Abstract
This work demonstrates the potential of Moringa stenopetala bark powder as an adsorbent for the removal of heavy metals from wastewater. The bark powder was characterised using FTIR, XRD, zeta potential, TGA, SEM and BET techniques. Several processing parameters such as; contact time, adsorbent dose, concentration, pH, agitation speed and temperature were optimised. Using the optimum conditions the maximum removal efficiency of three heavy metals, Cd (II), Pb (II) and Cu (II) were 99.08, 99.68 and 99.60% from synthetic wastewater respectively. When applied to industrial real wastewater the removal efficiency was 94.80, 95.50 and 94.23% for Cd (II), Pb (II) and Cu (II) respectively. The adsorption equilibria observed is in accordance to the Freundlich isotherm than the Langmuir isotherm. The maximum adsorption capacity of 38.46 ± 0.21, 35.71 ± 0.86 and 34.48 ± 0.93 mg g−1 was observed for Cd (II), Pb (II) and Cu (II). The interaction of the cationic species with the bark powder was predominately via chemisorption rather than physisorption. The adsorption of the three metals ions,Cd (II), Pb (II) and Cu (II) was well defined by the pseudo-second order model (R2 = 1). The thermodynamic parameters such as ΔS, ΔH and ΔG were also determined. The calculated values of ΔH and ΔS were positive which indicated that the adsorption of metal ions on the adsorbent was an endothermic process. However, ΔG exhibited the negative values confirming that the adsorption process was spontaneous.
Published Version
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