Journal of Chemical Technology and Biotechnology J Chem Technol Biotechnol 79:1251–1258 (online: 2004) DOI: 10.1002/jctb.1119 Recovery and reuse of chromium from tannery wastewaters using Turbinaria ornata seaweed Rathinam Aravindhan, Balaraman Madhan, Jonnalagadda Raghava Rao ∗ and Balachandran Unni Nair ∗ Chemical Laboratory, Central Leather Research Institute, Adyar, Chennai 600 020, India Abstract: Brown seaweed (Turbinaria spp) was pre-treated with sulfuric acid, calcium chloride and magnesium chloride and tested for its ability to remove chromium from tannery wastewater. Protonated seaweeds gave better uptake of chromium compared with calcium and magnesium treatments. Chromium uptake was optimal at pH 3.5. Turbinaria weed exhibited maximum uptake of about 31 mg of chromium for one gram of seaweed at an initial concentration of 1000 ppm of chromium. Freundlich and Langmuir adsorption isotherm models were used to describe the biosorption of chromium(III) by Turbinaria spp. The chromium-loaded seaweed was reused as a reductant in the preparation of the tanning agent basic chromium sulfate (BCS). Leathers made from this tanning agent had properties comparable to conventionally processed chrome-tanned leathers.  2004 Society of Chemical Industry Keywords: tannery wastewater; chromium; bioaccumulation; Turbinaria spp; seaweed; isotherms 1 INTRODUCTION The processes used in leather manufacture in developing countries remain traditional and are not optimized in regard to chemical and water usage. The industry is perceived as having high pollution potential and is therefore facing a severe challenge. The units of the tanning process that present the greatest perceived environmental impact are dehairing and chrome tanning. 1 The tanning process aims at converting putrescible hide or skin into non-putrescible leather. Worldwide, 80–90% of tanneries adopt the chrome-tanning process, which discharges wastewater containing up to 1500 – 3000 ppm of chromium. 2 However, current high-exhaust tanning methodologies reduce the chromium concentration in wastewater to around 500–1000 ppm. Chromium, in its hexavalent state, is known to be carcinogenic. 3 Chromium(III), an essential trace element, can also be toxic at higher concentrations. 4–6 Two methods of chromium recovery/reuse from wastewater are currently used. The first is precipitation of chromium as chromium hydroxide (Cr(OH) 3 ), fil- tration and subsequent dissolution in a known quantity of sulfuric acid to form basic chromic sulfate for reuse in the tanning process. 7–9 The second method is direct recycling, which involves filtration of the waste liquor followed by chemical replenishment. 10,11 Both methods have marked advantages and disadvantages, depending on the volume of production of the tanning plant. 12 Other possible methods include chemical reduction followed by precipitation, ion exchange, membrane technologies 13 – 15 and adsorption by several types of adsorbents, such as activated carbon, bone charcoal, cork, yohimbe bark wastes, waste activated sludge, fly ash, natural zeolites and others. 16 – 27 Most of these methods and materials have drawbacks such as high capital or operational costs and are therefore uneconomical for small-scale plants. There is a need for the development of a low cost methodology using easily available materials which can adsorb chromium effectively. Bioaccumulation of chromium from wastewaters alone does not combat chrome pollution. Suitable methods for the proper disposal or reuse of the chromium-loaded biomass are needed in order to ensure a holistic approach for minimizing chrome pollution. Basic chromium sulfate (BCS) tanning salt is generally prepared by the direct reduction of dichromate with sugar–sulfuric acid mixture or sul- fur dioxide. 28,29 It has been shown that the chrome liquors prepared by different reducing agents differ in their properties largely due to the formation of different types of intermediates. 30 The use of a variety of reduc- ing agents such as coconut pith, bagasse, glycerol, oils ∗ Correspondence to: Jonnalagadda Raghava Rao and Balachandran Unni Nair, Chemical Laboratory, Central Leather Research Institute, Adyar, Chennai 600 020, India E-mail: clrichem@mailcity.com (Received 6 May 2003; revised version received 12 May 2004; accepted 17 May 2004) Published online 27 August 2004  2004 Society of Chemical Industry. J Chem Technol Biotechnol 0268–2575/2004/$30.00 1251