Evaluating the degradation of Rhodamine B using a sequential batch three-dimensional electrode reactor

This study investigated the efficiency of a sequential batch three-dimensional electrode reactor (3DER) using stainless steel electrodes and Mn-loaded steel slag as the particle electrodes (PE) to degrade refractory organics. The PE, a micron-grade material consisting primarily of SiO 2 , Fe 2 O 3 , and MnO 2 , exhibits excellent electric conductivity and catalysis ability. Then, a single-factor experiment determined the optimal conditions for removing 20 mg·L −1 of RhB in the 3DER. It involved introducing 5 mM H 2 O 2 and 1.0 g·L −1 PE to 200 mL of simulated wastewater under acidic-to-neutral conditions, under a current density of 57.14 mA·cm −2 and 15 mm distance between 2D electrodes. Approximately 99.52% RhB removal after 15 min of reaction was achieved. Although the inorganic ions in actual water negatively affect the 3DER performance, the system still showed excellent applicability in treating wastewater. In addition, the RhB degradation pathway was explored by determining the reactive oxidizing species (ROS) and intermediate products. The results illustrated that HO• (the main ROS that degraded organics) and SO 4 •− existed in the 3DER. Through de-ethylation, ring-opening, and C-C or C C bone rupturing, RhB degraded to chain organics with simple molecular structures before finally mineralizing to CO 2 , H 2 O, NO 3 - , and NH 4 + . In summary, this research informs on the potential of 3DER for removing refractory organics from water.