Journal of Hazardous Materials 164 (2009) 1480–1486 Contents lists available at ScienceDirect Journal of Hazardous Materials journal homepage: www.elsevier.com/locate/jhazmat Remediation of phosphate-contaminated water by electrocoagulation with aluminium, aluminium alloy and mild steel anodes Subramanyan Vasudevan ∗ , Jothinathan Lakshmi, Jeganathan Jayaraj, Ganapathy Sozhan Central Electrochemical Research Institute (CSIR), Karaikudi 630006, India article info Article history: Received 8 February 2008 Received in revised form 16 July 2008 Accepted 19 September 2008 Available online 26 September 2008 Keywords: Electrocoagulation Phosphate Aluminium alloy anode Kinetics Isotherm abstract The present study provides an electrocoagulation process for the remediation of phosphate-contaminated water using aluminium, aluminium alloy and mild steel as the anodes and stainless steel as the cathode. The various parameters like effect of anode materials, effect of pH, concentration of phosphate, current density, temperature and co-existing ions, and so forth, and the adsorption capacity was evaluated using both Freundlich and Langmuir isotherm models. The adsorption of phosphate preferably fitting the Lang- muir adsorption isotherm suggests monolayer coverage of adsorbed molecules. The results showed that the maximum removal efficiency of 99% was achieved with aluminium alloy anode at a current density of 0.2 A dm -2 , at a pH of 7.0. The adsorption process follows second-order kinetics. © 2008 Elsevier B.V. All rights reserved. 1. Introduction As is well known, eutrophication is one of the main problems nowadays encountered in the monitoring of environmental water sources in industrialized countries. This phenomenon, which is responsible for the dramatic growth of algae occurring in drink- ing water, is caused by the excess phosphate concentration in the effluents from municipal or industrial plants discharged to the environment. In the countryside, where agriculture and animal husbandry are the main industries, wastes from these activities will contribute to the accumulation of phosphorus in soil and water bodies. These phosphorus compounds, dissolved in surface or groundwaters, are responsible for eutrophication in closed water systems, especially in lakes and enclosed bays where the water is almost stagnant [1]. The U.S. discharge limit of phosphate is 0.5–1.0mg/L P. The Indian discharge limits for phosphate is 5mg/L as P [2]. To meet water quality standards, further treatment of water is required. Phosphate removal from wastewater has received con- siderable attention since the late 1960s [3]. Phosphate removal techniques fall into three main categories: physical, chemical, and biological. Physical methods have proven to be either too expensive, as in the case of electrodialysis and reverse osmosis, or inefficient, ∗ Corresponding author. Tel.: +91 4565 227554; fax: +91 4565 227779. E-mail addresses: svdevan 2000@yahoo.com, vasudevan65@gmail.com (S. Vasudevan). removing only 10% of the total phosphate [4]. Chemical treatment is widely used for phosphate removal. The common chemicals used for treatments are aluminium sulfate and ferric chloride. At present, chemical treatments are not used due to disadvantages like high costs of maintenance, problems of sludge handling and its disposal, and neutralization of the effluent [5–7]. In a biological treatment plant, it is necessary to transfer phosphate from the liquid to the sludge phase, and the removal efficiency usually does not exceed 30%, which means that remaining phosphate should be removed by another technique [8]. The phosphate removal from wastewater by adsorption using different materials has also been explored. The major disadvantages of this studied adsorbent are low efficiency and high cost [9–15]. Recent research has demonstrated that electrochemistry offers an attractive alternative to above-mentioned traditional meth- ods for treating wastewaters [16–22]. Electrochemical coagulation, which is one of these techniques, is the electrochemical production of destabilization agents that brings about charge neutralization for pollutant removal, and it has been used for water or wastew- ater treatment. Usually, aluminium or iron plates are used as electrodes in the electrocoagulation process. Electrochemically generated metallic ions from these electrodes can undergo hydrol- ysis near the anode to produce a series of activated intermediates that are able to destabilize the finely dispersed particles present in the water/wastewater to be treated. The destabilized particles then aggregate to form flocs [23]. The advantages of electrocoagulation include high particulate removal efficiency, a compact treatment facility, relatively low cost, 0304-3894/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jhazmat.2008.09.076