Biosorption of Pb2+ and Cd2+ from Simulated Wastewater Using Melina (Gmelina arborea) Tree Leaves Powder

Abstract

Increased anthropogenic activities have led to serious environmental problems due to pollution caused by toxic materials such as heavy metals whose levels are rising in the environment. The inefficiency and high cost of conventional methods of waste treatment have prompted the investigation of environmentally friendly and cheaper methods of treatment using natural products. In this study, G. arborea leaves powder was investigated with a view of using it as cheap material for the biosorption of Pb2+ and Cd2+   from wastewater. The effects of operational parameters like pH, biosorbent dose [g/L], initial metal ions concentration [mg/L], contact time [minutes] and stirring speed [rpm] on the biosorption efficiency [%] were determined. The optimum solution pH for Pb2+ and Cd2+adsorption was 5.0 and peak adsorption of 91.33% and 82.53% for Pb2+ and Cd2+, respectively. 5 g/L Melina leaves were enough to achieve peak removal of both metal ions. The removal of the metal ions was comparatively quick, and stability was achieved after 30 minutes. The optimum stirring speed was 250 rpm for both metal ions. The uptake efficiency of the biosorbent was determined by Langmuir and Freundlich isotherm models. The value of Langmuir isotherm separation parameter [RL] of Pb2+ ion [0.0446 - 0.78125] and Cd2+ [0.1005- 0.9482] were within range of 0 -1 indicating favorable biosorption for both metal ions. The degree of non-linearity [n] values between Pb2+ [12.79] and Cd2+ [11.79] solution concentration and biosorption in Freundlich equation were greater than 1, indicating physical biosorption of Pb2+ and Cd2+ on to G. arborea leaves. G. arborea can serve as efficient biosorbent not only for Pb2+ and Cd2+ ions but also for other heavy metal ions in a wastewater stream