Review of Treatment Technologies for the Removal of Phenol from Wastewaters

Phenol is an important chemical used in many industries as a raw material, such as, pharmaceutical and rubber, oil and petroleum refineries, pulp and paper manufacturing plants, iron and steel, etc. Phenol and its derivatives are one of the largest groups of environmental pollutants owing to their presence in many industrial effluents because of their widespread use. In addition, leakage accidents that occur during the transportation and storage of phenol cause contamination of the water resources with phenol. It is in the list of priority pollutants of US Environmental Protection Agency (EPA) and it has toxic, carcinogenic and mutagenic effects on humans, animals and aquatic organisms. Therefore, wastewaters containing phenol should be treated before discharge due to its high toxicity even at low concentrations. Over the last decade, the treatment of wastewater contaminated with phenol and phenolic compounds has attracted great attention due to their toxicity and low biodegradability properties. Several treatment processes are used to remove and/or recover phenol and phenolic compounds from wastewaters in the literature and all of them have some advantages and drawbacks. In this review, an extensive research has been carried out to investigate the available treatment technologies for the removal/recovery of phenol and phenolic compounds from industrial wastewaters. Studies on phenol removal by distillation, extraction, adsorption, membrane processes, oxidation and biological treatment processes are summarized and discussed in detailed. In addition, operational problems and the latest improvements of these processes are pointed out based on the removal efficiencies. The initial phenol concentration is found to be a critical parameter for the selection of treatment method. For all treatment processes, recent studies are focused on to overcome high operational costs while providing increases in removal efficiency. Among the treatment processes, adsorption is still found to be the most effective process and a list of adsorbents for phenol removal is also presented.