An overview of analytical techniques for heavy metal ion detection and removal from industrial sewage

Abstract

Removal of heavy metal ions from wastewater is of paramount importance for a clean environment and human health. Various reported processes have addressed the removal of heavy metal ions from various wastewater sources. These processes can be divided into adsorption, membrane, chemical, electrical, and photo catalytic processes. This article provides a comprehensive and critical overview of these methods, discussing the media/sorbents used, removal efficiency, operating conditions, and advantages and disadvantages of each method. We also summarize the main results of previous studies reported in the literature. It should be noted that recent research has generally focused on adsorption techniques. The main obstacles to the adsorption process are the ability to simultaneously remove different types of ions, the long retention time of the adsorbent and cycle stability. Although chemical and membrane processes are practical, high levels of sludge formation and post-treatment requirements are key issues that must be addressed in chemical processes. Suppression of fouling and scaling can further improve membrane separation. However, pretreatment and regular cleaning of the membrane incurs additional costs. Electrical methods have also been reported to be efficient. However, in addition to overcoming the problem of massive sludge formation, industrial scale separation is required. Electrical and photo catalytic-based methods are not yet mature. Future research should focus on environmentally friendly, inexpensive, and sustainable materials and methods.