Efficient degradation of methylene blue by cobalt-lanthanum bimetallic MOFs with synergistic activation of peroxymonosulfate: Dominant role of singlet oxygen and hypervalent metal species

Background

The heterogeneous catalytic system of metal-organic frameworks (MOFs)-activated peroxymonosulfate (PMS) can effectively remove organic pollutants, and has become a research hotspot in the field of wastewater treatment.

Methods

In this work, novel bimetallic MOFs (CLB-2:1) were prepared from a one-step solvothermal method with the simultaneous introduction of transition metal cobalt and rare earth metal lanthanum.

Significant findings

With methylene blue (MB) as the target pollutant, the degradation rate of the CLB-2:1/PMS system can reach 97.54 % within 10 min, and the corresponding reaction rate constant (k_obs) is 0.7519 min⁻¹. This system maintains high stability and catalytic activity in a wide pH range and different water quality conditions. Notably, the CLB-2:1/PMS system can effectively treat various organic dyes, and is widely applicable to alleviating the pollution of printing and dyeing effluents. Mechanism studies have shown that non-radical pathways such as singlet oxygen (¹O₂) and high-valent metal species play a leading role in the reaction process. Based on LC-MS test analysis, combined with density functional theory (DFT) calculations, the MB possible degradation pathway was proposed. In general, the bimetallic MOFs/PMS system constructed here has great application prospects in the field of organic wastewater pollution treatment.