ABSTRACT

The perfonnance of eggshell particles as adsorbent for heavy metals removal from aqueous solution was investigated. This was motivated by the increasing pollution of Rivers by industrial effluent discharge. Effects of dosage, pH, initial metal concentration, temperature and contact time on the adsorption of lead (II) ion (P'), copper (Il) ion (Cu') and iron (III) ion (Fe") from aqueous solution were studied. Various adsorption isotherms and kinetics were used to find the model(s) that best match the experimental data. Error analysis was also carried out to validate the best fit adsorption isothenns. From the results, the amount of metals removed increased with increase in adsorbent dosage, pH and contact time. Thus, from 0.25 - l .0g dosage: the percentage removal increased from 69.81- 83.43% for Pb 2 +, 54.51 - 78.24% for Cu and 82.15 -91.16% for Fe'. Also, from 3.5 - 9.0 pH, the percentage of P, Ci and Fe removed increased from 71.68 - 84.18%, 64.79 - 80.48% and 78.56 -92.09% respectively. Only a marginal increase was recorded after pH of 6.0. At 30- 120 min contact time, the percentage of P, Cu and Fe adsorbed als:» increased from 63.14 - 83.43%, 52.68 -- 78.24% and 67.84- 91.16% respectively. Pb 2 + adsorptio--;.·:eached equilibrium at about 60 minutes, while that of Cu 2+ and Fe was attained at about 90 r:inutes. In contrast, the percentage of P, Cu and Fe? adsorbed decreased with increase in mitial metal concentration and temperature. Thus, from 10 - 50mg/L initial concentration, the percentage removed decreased from 83.43 - 71.97%, 78.24 - 66.78% and 91.16 -76.77%, for P, Cu and Fe' respectively. Similarly, from 28 C (rocm temperature) - 60 °C, the percentage removed decreased from 83.43 - 73.23%, 78.24 71.02% and 91.16 -84. 796%, for P?', C?' and Fe 3 ... respectively. Between 28 °C and 40 C, the adsorption slightly increased. From the isotherm analysis, predicted equilibrium aci::-·:rption capacity, Q,, and error analysis, it was shown that Redlich-Peterson isothenn fitted bett< r than the other isothenns. Though, the Langmuir and Temkin isotherms also fitted the adsorption process. Finally, Q obtained from the pseudo second order kinetics are closer to values evaluated from the experimental data compared to the pseudo first order kinetics. Hence, the pseudo second order kinetics is most suitable for the adsorption process