Removal of phenols and dyes from aqueous solutions using graphene and graphene composite adsorption: A review

In recent years, there has been growing awareness that by 2050, many countries will experience critical issues related to water scarcity. The need to recycle/reuse wastewater after pollution treatment is a major concern worldwide for ensuring water security at the national level. Treatment technologies to remove major pollutants, namely, heavy metals, anionic impurities and the vast range of organic compounds, have received substantial attention from the scientific community. Water resource pollution is increasing due to an increasing world population and its corresponding activities. Amongst the different technologies used to decrease pollutant levels in water, adsorption technology is highly effective even at low pollutant concentrations. Carbonaceous materials and their composites have been widely used due to their unique surface properties and high adsorption capacities, but better adsorbents with higher pollutant adsorption capacities and faster uptake are still needed. Recently, the development of graphene-based adsorbents, with their highly active surfaces and large surface areas, has created much excitement. Therefore, an updated review is needed to summarize this graphene research. This review provides a summary of the literature in the field of adsorptive removal of organics from water, with a focus on phenols and dyestuffs. The synthesis methods, characterization techniques, adsorption behaviors, experimental parameters, mechanisms, thermodynamics, the effect of coexisting ions and regeneration–desorption processes are considered. Finally, research challenges and knowledge gaps – limited regeneration and solute recovery studies, the behavior of mixed pollutants effluents, designing graphenic adsorbents for specific pollutants, treatment system economic analyses - in the field are discussed.