ReviewUse of iron oxide nanomaterials in wastewater treatment: A review
Highlights
► The review outlined latest applications of iron oxide nonmaterials in wastewater treatment. ► The outlook for potential applications and further challenges was also provided. ► The likely fate of the nanomaterials discharged to the environment was addressed.
Introduction
The spread of a wide range of contaminants in surface water and groundwater has become a critical issue worldwide, due to population growth, rapid development of industrialization and long-term droughts (Cundy et al., 2008, Chong et al., 2010, Zeng et al., 2011). It is thus of necessity to control the harmful effects of contaminants and improve the human living environment. Contaminants persisting in wastewater include heavy metals, inorganic compounds, organic pollutants, and many other complex compounds (O'Connor, 1996, Fatta et al., 2011, Li et al., 2011). All of these contaminants releasing into the environment through wastewater are harmful to human beings and ecological environment. Consequently, the need for contaminants removal has become a must (Jiang et al., 2006, Huang et al., 2010, Pang et al., 2011a).
In an effort to combat the problem of water pollution, rapid and significant progresses in wastewater treatment have been made, including photocatalytic oxidation, adsorption/separation processing and bioremediation (Huang et al., 2006a, Zelmanov and Semiat, 2008, Long et al., 2011, Pang et al., 2011a, Pang et al., 2011b). However, their applications have been restricted by many factors, such as processing efficiency, operational method, energy requirements, and economic benefit. Recently, nanomaterials (NMs) have been suggested as efficient, cost-effective and environmental friendly alternative to existing treatment materials, from the standpoints of both resource conservation and environmental remediation (Friedrich et al., 1998, Dimitrov, 2006, Dastjerdi and Montazer, 2010).
Nanotechnology holds out the promise of immense improvements in manufacturing technologies, electronics, telecommunications, health and even environmental remediation (Gross, 2001, Kim et al., 2005, Moore, 2006). It involves the production and utilization of a diverse array of NMs, which include structures and devices with the size ranging from 1 to 100 nm and displays unique properties not found in bulk-sized materials (Stone et al., 2010, Wang et al., 2010). Several kinds of nanomaterials, such as carbon-based NMs (Mauter and Elimelech, 2008, Upadhyayula et al., 2009) and TiO2 NMs (Khan et al., 2002, Shankar et al., 2009), have been widely studied and extensively reviewed. However, iron oxide-based NMs need to be studied in greater detail.
This review evaluates the important properties of iron oxide NMs. It highlights not only recent developments in the application of iron oxide NMs for wastewater treatment, but also gaps which limited their large-scale field application. Primary attention is given to recent development in the utilization of iron oxide NMs as nanosorbents, followed by critical discussion on their application as photocatalysts. Furthermore, the practical potential of iron oxide based immobilization technology for improving pollutant removal efficiency is elaborated. The likely fate of NMs discharged in the environment and associated remediation method are also discussed. A detailed description of synthesis method, properties and characterization of iron oxide NMs is beyond the scope of this article, but can be found in Laurent et al. (2008) and Teja and Koh (2009). The structure of this review is illustrated in Fig. 1.
Section snippets
Iron oxide nanomaterials
Iron oxides exist in many forms in nature. Magnetite (Fe3O4), maghemite (γ-Fe2O3), and hematite (α-Fe2O3) are the most common forms (Cornel and Schwertmann, 1996, Chan and Ellis, 2004). In recent years, the synthesis and utilization of iron oxide NMs with novel properties and functions have been widely studied, due to their size in nano-range, high surface area to volume ratios and superparamagnetism (McHenry and Laughlin, 2000, Afkhami et al., 2010, Pan et al., 2010). Particularly, the easy
Iron oxide nanomaterials in wastewater treatment
Selection of the best method and material for wastewater treatment is a highly complex task, which should consider a number of factors, such as the quality standards to be met and the efficiency as well as the cost (Huang et al., 2008, Oller et al., 2011). Therefore, the following four conditions must be considered in the decision on wastewater treatment technologies: (1) treatment flexibility and final efficiency, (2) reuse of treatment agents, (3) environmental security and friendliness, and
Iron oxide nanomaterials in environment
It is recognized that there are many potentially serious issues concerning the environmental fate of engineered NMs and their potential impacts on human health. Currently, there are very few information on the background concentrations and physical–chemical forms of NMs in the environment due to limitations in separation and analytical methodologies, although some laboratory based studies have been carried out. However, such information is urgently required and a major advance in knowledge
Conclusions
Wastewater treatment and reuse is a practice related not only to a number of benefits in regards to water balances and management but also to a number of question marks. Immediate research must be launched towards this direction so as to safeguard human health and environmental ecosystems. Nanomaterials, with unique physical and chemical properties, have a tremendous potential for contaminants removal. To bring the NMs development a step forward, NMs prioritization and further application
Acknowledgments
The study was financially supported by the Programs for Changjiang Scholars and Innovative Research Team in University (IRT0719), the National Natural Science Foundation of China (50808073, 50978088, 51039001), the Hunan Key Scientific Research Project (2009FJ1010), the Environmental Protection Technology Research Program of Hunan (2007185), the Hunan Provincial Natural Science Foundation of China (10JJ7005) and the New Century Excellent Talents in University (NCET-08-0181).
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