The adsorption of dye molecules is an important process for the photodegradation removal of dye pollutants. In this work, a semiconductor photocatalyst of Cr-doped ZnO nanorods (Cr-ZnO NRs) was synthesized, and its adsorption-photocatalysis synergy (APS) effect was investigated for anionic methyl orange (MO-) and cationic methylene blue (MB+). The detailed thermodynamic information (including adsorption maximum capacity qmax, adsorption equilibrium constant Kads and adsorption efficiency AE %) and dynamic information (including adsorption rate constant ka, degradation rate constant kd and degradation efficiency DE %) were obtained to evaluate the different reaction performances for MO- and MB+. With qmax(MB+) = 40.59 mg g-1 > qmax(MO-) = 15.95 mg g-1, ka(MB+) = 20.61 min-1 > ka(MO-) = 4.62 min-1, and AE(MB+) = 40% > AE(MO-) = 9%, Cr-ZnO NRs showed much superior adsorption performance for MB+ than MO-. With kd (MB+) = 0.0430 min-1 > kd (MO-) = 0.0014 min-1 and DE(MB+) = 98% > AE(MO-) = 20%, Cr-ZnO NRs also showed much superior photodegradation performance for MB+ than MO-. The APS mechanism of Cr-ZnO NRs is revealed to be multiple π-π interactions and stronger electrostatic attractions dominant for enhanced adsorption of MB+ and higher AE and more photocatalytic active species dominant for enhanced photodegradation of MB+. The APS was furthermore characterized and verified by zeta potential analysis, Fourier transform infrared investigation, and fluorescence imaging. The results indicate that Cr-ZnO NRs are promising adsorbent and photocatalyst candidates favorable for positive MB+ than negative MO-. Such an APS investigation can effectively help to improve the photodegradation treatment performance of photocatalysts for dye pollutant removal.

中文翻译：

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Cr-掺杂的ZnO吸附-光催化协同去除有机染料污染物的协同效应研究。

染料分子的吸附是光降解去除染料污染物的重要过程。在这项工作中，合成了一种Cr掺杂的ZnO纳米棒（Cr-ZnO NRs）的半导体光催化剂，并研究了其对阴离子甲基橙（MO-）和阳离子亚甲基蓝（MB +）的吸附-光催化协同作用（APS）。获得了详细的热力学信息（包括吸附最大容量qmax，吸附平衡常数Kads和吸附效率AE％）和动力学信息（包括吸附速率常数ka，降解速率常数kd和降解效率DE％），以评估不同的反应性能。 MO-和MB +。当qmax（MB +）= 40.59 mg g-1> qmax（MO-）= 15.95 mg g-1时，ka（MB +）= 20.61 min-1> ka（MO-）= 4.62 min-1，AE（MB +） = 40％> AE（MO-）= 9％，Cr-ZnO NRs对MB +的吸附性能优于MO-。当kd（MB +）= 0.0430 min-1> kd（MO-）= 0.0014 min-1并且DE（MB +）= 98％> AE（MO-）= 20％时，Cr-ZnO NRs也显示出优异的光降解性能MB +比MO-。Cr-ZnO NRs的APS机理显示为多个π-π相互作用和更强的静电引力（主要用于增强MB +的吸附）和更高的AE，以及更多的光催化活性物质（主要用于增强MB +的光降解）。此外，还通过ζ电势分析，傅立叶变换红外研究和荧光成像对APS进行了表征和验证。结果表明，Cr-ZnO NRs是有希望的吸附剂和光催化剂候选物，对MB +的阳性反应优于MO-的阴性反应。