Surface charge behavior of natural and modified adsorbents: Insights into pHzpc, mechanisms, and methodological perspectives

Understanding the point of zero charge (pHzpc) and surface charge behavior of adsorbents is fundamental to predicting their adsorption efficiency, especially for charged contaminants in aqueous systems. The pHzpc is a critical parameter that indicates the pH at which the adsorbent surface carries no net charge, influencing its interaction with different ions in solution. This review explores the effectiveness of pHzpc, the mechanisms governing surface charge development, and the experimental procedures used to measure and control these properties. The review also discusses various factors affecting surface charge, such as surface chemistry, ionic strength, temperature, and adsorbate type. Recent advances in the modification of adsorbents—through techniques such as thermal activation, chemical treatment, and nanoparticle decoration—are highlighted, providing insights into optimizing adsorbent performance for specific applications. Furthermore, the review synthesizes findings from recent studies on natural, synthetic, and modified adsorbents, illustrating their role in water purification, industrial effluent treatment, and environmental remediation. This comprehensive overview underscores the significance of surface charge characteristics in designing efficient adsorbents for tackling environmental contamination challenges. • Explains the significance of pHzpc in governing adsorbent surface charge behavior. • Reviews mechanisms controlling surface charge development in aqueous systems. • Summarizes methods for measuring and tuning pHzpc of adsorbents. • Examines effects of surface chemistry, ionic strength, temperature, and adsorbates. • Highlights advanced modification strategies to enhance adsorption performance.