Coagulation-centered three-step approach for removing by-product organic pollutants from tetrabromobisphenol A industrial wastewater: Experimental and theoretic investigations

Abstract

The challenge of meeting discharge standards for tetrabromobisphenol A (TBBPA) production wastewater, characterized by high concentrations of organic by-products, necessitates effective treatment methods. This study identifies 2,4-dibromophenol, 2,6-dibromophenol, 2,4,6-tribromophenol, chlorobenzene, and toluene as the primary organic by-product pollutants. A coagulation-centered three-step approach was established for TBBPA industrial wastewater treatment. The initial step involves acidification treatment to exploit the reduced solubility of 2,4-dibromophenol, 2,6-dibromophenol, and 2,4,6-tribromophenol under acidic conditions, with the optimal pH determined as 2.7–3.1. An acid-activated montmorillonite coagulant (AMC), prepared through roasting and high-pressure acid leaching, exhibits a distinctive "Core-shell" structure, contributing significantly to the combined coagulation and adsorption mechanism. The acid-soluble aluminum salts in AMC form positively charged flocs, electrostatically attracting negatively charged organic compounds in the wastewater. Simultaneously, the porous insoluble silicon framework displays strong adsorption capacity for pollutants. The removal efficiencies for toluene, chlorobenzene, 2,4-dibromophenol, 2,6-dibromophenol, and 2,4,6-tribromophenol reached 88.2%, 89.1%, 88.8%, 87.1%, and 89.4%, respectively. Elemental analysis reveals that the coloration of the wastewater stems from complexation reactions between phenolic compounds and Fe3+, originating from the corrosion of iron or steel reaction vessel. Post-treatment with cation exchange resin resulted in removal efficiencies of 5.2%, 59.1%, 80.2%, 77.9%, and 88.3% for the five substances, respectively. This study outlines a crucial pathway for the effective purification of TBBPA wastewater.