COMPARATIVE Pb(II) ADSORPTION BY ACTIVATED CARBON FROM AFRICAN STAR APPLE (Chrysophylumalbidum) AND PAWPAW (Carica papaya) SEEDS

Abstract

Two types of phosphate-activated carbon were prepared from African star apple (Chrysophylumalbidum) (CAAC) seed shell and pawpaw (Carica papaya) (CPAC) seeds, characterized, and employed for Pb(II) ion sorption from simulated contaminated water by studying the sorption rates and effects of pH, dosage and temperature. Experimental data were assessed using kinetic models, and thermodynamic properties were investigated. Characterizations suggested hydroxyl, carboxyl, amides, and phosphate functional groups were active in Pb(II) ion adsorption. The Pb(II) ion uptake was swift, as equilibrium was attained within 60 minutes for both adsorbents. The pseudo-second-order (PSO) and fractal pseudosecond-order (FPSO) kinetics models fitted the rate data. The effective adsorbent dose for 50 mL of contaminant solution was 1.0 g for both CAAC and CPAC adsorbents, and the pH of optimum sorption was 5. The Pb(II) ion sorption process was exothermic for both adsorbents. The process was increasingly spontaneous with higher temperatures and reduced entropy as the process transitioned towards equilibrium. BothCAAC and CPAC adsorbents may be employed in water treatment over a wide temperature range. Comparatively, both adsorbents exhibited
similar sorption strength