The paper provides a comprehensive and critical review of methods for removing heavy metal ions from wastewater, focusing on adsorption, membrane, chemical, electric, and photocatalytic treatments. It discusses the agents/adsorbents used, removal efficiency, operating conditions, and the pros and cons of each method. The review highlights that adsorption techniques are currently the most popular, but they face challenges such as the ability to remove different ion types concurrently, high retention time, and cycling stability of adsorbents. Chemical and membrane methods are also practical but suffer from issues like large-volume sludge formation and fouling. Electric and photocatalytic methods are less mature but show potential. The paper emphasizes the need for eco-friendly, cost-effective, and sustainable materials and methods, particularly in real wastewater applications rather than synthetic ones. Future research should aim to improve the efficiency, stability, and scalability of these methods.The paper provides a comprehensive and critical review of methods for removing heavy metal ions from wastewater, focusing on adsorption, membrane, chemical, electric, and photocatalytic treatments. It discusses the agents/adsorbents used, removal efficiency, operating conditions, and the pros and cons of each method. The review highlights that adsorption techniques are currently the most popular, but they face challenges such as the ability to remove different ion types concurrently, high retention time, and cycling stability of adsorbents. Chemical and membrane methods are also practical but suffer from issues like large-volume sludge formation and fouling. Electric and photocatalytic methods are less mature but show potential. The paper emphasizes the need for eco-friendly, cost-effective, and sustainable materials and methods, particularly in real wastewater applications rather than synthetic ones. Future research should aim to improve the efficiency, stability, and scalability of these methods.