Adsorption of Arsenite and Fluoride on Untreated and Treated Bamboo Dust - Management of Natural Resources in a Changing Environment - page 160

Adsorption of Arsenite and Fluoride
on Untreated and Treated Bamboo Dust

Sanjoy Kumar Nath and Krishna G. Bhattacharyya

Introduction

Pollution of water with anionic contaminants represents an important environmen-
tal concern due to the toxicity of these ions and their accumulation throughout the
food chain. The fresh water wealth of India is under threat due to variety of natural
and human influences. The high concentration of some toxic elements in anionic
state such as fluorine as fluoride, and arsenic as arsenite and arsenate, etc. is of con-
cern as they cause serious health hazards.
Of all chemical elements in the Periodic Table, fluorine is the most electronega-
tive and the most reactive element. Because of its great reactivity, fluorine cannot be
found in nature in its elemental state, it exists as fluorides. It occurs in nature and it
is an essential constituent for both humans and animals in low concentration (Liang
et al. 2006 ). Fluorine, a fairly common element of the earth's crust, is present in the
form of fluorides in a number of minerals and in many rocks and hence it can be
leached out by rainwater thereby allowing it to contaminate ground and surface
water. On the other hand, several fluoride compounds have industrial applications
(e.g. it is extensively used in semiconductors, fertilizers, aluminium industries, and
nuclear applications) and are used widely and these also contribute to fluoride pol-
lution (Oguz 2005 ).
Fluoride in drinking water has dual significance. If its content is less than the per-
missible limit, it may result in problems like dental caries. On the other hand, excess
fluoride in drinking-water causes harmful effects such as dental and skeletal fluorosis.
World Health Organization (WHO) recommends a permissible range of
0.1-1.5 mg/L. The standard for India is between 1 and 1.5 mg/L. Thus, the requirement
of fluoride content varies among countries and depends on the geography and the age