A review on the adsorption of phenols from wastewater onto diverse groups of adsorbents

Phenol and its derivatives are used in numerous industrial processes; these compounds are highly toxic and corrosive, classified as priority pollutants. One of the effective processes for the removal of phenols is adsorption. Numerous and various adsorbents in nature have been researched for this purpose in the past decade. Their adsorption capacities vary from 1 to >1000 mg/g, and are influenced by such factors as the adsorbent's surface area, pH, temperature, concentration of phenol and surface functional groups, contact time, etc. In this review, adsorbents tested for the removal of phenol and phenol compounds have been classified into four groups: carbonaceous adsorbents, clay and natural mineral adsorbents, polymer-based adsorbents, and novel adsorbents. The highest adsorption capacities were attained by polymer-based adsorbents (>1000 mg/g), whereas natural clays and novel adsorbents showed adsorption capacities of the lower range as compared to the carbonaceous adsorbents. The major advantage of phenol adsorption over other applicable processes is the high potential for phenol recovery and reuse.