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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]

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]