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Water 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
