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Top1. Introduction
Phenol is a colourless, hygroscopic and crystalline substance, which turns pink in air owing to its oxidation. It is a derivative of benzene, is an important raw material and/or product of chemical and allied industries (e.g. petrochemicals, oil refineries, plastics, leather, paint, pharmaceutical, steel industries, pesticides, antiseptics, dyes, antirust products, synthetic resins, biocides, photographic chemicals, ink, varnishes, etc.) (Kujawski et al., 2004; Adak et al., 2006). Phenol includes a variety of hydroxybenzenes and substituted hydroxybenzenes. These are common water pollutants. The major sources containing phenols are the wastewaters from processing manufacturing industries engaged in oil refining, coal tar processing, petrochemical production, coke oven byproducts, plastic industry, ceramic plants, textile processing, leather processing, synthetic rubber processing, pesticides & insecticides production, manufacture of dyes and dyeing, pharmaceutical, steel industries, glass production, phenolic resin industries etc. (Singh et al., 2008; Goud et al., 2005; Mohanty et al., 2008).
Phenolic compounds are water soluble and highly mobile and hence are likely to reach drinking water sources downstream from discharges, where, even at low concentrations, they can cause severe odour and taste problems and pose risks to populations. Phenols may also come to the environment through the agricultural runoff and domestic waste (Burleigh et al., 2002; Hairuddin et al., 2019; Karri et al., 2017; Karri et al., 2017). Chronic toxic effects due to phenols reported in humans include vomiting, difficulty in swallowing, anorexia, liver and kidney damage, headache, fainting and other mental disturbances. That phenol is highly toxic and difficult to degrade biologically have led to setting up of rigid limits on the acceptable level of phenol in the environment. According to the recommendation of World Health Organization (WHO), the permissible concentration of phenolic contents in potable waters is 1 μg L−1 (Schulze, 1986) and the regulations by the Environmental Protection Agency (EPA), call for lowering phenol content in wastewaters less than 1 mg L−1 (Dutta et al., 1998).
The presence of phenols and phenolic compounds in wastewater is a major problem for adverse effects on aquatic life and stringent environmental regulations attracts the attention of chemists and environmental engineers for its control (Shyamala, 2016; Shayamala, 2017; Ayawei et al., 2015; Theivarasu & Mylsamy 2011). Therefore, removal of phenols from waters and wastewaters is an important issue in order to protect public health and environment.