Water Research 36 (2002) 1783–1793 Kinetics of adsorption of Co(II) removal from water and wastewater by ion exchange resins S. Rengaraj, Seung-Hyeon Moon* Department of Environmental Science and Engineering, Kwangju Institute of Science and Technology, Kwangju 500-712, South Korea Received 2 March 2001; received in revised form 12 July 2001; accepted 27 July 2001 Abstract The capacity of ion exchange resins, IRN77 and SKN1, for removal of cobalt from aqueous solution has been investigated under different conditions namely initial solution pH, initial metal-ion concentration, and contact time. The equilibrium data obtained in this study have been found to fit both the Langmuir and Freundlich adsorption isotherms. The adsorption of Co(II) on these resins follows first-order reversible kinetics. The film diffusion of Co(II) in these ion exchange resins was shown to be the main rate limiting step. The studies showed that these cation exchange resins can be used as efficient adsorbent material for the removal of Co(II) from aqueous solutions. r 2002 Elsevier Science Ltd. All rights reserved. Keywords: Cobalt(II); Ion exchange resin; Adsorption isotherms; Adsorption kinetics; Wastewater 1. Introduction Heavy metal contamination exists in the aqueous waste streams of many industries, such as metal plating facilities, mining operations, nuclear power plant and tanneries. The soils surrounding many military bases are also contaminated and pose a risk of ground water and surface water contamination due to the heavy metals. Some metals associated with these activities are cad- mium, chromium, cobalt, lead and mercury. Heavy metals are not biodegradable and tend to accumulate in living organisms, causing various diseases and disorders [1–3]. Cobalt, a natural element present in certain ores of the Earth’s crust, is essential to life in trace amounts. It exists in the form of various salts. Pure cobalt is an odorless, steely-gray, shiny, hard metal. Everyone is exposed to low levels of cobalt in air, water and food. An average of 2 g dm 3 in drinking water has been estimated. Cobalt has both beneficial and harmful effects on health. Important natural sources of cobalt in the environment are soil, dust and sea water. Cobalt and its salts are used in nuclear medicine, enamels and semiconductors, grinding wheels, painting on glass and porcelain, hygrometers and electroplating; as a foam stabilizer in beer, in vitamin B12 manufacture, as a drier for lacquers, varnishes and paints, and as a catalyst for organic chemical reactions. The permissible limits of cobalt in the irrigation water and livestock watering are 0.05 and 1.0 mg dm 3 , respectively (Environmental Bureau of Investigation, Canadian Water Quality Guidelines). The effects of acute cobalt poisoning in humans are very serious, among them are asthma like allergy, damage to the heart, causing heart failure, damage to the thyroid and liver. Cobalt may cause mutations (genetic changes) in living cells. Exposure to ionizing radiation is associated with an increased risk of developing cancer. Some isotopes of cobalt do emit ionizing radiation. With a better awareness of the problems associated with cobalt, research studies related to the methods of removing cobalt from wastewater have drawn attention increasingly. *Corresponding author. Tel.: +82-62-970-2434; fax: +82- 62-970-2434. E-mail address: shmoon@kjist.ac.kr (S.-H. Moon). 0043-1354/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII:S0043-1354(01)00380-3