128Owing to the environmental impact as well as the growing awareness among the public, it is imperative to remove or reduce the concentration of heavy metals to environmentally acceptable levels before being discharged to open stream. The conventional methods for removing heavy metals suffer from many drawbacks such as high cost, sludge disposal problem, complex technology, and limited applicability. Therefore, intensive research has been carried out using low-cost materials to remove these heavy metals at an affordable cost. This chapter examines (i) some commonly found heavy metals in wastewater, (ii) main treatment technologies and their limitations, (iii) various studies using waste materials from agriculture and industry or naturally occurring biosorbents, (iv) chemical properties and characterization studies on the low-cost adsorbents, (v) influential parameters in affecting the removal efficiency, and (vi) equilibrium, kinetic models, and process design used in the adsorption process.