Biosorption of Lead and Cadmium from Aqueous Solution in Single and Binary Systems Using Avocado Pear Exocarp: Effects of Competing Ions

The potentials of avocado pear (Pearsea americana) exocarp for the removal of lead and cadmium ions from solutions were characterized in single metal and binary metal systems. The native Pearsea americana was characterized using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The Pearsea americana exocarp adsorbed 98% of lead at the optimum pH value of 4 and 83% of cadmium at pH 5 in a single system. The optimum contact times for lead and cadmium ions were 30 and 60 minutes, respectively. The biosorption of lead and cadmium ions followed a pseudo second-order kinetic model. The equilibrium measurements were better described by the Langmuir and Freundlich models than the Temkin model. The biosorption processes for lead and cadmium ions onto the Pearsea americana exocarp are spontaneous and exothermic. The binding capacities of lead and cadmium ions were reduced in the presence of interfering ions such as calcium, magnesium and sodium. The study therefore demonstrated that the Pearsea americana exocarp may be used as a biosorbent for the treatment of water contaminated by lead or cadmium.