Removal of the Azo Dye Congo Red from Aqueous Solutions by the Marine Alga Porphyra yezoensis Ueda

Batch adsorption experiments were carried out using nonliving biomass of Porphyra yezoensis Ueda (red alga) for the removal of Congo red from aqueous solutions at 25°C. The effects of process parameters such as contact time, adsorbent concentration and ionic strength were investigated. The raw biomass and Congo red loaded biomass were characterized by Fourier transform infrared spectroscopy (FTIR). The pseudo first order, pseudo second order and intraparticle diffusion models were tested. The results showed that adsorption of Congo red followed pseudo second order kinetics very well. Langmuir and Freundlich equations were applied to the data related to the adsorption isotherms, and the observed maximum adsorption capacities (q_m) were 71.46 mg/g at 25°C. Adsorbent concentration and ionic strength had a marked effect on Congo red adsorption.