On the performance of bioadsorption processes for heavy metal ions removal by low-cost agricultural and natural by-products bioadsorbent: a review

Nowadays, heavy metal ions produced from industrial and human activities are considered as a major source of environmental contamination that led to deterioration of many ecosystems and social health. This situation represents a big challenge to develop sustainable treatment methods to remove these contaminations. Among the treatment processes that are being applied to remove these hazardous wastes from different types of wastewater, bioadsorption process using low-cost bioadsorbents has been proven as one of the most feasible decontamination method. Unlike other treatment methods, bioadsorption which represents a biotechnological innovation is simple and permits regeneration of toxic metallic sludge. For this reason, this review is devoted to give the reader suitable information about the risk of heavy metal ions and an overview of some potential of biosorbents such as natural or modified agricultural wastes and microorganisms used as bioadsorbents. It was clear that surface modification improves their bioadsorption capacities and performance. In addition, some attention has been given to the role of some functional groups in forming bonds with the ions and the mechanism of the removal process. Since mathematical modelling is one of the important features of engineering processes, this review concentrated on different kinetic, isotherm and diffusion models that have been developed to describe bioadsorption processes. Moreover, the effect of some parameters such as temperature and pH on the bioadsorption process was reviewed and discussed.