Search

In this work, a magnetic h-Fe 3 O 4 @phos-PDA nanocomposite composed of ferroferric oxide hollow nanosphere and phosphate-modified polydopamine shell was successfully prepared by a facile one-step method. The h-Fe 3 O 4 @phos-PDA nanocomposite has excellent adsorption properties for U (VI) under the action of phosphate and amine functional groups. The maximum adsorption capacity of h-Fe 3 O 4 @phos-PDA for U(VI) in pH= 5 aqueous solution reached 526.35 mg/g at 298 K, and the adsorption process conformed to the Langmuir isotherm model. The analysis of kinetic adsorption data educed that the adsorption process followed the pseudo-second-order model and reached equilibrium in just 16 min. XPS analysis indicated that phosphate and amine functional groups play a vital role in the complexation between the phos-PDA shell and U (VI). In addition, actual soil remediation experiments indicated that the h-Fe 3 O 4 @phos-PDA nanocomposite could reduce the radiation intensity of α-ray in uranium-contaminated soil by about 82.3%, demonstrating its great engineering application potential. [Display omitted] • The h-Fe 3 O 4 @phos-PDA has excellent adsorption performance for U(VI). • The maximum capacity of U(VI) adsorbed by h-Fe 3 O 4 @phos-PDA reached 526.35 mg/g. • The synthesis method of h-Fe 3 O 4 @phos-PDA is simple and easy to operate. • The h-Fe 3 O 4 @phos-PDA can reduce the radiation intensity of uranium-bearing soil. [ABSTRACT FROM AUTHOR]

A novel core-shell nanocomposite composed of magnetic h-Fe 3 O 4 (hollow Fe 3 O 4) core and phos-LDH (phosphate-modified layered double hydroxides) shell was synthesized, and it exhibited excellent adsorption capacity for U(VI) in water and soil. [Display omitted] • A magnetic h-Fe 3 O 4 @phos-LDH nanocomposite was prepared successfully. • Nanocomposite exhibited good adsorption performance for U(VI). • Electromagnetic separation system was used to separate magnetic adsorbents from soil. Herein, a novel nanosphere composed of a magnetic h-Fe 3 O 4 (hollow ferroferric oxide) core and a phos-LDH (phosphate-modified layered double hydroxide) shell was synthesized. The h-Fe 3 O 4 @phos-LDH nanocomposite with rich phosphate groups and large specific surface area (93.53 m2/g) can be exploited for uranium (VI) elimination. Batch experiments were conducted to investigate the impacts of various conditions (pH, time, and temperatures) on U(VI) removal process. The maximum capacity of U(VI) adsorbed by h-Fe 3 O 4 @phos-LDH reached up to 542.6 mg/g at 298.15 K, and the adsorption isotherms were followed the Langmuir model. Thermodynamics analyses illustrated that the U(VI) adsorbed by h-Fe 3 O 4 @phos-LDH was a spontaneous and endothermic process. The characterization analysis manifested that the phosphate groups of the phos-LDH shell played a leading role in adsorption. More importantly, the removal of U(VI) from the soil by h-Fe 3 O 4 @phos-LDH with the assistance of an electromagnetic separation system was also investigated. The results indicated that h-Fe 3 O 4 @phos-LDH could remove more than 90% of U(VI) in soil. These findings demonstrated this work could be considered as a valuable research for the environment remediation. [ABSTRACT FROM AUTHOR]

Illustration for the fabrication of PANI-GO-Fe3O4 nanomaterials by hydrothermal method and in-situ polymerization. • The lamellar structure PANI-GO-Fe 3 O 4 was prepared by Fe 3 O 4 nanoparticles embedded in the PANI-coated GO template by in-situ polymerization. • Special lamellar structure effectively improves the adsorption performance of PANI-GO-Fe 3 O 4 ,and the maximum adsorption capacities of CR and MO dyes are 252.7 and 181.0 mg g−1, respectively. • The adsorption behavior is spontaneous and endothermic, and a high adsorption performance of PANI-GO-Fe 3 O 4 is attributed to the interaction of π-π stacking/electrostatic interactions with dyes. • Langmuir adsorption isotherm model indicated the existence of saturated active sites and its chemisorption mechanism. Magnetic separation performance and reproducibility show the superiority of adsorbent materials. Although adsorption by nanomaterial adsorbents represents a promising approach to remove the dye pollutants in water, the easy agglomeration and low recycling has limited such a prospective application. Herein, we developed a lamellar PANI-GO-Fe 3 O 4 hybrid nanosheet adsorbent by an in-situ polymerization strategy in a hydrothermal reactor with Fe 3 O 4 as an intercalant and GO (graphene oxide) as a template for PANI. Besides the merits of easy magnetic separation ability, the PANI-GO-Fe 3 O 4 hybrid adsorbent also shows a high adsorption capacity of 252.7 and 181.0 mg/g for congo red (CR) and methyl orange (MO) dyes, respectively, quite higher than that of PANI-Fe 3 O 4 and many similar adsorbents in literature. The adsorption behavior followed the quasi-secondary kinetic model and the adsorption isotherms were well fitted with the Langmuir model at 298 K, 313 K and 333 K. After 5 cycles of adsorption and desorption, the removal rates of CR and MO dyes by PANI-GO-Fe 3 O 4 can still reach 88.5% and 76.3%. The superiority of PANI-graphene-Fe 3 O 4 hybrid adsorbent was mainly ascribed to its high dispersibility, thin nanosheets morphology, and π–π stacking/electrostatic interactions with the dyes. This work provides a new direction to promote the separable high-performance adsorbents for removing the ionic dyes contamination from waste water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Novel porous Mg-doped biochar/bentonite beads were synthesized for concurrent removal of phosphate and ammonium. • SA-Mg@BC/BT showed a high adsorption capacity and stability to phosphate and ammonium. • Fixed-bed column experiments also validated the high performance of SA-Mg@BC/BT treating actual wastewater. • High porosity, MgO active sites and functional groups contributed to the enhanced adsorption capacity. • Nutrient leaching and pot experiments verified the slow-release performance of NP loaded SA-Mg@BC/BT. This study reports a strategy for concurrent removal of phosphate and ammonium by a new adsorbent of Mg-doped biochar/bentonite composite bead (SA-Mg@BC/BT), with a high specific surface area and abundant functional groups to facilitate the adsorption process. The maximum phosphate and ammonium adsorption capacities of SA-Mg@BC/BT reached 132.2 mg/g and 39.5 mg/g respectively, apparently surpassing those of SA-BC/BT in this study and other relevant adsorbents in literatures. The removal ability for phosphate kept stable with coexisting monovalent anions (NaCl, MgCl 2 , KNO 3 and KF), while decreased slightly in the presence of divalent anions (MgSO 4 , CaSO 4 and K 2 SO 4). Interestingly, the adsorption capacity for the ammonium removal was even found enhanced by divalent salts (12.0%, 23.9% and 15.0 for MgCl 2 , MgSO 4 and CaSO 4 respectively) and K 2 SO 4 (17.9%). For the actual wastewater, the excellent concurrent removal ability of 98.3% for phosphate and 35.6% for ammonium was validated, and adsorption capacity in actual wastewater was almost the same as that in simulated wastewater. Such an excellent concurrent removal ability for phosphate and ammonium by SA-Mg@BC/BT can be ascribed to the struvite crystallization, ion exchange and Mg-P complexation formation. Finally, the leaching and pot experiments indicated the slow-release ability of the adsorption saturated SA-Mg@BC/BT as a fertilizer, providing a new possibility of nutrient recovery. [ABSTRACT FROM AUTHOR]

The effective removal of phosphorus (P) has been a recent hot topic due to water eutrophication hazards and zero-liquid discharge (ZLD) regulations. In this study, MgO-loaded bentonite (Bt) was immobilized by sodium alginate (SA), and then freeze-dried to form beads (SA-MgO@Bt). For comparison, SA-immobilized pure Bt was freeze-dried to form another kind of bead (SA-Bt), and SA-immobilized Bt with MgO loading was oven-dried to form a third type of bead (OSA-MgO@Bt). The specific surface area (SSA) of SA-MgO@Bt was measured to be 59.5 m2/g, 2.2 and 1.4 times that of SA-Bt and OSA-MgO@Bt. The total pore volume of SA-MgO@Bt was also verified to be much higher than that of the other two beads. Overall, SA-MgO@Bt exhibited a maximum adsorption capacity of 70.5 mg/g, a high removal efficiency above 91% in a wide pH range from 3 to 10, and a high selectivity for phosphate from high-salinity water, surpassing those of SA-Bt and OSA-MgO@Bt, and related adsorbents reported in literature. For the fixed-bed column experiments with a water flow rate of 1.0 mL/min, the phosphate concentration could still be reduced from 50 mg/L to 0.5 mg/L even after 8 h. Based on the dynamics, isotherms, and microstructural analysis, the ligand exchange and Mg–P complexation formation, in addition to the electrostatic attraction mode, were also proposed to contribute to the adsorption performance of SA-MgO@Bt. Finally, the pot experiments also validated the feasibility of the as-obtained phosphate-adsorbed SA-MgO@Bt beads as a slow-release-fertilizer for the growth of mint, providing new possibilities of P resource utilization. [Display omitted] •Novel porous MgO-loaded bentonite beads were synthesized for phosphate removal. •SA-MgO@Bt showed a high adsorption selectivity to phosphate in aqueous solution. •Fixed-bed column experiments also validated the high performance of SA-MgO@Bt. •High porosity and MgO active sites contributed to the enhanced adsorption capacity. •Pot experiments showed that P loaded SA-MgO@Bt can be used as fertilizer. [ABSTRACT FROM AUTHOR]

The development of an effective phosphate removal strategy is still considered to be an important challenge in the field of wastewater remediation. In this study, novel alginate immobilized Zr-bentonite hydrogel beads were synthesized assisted by Zr-modification and Na 2 CO 3 + HCl pore forming (abbreviated as NH-SA-ZrBT), that led to an enhancement in the specific surface area and porosity. The novel NH-SA-ZrBT adsorbent exhibited a high stability and adsorption selectivity for phosphate from complex water environments with various competitive anions, NaCl salinity and humic acid. The isotherm was fitted well by both Langmuir and Freundlich models, suggesting that the adsorption process was the chemisorption and the hydrogel beads could function through a variety of mechanisms. The maximum adsorption capacity of NH-SA-ZrBT for phosphate was calculated to be 63.61 mg/g at 25 °C by Langmuir model and had a high retention of 92.2% after five adsorption-desorption cycles. The kinetic data were better fitted by the pseudo-second model. Considering the zeta potential and XPS data before and after the phosphate adsorption, the adsorption mechanism was proposed to be a combination of electrostatic attraction, ligand exchange and inner sphere complexation. The present study demonstrates a new strategy for the fabrication of stable, separable and low-cost bentonite-containing hydrogel beads for phosphate removal from complex wastewater. Unlabelled Image • Alginate immobilized ZrBT beads were synthesized by a facile crosslinking method. • Zr modification and pore forming treatment enhanced the porosity and adsorption. • Selectivity remained high even with competitive ions, high salinity and humic acid. • Electrostatic interaction, ligand exchange and complexation dominate the adsorption. [ABSTRACT FROM AUTHOR]