Studies on the effect of pH on the sorption of cadmium (ll), nickel (II), lead (II) and chromium (VI) from aqueous solutions by African white star apple ( Chrysophyllum albidium ) shell

The cleaning of our environment should be carried out with the use of natural products instead of chemicals so as to reduce pollution. This study investigates the potential of an agricultural waste in scavenging heavy metal ions from aqueous solution. The role of pH in the removal of cadmium (ll), nickel (II), lead (II) and chromium (VI) from aqueous solution by bio-sorption using African white star apple was examined. The adsorption process was found to be highly pH-dependent and the results indicate that the optimum pH for sorption of Cd (ll) and Ni (ll) was 6.0 while Pb (ll) was 7.0 and maximum percentage removals recorded were 64.69 and 76.88% for Cd (ll), 61.04 and 72.28% for Ni (ll) and 55.60 and 67.44% for Pb (ll) for the two adsorbents, UAWA and MAWA. Cr (VI) exhibited a different pH dependence having the optimum pH for its removal as 2.0 for both adsorbents. Maximum percentage removals recorded were 69.00 and 77.40% by the two adsorbents presented in the original order. The results from this study showed that chemically modified and unmodified African white star apple can be a good sorbent for these heavy metal ions. Key words: Adsorption, heavy metals, Chrysophyllum albidium , sorption, biosorbent, mercaptoacetic acid.