ABSTRACT
With an increase in population worldwide, a significant increase in industries has taken place, which has led to a severe issue of water pollution. Various industries like electroplating, textile, tanning, steel production as well as mining operations are some of the major sources of water pollution. Unlike other organic pollutants, heavy metals are not degradable into harmless products and have severe health effects on human beings, animals and plants. The toxicity of heavy metals in industrial effluents can be minimized by different conventional methods, including chemical precipitation, ion exchange, membrane process, electrochemical method and adsorption. Among them, adsorption is one of the most efficient methods due to its economic feasibility. Some of the most efficient precursor materials used for the synthesis of adsorbents are agricultural wastes, i.e., straws, husks, shells, leaves, stalks, bagasse, etc. These materials are abundantly available, cost-efficient and environment friendly. It is well accepted that cellulose material extracted from agricultural by-products exhibits significant adsorption capacity. On the other hand, lignin extracted from agricultural by-products, from wood and even from black liquor of industrial waste also has comparable adsorption ability to other materials. In this chapter, various conventional methods for wastewater treatment, with a special emphasis on the adsorption method, are discussed. The chapter also reveals the present state of research on naturally occurring or modified cellulose and lignin materials and their comparative adsorption efficiency for removing heavy metals from industrial effluent.
