Removal of Sulphur Black Dye from its Aqueous Solution Using Alginate from Sargassum sp. (Brown Algae) as a Coagulant G. Vijayaraghavan a,b and S. Shanthakumar a a Environmental Engineering Division, School of Mechanical and Building Sciences, VIT University, Vellore 632014, India; shanthakumar.s@vit.ac.in (for correspondence) b Department of Chemical Engineering, Adhi Parasakthi Engineering College, Melmaruvathur 603319, India Published online 00 Month 2015 in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ep.12144 This study deals with the coagulation potential of alginate extracted from marine algae Sargassum sp. for the removal of sulphur black dye from its aqueous solution. The alginate extraction was found to be efficient (44.8%) and the extracted alginate was characterized by Fourier transform infrared spectroscopy and Scanning electron microscopy techniques. Batch experiments (coagulation test) were per- formed to investigate the effect of alginate dose (10-60 mg/L), calcium dose (1-6 g/L) and initial dye concentration (50- 250 mg/L) on dye removal. The maximum dye removal (98.2%) was achieved under the optimal conditions of the initial dye concentration 200 mg/L, Calcium dose 6 g/L, and alginate dose 30 mg/L. The kinetics study for the coagulation process was carried out and found that it suitably fits in second-order kinetics model. The literature on application of algal alginate for various wastewater treatment methods were compared with the present study and the results obtained revealed that the alginate from Sargassum sp. can be used as an efficient coagulant for the removal of sulphur black dye. V C 2015 American Institute of Chemical Engineers Environ Prog, 00: 000–000, 2015 Keywords: brown algae, Sargassum sp, sulphur black dye, coagulation INTRODUCTION Among various industries, textile industries commonly release a very large amount of wastewater mainly consist of fabric dyes [1]. In general, all the textile industries are han- dling a huge quantity of chemicals viz. dyes, sodium sul- phide and Glauber salt (in dye bath solution), and Hydrogen peroxide (oxidizing agent). Sulphur black dyes has its appli- cations in a number of industries and one of the most popu- lar colorants used on cellulosic fibers and their blends [2]. It is estimated that about one half of the volume of dye used on cellulosic fibers is Sulphur dyes, in which about 80% is the sulphur black dye [3]. sulphur dyes are very cheap and easily available, because of which it is used mainly for dye- ing textile cellulosic materials or blends of cellulosic fibers [4,5]. The extensive use of dyes often causes pollution prob- lems. Sulphur dyes require a complex application procedure because they are practically insoluble in water and have no affinity for cellulose fibers in such a state. Hence, sulphur dyes have to be converted into the water-soluble form before dyeing which have substantively towards fibers and after absorption into the fibers it should be re-oxidized to the original water-insoluble dye pigment form [6]. All these processes require more chemicals and reagents, thus the usage of sulphur dye generates toxic effluents. The color removal by coagulation is a widely employed treatment process. Coagulation of dye-containing wastewater has been used for many years either as main or pretreatment because of its low capital cost. However, the main limitation is the generation of sludge. Generally, the sludge production can be minimized if the effluent is treated directly after the dyeing process (i.e., dye bath effluent). The effectiveness of coagulation can be enhanced by proper selection of coagu- lant/flocculant aids, optimization of the process parameters such as initial pH, dosage of coagulant, settling time, etc. [7] and hence, the selection of suitable coagulant will be the key factor for the efficient coagulation process. Normally, chemical coagulants like Aluminum Sulphate and Ferric chlo- ride are used as a commercial coagulant. These chemical coagulants are disadvantageous because of its cost, sludge produced from the process and its effect on water resources, especially when the sludge contain high levels of toxic mat- ters. Natural coagulants have the potential to overcome these disadvantages because of its inherent advantages. Over the recent years, the use of natural polymeric materials has gained momentum in wastewater treatment by using the available biological resources. The natural polymers such as polysaccharides have been suggested to be moderately effi- cient because of their low molecular weights and high shear stability and they were noted to be cheap and easily avail- able from reproducible resources. Additional advantages of these natural coagulants include safety for human health, biodegradability, and a wider effective dose range of floccu- lation for various colloidal suspensions [8–10]. Hence, in recent years, natural organic polymers such as S. Potatorum (Nirmali), Moringa oleifera, Cactus opuntia, Tannin, Chitosan have been studied for their flocculating capability to replace inorganic coagulants [11–14]. The most abundant marine bio- polymer is Alginate and its source is found in the cell walls and the intracellular spaces of brown seaweed [15]. A large amount of Alginate material is present in nature because of V C 2015 American Institute of Chemical Engineers Environmental Progress & Sustainable Energy (Vol.00, No.00) DOI 10.1002/ep Month 2015 1