Effective Use of Biomass Wastes for Removing Hazardous Inorganic Ions from Aquatic Environment

Abstract

In recent years, pollution of water by various toxic materials has become serious all over the world especially in developing countries, caused by the development of industries in these countries. Among toxic materials, although mercury and lead are the most toxic, arsenic and fluorine are also toxic. Especially, pollution of underground water by arsenic in Bangladesh and India is well known. Although mercury and lead exist as cationic species in aquatic environments, majority of toxic inorganic materials exist as anionic species. For example, arsenic (III and V) exists oxo-anions such as arsenite (AsO3) and arsenate (AsO4), respectively. To avoid the pollution by these toxic elements, severe standards are required for effluents from industries in each country. For example, the typical standards in Japan are as follows; chromium (VI): 0.5, selenium: 0.1, arsenic: 0.1, flourine: 8 (unit; mg/dm3). To clear these standards, various techniques have been developed to date and some of them have been commercialized. The typical techniques are precipitation, electrochemical treatments, Donnan dialysis, ion exchange and adsorption. However, these conventional techniques are suffering from some drawbacks such as poor selectivity, high operation costs and so forth.