26
A. A. Inyinbor et al.
from casein [109–112]. Reverse osmosis has found relevance in the purification of
portable water contaminated with different salts, heavy metals, dyes and it is also
gaining relevance in the industries. Reverse osmosis was used in the reclamation of
municipal wastewater where secondary effluent was treated [113]. Effective sequestration of hazardous cationic and anionic pollutants has been reported using reverse
osmosis and some functionalized adsorbents as fillers [114]. Al-Bastaki [115] also
investigated the uptake of methyl orange dye together with Na 2 SO 4 salt from artificial
wastewater utilizing reverse osmosis [115]. Despite the application of the method,
the disadvantage is that it is expensive to purify a large volume of water.
6.2 Electrodialysis
This is an electrochemical process involving the separation of salt from water by
ion transfer. This technique is only effective in the removal of ionizable species, for
instance, common salt (NaCl) which exists in solution as Na
+ and Cl
− . Some species,
such as silica, which does not ionize are unaffected by electrodialysis, but can be
removed by reverse osmosis. The knowledge of electrolysis plays out vividly in electrodialysis. Here, however, filters or membranes are used interspaced and alternately
between the electrodes. Positively charged filters will allow the free flow of negative
ions while hindering cations. In the same manner, negatively charged filters allow
the free flow of positives ions and hinders anions. Series of a compartment within
the tank stores the separated ions. Hence, cells with increased salts concentration are
in alternate arrangement with cells depleting the salts. Desalinated water then flows
for collection. Electrodialysis is a good technique in brackish water treatment, but
has not been employed in well explored for desalination of seawater for economic
reasons [116].
6.3 Ion Exchange
Production of potable water from wastewater using ion exchange has been explored
in recent times as an alternative to conventional treatment techniques. This process is
simple and does not require energy for its operation [117]. The ion exchange attracts
pollutants with the opposite charge for ease of removal and treatment of wastewater.
For instance, an anion pollutant attracts a cationic ion exchange material. Various
natural and synthetic materials can be used to exchange ions thus softening hard
waters and treatment of polluted water [118]. Biomasses are a form of natural ion
exchanger, biodegradable in nature and originate from animal residues, agriculturalbased residue, microbes and wood amongst others. Biomasses are readily available
and easy of disposal due to its high level of biodegradability. Clays with high iron and
aluminum content are good ion exchange adsorbent. It can be easily acquired, and it is
characterized by good hydrodynamic properties [119]. Resins, one of the foremost
A. A. Inyinbor et al.
from casein [109–112]. Reverse osmosis has found relevance in the purification of
portable water contaminated with different salts, heavy metals, dyes and it is also
gaining relevance in the industries. Reverse osmosis was used in the reclamation of
municipal wastewater where secondary effluent was treated [113]. Effective sequestration of hazardous cationic and anionic pollutants has been reported using reverse
osmosis and some functionalized adsorbents as fillers [114]. Al-Bastaki [115] also
investigated the uptake of methyl orange dye together with Na 2 SO 4 salt from artificial
wastewater utilizing reverse osmosis [115]. Despite the application of the method,
the disadvantage is that it is expensive to purify a large volume of water.
6.2 Electrodialysis
This is an electrochemical process involving the separation of salt from water by
ion transfer. This technique is only effective in the removal of ionizable species, for
instance, common salt (NaCl) which exists in solution as Na
+ and Cl
− . Some species,
such as silica, which does not ionize are unaffected by electrodialysis, but can be
removed by reverse osmosis. The knowledge of electrolysis plays out vividly in electrodialysis. Here, however, filters or membranes are used interspaced and alternately
between the electrodes. Positively charged filters will allow the free flow of negative
ions while hindering cations. In the same manner, negatively charged filters allow
the free flow of positives ions and hinders anions. Series of a compartment within
the tank stores the separated ions. Hence, cells with increased salts concentration are
in alternate arrangement with cells depleting the salts. Desalinated water then flows
for collection. Electrodialysis is a good technique in brackish water treatment, but
has not been employed in well explored for desalination of seawater for economic
reasons [116].
6.3 Ion Exchange
Production of potable water from wastewater using ion exchange has been explored
in recent times as an alternative to conventional treatment techniques. This process is
simple and does not require energy for its operation [117]. The ion exchange attracts
pollutants with the opposite charge for ease of removal and treatment of wastewater.
For instance, an anion pollutant attracts a cationic ion exchange material. Various
natural and synthetic materials can be used to exchange ions thus softening hard
waters and treatment of polluted water [118]. Biomasses are a form of natural ion
exchanger, biodegradable in nature and originate from animal residues, agriculturalbased residue, microbes and wood amongst others. Biomasses are readily available
and easy of disposal due to its high level of biodegradability. Clays with high iron and
aluminum content are good ion exchange adsorbent. It can be easily acquired, and it is
characterized by good hydrodynamic properties [119]. Resins, one of the foremost