Abstract
M.Sc. (Nanoscience)
Water scarcity and pollution is a worldwide problem that affects everyone especially in South Africa. This work is aimed at developing an adsorbent that is inexpensive and easily applicable in removing heavy metals in water especially in rural areas of African countries. Therefore the use of a local fruit waste from avocado peels for adsorption of AsIII, CdII and CrVI from standard solutions and real water samples was investigated. The powdered avocado peels was saponified by NaOH in order to increase the oxygen containing groups on the surface of the adsorbent which in turn will enhance AsIII, CdII and CrVI adsorption on avocado peels. The functional groups found on the avocado peels were characterised by FTIR, SEM, EDS and BET.
The batch extraction method was applied in adsorbing AsIII, CdII and CrVI from after optimizing the following parameters pH, adsorbent mass, analyte concentration, contact time and temperature. The metal ion’s determinations were done separately by using anodic stripping voltammetry (ASV). Then 54%, 74% and 51 of AsIII, CdII and CrVI, respectively were removed from a real water samples collected from East London, in South Africa. The data fitted well in Langmuir isotherm because the correlation coefficients were 0.9657, 0.9707 and 0.9681 for AsIII, CdII and CrVI, respectively.
The adsorbent had a good stability because it was applied separately for AsIII, CdII and CrVI adsorption for 7 cycles and similar results were obtained. The data from ASV method for AsIII, CdII and CrVI detection was compared to ICP-OES using a t-test at 95% confidence limit. The calculated values were less than the critical values, confirming that the two methods were in good agreement.