A Review on Heavy Metal Removal Techniques: A Comparative Study of Physical, Chemical, and Biological Techniques

Contamination of water resources with heavy metals poses serious environmental and public health problems due to their toxic, persistent, and bioaccumulative nature. Common heavy metals such as lead (Pb), cadmium (Cd), mercury (Hg), arsenic (As), nickel (Ni), and chromium (Cr) are abundant in industrial and municipal wastewater. Effective removal of these metals is essential to ensure water quality, protect aquatic ecosystems, and maintain ecological balance. This review provides a comprehensive comparative analysis of three main categories of heavy metal removal methods: physical, chemical, and biological techniques. Physical methods such as membrane filtration, coagulation-flocculation, and adsorption are widely used for their operational simplicity and efficiency. Chemical methods including precipitation, electrochemical treatment, and solvent extraction are effective but may generate secondary contaminants. Biological approaches such as bioremediation and phytoremediation offer environmentally friendly and sustainable alternatives. Additionally, emerging technologies like nanotechnology-based materials and hybrid processing systems are discussed for their potential to improve removal efficiency and sustainability. The comparative evaluation highlights the advantages and limitations of each method in terms of removal efficiency, cost, environmental impact, and scalability. The analysis concludes that hybrid or integrated treatment systems combining multiple methods provide higher efficiency and represent a promising approach for treating complex wastewaters contaminated with heavy metals.