Phytoremediation potential of duckweed (Lemna minor L.) in degradation of C.I. Acid Blue 92: Artificial neural network modeling A.R. Khataee a,n , A. Movafeghi b , S. Torbati a,b , S.Y. Salehi Lisar b , M. Zarei a a Department of Applied Chemistry, Faculty of Chemistry, University of Tabriz, Tabriz 5166616471, Iran b Department of Plant Biology, Faculty of Natural Science, University of Tabriz, Tabriz 5166616471, Iran article info Article history: Received 9 January 2012 Received in revised form 14 March 2012 Accepted 21 March 2012 Available online 10 April 2012 Keywords: Phytoremediation Lemna minor L. Biodegradation Textile dye Artificial neural network abstract In present study, the potential of duckweed (Lemna minor L.) for degradation of an azo dye C.I. Acid Blue 92 (AB92) has been investigated. The effect of operational parameters such as initial dye concentration, pH, temperature and amount of plant on the efficiency of biological decolorization process was determined. The reusability of Lemna minor L. in long term repetitive operations was also examined. Growth and some biochemical parameters (photosynthetic pigments content, superoxide dismutase, catalase and peroxidase activity) were used to detect the toxic effects of AB92 on duckweed plant. The biological degradation compounds formed in the present process were analyzed by GC-MS technique. In addition, an artificial neural network (ANN) model was expanded to predict the biological decolorization efficiency. The obtained data indicated that ANN provide realistic predictive performance (R 2 ¼0.954). & 2012 Elsevier Inc.. All rights reserved. 1. Introduction Urban industrialization and population growth have placed major pressure on environment, potentially threatening the envir- onmental sustainability (Pilon-Smits, 2005; Robinson et al., 2001; Venkata Mohan et al., 2002). Among various industries, the textile industry discharge large amount of synthetic dyes and dye stuffs into aquatic systems that have carcinogenic and mutagenic effects and are potentially toxic to all living organisms (Forgacs et al., 2004; Kabra et al., 2011; Megateli et al., 2009). Different physico-chemical methods like adsorption, coagulation, ozonation, electrolysis, etc., are being used for the purification and decolorization of dyeing wastewater (Aksu, 2005; Forgacs et al., 2004; Robinson et al., 2001). These methods have yet disadvantage due to generating large amount of sludge that may, in turn, result in secondary pollution and involve complicated procedure which are economically unfea- sible (Al-Degs et al., 2008; Garg et al., 2004; Zhang et al., 2004). In recent years, bioremediation has emerged as an alternative technology that use living organisms for recovery or cleanup of contaminated sites (soil, sediment, air and water) (Forgacs et al., 2004). A wide variety of organisms are able to degrade textile dyes, including bacteria (Chen et al., 2003), fungi (Ma ´ ximo et al., 2003; Renganathan et al., 2008, 2006), yeast (D¨ onmez, 2002), and algae (Daneshvar et al., 2007a; Khataee et al., 2010a, 2010b). It has been found that plants also can be used as a remediation tool (Pilon- Smits, 2005; Saranya et al., 2011; Susarla et al., 2002). Plant assays are highly sensitive to many environmental pollutants, including heavy metals (Wang and Freemark, 1995) but few cases have been reported that the plants have the potential capacity to degrade textile dyes (Aubert and Schwitzgue ´ bel, 2004). Among different plant species, Lemna minor L. possesses physiological properties such as small size, high multiplication rates and vegetative propa- gation. These characteristics make L. minor as an ideal test system for water quality studies to monitor heavy metal and other aquatic pollutants (Radic et al., 2010; Radic ´ et al., 2011; Stomp, 2005; Wang, 1990). The main objective of the present study is to assess the potential of L. minor for phytoremediation of C.I. Acid blue. The effects of experimental parameters such as initial dye concentra- tion, pH, temperature and amount of plant on phytoremediation rate were determined. Furthermore, we endeavored to investigate the changes in activity of the major enzymes that can be involved in plant resistance to dye and/or its metabolism including super- oxide dismutase (SOD, EC 1.15.1.1.), catalase (CAT, EC 1.11.1.6) and peroxidase (POD, EC 1.11.1.7). Also we attempt to identify and characterize the possible metabolites of the dye by using GC-MS technique. Another aspect of the present study is to demonstrate whether artificial neural network can be used to predict biological decolorization efficiency of L. minor. 2. Materials and methods 2.1. Plant material and growth condition L. minor is a species of Lemnaceae family with a subcosmopolitan distribution, occurring everywhere that fresh water ponds and slow-moving streams occur Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/ecoenv Ecotoxicology and Environmental Safety 0147-6513/$ - see front matter & 2012 Elsevier Inc.. All rights reserved. http://dx.doi.org/10.1016/j.ecoenv.2012.03.021 n Corresponding author. Fax: þ98 411 3340191. E-mail addresses: a_khataee@tabrizu.ac.ir, ar_khataee@yahoo.com (A.R. Khataee). Ecotoxicology and Environmental Safety 80 (2012) 291–298