Performance of sea macro-algae in pollution control: Iron and Manganese removal from water

Abstract

There are various techniques and methods used to remove metal ions from industrial effluents. Such methods include ion exchange, electrolysis, electrodialysis and the use of activated carbon in adsorption. However, most of these methods are expensive and may require importation of expensive materials. Also some are not very effective when strict limits of pollution are introduced. This calls for the need to search for an efficient and cost effective method that utilizes locally available materials. This study has identified three abundant locally available sea macro-algae species; Sargassum sp, Padina sp. and Ulva sp. as potential biosorbents for removal of selected metal ions (Iron and Manganese). In screening experiment of these seaweed species, they all seem promising for use in treatment of effluents containing Iron and Manganese.This study has established that, for Manganese ion removal, maximum uptake of Sargassum sp. is 82.5 mg-Mn2+/gm-biomass, maximum uptake of Padina sp. is 175mg-Mn2+/gm biomass, and the maximum uptake of Ulva sp. at 214.5 mg-Mn2+/gm-biomass is the highest of the sea macro-algae species employed. The uptake of conventional adsorbent activated carbon used for control purposes at 231.3 mg-Mn2+/gm-activated carbon, was higher than the uptake of the best biomass Ulva sp. For iron ion removal, the screening experiments show that Sargassum sp. had its maximum uptake capacity at 48.8 mg-Fe3+/gm-biomass. Maximum uptake capacity of Padina sp. is 50.3 mg-Fe3+/gm-biomass and the maximum uptake capacity of Ulva sp. at 52.3 mg-Fe3+/gm-biomass was once again the best of the sea macro-algae species screened. Activated carbon maximum uptake capacity at 52.8mg-Fe3+/gm-activated carbon is comparable to the maximum uptake capacity of Ulva sp. Besides screening work to identify potential biosorbents, experiments undertaken covered optimization studies to establish optimum pH, biomass loading and contact time. While optimum loading values varied with sea macro-algae species employed and metal ion being removed, optimum pH and contact time in both iron and manganese biosorption was 3 and 15 minutes, respectively. The study has established that, the three sea macro-algae species are effective in iron and manganese biosorption. Biomass loading is small and accumulation is rapid, however metal ion removal is very much dependent on pH.

Journal of Building and Land Development Vol. 13 (1) 2006: pp. 50-57