266
decreases because of the absence of vacant sites on adsorbent for metal ions
(Demirbas et al. 2009).
Electrostatic forces also have influence on the adsorption mechanism.
Electrostatic forces involve attraction between charged clouds of atoms. It is heavily
dependent on operating conditions mainly on pH of the aqueous solution. At lower
pH, various functional groups like carboxyl and hydroxyl are protonated and much
more challenging for metal cations to accommodate active sites of adsorbent over
H 3 O
+
, consequently resulting in electrostatic repulsion as well as preventing adsorption. Adsorption of metal ions increases as pH increases because of the decrease in
electrostatic repulsion. The removal efficiency of adsorbent is also influenced by
relative value of pH that is point zero charge pH PZC . At the point zero charge, adsorbent surface has no charge at all. When solution pH is less than pH PZC , adsorbent
surface gets positively charged, but at pH greater than the pH PZC , surface of the
adsorbent became negative (Joseph et al. 2019). Therefore the negative charge density of adsorbent surface at pH > pH PZC enhances cation adsorption capacity, and
reverse is true for pH < pH PZC .
10.5 Conclusion
Environmental pollution becomes main hurdle for our sustainable development.
Remediation of toxic hazardous metal is one of the concerned issues to be dealt
with. Therefore there are load of studies available in literature on heavy metal
removal from domestic, municipal, and industrial wastewater. In this chapter we
restrict our studies only on low-cost adsorbents capable of eliminating risk of environmental contamination by heavy metals. Adsorbents like clay, coal, peat moss,
zeolite, and chitosan are indeed very cheap and effective for this purpose. Along
with conventional adsorbents, agricultural and industrial wastes are emerging out as
efficient alternative for heavy metal removal. Most of the research study shown
keen interest for enhancement of adsorption capabilities of these waste materials by
chemical or thermal modification. The vital facts indulge with metal adsorption are
adsorbate concentration, temperature, pH, extent of surface modification, and adsorbent characteristics. In spite of considerable adsorption performance, low-cost
adsorbents seek for proper studies in terms of technicality and overall process efficiency to be commercialized.
Acknowledgments The first author expresses appreciation to all co-authors for their contribution
in literature review.
M. Maharana et al.
decreases because of the absence of vacant sites on adsorbent for metal ions
(Demirbas et al. 2009).
Electrostatic forces also have influence on the adsorption mechanism.
Electrostatic forces involve attraction between charged clouds of atoms. It is heavily
dependent on operating conditions mainly on pH of the aqueous solution. At lower
pH, various functional groups like carboxyl and hydroxyl are protonated and much
more challenging for metal cations to accommodate active sites of adsorbent over
H 3 O
+
, consequently resulting in electrostatic repulsion as well as preventing adsorption. Adsorption of metal ions increases as pH increases because of the decrease in
electrostatic repulsion. The removal efficiency of adsorbent is also influenced by
relative value of pH that is point zero charge pH PZC . At the point zero charge, adsorbent surface has no charge at all. When solution pH is less than pH PZC , adsorbent
surface gets positively charged, but at pH greater than the pH PZC , surface of the
adsorbent became negative (Joseph et al. 2019). Therefore the negative charge density of adsorbent surface at pH > pH PZC enhances cation adsorption capacity, and
reverse is true for pH < pH PZC .
10.5 Conclusion
Environmental pollution becomes main hurdle for our sustainable development.
Remediation of toxic hazardous metal is one of the concerned issues to be dealt
with. Therefore there are load of studies available in literature on heavy metal
removal from domestic, municipal, and industrial wastewater. In this chapter we
restrict our studies only on low-cost adsorbents capable of eliminating risk of environmental contamination by heavy metals. Adsorbents like clay, coal, peat moss,
zeolite, and chitosan are indeed very cheap and effective for this purpose. Along
with conventional adsorbents, agricultural and industrial wastes are emerging out as
efficient alternative for heavy metal removal. Most of the research study shown
keen interest for enhancement of adsorption capabilities of these waste materials by
chemical or thermal modification. The vital facts indulge with metal adsorption are
adsorbate concentration, temperature, pH, extent of surface modification, and adsorbent characteristics. In spite of considerable adsorption performance, low-cost
adsorbents seek for proper studies in terms of technicality and overall process efficiency to be commercialized.
Acknowledgments The first author expresses appreciation to all co-authors for their contribution
in literature review.
M. Maharana et al.