**2. Classification of phenolic compounds**

Phenolic compounds are a class of organic compounds with a hydroxyl group(s) directly bonded to one or more aromatic rings. The first member of chemicals belonging to this cat‐ egory of organic compounds is called phenol, also known as carbolic acid, benzophenol or hydroxybenzene with the chemical formula of C6 H5 OH (**Figure 1**). All other members of the group are derivatives of phenol [6].

Phenolic compounds are classified into different groups based on different factors. Among these factors of categorisation are the carbon chain, basic phenolic skeleton or the number of phenol units present in the molecule, distribution in nature and location in plants.

Phenolic Compounds in Water: Sources, Reactivity, Toxicity and Treatment Methods http://dx.doi.org/10.5772/66927 421

**Figure 1.** Structure of phenol.

abundant in nature and are associated with the colours of flowers and fruits [2]. Others are

The entrance of phenolic compounds into the aquatic environment results from natural, industrial, domestic and agricultural activities. Their presence may be due to the degrada‐ tion or decomposition of natural organic matter present in the water, through the disposal of industrial and domestic wastes into water bodies and through runoffs from agricultural lands [3]. These chemicals, upon entry into the water, have the tendency of undergoing transforma‐ tions into other moieties that can even be more harmful than the original compounds. This transformation is normally due to their interaction with physical, chemical and biological or

Phenolic compounds have been enlisted by the United States Environmental Protection Agency (USEPA) and the European Union (EU) as pollutants of priority concern. This enlist‐ ment is due to the fact that these chemicals are noted to be toxic and have severe short‐ and long‐term effects on humans and animals [5]. The occurrence of phenolic compounds in the aquatic environment is therefore not only objectionable and undesirable but also poses a dan‐ ger as far as human health and wildlife are concerned. As a result, a number of wastewater treatment techniques have been developed and used for the removal of phenolic compounds from industrial, domestic and municipal wastewaters prior to their disposal into water bodies so as to minimise the devastating effects of these chemicals on human and aquatic lives. Some of these techniques include extraction, polymerisation, electro‐Fenton process, photocatalytic

This chapter presents a general overview of selected topics in relation to phenolic compounds. It dwells on the sources and reactivity of phenolic compounds in water, their toxic effects on humans and methods of their removal from water. Specific emphasis is placed on the tech‐ niques of their removal from water with attention on both conventional and advanced meth‐ ods. Among these methods are adsorption, extraction, polymerisation, electro‐coagulation, photocatalytic degradation, biological methods, electro‐Fenton method, advanced oxidation processes, adsorption and ion exchange and membrane‐based separation techniques.

Phenolic compounds are a class of organic compounds with a hydroxyl group(s) directly bonded to one or more aromatic rings. The first member of chemicals belonging to this cat‐ egory of organic compounds is called phenol, also known as carbolic acid, benzophenol or

Phenolic compounds are classified into different groups based on different factors. Among these factors of categorisation are the carbon chain, basic phenolic skeleton or the number of

phenol units present in the molecule, distribution in nature and location in plants.

H5

OH (**Figure 1**). All other members of the

synthesised and are used in varied aspects of mankind's everyday life.

420 Phenolic Compounds - Natural Sources, Importance and Applications

microbial factors in the water [4].

degradation and so on.

**2. Classification of phenolic compounds**

hydroxybenzene with the chemical formula of C6

group are derivatives of phenol [6].
