ORIGINAL PAPER High adsorption of dyes by water hyacinth fixed on alginate Courtie Mahamadi • Epias Mawere Received: 3 July 2013 / Accepted: 17 November 2013 Ó Springer-Verlag Berlin Heidelberg 2013 Abstract Pollution from synthetic dyes has emerged to be a significant environmental issue over the past few decades. This has mainly been triggered by the increasing global dye production, possible toxic effects, undesirable colour and high persistence in the environment. Biosorption, which involves dye removal from aqueous solution by passive linkage in live and dead biomass, has shown great potential in removing dyes from aquatic environments. Among aquatic macrophytes, water hyacinth, Eichhornia crassipes, has shown great potential as a biosorbent. In this work, we investigated the removal of two basic dyes, methylene blue and crystal violet, using E. crassipes immobilized on algi- nate. Results showed that the Langmuir model better described the equilibrium sorption data when compared to the Freundlich model. Optimum amounts of methylene blue and crystal violet dyes were adsorbed in the alkaline pH range (8–10), 8 % biomass dose, and the amount of dye removed increased with increasing initial dye concentration. The equilibrium monocomponent adsorption capacities for the dyes were 111.1 and 43.5 mg/g, while the binary adsorption capacities were 26.1 and 11.6 mg/g for methy- lene blue and crystal violet, respectively. To conclude, we show for the first time that E. crassipes fixed on alginate beads can uptake and adsorb methylene blue and crystal violet dyes very effectively in batch systems and show great potential for dye removal from aquatic environments. Keywords Eichhornia crassipes  Biosorption  Immobilization  Equilibrium isotherms  Kinetic  Methylene blue  Crystal violet Introduction Environmental pollution problems arising from the use of synthetic dyes have attracted significant attention over the past few decades. This has mainly been triggered by increasing global dye production, their possible toxic effects, highly visible and undesirable colour, and their persistence in the environment (Maurya et al. 2006). The net result has been a decrease in the supply of fresh, usable water and increased cost of purifying it for many countries. Various treatment processes such as physical separation, advanced chemical oxidation, and biological degradation have been widely investigated to remove dyes from wastewaters (Lourenco et al. 2001; Selvam et al. 2008; Khataee et al. 2013). However, these methods are expen- sive to operate and are likely to produce toxic by-products. Activated carbon is regarded as an effective adsorbent due to its large surface area, low density and chemical stability, but expensive adsorbent due to its high costs of manufac- turing and regeneration (Rao and Ashutosh 1994). Out of economic consideration, it is not used for large-scale effluent treatment. Recently, biological treatment techniques that use organisms including bacteria, fungi, algae and plants have been developed as low-cost and eco-friendly viable alter- native (Vafaei et al. 2012). In particular, biosorption, which involves dye removal from aqueous solution by passive linkage in live and dead biomasses in a mechanism that is not controlled by metabolic steps, is proving to be a pop- ular alternative owing to its several advantages. The initial incentives of the process include low cost of biosorbents, simplicity of design, great efficiency for metal removal at low concentration, potential for biosorbent regeneration and metal recovery, high velocity of sorption and desorp- tion, limited generation of secondary residues and more C. Mahamadi (&)  E. Mawere Chemistry Department, Bindura University of Science Education, P. Bag 1020, Bindura, Zimbabwe e-mail: courtiema@yahoo.com 123 Environ Chem Lett DOI 10.1007/s10311-013-0445-z