Page 356 - Industrial Wastewater Treatment, Recycling and Reuse

328 Industrial Wastewater Treatment, Recycling, and Reuse

3. Lower sensitivity to process variation.
4. Greater efficiency.
5. Insensitivity to toxic pollutants.
6. No formation of harmful substances.
7. Wider applicability because it can remove or minimize different types of
pollutants.
The adsorption process can be either physical or chemical in nature. Physical
adsorption involves weak forces that are reversible and occur mostly at low
temperatures. On the other hand, chemisorption or chemical activation
occurs at high temperatures, involving significant activation energy along
with the participation of strong chemical bonds that are usually irreversible
in nature. Activated carbon (AC) is one of the most widely used adsorbents
for the removal of organic contaminants from wastewater that is refractory
or biologically resistant in nature. The large surface area, high adsorption
capacity, and high surface reactivity are the positive points. The problem
of high initial cost of AC or polymeric adsorbents/specialty materials
coupled with the problems of regeneration has necessitated the use/search
for alternative adsorbents. Newer materials derived from biomass can be
substantially effective in this regard.
The conventional treatment technologies implemented in industrialized
nations are expensive to build, operate, and maintain in developing coun-
tries. The present research is one such effort to develop affordable treatment
technologies particularly important for developing and underdeveloped
countries. Thus, in spite of several technologies available, our main focus
is on adsorption technology and development of newer low-cost adsorbent
materials for application in phenolic wastewater treatment. This chapter
reviews developments in this regard with new data and analysis.

8.2 NEWER ADSORBENTS AND THE POTENTIAL FOR THEIR
APPLICATION IN PHENOLIC WASTEWATER TREATMENT
Wastewater treatment using the adsorption technique has been a subject of
much exciting research and various novel materials. Low-cost adsorbents
have been proposed for a myriad variety of toxic chemicals in wastewater.
Existing and developed materials can be further modified to increase capac-
ity or activity by means of several pretreatment/activation methods that
result in much greater efficacy in their applications. AC, owing to its high
surface area and porosity, is certainly a near-perfect candidate for treatment
of almost all kinds of contaminants. But the limitation of huge capital