Comparative study of Waste-Derived and conventional sorbents for heavy metal removal from water

In this paper, the effectiveness of various waste sorbents (coffee grounds, hazelnut shells, and compost) was compared with sorbents such as chitosan and bentonite for the removal of heavy metals: zinc, lead, cadmium, and copper (Zn, Pb, Cd, Cu, respectively) from aqueous solution. Their composition, ash content, and moisture content were characterized. The BET method was used to determine the surface area. The size and type of pores were determined using the BJH and DFT methods. The presence of functional groups was identified using FTIR. The sorbents differed significantly in terms of pore quantity and size, as well as specific surface area. The highest specific surface area of 40 m²/g was determined for bentonite, while for coffee it was below the detection limit, at 2 m²/g. FTIR analysis confirmed the presence of numerous and diverse functional groups characteristic of each sorbent, e.g., C = O, C-O-C, O-H. All materials effectively removed heavy metals. For the smallest mass of sorbents used (0.1 g), the following metal removal efficiencies were achieved: 95% Zn (chitosan), 99% Cu (compost), 95% Pb (hazelnut shell), and 72% Cd (hazelnut shell). Bentonite proved to be the least effective sorbent of all the materials analyzed.