222
8.5 Conclusion
The Earth’s crust naturally consists of heavy metals (including Pt, Pd, Ag, Cu, Cd,
etc.) and their components. Abrasion and dissolution of mother rocks also contribute to their presence in the environment. In addition to natural sources, these pollutants also enter in ecosystems through wastewaters generating from human-induced
activities such as the operation of chemical preparing and tanning and from various
industries such as leather industries, electronic and electric industries, etc. Some of
the organic pollutants are vulnerable toward biological degradation, but metal ions
cannot degenerate into harmless end product and are persistent in the environment.
These pollutants are the chief source of environmental pollution, and their removal
from various environmental components is necessary. These metallic ions (toxic
elements) even in less concentration pollute drinking water and can be easily accumulated by living organisms (human body), causing different lethal disorders and
illnesses. Therefore, it is inevitable to eliminate these toxicants from industrial slug
and wastewater. A large number of approaches such as coagulation, solvent extraction, chemical and electrochemical techniques, ultrafiltration, and reverse osmosis
have been used for the removal of toxicants. However, most of these processes are
unsuitable and unsatisfactory due to the disposal of dirt, their excessive operational
price, less productivity, and less effectiveness. Additionally, they are not applicable
for large number of pollutants, and are less efficient for the treatment of small quantity of metal ions and other treatment problems because of continuous production of
toxic sludge hinder their effective utilization for wastewater treatment. The process
of adsorption is one of the most popular, convenient, superior, and beneficial strategies above any other processes for the treatment of polluted industrial effluents and
removal of contamination from water supplies.
The main advantage of adsorption is the regeneration of sorbents with appropriate desorption process, and most of such regenerations need low maintenance cost
with excess efficiency and is easy to operate. Various conventional and nonconventional adsorbents are used for this purpose such as activated carbon, activated alumina, carbon nanotubes, polymer clay composite, metal oxide-based nanoadsorbents,
clays, zeolites, lignin, chitosan, eggshell, etc. The main downside related to these
sorbents including their small sorption potential comparatively poor complexation
with toxicants. Recent endeavors are devoted to using agricultural waste as low-cost
adsorbent. There are many kinds of agricultural waste such as rise husk, coconut
husk, hazelnut, sawdust of maple, peanut, cotton seeds, walnut, black locust and
oaks, pecan, soybeans, and corncobs that have been reported as promising materials. Round nutshells in natural or altered form were also used for nickel removal
from aqueous media. Literature showed that chromium adsorption rate using agricultural waste is quite high and ranged from 50–100%. Similar excellent results
were obtained for other heavy metal remediation using low-cost agricultural waste
adsorbents.
A. Sabir et al.
8.5 Conclusion
The Earth’s crust naturally consists of heavy metals (including Pt, Pd, Ag, Cu, Cd,
etc.) and their components. Abrasion and dissolution of mother rocks also contribute to their presence in the environment. In addition to natural sources, these pollutants also enter in ecosystems through wastewaters generating from human-induced
activities such as the operation of chemical preparing and tanning and from various
industries such as leather industries, electronic and electric industries, etc. Some of
the organic pollutants are vulnerable toward biological degradation, but metal ions
cannot degenerate into harmless end product and are persistent in the environment.
These pollutants are the chief source of environmental pollution, and their removal
from various environmental components is necessary. These metallic ions (toxic
elements) even in less concentration pollute drinking water and can be easily accumulated by living organisms (human body), causing different lethal disorders and
illnesses. Therefore, it is inevitable to eliminate these toxicants from industrial slug
and wastewater. A large number of approaches such as coagulation, solvent extraction, chemical and electrochemical techniques, ultrafiltration, and reverse osmosis
have been used for the removal of toxicants. However, most of these processes are
unsuitable and unsatisfactory due to the disposal of dirt, their excessive operational
price, less productivity, and less effectiveness. Additionally, they are not applicable
for large number of pollutants, and are less efficient for the treatment of small quantity of metal ions and other treatment problems because of continuous production of
toxic sludge hinder their effective utilization for wastewater treatment. The process
of adsorption is one of the most popular, convenient, superior, and beneficial strategies above any other processes for the treatment of polluted industrial effluents and
removal of contamination from water supplies.
The main advantage of adsorption is the regeneration of sorbents with appropriate desorption process, and most of such regenerations need low maintenance cost
with excess efficiency and is easy to operate. Various conventional and nonconventional adsorbents are used for this purpose such as activated carbon, activated alumina, carbon nanotubes, polymer clay composite, metal oxide-based nanoadsorbents,
clays, zeolites, lignin, chitosan, eggshell, etc. The main downside related to these
sorbents including their small sorption potential comparatively poor complexation
with toxicants. Recent endeavors are devoted to using agricultural waste as low-cost
adsorbent. There are many kinds of agricultural waste such as rise husk, coconut
husk, hazelnut, sawdust of maple, peanut, cotton seeds, walnut, black locust and
oaks, pecan, soybeans, and corncobs that have been reported as promising materials. Round nutshells in natural or altered form were also used for nickel removal
from aqueous media. Literature showed that chromium adsorption rate using agricultural waste is quite high and ranged from 50–100%. Similar excellent results
were obtained for other heavy metal remediation using low-cost agricultural waste
adsorbents.
A. Sabir et al.