The elimination of heavy metal ions from wastewater is crucial for maintaining human health and a clean environment. Various described techniques were used to remove heavy metal ions from different types of wastewater. These techniques can be divided into treatments based on adsorption, membranes, chemicals, electricity, and photocatalysis. The employed agents/adsorbents, removal efficiency, operating circumstances, and advantages and disadvantages of each technique are all covered in-depth and critically in this paper's assessment and discussion of these approaches. In addition, a summary of the principal discoveries from earlier research is provided in the literature. It is generally observed that adsorption techniques have been the subject of the majority of current investigations. The capacity to remove many ion types simultaneously, long retention times, and adsorbent cycling stability are the main challenges facing adsorption techniques. The large-volume sludge generation and post-treatment requirements are crucial problems that must be resolved for chemical procedures, even though the membrane and chemical processes are feasible. Further advancements in membrane separation may result from fouling and scaling inhibition. Pre-treatment and routine membrane cleaning, however, come at an extra expense. Electrical-based techniques have also been found to be effective; however, in addition to addressing the problem of large-volume sludge development, industrial-scale separation is required. Techniques based on electricity and photocatalysis are still in their infancy. Real wastewaters should be used more often in heavy metals removal research rather than simulated ones. Future investigations ought to concentrate on sustainable, affordable, and environmentally friendly materials and procedures.