Environ Sci Pollut Res DOI 10.1007/s11356-014-3809-4
RESEARCH ARTICLE
Organic additives enhance Fenton treatment of nitrobenzene at near-neutral pH Gang Xie & Lincheng Zhou & Weijie Gao & Yanfeng Li
Received: 29 July 2014 / Accepted: 2 November 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract Nitrobenzene (NB) is considered a toxic and potential carcinogen. Continuous contamination has resulted in an urgent need for remediation. Fenton reagent provides an advanced oxidation process that is capable of remediating recalcitrant nitroaromatic compounds, such as NB. However, one drawback of Fenton chemistry is that the reaction requires acidic pH to prevent precipitation of iron. Our studies have investigated Fenton conversion of NB at near-neutral pH with several organic additives: β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (HPCD), carboxymethyl-βcyclodextrin (CMCD), and polyethylene glycol (molecular weight (MW)=200, 400, and 600) for developing a process for treating NB-contaminated waters. The main factors influencing NB conversion, such as iron concentration, hydroxyl radicals (·OH) scavengers, and kinds or concentration of organic additives, were examined. Meanwhile, the reactive mechanisms and kinetics were investigated for Fenton conversion of NB. The results show that organic additives for Fenton process should be a good alternative for the advanced treatment of NB at near-neutral pH. Responsible editor: Philippe Garrigues G. Xie : L. Zhou : W. Gao : Y. Li (*) State Key Laboratory of Applied Organic Chemistry, College of Resources and Environment, Institute of Biochemical Engineering and Environmental Technology, Lanzhou University, Lanzhou 730000, People’s Republic of China e-mail: [email protected] G. Xie : L. Zhou : W. Gao : Y. Li State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Institute of Biochemical Engineering and Environmental Technology, Lanzhou University, Lanzhou 730000, People’s Republic of China G. Xie Center of Forecasting and Analysis, College of Petrochemical Engineering, Lanzhou University of Technology, Lanzhou 730050, People’s Republic of China
Keywords Fenton . Organic additives . Advanced oxidation processes (AOPs) . Nitrobenzene
Introduction Nitrobenzene (NB) is an important reagent widely used as a raw material in several industrial processes related to pesticides, explosives, colorants, and paper pulp production (Carlos et al. 2008). As a toxic and suspected carcinogenic compound, NB has been on the US Environmental Protection Agency (EPA) priority pollutant list and its maximum allowable concentration is 1 mg L−1 in wastewaters (Majumder and Gupta 2003), even lower concentration values are demanded. Nowadays, the industrial wastewater laden with NB has severely polluted the environment and poses a great threat to human health (Jing and Xu 2004; Lu 2004; Xu and Jing 2002), especially in developing countries. For example, April 11, 2014, Lanzhou, the capital of northwest China’s Gansu Province, was suffered from major drinking water pollution owing to underground water mixed with residual oil in the duct that is located near a subsidiary of China National Petroleum Corp. Tests at a water plant at 8:30 a.m. on the same day showed that tap water contained 160 mg L−1 of benzene, much more than the national limit of 10 mg L−1, resulting in panic among the citizens (Xu and Xu 2014). Since the electron-withdrawing nitro groups inhibit the bioconversion of nitro-substituted aromatic compounds (Bruhn et al. 1987), conventional biological approaches are ineffective in treating NB-rich wastewater. Therefore, researchers have made intense efforts to develop efficient and cost-effective methods for NB conversion (Bhatkhande et al. 2005; Chamarro et al 2001; Liu et al. 2012; Mantha et al. 2001; Mu et al. 2004; Zhao et al. 2009; Zhang et al. 2007). Fenton reagent is an aqueous solution with ferrous iron (Fe2+) and hydrogen peroxide (H2O2) for generation of
Environ Sci Pollut Res
hydroxyl radicals (·OH) (Eq. (1), Table 1). Due to the strong oxidizing potential of the ·OH, Fenton reagent has been considered to be an advanced oxidation process (AOP) capable of conversion of a wide variety of toxic pollutants, such as polycyclic aromatic hydrocarbons, chlorinated aromatic and aliphatic compounds, and nitroaromatic compounds (Hess et al. 2003; Li et al. 1997; Matta et al. 2007; Przado et al. 2007; Teel and Watts 2002), which are difficult to be removed by biological processes (Parsons 2004). The biggest limitation to the Fenton’s reagent is that Fe3+ precipitates out to amorphous ferric oxyhydroxides. Precipitation of Fe3+ reduces the amount of available Fe3+ which in turn reduces the amount to recycled Fe2+. Without the recycled Fe2+, the production of hydroxyl radical ceases. Therefore, Fenton reactions are most effective under conditions of low pH (
RESEARCH ARTICLE
Organic additives enhance Fenton treatment of nitrobenzene at near-neutral pH Gang Xie & Lincheng Zhou & Weijie Gao & Yanfeng Li
Received: 29 July 2014 / Accepted: 2 November 2014 # Springer-Verlag Berlin Heidelberg 2014
Abstract Nitrobenzene (NB) is considered a toxic and potential carcinogen. Continuous contamination has resulted in an urgent need for remediation. Fenton reagent provides an advanced oxidation process that is capable of remediating recalcitrant nitroaromatic compounds, such as NB. However, one drawback of Fenton chemistry is that the reaction requires acidic pH to prevent precipitation of iron. Our studies have investigated Fenton conversion of NB at near-neutral pH with several organic additives: β-cyclodextrin (β-CD), hydroxypropyl-β-cyclodextrin (HPCD), carboxymethyl-βcyclodextrin (CMCD), and polyethylene glycol (molecular weight (MW)=200, 400, and 600) for developing a process for treating NB-contaminated waters. The main factors influencing NB conversion, such as iron concentration, hydroxyl radicals (·OH) scavengers, and kinds or concentration of organic additives, were examined. Meanwhile, the reactive mechanisms and kinetics were investigated for Fenton conversion of NB. The results show that organic additives for Fenton process should be a good alternative for the advanced treatment of NB at near-neutral pH. Responsible editor: Philippe Garrigues G. Xie : L. Zhou : W. Gao : Y. Li (*) State Key Laboratory of Applied Organic Chemistry, College of Resources and Environment, Institute of Biochemical Engineering and Environmental Technology, Lanzhou University, Lanzhou 730000, People’s Republic of China e-mail: [email protected] G. Xie : L. Zhou : W. Gao : Y. Li State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Institute of Biochemical Engineering and Environmental Technology, Lanzhou University, Lanzhou 730000, People’s Republic of China G. Xie Center of Forecasting and Analysis, College of Petrochemical Engineering, Lanzhou University of Technology, Lanzhou 730050, People’s Republic of China
Keywords Fenton . Organic additives . Advanced oxidation processes (AOPs) . Nitrobenzene
Introduction Nitrobenzene (NB) is an important reagent widely used as a raw material in several industrial processes related to pesticides, explosives, colorants, and paper pulp production (Carlos et al. 2008). As a toxic and suspected carcinogenic compound, NB has been on the US Environmental Protection Agency (EPA) priority pollutant list and its maximum allowable concentration is 1 mg L−1 in wastewaters (Majumder and Gupta 2003), even lower concentration values are demanded. Nowadays, the industrial wastewater laden with NB has severely polluted the environment and poses a great threat to human health (Jing and Xu 2004; Lu 2004; Xu and Jing 2002), especially in developing countries. For example, April 11, 2014, Lanzhou, the capital of northwest China’s Gansu Province, was suffered from major drinking water pollution owing to underground water mixed with residual oil in the duct that is located near a subsidiary of China National Petroleum Corp. Tests at a water plant at 8:30 a.m. on the same day showed that tap water contained 160 mg L−1 of benzene, much more than the national limit of 10 mg L−1, resulting in panic among the citizens (Xu and Xu 2014). Since the electron-withdrawing nitro groups inhibit the bioconversion of nitro-substituted aromatic compounds (Bruhn et al. 1987), conventional biological approaches are ineffective in treating NB-rich wastewater. Therefore, researchers have made intense efforts to develop efficient and cost-effective methods for NB conversion (Bhatkhande et al. 2005; Chamarro et al 2001; Liu et al. 2012; Mantha et al. 2001; Mu et al. 2004; Zhao et al. 2009; Zhang et al. 2007). Fenton reagent is an aqueous solution with ferrous iron (Fe2+) and hydrogen peroxide (H2O2) for generation of
Environ Sci Pollut Res
hydroxyl radicals (·OH) (Eq. (1), Table 1). Due to the strong oxidizing potential of the ·OH, Fenton reagent has been considered to be an advanced oxidation process (AOP) capable of conversion of a wide variety of toxic pollutants, such as polycyclic aromatic hydrocarbons, chlorinated aromatic and aliphatic compounds, and nitroaromatic compounds (Hess et al. 2003; Li et al. 1997; Matta et al. 2007; Przado et al. 2007; Teel and Watts 2002), which are difficult to be removed by biological processes (Parsons 2004). The biggest limitation to the Fenton’s reagent is that Fe3+ precipitates out to amorphous ferric oxyhydroxides. Precipitation of Fe3+ reduces the amount of available Fe3+ which in turn reduces the amount to recycled Fe2+. Without the recycled Fe2+, the production of hydroxyl radical ceases. Therefore, Fenton reactions are most effective under conditions of low pH (
