Construction and demolition waste as a high-efficiency advanced process for organic pollutant degradation in Fenton-like reaction to approach circular economy

The Fenton-like reaction is a promising organic wastewater treatment reaction among advanced oxidation processes (AOP), which has emerged to replace the conventional Fenton reaction. Recycled construction and demolition waste (CDW), which is porous and rich in iron, manganese, and magnesium, can be reused as a Fenton-like catalyst. This study proposes an AOP wastewater treatment strategy using recycled porous CDW mixed with hydrogen peroxide (H₂O₂) to decompose methylene blue (MB) wastewater. According to the apparent first-order rate (K_app) of 10 ppm MB adsorption, CDW-3, having the highest specific surface area, also has the highest K_app of 0.23 min^-1 g^-1. The optimized conditions recommended by the Taguchi method include a 0.3 g mL^-1 CDW-3 concentration, a 0.254 g mL^-1 H₂O₂ concentration, and 10 ppm MB, resulting in an about 2.01 min^-1K_app value. In addition, MB concentration is observed as the most influential factor for K_app, which decreases with increasing MB concentration and is about 0.62 min^-1 at 1000 ppm MB. Repeating the Fenton-like reaction five times at 100 p.m. MB using the same CDW-3, the K_app is about 0.64 min^-1, which is 86% of the initial run. The synergistic effect index (ξ) is defined to quantify the level of interaction between CDW and H₂O₂, which produces free radicals during the Fenton-like process. The ξ of CDW-3 is about 2.16. Overall, it is demonstrated that CDW is a promising catalyst for Fenton-like reactions, and the synergistic effect index (ξ) can be used as a reference index to evaluate the catalytic generation of free radicals between the catalyst and H₂O₂.