This review article discusses the removal of heavy metal ions from wastewater using various methods, including adsorption, membrane, chemical, electric, and photocatalytic-based treatments. The article critically evaluates these methods in terms of their agents/adsorbents, removal efficiency, operating conditions, and pros and cons. It highlights that most recent studies have focused on adsorption techniques, which 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 practical but have issues with large-volume sludge formation and post-treatment requirements. Membrane fouling and scaling inhibition can improve membrane separation, but pre-treatment and periodic cleaning add costs. Electric- and photocatalytic-based methods are less mature. The review emphasizes the need for using real wastewater rather than synthetic ones in studies. Future research should focus on eco-friendly, cost-effective, and sustainable materials and methods. The article discusses various adsorbents, including carbon-based, chitosan-based, mineral, magnetic, and biosorbents. It highlights the advantages and limitations of each type, such as the high surface area and adsorption capacity of carbon-based materials, the low mechanical strength and poor stability of chitosan-based materials, and the high cation exchange capacity of mineral adsorbents. Magnetic adsorbents are noted for their low cost, easy synthesis, and reusability. Biosorbents are effective due to their numerous functional groups, but their removal efficiency can be affected by pH and temperature. Metal-organic frameworks (MOFs) are promising for sorption applications but have issues with stability in water. The article also covers membrane-based methods such as ultrafiltration, nanofiltration, microfiltration, reverse osmosis, and forward osmosis. These methods are effective for removing heavy metal ions but face challenges such as membrane fouling and high energy consumption. Chemical-based methods like precipitation, coagulation-flocculation, and flotation are mature but have issues with sludge volume and toxicity. Electric-based methods such as electrochemical reduction, electrocoagulation, electroflotation, and electrooxidation are effective but require further development for industrial applications. Photocatalytic-based methods using titanium dioxide are effective but require further research for practical implementation. The review concludes that future research should focus on eco-friendly, cost-effective, and sustainable materials and methods for heavy metal ion removal from wastewater.This review article discusses the removal of heavy metal ions from wastewater using various methods, including adsorption, membrane, chemical, electric, and photocatalytic-based treatments. The article critically evaluates these methods in terms of their agents/adsorbents, removal efficiency, operating conditions, and pros and cons. It highlights that most recent studies have focused on adsorption techniques, which 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 practical but have issues with large-volume sludge formation and post-treatment requirements. Membrane fouling and scaling inhibition can improve membrane separation, but pre-treatment and periodic cleaning add costs. Electric- and photocatalytic-based methods are less mature. The review emphasizes the need for using real wastewater rather than synthetic ones in studies. Future research should focus on eco-friendly, cost-effective, and sustainable materials and methods. The article discusses various adsorbents, including carbon-based, chitosan-based, mineral, magnetic, and biosorbents. It highlights the advantages and limitations of each type, such as the high surface area and adsorption capacity of carbon-based materials, the low mechanical strength and poor stability of chitosan-based materials, and the high cation exchange capacity of mineral adsorbents. Magnetic adsorbents are noted for their low cost, easy synthesis, and reusability. Biosorbents are effective due to their numerous functional groups, but their removal efficiency can be affected by pH and temperature. Metal-organic frameworks (MOFs) are promising for sorption applications but have issues with stability in water. The article also covers membrane-based methods such as ultrafiltration, nanofiltration, microfiltration, reverse osmosis, and forward osmosis. These methods are effective for removing heavy metal ions but face challenges such as membrane fouling and high energy consumption. Chemical-based methods like precipitation, coagulation-flocculation, and flotation are mature but have issues with sludge volume and toxicity. Electric-based methods such as electrochemical reduction, electrocoagulation, electroflotation, and electrooxidation are effective but require further development for industrial applications. Photocatalytic-based methods using titanium dioxide are effective but require further research for practical implementation. The review concludes that future research should focus on eco-friendly, cost-effective, and sustainable materials and methods for heavy metal ion removal from wastewater.