Flocculation and Electron-Beam-Assisted Flocculation for the Removal of Pharmaceutical Compounds: An Integrated Review of Chemical, Natural, Electrochemical, and Hybrid Coagulation Systems

Pharmaceutical compounds, particularly antibiotics, are increasingly detected in aquatic environments because of their persistence, mobility, and incomplete removal in conventional wastewater treatment. Concentrations from ng/L to several μg/L have been recorded in surface water, groundwater, and treated effluents in over 100 countries, highlighting increasing concerns about antimicrobial resistance and ecotoxicological risks. Coagulation–flocculation-based processes, including chemical coagulation, electrocoagulation, and natural coagulants, have therefore been widely explored for pharmaceutical removal. Hybrid systems have also been investigated as practical routes to enhance overall treatment efficiency. Evidence from the literature shows that conventional aluminum-based coagulation often achieves limited removal of hydrophilic pharmaceuticals, whereas iron-based systems, electrocoagulation, natural coagulants, and oxidation coagulation hybrids can deliver substantially higher efficiencies under optimized conditions. Studies have demonstrated that matrix complexity, coagulant type, pH, ionic strength, and coagulant speciation strongly influence performance. These findings provide an important basis for positioning electron beam treatment as a complementary step that can transform dissolved pharmaceuticals into species more amenable to subsequent flocculation and separation. This review integrates detailed coagulation literature into a broader treatment framework and highlights why electron-beam-assisted flocculation deserves further investigation as a synergistic treatment strategy.