Spinel ferrite magnetic adsorbents: Alternative future materials for water purification?

Environmental implications and applications of engineered nanoscale magnetite and its hybrid nanocomposites: A review of recent literature.

Alginate-based composites have been extensively studied for applications in energy and environmental sectors due to their biocompatible, nontoxic, and cost-effective properties. This review is designed to provide an overview of the synthesis and application of alginate-based composites. In addition to an overview of current understanding of alginate biopolymer, gelation process, and cross-linking mechanisms, this work focuses on adsorption mechanisms and performance of different alginate-based composites for the removal of various pollutants including dyes, heavy metals, and antibiotics in water and wastewater. While encapsulation in alginate gel beads confers protective benefits to engineered nanoparticles, carbonaceous materials, cells and microbes, alginate-based composites typically exhibit enhanced adsorption performance. The physical and chemical properties of alginate-based composites determine the effectiveness under different application conditions. A series of alginate-based composites and their physicochemical and sorptive properties have been summarized. This critical review not only summarizes recent advances in alginate-based composites but also presents a perspective of future work for their environmental applications.

Alginate-based composites for environmental applications: A critical review.

As a novel material, double network hydrogels have attracted great attention in recent years for their excellent mechanical properties; however, several other characteristics are yet to be improved. Here we report the synthesis of a novel alginate/reduced graphene oxide (RGO) double-network (GAD) hydrogel through a facile method, and investigate the GAD's mechanical properties, stability, and adsorption capacity in comparison with those of an alginate/RGO single network hydrogel (GAS). To produce the GAD, the first network of alginate is formed with randomly distributed graphene oxide (GO), resulting in the GAS; then the GAS is treated by a hydrothermal reduction, through which the GO is reduced and self-assembles into a second RGO network interpenetrating with the first, alginate network, forming the double-network GAD. The mechanism of the GAD formation is investigated and the property differences between the GAS and the GAD are examined. The resulting GAD exhibits a higher Young's modulus than the GAS, and the modulus increases with GO concentrations. The GAD also has a lower swelling ratio than the GAS, which leads to improved gel stability in highly concentrated alkali/salt solutions. The GAD beads exhibit an excellent adsorption capacity (Cu2+, 169.5 mg g−1 and Cr2O72−, 72.5 mg g−1) for heavy metal ions, far better than that of the GAS. Even after 10 regeneration cycles, both GAS and GAD can still retain their considerable adsorption capacity for metals. The results of this work are of great significance to double network gel research, especially for environmental applications. With good stability, adsorption capacity, and regeneration ability, the double network gel could be a promising adsorbent nanomaterial for pollutant removal from aqueous solutions.

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Alginate/graphene double-network nanocomposite hydrogel beads with low-swelling, enhanced mechanical properties, and enhanced adsorption capacity

Functionalizing biochar with Mg–Al and Mg–Fe layered double hydroxides for removal of phosphate from aqueous solutions

Water decontamination via the removal of Pb (II) using a new generation of highly energetic surface nano-material: Co(+2)Mo(+6) LDH.

This paper deals with the experimental investigation related to the removal of Fe(II) from aqueous solutions by synthesized NiFe 2 O 4 –alginate composite beads and nano-NiFe 2 O 4 at different temperatures and constant stirring rate of 150 rpm. The adsorption process was optimized by Response surface methodology RSM/CCD and studied as a function of contact time, pH and adsorbent mass. The results revealed that the maximum adsorption capacities were 158.4 and 69.8 mg/g for NiFe 2 O 4 –alginate composite beads and nano-NiFe 2 O 4 when the initial Fe(II) concentrations were 350 and 250 mg/L at 318 K, respectively. The kinetics of Fe(II) removal by synthesized materials were best described by the pseudo-second-order model and the adsorption isotherms were seen to be consistent with Langmuir’s adsorption isotherm. Also, the thermodynamic parameters of the adsorption (Gibbs free energy, entropy, and enthalpy) were discussed. Therefore, the results demonstrated that the adsorption process was spontaneous and endothermic and the synthesized NiFe 2 O 4 –alginate composite beads material could act as a highly-effective nano-adsorbent of Fe(II) removal more than nano-NiFe 2 O 4 from the aqueous solutions.

Removal of ferrous ions from their aqueous solutions onto NiFe2O4–alginate composite beads

Sodium alginate and magnetic iron oxide nanoparticles were combined to produce magnetic nanocomposite beads that were used for the removal of Cu(II) from aqueous solutions at a temperature of 25 °C...

Magnetic nanocomposite beads: synthesis and uptake of Cu(II) ions from aqueous solutions

A Mg–Zn–Al (LDH)/MMT nanocomposite was prepared by physical interaction between Mg–Zn–Al layered double hydroxide (LDH) and montmorillonite (MMT) (20 wt%). The chemical structure of the prepared Mg–Zn–Al (LDH)/MMT nanocomposite was characterized by X-ray diffraction, Fourier transform infrared spectroscopy and N2-adsorption/desorption (BET) measurements. The Mg–Zn–Al (LDH)/MMT nanocomposite was evaluated as an adsorbent for the removal of Mn(II) metal ions from contaminated water. The effect of initial Mn(II) ion concentration (mg/L), solution pH, amount of adsorbent (g/L), stirring rate (rpm) and contact time (min) on the adsorption capacity of the Mg–Zn–Al (LDH)/MMT nanocomposite were studied at 298, 308 and 318 K. The results indicated that the Mg–Zn–Al (LDH)/MMT nanocomposite exhibits high adsorption efficiency in the removal of Mn(II) metal ions from contaminated water. The results showed that the optimum conditions of Mn(II) metal ions adsorption from the aqueous medium using the Mg–Zn–Al (LDH)/MMT nanocomposite adsorbent were: initial Mn(II) metal ion concentration of 80 mg/L at pH of 6.0 in the presence of 0.25 g/L of Mg–Zn–Al (LDH)/MMT nanocomposite using a stirring rate of 160 rpm for 105 min. The maximum adsorption capacities achieved in these conditions were 24.5, 26.4 and 28.9 mg/g at 298, 308 and 318 K, respectively.

Potential of Mg–Zn–Al layered double hydroxide (LDH)/montmorillonite nanocomposite in remediation of wastewater containing manganese ions

Novel Ca–Al–Zn layered double hydroxide (LDH) was synthesized by co-precipitation method and its calcined product (calcined Ca–Al–Zn LDH) was obtained by heating at 450°C for 4.0 h. The calcined and uncalcined products of Ca–Al–Zn LDHs were used as adsorbents to remove copper ions from aqueous solutions. The structure, composition, and morphology of the synthesized calcined and uncalcined products were approved by X-ray diffraction, FT-IR, N2 adsorption–desorption isotherm, and scanning electron microscopy. The removal capacities of calcined layered double hydroxide are higher than that of uncalcined LDH at ambient temperature, different pH, constant shaking rate 160 rpm, and different copper/adsorbent ratios. According to the analytical results and the experimental data, we were successful to prepare a novel LDH adsorbent for the Cu(II) removal, where the removal of the copper ions reached a maximum value at pH 6.0, shaking, 160 rpm, adsorbent mass 0.25 g/l and after 120 min to be 15.4 and 20.5 m...

A.A. Bakr

Papers

Water decontamination via the removal of Pb (II) using a new generation of highly energetic surface nano-material: Co(+2)Mo(+6) LDH.

Removal of ferrous ions from their aqueous solutions onto NiFe2O4–alginate composite beads

Magnetic nanocomposite beads: synthesis and uptake of Cu(II) ions from aqueous solutions

Potential of Mg–Zn–Al layered double hydroxide (LDH)/montmorillonite nanocomposite in remediation of wastewater containing manganese ions

Copper ions removal from aqueous solutions by novel Ca–Al–Zn layered double hydroxides