Fe(II)/Chlorine‐Driven Advanced Oxidation of Textile Dyes in a Tubular Microreactor: Continuous‐Flow Performance and Matrix Effects

Abstract

ABSTRACT The Fe(II)/chlorine system has emerged as a promising advanced oxidation technology for water treatment, yet its application in continuous‐flow systems remains unexplored. This study presents the first comprehensive investigation of the Fe(II)/chlorine process in a tubular microreactor, a setup that significantly enhances mass transfer and reaction efficiency, particularly for rapid reaction kinetics such as those in the Fe(II)/chlorine system. The degradation of the model pollutant Basic Yellow 28 (BY28) was systematically assessed under varying operational conditions, including reactant dosages, flow rates, reactor length, and pH. The results demonstrated that increasing chlorine flow rates and Fe(II) concentrations improved oxidative performance, achieving up to 81.8% TOC removal at pH 3 with 120 μL/s chlorine. Under moderate acidic conditions (pH 5, 0.1 mM Fe(II)), TOC removal reached 80.1%, highlighting the process's efficiency across a broad pH range, that is, with a maximum degradation recorded at a chlorine flow rate of 80 μL/s (90% at pH 3 and 80% at pH 5). According to chemical probing with benzoic acid and hydroxylamine, reactive oxygen and chlorine species (ROS/RCS) and ferrate are likely the primary oxidants responsible for the process performance. Water matrix composition significantly influenced process performance, with chloride and nitrite acting as strong scavengers of ROS, RCS, and ferrate species, while nitrate completely inhibited oxidation. Additionally, surfactants exhibited varying degrees of inhibition, with SDS exerting the least suppressive effect and Tween 80 causing the most substantial reduction in dye conversion. These competitive interactions between target pollutants and coexisting organic and inorganic constituents highlight the complexity of real wastewater treatment. Despite these interferences, the Fe(II)/chlorine system in continuous‐flow mode maintained high oxidative efficiency, demonstrating its potential for practical environmental applications. Future optimization should focus on tailoring operational parameters to specific water matrices, mitigating scavenger effects, and integrating process modeling to enhance system robustness. This study provides a critical foundation for advancing Fe(II)/chlorine‐based processes toward wastewater treatment in continuous mode.