0011-9164/05/$– See front matter © 2005 Elsevier B.V. All rights reserved Desalination 181 (2005) 233–241 Reductive dissolution of magnetite in ethylenediaminedisuccinic acid solutions A.M. Al-Mayouf*, A.S.N. Al-Arifi Department of Chemistry, College of Science, King Saud University, PO Box 2455, Riyadh 11451, Saudi Arabia Tel. +966 (1) 467-5959; Fax: +966 (1) 467-5992; email: amayouf@ksu.edu.sa Received 27 April 2004; accepted 10 February 2005 Abstract Ethylenediaminedisuccinic acid (EDDS) was used to dissolve magnetite reductively. Fe 2+ ions increased the dissolution rate, and this increase depended on the solution acidity, temperature and [EDDS]:[Fe 2+ ] ratios. The EDDS–Fe 2+ complex was able to dissolve magnetite film coated on an iron surface. Iron metal enhanced the dissolution of magnetite from its surface. However, metal exposed to the solution suffered more corrosion than iron free of magnetite. Keywords: EDDS; Magnetite; Reductive; Dissolution; Iron; Galvanic 1. Introduction Iron is used extensively in industry. Corrosion products are formed on its surface during opera- tions, especially when in contact with water. Oxides are the most common deposits encoun- tered. They are usually caused by corrosion or from precipitation of soluble iron brought into the system by the make-up water. These oxides reduce the efficiency of water lines, boilers, cooling coils in water-cooled nuclear reactors and heat-exchanger equipment and can increase under deposits of corrosion. Therefore, removal of deposits will maximize thermal efficiency and *Corresponding author. capacity in steam generators and evaporators and enhance the service lifetime of such equipment. Mechanical cleaning, which depends on proce- dures such as water hydroblasting and the use of abrasive sponge balls, cannot effectively remove the firmly adherent deposits [1]. Magnetite (Fe 3 O 4 ) is formed on iron surfaces under reducing environments and at high tem- peratures. Chemical cleaning procedures that depend on suitable solution formulations contain- ing chelants were developed to dissolve or to decontaminate the iron surface from magnetite formed on the surface and are considered to be the most practical means of removing internal deposits.