Carboxylated alginic acid prepared through oxidation reaction with potassium permanganate had a high uptake capacity of 3.1 mmol/g dry mass at pH 4 and showed higher affinity to heavy metals compared to alkaline metals (Ca2+, Mg2+) in mixed metal system. The pHzpc value of the carboxylated alginic acid was 2.31, which was lower than pHzpc (2.83) of natural alginic acid. The increased number of carboxyl groups was confirmed by IR and 13C-NMR spectrum analysis, elemental analysis and carboxyl group number count. Lead adsorption by carboxylated alginic acid is an endothermic process since binding was increased as the temperature increased. When the temperature of wastewater is higher than room temperature, carboxylated alginic acid has an advantage over general adsorbents whose uptake capacity decreases as the temperature increases. Also, lead adsorbed on carboxylated alginic acid was desorbed effectively by about 80% by nitrilotriaceticacid.