Cadmium biosorption by non-living aquatic macrophytes Egeria densa

In this work the removal potential on Cd²⁺ by the non-living Egeria densa biomass has been studied. The influence of the metal solution pH, the plant drying and the metal solution temperature, and biosorbent grain size was previously studied in batch systems. The cadmium adsorption rate has increased when the pH was increasing, but at pH 5, the cadmium precipitation has begun to occur, avoiding such high pH values in other tests. The cadmium removal was around 70% at 30°C biomass dried and solution temperatures, assuming as the best temperature conditions. No significant influence was observed in cadmium removal due to the grain size effect. The biosorption kinetic data were well fitted by a pseudo-second order model. The equilibrium time in experiments was around 45 min with a 70% Cd removal. The equilibrium data at pH 5 were described rather better by the Langmuir isotherm than the Freundlich one, with an adsorption rate and maximum metal content values of 0.40 L  g⁻¹ and 1.28 meq  g⁻¹, respectively, for Langmuir model. The kinetic parameter values are near to other biosorbents, indicating that the macrophytes E. densa could be used as biosorbent material in industrial effluent treatment system.