Removal of Cd 21 , Cu 21 , Ni 21 , and Pb 21 Ions from Aqueous Solutions Using Tururi Fibers as an Adsorbent Diego Q. Melo, 1 Carla B. Vidal, 2 Andr  e Leandro da Silva, 3 Raimundo N. P. Teixeira, 2 Giselle Santiago Cabral Raulino, 2 Thiago C. Medeiros, 1 Pierre B. A. Fechine, 1 Selma Elaine Mazzeto, 3 Denis De Keukeleire, 4 Ronaldo F. Nascimento 1 1 Department of Analytical Chemistry and Physical Chemistry, Federal University of Cear a, Fortaleza, Cear a, Brazil 2 Department of Hydraulic and Environmental Engineering, Federal University of Cear a, Fortaleza, Cear a, Brazil 3 Department of Organic and Inorganic Chemistry, Federal University of Cear a, Fortaleza, Cear a, Brazil 4 Faculty of Pharmaceutical Sciences, Laboratory of Pharmacognosy and Phytochemistry, University of Gent, 9000 Gent, Belgium Correspondence to: R. F. Nascimento (E - mail: ronaldo@ufc.br) ABSTRACT: This work investigates the removal of Cd 21 , Cu 21 , Ni 21 , and Pb 21 ions from aqueous solutions using tururi fibers as an adsorbent under both batchwise and fixed-bed conditions. It was found that modification of the tururi fibers with sodium hydroxide increased the adsorption efficiencies of all metal ions studied. The fractional factorial design showed that pH, adsorbent mass, agita- tion rate, and initial metal concentration influenced each metal adsorption differently. The kinetics showed that multi-element adsorption equilibria were reached after 15 min following pseudo-second-order kinetics. The Langmuir, Freundlich, and Redlich– Peterson models were used to evaluate the adsorption capacities by tururi fibers. The Langmuir model was found to be suitable for all metal ions. Breakthrough curves revealed that saturation of the bed was reached in 160.0 mL with Cd 21 and Cu 21 , and 52.0 mL with Ni 21 and Pb 21 . The Thomas model was applied to the experimental data of breakthrough curves and represented the data well. V C 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40883. KEYWORDS: adsorption; applications; cellulose and other wood products; separation techniques Received 18 February 2014; accepted 13 April 2014 DOI: 10.1002/app.40883 INTRODUCTION Metal ions may be present in toxic concentrations in the air due to the incineration of municipal and industrial wastes as well as in water intoxicated by industrial effluents. This context, the industry of metal finishing and electroplating units are one of the major sources of pollutants which contribute greatly to the pollution load of the receiving water bodies and therefore increase the environmental risks. 1–3 The metal concentrations vary greatly. However, on average concentrations range 20–600 mg L 21 . 4 Thus, in the absence of degradation pathways, metal ions may accumulate in the environment. There are various technologies for removing toxic metal ions from aqueous solu- tions including chemical precipitation, reverse osmosis, ion flo- tation, evaporation, ion exchange, and adsorption, the latter being the most promising technique. 2 Various lignocellulose-derived materials have been studied as adsorbents including cellulosic substrates, 3 sugar cane bagasse, 4,5 cashew bagasse, 6 and coconut shell. 2,7–9 A major advantage of using natural fibers as adsorbents is the ready availability of renewable sources in nature, the low costs, the biodegradability as well as the excellent mechanical properties. Natural fibers of vegetable origin are complex composite materi- als, consisting primarily of cellulosic microfibrils in an amor- phous matrix of lignin and hemicellulose. Originally from the Amazon estuary, the palm of ubuc ¸u (Manicaria saccifera) carries fruits protected by a fibrous sheath called “tururi.” Despite the fact that these fibers have economic importance in a number of commercial sectors, there are no studies known on their physi- cal and chemical properties for potential use in adsorption processes. This work focuses on removal of Cd 21 , Cu 21 , Ni 21 , and Pb 21 ions from aqueous solutions using tururi fibers as an adsorbent. MATERIALS AND METHODS Materials Analytical-grade chemicals and ultrapure water (Millipore Direct Q3 Water Purification System) were used to prepare the solutions. Multi-element stock solutions of Cd 21 , Cu 21 , Ni 21 , and Pb 21 (500 mg L 21 ) were prepared with Cd(NO 3 ) 2 .4H 2 O, V C 2014 Wiley Periodicals, Inc. WWW.MATERIALSVIEWS.COM J. APPL. POLYM. SCI. 2014, DOI: 10.1002/APP.40883 40883 (1 of 12)