Screening of hexavalent chromium biosorbent from marine algae

A high-chromate-selective biosorbent with high adsorption capacity was soug ht by examining the chromate adsorption capacities of 48 species of red, br own, or green marine algae sampled from the east coast of Korea. Screening showed a red marine alga to have the most excellent adsorption characterist ics among them, and it was identified as Pachymeniopsis sp. The period at w hich Pachymeniopsis sp. was sampled did not affect the adsorption capacity of the alga, but the optimum period for mass collection was April to May. T he alga also showed high selectivity for chromate since its adsorption capa city for other heavy metal ions such as cadmium and manganese ions was rela tively low. An investigation of the adsorption isotherm of dried powder of Pachymeniopsis sp. for chromate adsorption at 25 degrees C showed a Langmui r-type dependence. The maximum chromate adsorption capacity of the selected alga was about 225 mg/g. Desorption of the adsorbed chromate from Pachymen iopsis sp. was done by treating the sample with 1 N NaOH. It was confirmed that ion exchange type adsorption was observed with an anion exchanger but not with a cation exchanger. It is therefore believed that the chromate ads orption is based on anionic exchange of Pachymeniopsis sp.