Photothermal-catalytic activation periodate over MnO2/g-C3N4 S-scheme heterojunction for rapidly tetracycline removal: intermediates, toxicity evaluation and mechanism

The MnO 2 /CN/PI/Vis system demonstrated excellent TC degradation performance due to the synergetic influence of the photothermal effect and the construction of S-scheme heterojunction . The Mn(IV)/Mn(III) redox cycles were prominently accelerated through the construction of MnO 2 /g-C 3 N 4 S-scheme heterojunction . The MnO 2 /CN S-scheme heterojunctions were prepared using the hydrothermal method, which significantly promoted periodate (PI) activation for the TC removal. Notably, the MnO 2 /CN-0.1 achieved a TC removal rate of 79.7 % within 25 min in the PI/Vis system, which was 1.39 and 3.68 times that of MnO 2 and g-C 3 N 4 , respectively. The improved TC degradation performance could be attributed to the synergetic effect of photothermal effect of MnO 2 and the S-scheme heterojunction. On the basis of the infrared thermography images, the photothermal properties of MnO 2 could increase temperatures of the reaction system, leading to the promotion of the PI activation. The formation of the MnO 2 /CN S-scheme not only effectively suppressed charge recombination, but also facilitated the Mn(IV)/Mn(III) redox cycle within the reaction. Under different pH and anion conditions, the MnO 2 /CN-0.1/PI system exhibited excellent capability in TC removal. Additionally, the toxicity of the degraded solution was evaluated based on the LC-MS test results and the growth experiment of Mung bean seeds. This work put forward an efficient approach on S-scheme photothermal catalysts to achieve efficient utilization of PI on TC degradation, which demonstrates a promising method for photothermal assistance PI activation to remediate the water environment efficiently.

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