Environmental Engineering Reference
In-Depth Information
of people involved. The high fluoride levels in drinking water and its impact on human
health in many parts of India have increased the importance of defluoridation studies.
Arsenicanditscompoundsarewellknownpoisonoussubstancesandarewidely
distributed in the earth crust, which is the main cause of epidemiological problems
to human health. The most common arsenic species found in aqueous media are the
oxoanionsofarsenateandarsenite.Arseniccontaminationisaseriousenvironmen-
tal problem, and its increasing concentration in natural water has been reported in
many areas all over the world including in large areas in Bangladesh (Yokota et al.
2001
) and West Bengal of India (Maiti et al.
2007
). Recent reports reveal that
groundwaterofNorthEasternIndiaespeciallythatoftheAssamvalleyareaffected
by arsenic contamination especially in the districts of the Brahmaputra flood plain
viz.Barpeta,Dhemaji,Dhubari,DarrangandGolaghat.
Arsenicinwaterisremovedbydifferentmethods,viz.precipitationwithlime,
co-precipitation with ferric sulfate, precipitation with alum or with sodium sulfide
and hydrogen sulfide. Iron coprecipitation method has been reported as one of the
most successful methods in lowering the arsenic content to drinking water standard
level, but it suffers from the post-treatment problem of disposal of the alkaline sludge
producedduringthetreatment(Ghimireetal.
2003
).Anumberofotheradsorptive
materials, such as impregnated activated carbon (Chang et al.
2010
), activated alu-
mina (Su et al.
2008
), exchange resin (Issa et al.
2011
), low cost (Chakravarty et al.
2002
) and natural materials (Jordan et al.
2009
; Gimenez et al.
2010
), have been
more or less successfully tested for the removal of toxic anions (Szlachta et al.
2012
).
During the last few years, many low cost materials, such as waste orange peel,
banana pith, bottom ash, de-oiled soya, rice husk, kaolin, bentonite clay, neem leaf
powder, powdered activated sludge perlite, powdered peanut hull, natural and modi-
fied clays like sepiolite, zeolite, saw dust, coconut shell, groundnut shell, rice straw,
duck weed, sewage sludge, saw dust carbon, agricultural waste and timber industry
waste carbons and gram husk, etc., have been tested as adsorbents for treating con-
taminated water (Mane and Vijay Babu
2011
; Demirbas
2009
). The wastes from
forestry and agricultural industries are abundant in nature, inexpensive, require little
processing and are shown to be effective water treatment materials (Demirbas
2009
).
Bamboo dust is an abundant by-product of the paper industry and is easily avail-
able at negligible price. The aim of the present work is to study the adsorption
capacity of bamboo dust under various conditions and its acid treated modified
forms as adsorbents.
Methodology
ReagentgradeNaF(Merck,Mumbai,India),NaAsO
2
(Devam Chemicals Calcutta),
HCl, HNO
3
and H
2
SO
4
(all from E. Merck, Mumbai, India) were used without fur-
ther purification.
For the adsorption experiments, stock solutions of fluoride and arsenite having
1,000 mg of F
−
andAs(III)perlitrewerepreparedbydissolvingappropriateamounts
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