Process Biochemistry 39 (2004) 2183–2191 The adsorption of copper(II) ions on to dehydrated wheat bran (DWB): determination of the equilibrium and thermodynamic parameters Ahmet Özer a , Dursun Özer a , Ayla Özer b,∗ a Deparment of Chemical Engineering, Fırat University, 23279 Elazı˘ g, Turkey b Deparment of Chemical Engineering, University of Mersin, 33343 Çiftlikköy-Mersin, Turkey Received 8 May 2003; received in revised form 8 October 2003; accepted 12 November 2003 Abstract The adsorption of copper(II) ions on to dehydrated wheat bran (DWB), a by-product of the flour process, was investigated as a function of initial pH, temperature, initial metal ion concentration and adsorbent dosage. The optimum adsorption conditions were initial pH 5.0, initial copper concentration 100 mg l -1 , temperature 60 ◦ C and adsorbent dosage 0.1 g. The adsorption equilibrium was described well by the Langmuir isotherm model with maximum adsorption capacity of 51.5 mg g -1 of copper(II) ions on DWB. The observation of an increase in adsorption with increasing temperature leads to the result that the adsorption of copper(II) ions on DWB is endothermic in nature. The thermodynamic parameters such as enthalpy, free energy and entropy changes were calculated and these values show that the copper(II)-DWB adsorption process was favoured at high temperatures. © 2003 Elsevier Ltd. All rights reserved. Keywords: Adsorption; Copper(II); Dehydrated wheat bran (DWB); Isotherm; Thermodynamic parameters 1. Introduction Copper is a widely used industrial metal whose applica- tions include electrical wiring, plumbing, air conditioning tubing and roofing. The properties of copper, which make it suitable for these applications, include high electrical and thermal conductivity, good corrosion resistance, ease of fab- rication and installation, attractive appearance, ready avail- ability, and high recyclability. Additionally, copper, which is an essential nutrient to humans and other life forms, is biostatic/biocidal to certain organisms. However, copper(II) is known to be one of the heavy metals most toxic to liv- ing organisms and it is one of the more widespread heavy metal contaminants of the environment [1]. The poten- tial sources of copper in industrial effluents include metal cleaning and plating baths, pulp, paper board mills, wood pulp production, and the fertilizer industry, etc. The conven- tional methods of copper(II) removal from wastewaters are precipitation, ion exchange, electrolysis, adsorption on ac- tivated carbon, etc. Since activated carbon is expensive, an ∗ Corresponding author. Tel.: +90-324-361-00-01x246; fax: +90-324-361-00-32. E-mail address: ayozer@mersin.edu.tr (A. Özer). alternative inexpensive sorbent able to drastically reduce the cost of a sorption system has always been searched [2,3]. Recently, Bailey et al. reviewed a wide variety of low cost sorbents for the removal of heavy metals [4].A low cost sorbent is defined as one which is abundant in nature, or is a by-product or waste material from another industry [5]. Some researcher reported that the agricultural by-products such as peat, wood, pine park, banana pith, rice bran, peanut shells, wool, rice milling by-products (hulls and bran) and leaves have been widely studied for metal re- moval from wastewater [6–8]. These materials can be used, either directly or after activation, in the adsorption process. Many examples are available in the literature concerning the direct use of these materials as adsorbents [8]. There are a few reports of heavy metal adsorption by wheat bran, as a by-product of a flour factory. Recently, Ravat et al. reported that the a lignocellulosic substrate extracted from wheat bran can be used for the removal of copper(II) ions [9]. The purpose of the present study was to investigate the adsorption of copper(II) ions on wheat bran dehydrated with sulphuric acid. The experiments were done in a batch system and copper adsorption was investigated with respect to initial pH, initial metal ion concentration, temperature and adsorbent dosage. The adsorption equilibrium was 0032-9592/$ – see front matter © 2003 Elsevier Ltd. All rights reserved. doi:10.1016/j.procbio.2003.11.008