Bioinspired ZnO-Based Solar Photocatalysts for the Efficient Decontamination of Persistent Organic Pollutants and Hexavalent Chromium in Wastewater

Abstract

Biomimetic/bioinspired engineering and sulfidation processes are effective strategies for improving the visible light-driven photocatalytic performance of ZnO photocatalysts. A facile electrodeposition process in high oxygen-flux conditions was used to synthesize well-defined fractal micro/nanoferns, consequently increasing the photocatalyst’s light-trapping capability and the accessible active surface. Next, a simple sulfidation process was used to form a thin layer of ZnS, producing ZnO@ZnS core@shell micro/nanoferns, thereby tuning the optoelectronic properties and extending the photoresponse to the visible region. The ZnO@ZnS micro/nanoferns exhibited clear superiority over other ZnO photocatalysts in the photooxidation of persistent organic pollutants (POPs) and the photoreduction of Cr(VI). Their excellent photocatalytic performance allowed the photodegradation under UV-filtered sunlight of nearly 97% of methylene blue after 60 min; the mineralization of >98% of a mixture of methylene blue, 4-nitrophenol, and rhodamine-B after 210 min; and the removal of nearly 65% of Cr(VI) after 180 min. In addition, the ZnO@ZnS micro/nanoferns demonstrated a good ability to decontaminate an inorganic-organic bipollutant system, with promising potential to leverage synergistic effects. Finally, these micro/nanoferns presented great recyclability and reusability for both photooxidation and photoremediation processes. These findings support that sulfidation and biomimetic engineering can be a superior route for designing efficient sunlight-driven ZnO-photocatalysts for water decontamination.

Synthesis of ZIF-8/Fly Ash Composite for Adsorption of Cu2+, Zn2+ and Ni2+ from Aqueous Solutions

“…Various heavy metal wastewater treatment techniques including ion exchange [4], ultrafiltration [5], chemical precipitation [6], electro-coagulation [7], reverse osmosis [8], adsorption [9], advanced oxidation [10,11], and flotation [12] have been adopted to remove copper, zinc, and nickel ions from aqueous solution. Among which, adsorption technique is recognized as the most promising one…”

Two-Dimensional Titanium Carbides (Ti3C2Tx) Functionalized by Poly(m-phenylenediamine) for Efficient Adsorption and Reduction of Hexavalent Chromium

“…It is extremely urgent to treat Cr(VI) contamination. In contrast, trivalent chromium (Cr(III)) usually has low levels of toxicity, is immobile, and even is an essential micronutrient for organisms [3][4][5]. At present, adsorption remains an effective method for Cr(VI) remediation [6], which involves the conversion from toxic Cr(VI) to mild Cr(III) in the adsorption process [7,8].…”

Advances and Challenges in Developing Efficient Graphene Oxide-Based ZnO Photocatalysts for Dye Photo-Oxidation

“…On top of that, ZnO has several deficiencies, including limited flexibility, the aggregation of nanostructures during irradiation, and high photocorrosion, all added to its high recombination and broad direct bandgap. Of those deficiencies, photocorrosion is an important parameter to consider, because photocatalyst leaching and dissolution during irradiation can significantly shorten the lifetime of photocatalysts as well as introduce other pollutants, especially Zn(II) ions, into treated water [25][26][27][28]. To date, various strategies have been examined for modulating the ZnO bandgap to minimize the recombination losses of charge carriers, extend the light response to visible light, and improve the photocorrosion resistance.…”