Recent Progress and Prospects in Catalytic Water Treatment

Presently, conventional technologies in water treatment are not efficient enough to completely mineralize refractory water contaminants. In this context, the implementation of catalytic processes could be an alternative. Despite the advantages provided in terms of kinetics of transformation, selectivity, and energy saving, numerous attempts have not yet led to implementation at an industrial scale. This review examines investigations at different scales for which controversies and limitations must be solved to bridge the gap between fundamentals and practical developments. Particular attention has been paid to the development of solar-driven catalytic technologies and some other emerging processes, such as microwave assisted catalysis, plasma-catalytic processes, or biocatalytic remediation, taking into account their specific advantages and the drawbacks. Challenges for which a better understanding related to the complexity of the systems and the coexistence of various solid-liquid-gas interfaces have been identified.

Highly Efficient and Stable Removal of Arsenic by Live Cell Fabricated Magnetic Nanoparticles

As concerns about public health and environmental problems regarding contamination by toxic substances increase worldwide, the development of a highly effective and specific treatment method is imperative. Although physicochemical arsenic treatment methods have been developed, microbial in vivo remediation processes using live cell fabricated nanoparticles have not yet been reported. Herein, we report the development of magnetic iron nanoparticles immobilized an extremophilic microorganism, Deinococcus radiodurans R1, capable of removing toxic arsenic species. First, in vivo synthesis of magnetic iron nanoparticles was successfully achieved with the D. radiodurans R1 strain and characterized by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), dynamic light scattering (DLS), zeta-potential, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) analysis. Second, the maximum removal capacity of the magnetic iron nanoparticle-immobilized D. radiodurans R1 strain (DR-FeNPs) for arsenic [As(V)] was evaluated under the optimized conditions. Finally, the removal capacity of DR-FeNPs in the presence of various competitive anions was also investigated to simulate the practical application. More than 98% of As(V) was efficiently removed by DR-FeNPs within 1 h, and the removal efficiency was stably maintained for up to 32 h (98.97%). Furthermore, the possibility of recovery of DR-FeNPs after use was also suggested using magnets as a proof-of-concept.

Facile synthesis of hollow mesoporous MgO spheres via spray-drying with improved adsorption capacity for Pb(II) and Cd(II)

Spherical-like MgO nanostructures have been synthesized efficiently via spray-drying combined with calcination using magnesium acetate as magnesium source. The products were characterized by means of X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and the specific surface areas were calculated using the Brunauer-Emmett-Teller (BET) method. The obtained spherical-like MgO nanostructures exhibit uniform pore sizes (7.7 nm) and high specific surface areas (180 m² g^-1). The adsorption kinetics and isotherm data agree well with pseudo-second-order model and Langmuir model, indicating the monolayer chemisorption of heavy metal ions. The spherical-like MgO nanostructures exhibited high adsorption performance for Pb(II) and Cd(II) ions, and the maximum adsorption capacities were up to 5214 mg g^-1 and 4187 mg g^-1, respectively. These values are much higher than those reported MgO-based adsorbents. Moreover, in less than 10 min, Pb(II) and Cd(II) ions in solution can be almost removed, which means that the spherical-like MgO possesses a high adsorption rate. XRD and FTIR analysis revealed the adsorption mechanism of Pb(II) and Cd(II) ions on MgO, which was mainly due to hydroxyl functional groups and ion exchange between Mg and heavy metal ions on the surface of MgO. These favorable performances recommend that the synthesized spherical-like MgO nanostructures would be a potential adsorbent for rapid removal of heavy metal ions from wastewater.

Multifunctional 3D K2Ti6O13 nanobelt-built architectures towards wastewater remediation: selective adsorption, photodegradation, mechanism insight and photoelectrochemical investigation

Efficient wastewater remediation was achieved via initial selective adsorption and subsequent photodegradation using multifunctional 3D K₂Ti₆O₁₃ NAs with promising photoelectrochemical application.

Effect of anion type on the synthesis of mesoporous nanostructured MgO, and its excellent adsorption capacity for the removal of toxic heavy metal ions from water

MgO nanostructures with controllable morphology and tunable textural properties synthesized via aqueous based route in the absence of organic templates were found to be excellent adsorbent for the removal of Pb(ii) and Cd(ii) ions from water.

Comparative study on arsenate removal mechanism of MgO and MgO/TiO2 composites: FTIR and XPS analysis

The arsenate removal mechanism using MgO and MgO/TiO₂ adsorbents was revealed by Fourier transform infrared and X-ray photoelectron spectroscopy.