Heavy metal biosorption by Alginic acid extracted from Sargassum sp.

Abstract

AttachedWater is the driving force for many natural processes on the earth. It is essential to protect the quality o f water for the survival o f all living beings. However, water pollution has increased significantly during the last few decades with the rapid industrialization processes. This work highlights a development o f a low cost, sustainable and efficient water purification sorbent extracted from a seaweed species grown in the coastal areas o f in Sri Lanka. Alginic acid extracted from Sargassum sp. collected at the coast o f Beruwela has been studied extensively as a candidate material to remove metal ions from natural and waste waters. The extracted alginic acid was characterized using FTIR spectroscopy. Metal absorption capacity, selectivity and the extent o f reusability o f alginic acid were determined for the metal ions ( Pb2+, Cu2+, Zn2+, Co2+, Ca2+, and Mg2+ ) by using respective metal ion solutions. Alginic acid has shown maximum adsorption towards Pb2+ ions with 488.5 mg/g capacity. Adsorption capacity for metal ions Cu2+, Zn2^, Co2+, Mg2+ and Ca2+ ions were 314.4 mg/g, 287.4 mg/g, 283.8 mg/g, 83.6 mg/g and 74.4 mg/g respectively. It showed more selectivity towards Pb2+ ions over the other ions in a metal ion solution. Reusability o f the aliginic acid for two adsorption-desorption cycles were experimented and determined that the metal ion removal capacity remains fairly constant. Furthermore, alginic acid showed an ability to remove Pb2+ ions completely from Pb2+ spike natural water sample, which initially contained 5.0 mg/L Pb2+ ion concentration. Ca2+ and Mg2+ ions removal capacities o f alginic acid from natural water system were 57.5 mg/g and 36.6 mg/g respectively. It can be concluded that alginic acid is an economical, sustainable remedy for water purification in Sri Lanka to remove heavy metal ions from waste water