Preparation and lead ion removal property of hydroxyapatite/polyacrylamide composite hydrogels

Efficient removal of lead (II) ions and methylene blue from aqueous solution using chitosan/Fe-hydroxyapatite nanocomposite beads

Chitosan is a well-known sorbent and effective in the uptake of anionic or reactive dyes, but it has deficiency in adsorption of basic dyes. In this work, chitosan/Fe-substituted hydroxyapatite composite beads were prepared in a different ratio via embedding of hydroxyapatite into chitosan solution for removal of basic dye and heavy metal from aqueous solution. The composite beads were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy in order to reveal their composition and surface morphology. In this particular study, methylene blue (MB) and lead (Pb (II)) ions were selected as representatives of dye and a heavy metal, respectively. The various experimental conditions affecting dye adsorption were explored to achieve maximum adsorption capacity. Moreover, the kinetic, thermodynamic and adsorption isotherm models were employed for the description of the heavy metal and dye adsorption processes. The results indicated that the prepared hydrogel is an efficient adsorbent for the aforementioned dye and metal concomitant with the ability of regeneration without losing the original activity and stability for water treatment applications.

Fabrication of interfacial functionalized porous polymer monolith and its adsorption properties of copper ions

The interfacial functionalized poly (glycidyl methacrylate) (PGMA) porous monolith was fabricated and applied as a novel porous adsorbent for copper ions (Cu(2+)). PGMA porous material with highly interconnected pore network was prepared by concentrated emulsion polymerization template. Then polyacrylic acid (PAA) was grafted onto the interface of the porous monolith by the reaction between the epoxy group on PGMA and a carboxyl group on PAA. Finally, the porous monolith was interfacial functionalized by rich amount of carboxyl groups and could adsorb copper ions effectively. The chemical structure and porous morphology of the porous monolith were measured by Fourier transform infrared spectroscopy and scanning electron microscopy. Moreover, the effects of pore size distribution, pH value, co-existing ions, contacting time, and initial concentrations of copper ions on the adsorption capacity of the porous adsorbents were studied.

Fabrication and Lead Ion Removal Property of Magnetic Hydroxyapatite Composite with Hierarchically Urchin-like Microstructure

The hierarchically urchin-like magnetic hydroxyapatite (HAp)/Fe3O4 composites were hydrothermally fabricated and were used for the removal of Pb (II) from aqueous solutions. The morphology, composition and properties of the magnetic HAp/Fe3O4 composites were fully characterized and investigated. The results showed that the HAp/Fe3O4 composites had a 3D urchin-like hierarchical structure with Fe3O4 nanoparticles dispersed among the building units. These urchin-like composites had high surface area and good magnetic responsibility. The equilibrium removal process of Pb (II) by the composites was correlated well with the Langmuir model, resulting in the maximum adsorption capacity of 223.71 mg/g. The high adsorption capacity and good magnetic responsibility suggest that the multifunctional composites have great potentials for heavy metal ion removal.

Recovery of ammonium onto wheat straw to be reused as a slow-release fertilizer

With the aim of improving fertilizer use efficiency and minimizing the negative impact of nitrogen pollution, a new multifunctional slow-release fertilizer was prepared by recovery of ammonium from aqueous solutions onto a superabsorbent composite. An eco-friendly superabsorbent composite based on wheat straw (WS) was synthesized and used as the carrier to control the release of nutrients. The adsorption studies with NH₄⁺ indicated that the superabsorbent composite showed good affinity for NH₄⁺, with an adsorption capacity of 7.15 mmol g⁻¹ when 20 wt % of WS was incorporated and that the adsorption system can reach equilibrium within 40 min. Afterward, the feasibility of reusing the composite as a multifunctional slow-release nitrogen fertilizer was investigated. The results showed that the product with good water-retention and slow-release capacities could regulate soil acidity and was economical and eco-friendly for application in agriculture and horticulture.

Remediation of Cu(II), Ni(II), and Cr(III) ions from simulated wastewater by dendrimer/titania composites

Generation 4 polyamidoamine (PAMAM) dendrimers with ethylenediamine cores (G4-OH) were immobilized on titania (TiO(2)) and examined as novel metal chelation materials. Characterization results indicate both the effective immobilization of dendrimers onto titania and retention of the dendrimer on titania following remediation. The effective remediation of Cu(II), Ni(II), and Cr(III), which are model pollutants commonly found in industrial electroplating wastewater, is demonstrated in this work. Important parameters that influence the efficiency of metal ion removal were investigated; e.g. solution pH, retention time, metal ion concentration, and composite material dosage. Metal ion removal was achieved over a wide metal concentration range within a 1 h equilibration time. Maximum metal ion removal was achieved at pH ≥7 for both Cu(II) and Cr(III), and pH ≥9 for Ni(II). Further, the dendrimer/titania composite materials were even more effective when metal ion mixtures were tested. Specifically, a dramatic increase was observed for Ni(II) chelation when in a mixture was compared to a pure nickel solution. These findings suggest new strategies for improving metal ion removal from industrial wastewater.

Shellac-coated iron oxide nanoparticles for removal of cadmium(II) ions from aqueous solution

This study describes a new effective adsorbent for cadmium removal from aqueous solution synthesized by coating a shellac layer, a natural biodegradable and renewable resin with abundant hydroxyl and carboxylic groups, on the surface of iron oxide magnetic nanoparticles. Transmission Electron Microscopy (TEM) imaging showed shellac-coated magnetic nanoparticle (SCMN) adsorbents had a core-shell structure with a core of 20 nm and shell of 5 nm. Fourier Transform Infrared Spectroscopic analysis suggested the occurrence of reaction between carboxyl groups on the SCMN adsorbent surface and cadmium ions in aqueous solution. Kinetic data were well described by pseudo second-order model and adsorption isotherms were fitted with both Langmuir and Freundlich models with maximum adsorption capacity of 18.80 mg/g. SCMN adsorbents provided a favorable adsorption capacity under high salinity conditions, and cadmium could easily be desorbed using mild organic acid solutions at low concentration.

Physicochemical characterization of hydroxyapatite and its application towards removal of nitrate from water

A laboratory study was conducted to investigate the efficiency of hydroxyapatite (HAP) towards removal of nitrate from synthetic nitrate solution. In the present research HAP synthesized from egg-shell was characterized using SEM, XRD, FTIR and TGA-DSC. The removal of nitrate was 96% under neutral conditions, using 0.3 g of adsorbent in 100 mL of nitrate solution having an initial concentration of 100 mg/L. An adsorption kinetic study revealed that the adsorption process followed first order kinetics. Adsorption data were fitted to a linearly transformed Langmuir isotherm with correlation coefficient (R(2))>0.98. Thermodynamic parameters were also calculated to study the effect of temperature on the removal process. In order to understand the adsorption type, equilibrium data were tested with the Dubinin-Radushkevich isotherm. The process was rapid and equilibrium was established within the first 40 min.

Removal of toxic metal ions with magnetic hydrogels

Hydrogels, based on 2-acrylamido-2-methyl-1-propansulfonic acid (AMPS) were synthesized via photopolymerization technique and used for the preparation of magnetic responsive composite hydrogels. These composite hydrogels with magnetic properties were further utilized for the removal of toxic metal ions such as Cd(II), Co(II), Fe(II), Pb(II), Ni(II), Cu(II) and Cr(III) from aqueous environments. It was revealed that hydrogel networks with magnetic properties can effectively be utilized in the removal of pollutants. The results verified that magnetic iron particle containing p(AMPS) hydrogel networks provide advantageous over conventional techniques. Langmuir and Freundlich adsorption isotherms were applied for toxic metal removal and both isotherms were fit reasonably well for the metal ion absorptions.