ABSTRACT
Background: Cadmium [Cd] is a heavy metal that is widely utilized in industries and contaminates soil and groundwater. There are several environmental problems related to cadmium, therefore, the technical and economic methods of removing Cd are of great importance. So this study was conducted to evaluate the efficiency of a type of plant to remove the Cd from aqueous environments
Methods: In this cross-sectional study, the adsorption of Cd examined from synthetic aqueous solutions was evaluated using the seed powder of Miracle tree [Moringa oleifera]. In this order, 70 samples were prepared and tested. To determine the absorption of metals by this sorbent, different pH [5, 7 and 9], sorbent dose [1.5, 3 and 5 g], temperature [20, 30 and 45 degree C], concentrations of Cd [2, 5, 10 and 20 ppm] and exposure time [0, 30, 60, 120, 180 and 210, 240 minutes until reaching equilibrium] were experimented upon, using atomic absorption spectrometer [Varian-AA240FS], and the residual concentration of Cd was read
Results: The highest removal efficiency of Cd under optimum condition [180 minutes and pH of 5] was 70%. The optimum sorbent dose was 1.5 g, which achieved a removal efficiency of 75%. The removal trend was an inverse of Cd concentration. The adsorption of Cd using M. oleifera fitted into both models [Freundlich and Langmuir], but was somewhat better fitted with the Freundlich model and followed pseudo second order kinetics
Conclusion: The results indicated that under optimized absorption conditions [pH: 5, sorbent: 1.5 g, temperature of 45 degree C, Cd concentration of 2 ppm and exposure time of 180 minutes], the removal rate of Cd was 80% and thus the nature of the adsorption reaction was endothermic. Based on the results obtained, the studied sorbent could be introduced as a practical sorbent to the Industrial society. In some sorbents, for M. oleifera, the adsorption capacity was determined based on the results obtained, and the adsorption capacity was found to be 0.1 mg/g. This means that, in order to remove any pollutant [in this case Cd], 10 times of the sorbent weight need to be added