on the ability of the gels to adsorb an anionic dye. The adsorption kinetics of the anionic dyes fitted the pseudo-first-order model (PFO). The estimated maximum adsorption capacities for the anionic dyes was 451 mg g-1 for PDMAEMA and 545 mg g-1 for DN gel.

Adsorption Behavior and Mechanism of Palladium on Diethylaminoethyl-Modified Polyglycidyl Methacrylate Macroporous Spheres

The recovery of precious metals, such as palladium (Pd), from wastewater, is an economically important field. The present study reports the application of polyglycidyl methacrylate (PGMA) macroporous spheres with diethylaminoethyl (DEAE) functional groups (PGMA-DEAE) for the adsorption of palladium ions [Pd(II)] from simulated wastewater solutions. The effects of pH, adsorption duration, and initial concentration of Pd(II) on the adsorption amount were evaluated systematically. The results revealed that within the experimental pH range, the adsorption efficiency of Pd(II) increased with increasing pH. In particular, between pH 4 and 6, the Pd(II) adsorption efficiencies were approximately 100%. At 298 K and pH ∼ 4, the adsorption capacity of PGMA-DEAE for Pd(II) was 1.22 mmol/g. The adsorption rates of PGMA-DEAE for Pd(II) were high, and the adsorption equilibrium was reached within 10 min. Ca(II), Mg(II), Co(II), Cu(II), Ni(II), and Fe(II) were selected as representative competitive adsorption metal ions. PGMA-DEAE had good separation selectivity for Pd(II) at pH 1-6 (all RPd/Me > 30), especially at pH ∼ 4 (all RPd/Me > 100). The SEM, TEM, EDS, TG, XRD, and XPS results indicated that in a high-acidity environment (CHCl ≥ 1 mol/L), Pd(II) was adsorbed on PGMA-DEAE through electrostatic attraction, while in a low-acidity environment (pH 1-6), Pd(II) was adsorbed on PGMA-DEAE through coordinated bonding between the Pd(II) ions and the N. PGMA-DEAE exhibited excellent stability and regeneration performance for five regeneration cycles.

Methacrylate-Based Polymeric Sorbents for Recovery of Metals from Aqueous Solutions

The industrialization and urbanization expansion have increased the demand for precious and rare earth elements (REEs). In addition, environmental concerns regarding the toxic effects of heavy metals on living organisms imposed an urgent need for efficient methods for their removal from wastewaters and aqueous solutions. The most efficient technique for metal ions removal from wastewaters is adsorption due to its reversibility and high efficiency. Numerous adsorbents were mentioned as possible metal ions adsorbents in the literature. Chelating polymer ligands (CPLs) with adaptable surface chemistry, high affinity towards targeted metal ions, high capacity, fast kinetics, chemically stable, and reusable are especially attractive. This review is focused on methacrylate-based magnetic and non-magnetic porous sorbents. Special attention was devoted to amino-modified glycidyl methacrylate (GMA) copolymers. Main adsorption parameters, kinetic models, adsorption isotherms, thermodynamics of the adsorption process, as well as regeneration of the polymeric sorbents were discussed.