Mg-Fe-Al-O spinel: Preparation and application as a heterogeneous photo-Fenton catalyst for degrading Rhodamine B.

It is an urgent need to develop new environmentally friendly spinel ferrites with high catalytic efficiency. In this work, a series of Mg-Fe-Al-O spinels with different ratios of Mg/Al were successfully synthesized by the reaction sintering method and were used as a heterogeneous photo-Fenton catalyst for degradation of Rhodamine B (RhB). The effect of different ratios of Mg/Al on the properties of Mg-Fe-Al-O spinel was characterized and analyzed through a range of advanced characterization techniques and DFT calculations. The influence factors on the photo-Fenton reaction catalyzed by Mg-Fe-Al-O spinels were systematically investigated. The results showed that the prepared Mg-Fe-Al-O spinels had larger lattice parameters, wider bandgap, and stronger magnetism, with the Mg content increased. Among them, Mg-9 (Mg0.88Fe1.88Al0.23O4) had the best catalytic performance in the photo-Fenton reaction. The degradation efficiency of RhB reached 98.45%, and the TOC removal efficiency was 83.47%. The elemental valence and PDOS of Mg-9 (Mg0.88Fe1.88Al0.23O4) spinels were closer to MgFe2O4. The photo-generated holes could directly oxidize water and hydroxyl to generate reactive oxygen species ·OH, improving the catalytic activity.

Feasible synthesis of coal fly ash based porous composites with multiscale pore structure and its application in Congo red adsorption.

Facing the great challenge that the increasing solid waste fly ash is difficult to treat and utilize properly, this paper reports a class of novel low-cost fly ash porous materials with high interconnected porosity fabricated by a facile foaming process. On this basis, composites with multiscale pore structures from the nanometer to macroscopic scale were designed and constructed by decorating layered double hydroxide (LDH) onto the inner channel surface. Such porous materials with 3D through-hole structures showed high interconnected porosity (up to 77.61%), suitable compressive strength (up to 23.79 MPa) and significant water permeation flux (549.86 m3∙m-2∙h-1 at 0.1 MPa). Moreover, the adsorption effect of dosage, initial concentration, pH, temperature and contact time on Congo red (CR) from simulated wastewater was investigated. The composites exhibited a good adsorption efficiency of ∼100% and adsorption capacities of 45.79 mg/g. The adsorption kinetic can be explained well by the pseudosecond-order kinetic equation and isotherm adsorption followed Langmuir isotherm model. This suggests that low-cost and eco-friendly fly ash composites have potential applications in industrial-scale wastewater treatment. This work also provides a general strategy to design and utilize fly ash porous materials for filtration and adsorption.