Photocatalytic purification of dye contaminated sea water by lanthanide (La3+, Ce3+, Eu3+) modified ZnO

•Lanthanide doped ZnO powders are prepared by green, simple and low cost method.•La doping in ZnO leads to complete RB mineralization within short irradiation time.•Optimal dopants content and catalysts preparation temperature are established.•The La-doped photocatalysts are more efficient than those doped with Eu and Ce.•Photocatalytic purification of contaminated sea water by RE doped ZnO is achieved.

The photocatalytic degradation of the textile dye Reactive Black 5 in distilled and sea water by Ln modified ZnO is studied for the first time under UV-light irradiation. The bleaching process is investigated from different aspects: the type of rare earth element, La3+ concentration and annealing temperature. The observed dye degradation rate increases with the La content up to 2 mol % and then decreases (2.5 and 3.0 mol%). It is found out that Ln modified ZnO photocatalyst achieves contaminants mineralization within a short irradiation time. The optimal dopants concentration and annealing temperature are experimentally established-powders, modified with 2 mol% La3+ and annealed at 100 °C, are the most efficient in Reactive Black 5 photodegradation in comparison with pure and (Ce3+, Eu3+) modified ZnO.

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