Removal of Aqueous Lead and Cadmium using Persea americana Seed Coat: Single and Binary Studies

The presence of heavy metals in water sources is worrisome because heavy-metal pollutants are associated with severe health problems. The resultant health challenges as a result of heavy metal pollution have necessitated the removal of these pollutants from wastewater before being discharged into the environment. This research was carried out to investigate the potentials of avocado pear (Persea americana) seed coat as biosorbent of lead(II) and cadmium(II), in single and binary metal systems, from aqueous solutions. Biosorbent particle sizes and dosage were varied in the study. Desorption of biosorbed metal ions was studied using sodium salt of ethylene diaminetetraacetic acid (EDTA) and hydrochloric acid (HCl). Biosorbent of 106 μm particle size gave the best uptake of lead and cadmium from aqueous solutions than those of 850, 1180, 1400 and 2000 μm particle sizes. Biosorption of lead(II) and cadmium(II) increased with an increase in biosorbent dosage (up to threshold dosage). The uptakes of lead(II) and cadmium(II) in single systems are higher than those of binary systems. Biosorption capacities of lead(II) were higher than those of cadmium(II) for both single and binary systems. The observation could be linked to low hydration energy of lead(II) compared with that of cadmium(II). Biosorbed lead(II) and cadmium(II) were desorbed using 1.0 mol/L EDTA (for single system) and 1.0 mol/L HCl (binary system). Lead and cadmium ions were easily desorbed from single metal system unlike binary system. In overall, the avocado pear biosorbent could be used for treatment of wastewater contaminated with lead(II) and cadmium(II).