www.sciencejournal.in Volume- 5 Issue- 1 (2016) ISSN: 2319–4731 (p); 2319–5037 (e) © 2016 DAMA International. All rights reserved. 236 REMOVAL OF HEAVY METALS FROM AQUEOUS SOLUTION BY RED ALGA GRACILARIA CORTICATA AS A NEW BIOSORBENT Abolfazl Teimouri 1 , Saeid Eslamian 2 , Atefe Shabankare 3 1 Department of Chemical Engineering, School of Chemical Engineering, Kherad Institute of Higher Education, Bushehr, Iran 2 Department of water Engineering, Isfahan University of Technology, Iran 3 Islamic Azad University, Tehran Medical Branch, Tehran, Iran ABSTRACT Red alga Gracilaria corticata biosorbent was evaluated as a new biosorbent of heavy metals from aqouse samples. On contacting copper, lead, zinc and cadmium solutions with red alga Gracilaria corticata biosorbent, during contact time of 40 min and pH 5. Metal ion biosorption increased as the ratio of metal solution to the biosorbent quantity decreased. Conversely, biosorption increased as the quantity of biosorbent increased to 15 g L -1 . The increase in initial metal ion concentration was associated with steep increase in biosorption at lower concentrations, progressively reaching towards plateau at higher metal concentrations. At equilibrium, the affinity of Red alga Gracilaria corticata biosorbent to biosorb metals was in the order of zinc> copper> lead> cadmium, which remained the same during the testing of variables of different factors. The biosorption data perfectly fit the Langmuir adsorption isotherms model with 0.985 regression coefficient (r 2 ) for all the metals. The fit on Freundlich adsorption isotherms model was acceptable but not as good. The metal-loaded Red alga Gracilaria corticata biosorbent was completely desorbed with 0.1N HCl. During repeated biosorption–desorption for five cycles, no loss in the efficiency of heavy metal removal from their respective solutions and the metal -loaded biosorbent was noted. The study points to the potential of a novel use of Red alga Gracilaria corticata biosorbent. KEYWORDS: Biosorbent; Red alga Gracilaria corticata; Heavy metals; Atomic absorption spectroscopy. 1. INTRODUCTION Heavy metal pollution of waters has a seriously detrimental impact on people and ecosystems that rely on such bodies of water (Salam et al., 2011; Suzuki et al., 2005). Heavy metals is a general collective term, which applies to the group of metals and metalloids with atomic density greater than 4 g/cm 3 , or 5 times or more, greater than water (Otero et al., 2009; Piotrowska-Niczyporuk et al., 2012; Salam et al., 2011; Suzuki et al., 2005; Yu et al., 2001). Water environmental pollution due to toxic heavy metals is a serious environmental and public health issue (Abdel -Aty et al., 2013; Baker et al., 1983; El-Sheekh et al., 2005; Esmaeili et al., 2008; Shaheen et al., 2013). The removal of heavy metals from mine drainage and industrial effluents has become important to maintain water quality standards that are suitable for environmental and human health (Aulio, 1983; Barakat and Kumar, 2015; Kapoor and Viraraghavan, 1998; Otero et al., 2009; Přibyl et al., 2008; Sangi et al., 2008; Xing et al., 2011; Yu et al., 2000). The main conventional methods used to remove heavy metals from aqueous solution are chemical precipitation, coagulation, ion exchange, solvent extraction and filtration, evaporation and membrane methods (Kapoor and Viraraghavan, 1998; Lazinsky and Sicko-Goad, 1983; Otero et al., 2009; Salam et al., 2011; Wang et al., 2003). However, many of these methods often involves high operational costs, and in many cases, it is insufficient to meet strict regulatory requirements. Adsorption by non-toxic adsorbent has been shown to be a feasible alternative for removing heavy metals from water (Ihsanullah et al., 2016; Wang et al., 2003; Xing et al., 2011; Yu et al., 2000, 2001). Synthetic adsorbents have extremely high potential for removing metals such as ion exchange resins or chelating resins, but the high cost of these materials limits their application to treatment facilities that process large volumes of wastewater. Therefore, numerous approaches have been studied to develop cheap and effective metal adsorbents. Biosorbents show a high capacity for assimilating heavy metals and are inexpensive materials (Saeed et al., 2005; Suzuki et al., 2005). Saeed and coworkers have revealed that, among available biosorbent materials, Papaya wood biomass, is highly effective, reliable, and easily available for the removal of heavy metals (Saeed et al., 2005). Among the advantages of this new biosorbent are its rapid and high adsorption–desorption property and reusability in repeated cycles. The