ABSTRACT
Heavy metal ions are considered one of the most pollutants in industrial wastewater. Heavy metal ions are present in aquatic systems due to mineral activities, chemical industries, batteries manufacturing, and electroplating. Their presence in the aquatic system has a potent effect on plants, animals, and humans. Several methods have been used to remove these metal ions from the wastewater including chelation, precipitation, and ion exchange, but the costs of these methods are very high. The use of agricultural and plant wastes can help in the removal of these ions with almost no cost. Several agricultural wastes including rice husks, wheat husks, rice bran, wheat bran, and activated carbon obtained from different plant wastes were described here. The use of these biosorbents is safe due to their fast biodegradation, low cost, and easy availability and no chemicals are used. The efficiency of several agricultural wastes in metal ions removal from contaminated wastewater is discussed. The adsorption isotherms of heavy metal adsorption including Freundlich isotherm, Langmuir isotherm, Temkin isotherm, Dubinin–Radushkevich equation, and Flory–Huggins isotherm are discussed. Adsorption kinetic models of metal ions have been discussed including pseudo-first-order model, pseudo-second-order model, and first-order reversible reaction model. The importance of heavy metal removal from the different tribological systems has been explained.
