Abstract:
This project work was carried out to assess the potentials of Avocado pear ( Pearsea
americana) exocarp for the removal of lead and cadmium ions both in single and in binary
metal system from aqueous solution. Effects of various parameters such as solution pH,
contact time, biosorbent particle sizes , biosorbent dose, temperature profile, metal ion
concentration and presence of sodium, calcium and magnesium as interfering ions were
studied. The desorption studies was also carried out. Result obtained shows that Pearsea
americana exocarp was 98 % effective for single metal and 49 % effective for the binary
metal system in removing lead from aqueous solution at an optimum pH of 4 ; 83 % and 41
% effective in removing cadmium both in single metal and binary metal system respectively
at pH of 5. The optimum contact time for lead and cadmium were 30 and 60 min
respectively. The sorption of lead and cadmium followed pseudo-second-order kinetic model.
This was further supported by intra-particle diffusion and Elovich models. Three different
isotherms: Langmuir, Freundlich and Temkim were used to analyze the equilibrium data, with
equilibrium sorption best fitted into Freundlich isotherm. The sorption of lead and cadmium
increased with increase in biosorbent dosage and decreased as the particle size increased. The
result shows that the sorption capacity decreases with increase in temperature from 25 °C to
70 °C. The result of thermodynamic paramters such as ΔG, ΔH and ΔS showed that the
sorption process is spontaneous and exothermic. The study therefore showed that Pearsea
americana exocarp could be used as a biosorbent for the treatment of water contaminated by
lead or cadmium.
