249
Therefore it is high time to develop easy and simple method for reclamation of
wastewater using low-cost adsorbent materials for our sustainable development
on earth.
10.2 Different Techniques Available for Heavy Metal
Removal: Pros and Cons
Due to known impacts of heavy metals on living organism as well as environment,
a major number of research have been done on developing different methods for
removal of heavy metals from water sources along with industrial wastewater,
municipal wastewater, and other wastewater sources. Methods which are most common on removing toxic metals from contaminated water sources are as follows:
ion-exchange, flocculation, chemical precipitation, coagulation, electrochemical
treatment, adsorption, membrane separation, and electro-dialysis (Carlos et al. 2013).
10.2.1 Chemical Precipitation
In chemical precipitation, heavy metals are either removed as hydroxide or sulfide
precipitate which is formed via the chemical reaction with hydroxide (such as
NaOH, Ca(OH) 2 ), and sulfides (such as Na 2 S and FeS). Firstly, heavy metals are
coagulated by lime, alum, iron salts, and other organic coagulants. These coagulants
lead to formation of insoluble precipitate which can be easily settled down by sedimentation and then separated by filtration. Finally treated water can be discharged
or reused (Pehlivan and Altun 2006). Copper and Chromium ions are eliminated
from effluent by hydroxide precipitation process (Mirbagheri and Hosseini 2005).
Cu
2+
, Cd
2+
, and Pb
2+
ions are removed by using pyrite and synthetic iron sulfide by
sulfide precipitation (Ozverdi and Erdem 2006). The main disadvantage of chemical
precipitation is the large amount of toxic sludge produced during the process
(Kurniawan et al. 2006).
10.2.2 Ion Exchange
In ion-exchange process, metal ions from dilute solution are exchanged with the
ion-exchange resin by electrostatic forces. Because of many advantages like high
removal efficiency and fast kinetics, ion exchange process has been broadly applied
to eliminate toxic metals from effluent. It is one of the most effective process for the
removal of toxic metals released from chemical industries into drinking water at
very low concentration making it the most promising process to be used (Dabrowski
10 Heavy Metal Removal by Low-Cost Adsorbents
Therefore it is high time to develop easy and simple method for reclamation of
wastewater using low-cost adsorbent materials for our sustainable development
on earth.
10.2 Different Techniques Available for Heavy Metal
Removal: Pros and Cons
Due to known impacts of heavy metals on living organism as well as environment,
a major number of research have been done on developing different methods for
removal of heavy metals from water sources along with industrial wastewater,
municipal wastewater, and other wastewater sources. Methods which are most common on removing toxic metals from contaminated water sources are as follows:
ion-exchange, flocculation, chemical precipitation, coagulation, electrochemical
treatment, adsorption, membrane separation, and electro-dialysis (Carlos et al. 2013).
10.2.1 Chemical Precipitation
In chemical precipitation, heavy metals are either removed as hydroxide or sulfide
precipitate which is formed via the chemical reaction with hydroxide (such as
NaOH, Ca(OH) 2 ), and sulfides (such as Na 2 S and FeS). Firstly, heavy metals are
coagulated by lime, alum, iron salts, and other organic coagulants. These coagulants
lead to formation of insoluble precipitate which can be easily settled down by sedimentation and then separated by filtration. Finally treated water can be discharged
or reused (Pehlivan and Altun 2006). Copper and Chromium ions are eliminated
from effluent by hydroxide precipitation process (Mirbagheri and Hosseini 2005).
Cu
2+
, Cd
2+
, and Pb
2+
ions are removed by using pyrite and synthetic iron sulfide by
sulfide precipitation (Ozverdi and Erdem 2006). The main disadvantage of chemical
precipitation is the large amount of toxic sludge produced during the process
(Kurniawan et al. 2006).
10.2.2 Ion Exchange
In ion-exchange process, metal ions from dilute solution are exchanged with the
ion-exchange resin by electrostatic forces. Because of many advantages like high
removal efficiency and fast kinetics, ion exchange process has been broadly applied
to eliminate toxic metals from effluent. It is one of the most effective process for the
removal of toxic metals released from chemical industries into drinking water at
very low concentration making it the most promising process to be used (Dabrowski
10 Heavy Metal Removal by Low-Cost Adsorbents