Activated carbon removal efficiency of microcystins in an aqueous cell extract ofMicrocystis aeruginosa andOscillatoria tenuis strains isolated from Egyptian freshwaters

The efficiency of absorption for microcystins (MCYSTs) produced by Egyptian strains of Microcystis aeruginosa and Oscillatoria tenuis, using different kinds of granular and powdered activated carbons, was evaluated by determining the adsorption isotherms (Kf and 1/n) for each carbon. Aqueous extracts of cyanobacterial cells containing MCYST at pH 8.5 were used because this pH mimics the Egyptian freshwater environment from which the strains were isolated. Extracts from each strain containing 2 mg/L microcystin, as determined by ELISA, were placed in 45 mL brown bottles containing activated carbon at 100–500 mg/L. The bottles were rotated at 16 rpm, at 22±1°C for 7 days. Results showed that, under these conditions, powdered activated carbons (PACs) were more efficient than granular activated carbons (GACs) in removing microcystins. Wood-based GAC and PAC were the most effective microcystin adsorbents. Nonactivated carbon was not suitable for adsorption of microcystins. MCYSTs from extracts of M. aeruginosa (MCYST-RR. -YR, and -WR) were adsorbed significantly better than MCYSTs from extracts of O. tenuis (MCYST-LR and -LHarg) with all of the activated carbons tested.