Azo dye removal by Moringa oleifera seed extract coagulation Jesu ´s Beltra´n-Heredia and Jesu ´s Sa´nchez Martı ´n* Department of Chemical Engineering and Physical Chemistry, Universidad de Extremadura, Avda. de Elvas, s ⁄ n. 06071, Badajoz, Spain Email: jsanmar@unex.es Received: 2 July 2008; Accepted: 12 August 2008 In this paper, the ability of Moringa oleifera seed extract–among other natural coagulants–to remove several different types of dyes has been researched. Moringa oleifera has been demonstrated to have a high removal ability for anionic dyes. This study is particularly focused on testing the removal of an azo dye such as Chicago Sky Blue 6B (CSB). It has taken out the fast kinetic of coagulant action and the high potential of this coagulant agent to treat wastewater from dyestuff. Up to 99% of CSB removal has been achieved with M. oleifera extract dosage of 150, 200 and 250 mg l )1 for 100, 160 and 200 mg l )1 of initial CSB concentration, respectively. Temperature does not affect the coagulant process and a pH level greater than 8 has a negative influence. Lower CSB percentage removal is achieved by increasing the initial dye concentration, but an optimum relationship between dye amount removed and M. oleifera extract amount has been established and it appears to be between 0.7 and 0.9, depending on the initial dye concentration and the bulk of the remaining dye concentration. Introduction The dyestuff industry is one of the largest in the world and the implications for economic and social conditions in many countries, especially India and China, are of high importance [1]. Depending on various factors such as fibre class, colour or industrial process, there are a number of dye substances which could be highly polluting if released into the environment. Over 50 000 tonnes of dye, containing hazardous substances which can damage aquatic and vegetal life, are discharged via effluent into the environment annually [2]. For many years, researchers have been working on ways of removing dyes from wastewater and different procedures have been developed; for example, adsorption onto materials such activated carbon [3,4] and physical and chemical degradation [5,6], in addition to a large number of other techniques such as Fenton’s oxidation, electrochemical degradation, ozonisation, etc. [7–9]. Dyes may be classified into several different groups, according to their usage in dyestuff, such as acid, basic, disperse and direct dyes. However, with regard to their chemical structure, many compounds are included as dye. In this work, we have considered four types of dyes: thiazinic (Methylene Blue, dye 1), triphenylmethane (Eriochromecyanine R, dye 3), anthraquinonic (Alizarin Violet 3R, dye 4) and azo dyes (CI Acid Red 88, dye 2; Palatine Fast Black WAN, dye 5; and Chicago Sky Blue 6B, dye 6). With the exception of dye 1, these are anionic dyes. A preliminary screening of the ability of Moringa oleifera to remove dyes was carried out on these four types of dye. Thereafter, we concentrated our investigation on Chicago Sky Blue 6B (CSB) as an example. This is a relatively cheap dye that is widely distributed and is mainly used to dye cotton fibres. As a part of the phenol azo dyes group, it is especially risky because of its potentially carcinogenic activity [10]. For several years, we have researched M. oleifera as a water treatment agent. As a tropical multipurpose plant, M. oleifera is very interesting from the point of view of future applications, as it is a widespread, easily available water treatment method. Moringa oleifera for water treatment can be used in two different ways: (i) one as a primary source of activated carbon [11,12] and (ii) 1 S + N N N CH 3 CH CH 3 CH 3 Cl – S N 2 N O – O O OH Na + 3 S O – O O O O – O – O O OH CH 3 CH 3 Na + Na + Na + doi: 10.1111/j.1478-4408.2008.00158.x 310 ª 2008 The Authors. Journal compilation ª 2008 Society of Dyers and Colourists, Color. Technol., 124, 310–317