Hydrophilic and positively charged polyethylenimine-functionalized mesoporous magnetic clusters for highly efficient removal of Pb(II) and Cr(VI) from wastewater

New Approaches for Pb(II) Removal from Aqueous Media Using Nanopowder Sodium Titanosilicate: Kinetics Study and Thermodynamic Behavior

Microporous sodium titanosilicate, Na2TiSiO5, has been successfully prepared using the sol-gel method. The structural and morphological characterization of synthesized product has been made via thermal analyses (TG-DTG), X-ray diffraction (XRD), and electron microscopy (SEM and TEM). Adsorption properties of the synthesized Na2TiSiO5 nanopowder for Pb(II) removal of aqueous media was investigated in different experimental conditions such as the contact time, the initial metal concentration, the pH, and the temperature. The Pb(II) adsorption on Na2TiSiO5 was discussed according to the kinetics and thermodynamics models. The adsorption kinetics of Pb(II) have been better described by the PS-order kinetic model which has the highest fitting correlation coefficients (R2: 0.996-0.999) out of all the other models. The adsorption results have been successfully fitted with the Langmuir and Redlich-Paterson models (R2: 0.9936-0.9996). The calculated thermodynamic parameters indicate that the Pb(II) adsorption is an endothermic process, with increased entropy, having a spontaneous reaction. The results have revealed a maximum adsorption capacity of 155.71 mg/g at 298 K and a very high adsorption rate at the beginning, more than 85% of the total amount of Pb(II) being removed within the first 120 min, depending on the initial concentration.

Polydopamine-assisted polyethylenimine grafting melamine foam and the application in wastewater purification

Melamine foam (MF) is a widely used commercial product and exhibits wide applications in many fields ranging from building, transportation to daily chemical product. Recent researches confirm that the special three-dimensional (3D) framework structure of MF can be an ideal substrate to prepare functional materials. In this work, the water-soluble polyethylenimine (PEI) was grafted onto the framework of MF to develop the water purification material toward heavy metal ions removal. The grafting of PEI on MF was achieved with the aids of polydopamine (PDA) coating and epoxy chloropropane (ECH) cross-linking successively. The 3D framework of MF could be well reserved and PEI was homogeneously grafted onto the framework surface. The adsorption capacity of the adsorbent was dependent upon the molecular wight of PEI. Lower PEI molecular weight endowed the adsorbent with better adsorption ability. The maximum adsorption capacity reached 328.95 mg/g, and the adsorbent exhibited extremely high adsorption stability with increasing cycling measurement numbers. Further results showed that the adsorbent also exhibited high reduction ability and induced about 62.5% toxic Cr(VI) to be reduced. This work confirms that the PEI-modified MF sample is a promising adsorbent in the removal of heavy metal ions and it can be used in wastewater treatment.

Multifunctional polyethylene imine hybrids decorated by silica bioactive glass with enhanced mechanical properties, antibacterial, and osteogenesis for bone repair

Inorganic/organic hybrids and bioactive glasses demonstrate promising potential as bone substitute biomaterials. A sol-gel hybrid consisting of silica bioactive glass and biodegradable polymer can combine the high bioactivity of a glass with the toughness of a polymer. In this study, multifunctional hybrids with a combination of organic-inorganic hybrid structure class II consisting of polyethyleneimine (PEI) generation 4 (G4) and bioactive glass with enhanced mechanical properties, mineralization, antibacterial, and osteogenesis activities were synthesized by the sol-gel method. Glycidoxypropyl) trimethoxysilane (GPTMS) with different concentrations was used as a covalent bonding agent between PEI polymer and bioactive glass. The effect of GPTMS content was assessed in the presence and absence of calcium in the hybrid structures in terms of morphology, wettability, mechanical properties, antibacterial activity, cell viability, and in vitro osteogenic differentiation properties. By increasing the amount of GPTMS, the compressive strength increased from 1.95 MPa to 2.34 MPa, which was comparable to human trabecular bone. All the hybrids presented antibacterial activity against Staphylococcus aureus, forming an inhibition zone of 13-16 mm. An increase in cell viability of 82.22% in PSCaG90 was obtained after 1 day of MG-63 cell culture. Alkaline phosphatase expression and mineralization of MG-63 cells increased in the PSCaG90 hybrid in the absence of an osteogenic medium compared to PSG60 and PSG90. The PSCaG90 hybrid indicated considerable in vitro osteogenic capacity in the absence of a differentiation medium, expressing high levels of bone-specific proteins including collagen I (COL1A1), Runt-related transcription factor 2 (RUNX2), osteopontin (OPN), and osteocalcin (OCN), compared to calcium-free hybrids. Overall, our results suggest that the presence of calcium in the PSCaG90 leads to a significant increase in osteogenic differentiation of MG-63 cells even in the absence of differentiation medium, which suggests these hybrid structures with multifunctional properties as promising candidates for bone repair.

Adsorption of Cr(VI) from aqueous solution by a litchi shell-based adsorbent

Cr(VI) is a toxic metal pollutant existing in industrial effluents. In this study, Fe₃O₄ and layered double hydroxide (LDH) were inserted into the litchi shell (LS) successively by the co-precipitation method to synthesize the modified magnetic litchi shell adsorbent (MMLS) for removing Cr(VI). The advantageous structure characteristics of MMLS were confirmed by XRD, FT-IR, SEM and the hysteresis loop characterization. The batch experiments of optimizing the conditions (pH, adsorbent dosage, initial concentration, coexisting ions) for removing Cr(VI) were accomplished to in simulated wastewater at room temperature. And the optimal pH of 3 and initial concentration of 100 mg/L in simulated wastewater were similar to that in the actual chrome-plated rinse water with the stable MMLS. The effect of coexisting ions indicated anions and Cr(VI) competed with each other for the adsorption site, but the interactions were negligible in actual chrome-plated rinse water. Chemisorption as a rate-limiting step was confirmed with a good fit of pseudo-second-order kinetics. And the adsorption behavior of MMLS can not be explained by a single theory according to Sips model. The desorption and recycle experiments demonstrated MMLS was reusable in actual chrome-plated rinse water.

Peptide-based targeted polymeric nanoparticles for siRNA delivery

The development of polymer-based nanoparticulate delivery systems for siRNA is important for the clinical success of gene therapy. However, there are some major drawbacks that need to be overcome. Short interfering RNA (siRNA) has been investigated as a potential therapeutic drug to silence disease-associated genes, but its usage is limited due to the lack of effective and safe nanocarriers. In this study, DOPE-PEI, a nanoparticle consisting of the fusogenic lipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) conjugated with low-molecular-weight, 600 Da, branched polyethylenimine (PEI) was produced and optimized for siRNA delivery. This delivery system was modified with other components such as 1,2-dioleoyl-sn-glycerol-3-phosphoethanolamine-N-[methoxy(polyethyleneglycol)2000] (DOPE-PEG2K), DOPE-PEG3.4K-bombesin and 1,2-dioleoyl-sn-glycerol-3-phosphoethanolamine/1,2-dioleoyl-3-trimethylammonium-propane (DOPE/DOTAP) and tested on PC-3 cells. The conjugation of DOPE to PEI polymer (DOPE-PEI) improved the efficiency of PEI to deliver siRNA into the cytosol and knockdown genes, but demonstrated high toxicity. The addition of DOPE-PEG2K reduced cellular toxicity by masking the surface positive charge of the DOPE-PEI/siRNA complex, with the incorporation of a gastrin-releasing peptide receptor (GRPR) targeting peptide and DOPE/DOTAP components improving the cellular uptake of siRNA into targeted cells and the siRNA knockdown efficiency.

Efficient Copper Removal from an Aqueous Anvironment using a Novel and Hybrid Nanoadsorbent Based on Derived-Polyethyleneimine Linked to Silica Magnetic Nanocomposites

Due to the extreme rise of sludge pollution with heavy metals (e.g. copper), the options for its disposal or treatment are decreasing. On the contrary, properly heavy metal-cleaned sludge can be used as an alternative sustainable energy and agriculture source. The aim of this study was to develop a novel nanoadsorbent, based on irreversibly linked amino-rich polymer onto previously silica-coated magnetic nanoparticles (MNPs) that can be applied efficiently for metal removal. MNPs were coated uniformly by 3 nm thick silica layer (core-shell structure), and were additionally modified with systematic covalent attachment of derived branched polyethyleneimine (bPEI). The formed structure of synthesized MNPs composite was confirmed with several analytical techniques. Importantly, nanoadsorbents exhibit high density of chelating amino groups and large magnetic force for easier separation. The importance of introduced bPEI, effect of pH, initial heavy metal concentration onto copper uptake efficiency and, further, nanoadsorbent regeneration, were studied and explained in detail. The adsorption isotherm was well fitted with Langmuir model, and the maximum adsorption capacity was shown to be 143 mg·g¹ for Cu2+. The reusability and superior properties of silica-coated MNPs functionalized with derived-bPEI for copper adsorption underlie its potential for the removal application from heavy metals contaminated sludge.

Novel magnetically separable anhydride-functionalized Fe3O4@SiO2@PEI-NTDA nanoparticles as effective adsorbents: synthesis, stability and recyclable adsorption performance for heavy metal ions

In this paper, a novel adsorbent, Fe₃O₄@SiO₂@PEI-NTDA, was first prepared by the immobilization of an amine and anhydride onto magnetic Fe₃O₄@SiO₂ nanoparticles with polyethylenimine (PEI) and 1,4,5,8-naphthalenetetracarboxylic-dianhydride (NTDA) for the removal of heavy metal ions from aqueous solutions. The structure of Fe₃O₄@SiO₂@PEI-NTDA was systematically investigated; the results confirmed that amine and anhydride groups were successfully covalently grafted onto the surface of Fe₃O₄@SiO₂, which showed a homogenous core–shell structure with three layers of about 300 nm diameter (Fe₃O₄ core: 200 nm, nSiO₂ layer: 20 nm, and PEI-NTDA layer: 20 nm). The adsorption performance of Fe₃O₄@SiO₂@PEI-NTDA NPs was evaluated for single Pb²⁺ and coexisting Cd²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ ions in an aqueous solution in a batch system. The amine and anhydride groups may have a synergistic effect on Pb²⁺ removal through electrostatic interactions and chelation; Fe₃O₄@SiO₂@PEI-NTDA NPs exhibited preferable removal of Pb²⁺ with maximum adsorption capacity of 285.3 mg g⁻¹ for Pb²⁺ at a solution pH of 6.0, adsorbent dosage of 0.5 g L⁻¹, initial Pb²⁺ concentration of 200 mg L⁻¹ and contact time of 3 h. The adsorption mechanism conformed well to the Langmuir isotherm model, and the adsorption kinetic data were found to fit the pseudo-second order model. Fe₃O₄@SiO₂@PEI-NTDA NPs could be recovered easily from their dispersion by an external magnetic field and demonstrated good recyclability and reusability for at least 6 cycles with a high adsorption capacity above 204.5 mg g⁻¹. The magnetic adsorbents showed high stability with a weight loss below 0.65% in the acid leaching treatment by 2 M HCl solution for 144 h. This study indicates that Fe₃O₄@SiO₂@PEI-NTDA NPs are new promising adsorbents for the effective removal of Pb²⁺ in wastewater treatment.

A magnetically separable adsorbent, anhydride-functionalized Fe₃O₄@SiO₂@PEI-NTDA, was successfully constructed for removal of heavy metal ions from aqueous solution.