Decolourisation of methylene blue and congo red dye solutions by adsorption using chitosan

Water pollution from industrial discharges is a worldwide problem and can have very harmful effects on the environment. In this study, adsorptive removal of two different dyes was investigated using a new natural, biodegradable adsorbent based on shrimp shells: chitosan in a batch adsorption operating system. Chitosan was synthesized from flowery prawn and then characterized using different analytical techniques. The results obtained show a remarkable removal rate in the first 30 min with optimum process conditions for both dyes. Linear forms of pseudo-first-order, pseudo-second-order kinetic, and the intra-particle diffusion kinetic model equations were used to describe the kinetic data of the dye removal process. The Langmuir and Freundlich adsorption isotherm models were used to analyze equilibrium data of adsorption of dyes by chitosan. The maximum adsorption capacities (Q(m)) of chitosan for methylene blue and congo red dye were in the range of 116.3 and 113.6 mg g(-1), respectively. The study shows that the dye adsorption process on chitosan can be described as both isotherm models used.