Conjugated microporous poly(pyrrole methylene) for simultaneous removal of acid red G and methylene blue

Abstract

Industrial wastewater containing mixed ionic dyes poses a significant treatment challenge. Herein, a conjugated microporous poly(pyrrole methylene) (Py-PPA-CMP) was synthesized using pyrrole and p-phthalaldehyde as monomers, and its adsorption performance was evaluated with the representative anionic dye Acid Red G (ARG) and cationic dye Methylene Blue (MB) as model pollutants. Under neutral conditions, the adsorption performance of Py-PPA-CMP in the dual-component system significantly surpassed that in single-component systems, with the equilibrium adsorption capacity for ARG increasing from 20 mg g⁻¹ to 109 mg g⁻¹ and for MB from 60 mg g⁻¹ to 147 mg g⁻¹. Remarkably, in the dual-component system, Py-PPA-CMP realized efficient simultaneous removal of ARG and MB across a wide pH range. ARG maintained high removal efficiencies (93–96%) under strongly acidic (pH 2), neutral (pH 7), and strongly alkaline (pH 11) conditions. Concurrently, MB removal was substantial (75%) at pH 2 and nearly reached completion (> 98%) at pH 7 and 11. This pH stability stands in stark contrast to that of single-pollutant systems, where adsorption is severely inhibited by pH-dependent electrostatic repulsion, resulting in a drastic decline in removal efficiency from 85% to 30%. This breakthrough overcomes the selective limitation of traditional adsorbents, highlighting its practical potential for complex wastewater treatment. Furthermore, this study establishes a design paradigm for the development of broad-spectrum dye adsorbents.