| dc.description.abstract | The presence of heavy metals in water sources is ever a growing concern due to their lethal effects on all living organisms through food chain. The optimization of wastewater purification processes requires a development of new operations based on low cost raw materials with high pollutant removal efficiency. Zinc which is one of the heavy metals is an essential element to humans but when in excess it causes a number of alminates for example zinc pox, corrosive to eyes, skin and mucous membranes. Several conventional physical and chemical wastewater treatment technologies including coagulation, filtration, evaporation recovery, precipitation, oxidation/reduction, electrochemical treatment, ion exchange and reverse osmosis have been used to remove heavy metals from aqueous systems. However, the above methods are economically unfavorable.
In this work, waste eggshells were used to evaluate their effectiveness in the removal of zinc from pharmaceutical waste water. Waste eggshells contain high contents of calcium carbonate (85–95%); therefore, their recycling or reuse has the potential to reduce environmental pollution while acting as a cost effective material for the immobilization of heavy metals in wastewater and soil.
The effect of pH on adsorption of Zn2+ ions onto eggshell was studied by mixing 0.5 g of the adsorbent with 100 ml of 100 ppm solution of the adsorbate at different pH values ranging from 2 - 10 at 24ºC. At lower pH values, zinc adsorption was low. As pH increased, zinc adsorption increased generally. The effect of contact time on adsorption Zn2+ ions was studied by mixing 0.5 g of the adsorbent with 100 ml of 100 ppm solution of the adsorbate with different contact times ranging from 30, 60, 90, 120, 150, 180 and 210 mins at ambient temperature and pH 7. It was observed that the removal of Zinc by the eggshells generally increased with increase in contact time. The effect of adsorbent dose on the adsorption of Zn2+ ions was studied by mixing different masses of the egg shell adsorbent ranging from 1, 2, 3, 4, 5, 6, 7, 8, to 9 g with 100 ml of each 100 ppm solution of the adsorbate at ambient temperature and pH 7. Zinc adsorption increases with increase in adsorbent dosage. Finally, an experiment was repeated for the optimal conditions obtained. The optimal conditions obtained were; 8g that is quantity of eggshell powder, Ph 8 and time of contact 180 minutes. The initial and final concentrations of zinc in the waste waters was 3.002 and 0.068 mg/L respectively. Zinc adsorption was 97.7% under the optimal conditions | en_US |
