**2.6 Industrial waste**

Industrial activities generate huge quantities of waste that are usually sent to landfill sites for disposal. These wastes possess a good adsorption capacity and are solve the problem of waste treatment. Waste products like fly ash [189–196], red mud [197–203] and slag [204, 205] have been effectively used owing to their appreciable capacity for removal of heavy metals from wastewater. Many industrial waste adsorbents have been employed for the remediation of Zn2+ from effluents. The maximum adsorption capacity for lignin was 73.2mg/g, 168mg/g for waste sludge and 55.82mg/g for cassava waste [206, 207]. **Table 3** gives various industrial wastes used for removal of heavy metals from wastewater and aqueous solutions.
