Chemical Engineering Journal 185–186 (2012) 178–186 Contents lists available at SciVerse ScienceDirect Chemical Engineering Journal jo u r n al hom epage: www.elsevier.com/locate/cej Rapid removal of chromium from aqueous solution using novel prawn shell activated carbon Mani Arulkumar a,1 , Kasinathan Thirumalai a,1 , Palanivel Sathishkumar b , Thayumanavan Palvannan a,∗ a Laboratory of Bioprocess and Engineering, Department of Biochemistry, Periyar University, Salem 636-011, Tamil Nadu, India b Division of Biotechnology, Advanced Institute of Environmental and Bioscience, College of Environmental and Bioresource Sciences, Chonbuk National University, Iksan 570-752, Jeonbuk, South Korea a r t i c l e i n f o Article history: Received 23 June 2011 Received in revised form 13 January 2012 Accepted 14 January 2012 Keywords: Activated carbon Adsorption Chromium Prawn shell Response surface methodology Tannery effluent a b s t r a c t The rapid removal of chromium ions from aqueous solutions using prawn shell activated carbon (PSAC) was established in the present study. Response surface methodology (RSM) was used to optimize the process variables for the maximum chromium removal. The optimization result shows that 0.04 g of PSAC was sufficient to remove 100.6 mg L -1 of chromium in 31.4 min time period. Adsorption of chromium obeyed both Freundlich and Langmuir adsorption isotherms and followed second-order kinetic reaction. This results suggest that the PSAC as a good candidate for the rapid removal of chromium from tannery effluent. © 2012 Elsevier B.V. All rights reserved. 1. Introduction The pollution of aquatic environment has been increased mainly due to the non-degradable hazardous compounds present in the effluents emanating from industries. Heavy metals are the most important constituents among toxic compounds in the effluents [1], which is used in industries for leather tanning, metal finish- ing, petroleum refining, wood preservation, corrosion inhibition in power plants, nuclear facilities and manufacturing of pigments, dyes, textiles, carpets, magnetic tapes, jet aircrafts and automobile parts [2,3]. Chromium exists in its stable oxidation state of hexavalent chromium (Cr VI) and trivalent chromium (Cr III), which are the main form of chromium found in many water bodies [1,4]. Chromate (CrO 4 2- ) and dichromate (Cr 2 O 7 2- ) are considered a greater health hazard than the other valency states [4]. Permissi- ble limit of chromium is 0.5 mg L -1 , but usually effluent discharged from the industries contained above the level [5,6]. Consumption of chromium contaminated drinking water may affect cell and humoral immunity through increasing the level of antibodies [7]. Considering, chromium’s toxic and carcinogenic nature, the max- imum levels permitted for trivalent chromium in wastewater is 5 mg L -1 and for hexavalent chromium is 0.05 mg L -1 [8,9]. In the ∗ Corresponding author. Tel.: +91 427 2345766/2345520; fax: +91 427 2345124. E-mail address: pal2912@yahoo.com (T. Palvannan). 1 The first two authors made equal contributions to this work. present study, we focused mainly on tannery industries because there are about 2161 tanneries in India excluding cottage indus- tries, which process around 500,000 tonnes of hides and skins annually which introduce 2000–5000 mg L -1 of chromium in the aqueous effluents [10–12]. Nearly 9,420,000 m 3 of wastewater was discharged from tan- nery industries annually [10]. Many tanneries are located in Vellore and Erode districts in Tamil Nadu, India and removal of dis- charged wastewater containing chromium is great challenge for the modern science. Chromium removal from aqueous system can be achieved with various methods such as chemical precipitation, ion exchange, membrane processes, electro dialysis and adsorp- tion [13–16]. Among all other investigated methods, activated carbon adsorption is a highly promising method for the chromium removal. However, the cost of activated carbon preparation from coal and other natural sources are too expensive. In search of new and alternative source as a precursor for the preparation of activated carbon from many biological materials with low or null cost have been studied. It includes agricultural wastes [17,18], natural wastes [19], stones and shells [20], bamboo [21], marine biomass Posidonia oceanica (L.)[22], marine macro- algal biomass Sargassum longifolium and Hypnea valentiae [23] etc. In the present study, we made an attempt to produce low cost acti- vated carbon with rapid adsorption properties from easily available and highly abundant marine/river waste. One such material is fresh water prawn (Penaeus esculentus) shell. Growing of prawn in cottage and industrial scale is one of the largest fast-growing trends commonly in India. After processing, 1385-8947/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2012.01.071