**1. Introduction**

Mitoxantrone and Toxicological Evaluation. Environmental Science and Pollution

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166 Organic Pollutants - Monitoring, Risk and Treatment

Organic pollution is the term used when large quantities of organic compounds. It origi‐ nates from domestic sewage, urban run-off, industrial effluents and agriculture wastewater. sewage treatment plants and industry including food processing, pulp and paper making, agriculture and aquaculture. During the decomposition process of organic pollutants the dissolved oxygen in the receiving water may be consumed at a greater rate than it can be replenished, causing oxygen depletion and having severe consequences for the stream biota. Wastewater with organic pollutants contains large quantities of suspended solids which re‐ duce the light available to photosynthetic organisms and, on settling out, alter the character‐ istics of the river bed, rendering it an unsuitable habitat for many invertebrates. Organic pollutants include pesticides, fertilizers, hydrocarbons, phenols, plasticizers, biphenyls, de‐ tergents, oils, greases, pharmaceuticals, proteins and carbohydrates [1-3].

Toxic organic pollutants cause several environmental problems to our environment. The most common organic pollutants named persistent organic pollutants (POPs). POPs are compounds of great concern due to their toxicity,persistence, long-range transport ability [4] and bioaccumulation in animals [5], travel long distances and persist in living organisms. POPs are carbon-based chemical compounds and mixtures (twelve pollutants) that include industrial chemicals such as polychlorinated biphenyls (PCBs),polychlorinated dibenzo-pdioxins and dibenzofurans (PCDD/Fs), and some organochlorine pesticides (OCPs), such as hexachlorobenzene (HCB) or dichloro-diphenyl-trichloroethane (DDT), dibenzo-p-dioxins (dioxins) and dibenzo-p-furans (furans) [6]. PCDD/Fs are released to the environment as byproducts of several processes, like waste incineration or metal production [7]. Many of these compounds have been or continue to be used in large quantities and due to their environ‐ mental persistence, have the ability to bioaccumulate and biomagnify [8].

© 2013 Rashed; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Rashed; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Efficient techniques for the removal of highly toxic organic compounds from water have drawn significant interest. A number of methods such as coagulation, filtration with coagu‐ lation, precipitation, ozonation, adsorption, ion exchange, reverse osmosis and advanced ox‐ idation processes have been used for the removal of organic pollutants from polluted water and wastewater. These methods have been found to be limited, since they often involve high capital and operational costs. On the other hand ion exchange and reverse osmosis are more attractive processes because the pollutant values can be recovered along with their re‐ moval from the effluents. Reverse osmosis, ion exchange and advanced oxidation processes do not seem to be economically feasible because of their relatively high investment and op‐ erational cost.

ent is minimum). The adsorption amount (qe, mmol g−1) of the molecules at the equilibrium

where V is the solution volume (L); M is the mass of monolithic adsorbents (g); and Co and

Other definition of adsorption is a mass transfer process by which a substance is transferred from the liquid phase to the surface of a solid, and becomes bound by physical and/or chemical interactions. Large surface area leads to high adsorption capacity and surface reactivity [10].

An adsorption isotherm is the presentation of the amount of solute adsorbed per unit weight of adsorbent as a function of the equilibrium concentration in the bulk solution at constant temperature. Langmuir and Freundlich adsorption isotherms are commonly used

Where *Ce* is the equilibrium concentration of solute (mmol L−1), *qe* is the amount of solute adsorbed per unit weight of adsorbent (mmol g−1 of clay), *Xm* is the adsorption capacity

The Freundlich isotherm describes heterogeneous surface adsorption. The energy distribu‐ tion for adsorptive sites (in Freundlich isotherm) follows an exponential type function which is close to the real situation. The rate of adsorption/desorption varies with the strength of the

Different types of adsorbents are classified into natural adsorbents and synthetic adsorbents. Natural adsorbents include charcoal, clays, clay minerals, zeolites, and ores. These natural materials, in many instances are relatively cheap, abundant in supply and have significant potential for modification and ultimately enhancement of their adsorption capabilities. Syn‐

(mmol g−1), or monolayer capacity, and *b* is a constant (L mmol−1 ).

energy at the adsorptive sites. The Freundlich equation is expressed as:

Where *k* (mmol g−1) and 1*/n* are the constant characteristics of the system [11].

Ce are the initial and equilibrium adsorbate concentrations, respectively.

qe = V Co-Ce /M ( ) (1)

http://dx.doi.org/10.5772/54048

169

Adsorption Technique for the Removal of Organic Pollutants from Water and Wastewater

*Ce qe bXm Ce Xm* / 1 / / , = + (2)

*logqe logk n logCe* = + 1 / , (3)

step was determined according to the following equation:

**2.1. Adsorption isotherms and models**

for the description of adsorption data. The Langmuir equation is expressed as:

**3. Types of adsorbents**

Among the possible techniques for water treatments, the adsorption process by solid adsorb‐ ents shows potential as one of the most efficient methods for the treatment and removal of or‐ ganic contaminants in wastewater treatment. Adsorption has advantages over the other methods because of simple design and can involve low investment in term of both initial cost and land required. The adsorption process is widely used for treatment of industrial wastewa‐ ter from organic and inorganic pollutants and meet the great attention from the researchers. In recent years, the search for low-cost adsorbents that have pollutant –binding capacities has in‐ tensified. Materials locally available such as natural materials, agricultural wastes and industri‐ al wastes can be utilized as low-cost adsorbents. Activated carbon produced from these materials can be used as adsorbent for water and wastewater treatment [9].
