Preparation of ceramsite adsorbent and its influencing factors on ammonia nitrogen adsorption: A review

Ammonia nitrogen, a refractory pollutant in the water environment, poses a significant threat to ecological balance and human health. Adsorption has emerged as an effective method for its treatment due to the versatility of adsorption materials. However, traditional adsorbents suffer from resource depletion, high costs and low efficiency. Therefore, the search for efficient, cost-effective adsorption materials is crucial for optimizing this method. In recent years, ceramsite-based adsorption materials have garnered attention as a promising solution. This review provides an overview of recent advancements in ceramsite adsorbents for ammonia nitrogen removal. The first section introduces the raw materials and the role of the main components in ceramsite preparation, followed by an analysis of the effects of sintering systems and preparation processes on the final product. Three modification methods-chemical surface modification, physical surface modification, and pore structure regulation-are then discussed to achieve efficient adsorption. In the second section, the mechanisms of ammonia nitrogen adsorption by ceramsite adsorbents are analyzed, focusing on adsorption isotherms (e.g., Langmuir and Freundlich models) and kinetics models (e.g., pseudo-second-order and intraparticle diffusion models). The mechanisms include ion exchange, surface adsorption, and pore adsorption. In the third part, the effects of ceramsite pore size, dosage, desorption, initial pH, ammonia nitrogen concentration and other cations on adsorption efficiency are analyzed, and the favorable range for adsorption is identified, which provides guidance for the preparation of high-efficiency ceramsite adsorbents. Finally, the future prospects of ceramsite adsorbents in ammonia nitrogen treatment are discussed. Ceramsite, with its wide range of raw materials, large specific surface area, controllable pore size, and potential for biofilm or modification, holds promise for effective ammonia nitrogen removal.