Synthesis Procedures and Their Implications on PANI Activity from a Wastewater Treatment Perspective

Polyaniline (PANI) has emerged as a promising material for wastewater treatment due to its high conductivity, chemical stability, and redox properties. However, its physicochemical characteristics are susceptible to the chosen synthesis method and operating conditions. Despite the growing number of studies exploring PANI for environmental applications, a well-defined and systematic basis for selecting optimal synthesis methods and conditions is still missing. This review critically analyzes the advantages and limitations of various PANI synthesis procedures, including chemical oxidative, electrochemical, enzymatic, and alternative polymerization methods, with a particular focus on how synthesis conditions (e.g., dopant type/concentration, oxidant, temperature) affect the conductivity, morphology, and surface area of the resulting polymer. Based on current evidence, chemical oxidative polymerization (COP) using 1 M HCl and ammonium persulfate (APS) at 0–5 °C and an APS/aniline molar ratio between 0.8 and 1.25 mol/mol is recommended to maximize conductivity and enhance performance for photocatalytic and adsorptive wastewater treatment. The review also highlights key knowledge gaps, particularly in downstream processing, and offers guidance for future research on scalable and sustainable PANI production.