Microwave Heating as a Sustainable Method for Development of Activated Carbons for Water Contaminants Removal

Activated carbons (ACs) are porous materials widely used as adsorbents, particularly in environmental remediation, due to their large surface area, tunable porosity, and surface chemistry. As demand grows for sustainable technologies to remove contaminants from water and air, the use of ACs is expected to rise accordingly. These materials are typically produced through high-temperature thermal processes, but conventional heating suffers from several drawbacks such as long processing times, slow heat transfer, and high energy consumption. These factors reduce process efficiency and worsen environmental impact. Microwave-assisted heating has emerged as a promising alternative for producing ACs, offering rapid and volumetric heating, shorter processing times, and reduced energy consumption. Despite these advantages, its broader application is limited by challenges related to heat distribution uniformity and scalability, which complicate the transition from laboratory to industrial scale. This chapter provides a comparative assessment of microwave-assisted and conventional heating methods for ACs preparation using different lignocellulosic biomasses and synthetic polymers as carbon precursors. The influence of the heating method on ACs yield, surface area, pore volume, pore size distribution, and surface functional groups is systematically examined. Results indicate that microwave processing can enhance surface area, increase both micro- and mesoporosity, and reduce energy demand by up to 40% compared to conventional techniques. The adsorption performance of the ACs is examined for the removal of representative heavy metals (Pb2+, Cd2+), pharmaceuticals (diclofenac, cephalexin, oxytetracycline), dyes (methylene blue), and phenol. Higher adsorption capacities for ACs synthesized with microwave heating assistance have been reported, likely due to the development of favorable textural features and surface functionalities. The discussion integrates experimental results from our own investigations with selected literature findings to elucidate the influence of the heating method on ACs development and performance. The chapter concludes with a discussion of both the benefits and technical challenges of microwave-assisted ACs synthesis and considers how this approach could make ACs production more energy-efficient and environmentally sustainable.