ABSTRACT
Water scarcity, pollution and security have emerged as major global challenges, necessitating the development of innovative, environmentally benign technologies to protect water resources and eliminate micropollutants. Among the numerous emerging pollutants found in water, pharmaceuticals and heavy metals are of particular concern due to their persistence, constant discharge into water bodies and potential to endanger wildlife and human health. The difficulty of traditional treatment approaches in reducing recalcitrant pollutant concentrations below desirable levels has paved the path for the emergence of tertiary treatment technologies. Adsorption stands out as a pledging treatment method in comparison with other tertiary treatment techniques due to numerous advantages, such as low energy consumption, high removal performance, lack of additional by-products, ease of operation and a wide range of on-field applications. Although commercial activated carbon has been extensively studied, its large-scale application is constrained by its high cost. As a result, the search for new technologies and environmentally sustainable materials for wastewater treatment using low-cost materials such as lignocellulosic-based materials has been intensified in order to reduce pharmaceutical and heavy metal pollutants. The primary goal of this review is to provide current information on the various sources of agricultural waste products and their potential for adsorption of various recalcitrant pollutants. Furthermore, the occurrence of pharmaceutical and heavy metal pollutants around the world, their fate in the environment, the effectiveness of operational parameters for removing these pollutants using lignocellulosic-based materials in their natural and modified form as a potential bioadsorbent, and the associated kinetics, isotherms and thermodynamics to understand bioadsorbent behavior have all been addressed. The adsorption mechanisms that remove pharmaceutical and heavy metal pollutants are explained here using acid-base, electrostatic, van der Waals, hydrophobic, ion exchange, surface complexation, precipitation and H-bonds, as well as n-π and π-π electron donor-acceptor (EDA) interactions. Aside from that, regeneration of used lignocellulosic-based bioadsorbents is being thoroughly investigated in order to solve the problem of solid waste generation. This review will help researchers who want to make low-cost, easily available, recyclable lignocellulosic-based bioadsorbents with better adsorption abilities for treating wastewater.
