Efficient removal of arsenite by a composite of amino modified silica supported MnO2/Fe-Al hydroxide (SNMFA) prepared from biotite

Advanced removal of phosphorus from urban sewage using chemical precipitation by Fe-Al composite coagulants

Phosphorus (P) removal is a significant issue in wastewater treatment. This study applies Fe-Al composite coagulant to the advanced treatment of different P forms in biological effluent. For 90% total P removal, the dosage of FeCl3-AlCl3 composite coagulant reduces by 27.19% and 43.28% than FeCl3 and AlCl3 only, respectively. Changes in effluent P forms could explain the phenomenon of composite coagulant dosage reduction. The suspended P in the effluent of composite coagulant is easier removed by precipitation than single coagulant. In this study, the hydrolysis speciations of Fe3+, Fe2+, and Al3+ at a pH range are calculated by Visual MINTEQ. Changes in the morphology of metal hydroxides correlate with P removal at pH 4-9. Besides, analyses of scanning electron microscope (SEM), Fourier transformed infrared (FTIR), and X-ray photoelectron spectroscopy (XPS) are performed on the coagulation precipitations. Fe2+ reacts directly with P to form flocs of Fe3(PO4)2, and Al2(SO4)3 assists in the sedimentation of the small-volume flocs. Al13 is a significant hydrolysis product of Al3+, and Fe and P would substitute for the peripheral AlVI of the Al13 structure to form stable Fe-O-Al covalent bonds.

Enhanced immobilization of Arsenic(III) and Auto-oxidation to Arsenic(V) by titanium oxide (TiO2), due to Single-Atom vacancies and oxyanion formation

Pollution control of As(III), a naturally occurring carcinogen, has recently gained a global attention, while due to the dominance of neutral H3AsO3 over a wide pH range, As(III) immobilization by most minerals is not efficient as As(V) immobilization. TiO2 shows promise for controlling As(III) pollution, and herein, a comprehensive study about As(III) adsorption by TiO2 and oxyanion formation is conducted by means of DFT + D3 methods. Both anatase and rutile are effective for As(III) adsorption, while As(III) adsorption affinities differ significantly and are -1.48 and -3.79 eV for pristine surfaces, ascend to -3.85 and -5.08 eV for O vacancies, and further to -5.37 and -5.26 eV for Ti vacancies, respectively. The bidentate binuclear complexes dominate for pristine surfaces, and O vacancies prefer OAs insertion into TiO2 lattice, while for Ti vacancies, all As(III) centers are auto-oxidized to As(V). Ti-3d, O-2p or/and As-4p rather than other orbitals contribute significantly to As adsorption, and O and Ti vacancies promote adsorption through stronger orbital hybridization. The superior adsorption for Ti vacancies originates from As(V) formation instead of bonding interactions. The formation of As oxyanions, which may occur spontaneously at pristine surfaces and is greatly promoted by O and Ti vacancies, enhances As(III) adsorption pronouncedly and becomes a viable strategy for As(III) immobilization. H2AsO3- and HAsO32- dominate for pristine surfaces and O vacancies, and for Ti vacancies, H2AsO4- and HAsO42- dominate over anatase whereas AsO43- also makes an important contribution over rutile. Results rationalize experimental observations available, and provide significantly new insights about the migration, bioavailability and fate of As(III) over TiO2 surfaces that facilitate the exploration of scavengers for As and other pollutants.

Recent advances in waste-derived functional materials for wastewater remediation

Water pollution is a major concern for public health and a sustainable future. It is urgent to purify wastewater with effective methods to ensure a clean water supply. Most wastewater remediation techniques rely heavily on functional materials, and cost-effective materials are thus highly favorable. Of great environmental and economic significance, developing waste-derived materials for wastewater remediation has undergone explosive growth recently. Herein, the applications of waste (e.g., biowastes, electronic wastes, and industrial wastes)-derived materials for wastewater purification are comprehensively reviewed. Sophisticated strategies for turning wastes into functional materials are firstly summarized, including pyrolysis and combustion, hydrothermal synthesis, sol-gel method, co-precipitation, and ball milling. Moreover, critical experimental parameters within different design strategies are discussed. Afterward, recent applications of waste-derived functional materials in adsorption, photocatalytic degradation, electrochemical treatment, and advanced oxidation processes (AOPs) are analyzed. We mainly focus on the development of efficient functional materials via regulating the internal and external characteristics of waste-derived materials, and the material's property-performance correlation is also emphasized. Finally, the key future perspectives in the field of waste-derived materials-driven water remediation are highlighted.