USE OF PULVERIZED OYSTER AND SNAIL SHELLS IN THE REMOVAL OF HEAVY METALS FROM HYDROCARBON CONTAMINATED SOILS

Oyster and Snail shells were used as adsorbents for the removal of heavy metals from an oil spill contaminated soil from Eneka Community in Obio-Akpor Local Government Area. Atomic Absorption Spectrophotometer was used to determine heavy metals concentrations in each of the seven soil samples before and after treatment with the pulverized oyster and snail shells. Results of the heavy metals in soil samples (A, B and C) before treatment were: Ni: 2.27 – 4.53 mg/kg (control sample 3.75 mg/kg); Cr: 48.80 – 58.10 mg/kg (control sample 47.70 mg/kg); Zn: 13.40 – 19.40 mg/kg (control sample 17.34), after treatment with pulverized Oyster shells (A1, B1 and C1) were in the range Ni: 1.31 – 3.54 mg/kg; Cr: 36.3 – 48.40mg/kg; Zn: 9.87 – 12.60mg/kg. Results of samples D, E and F before treatment with pulverized snail shell were: Ni: 1.70 – 3.97 mg/kg (control sample 3.61 kg/kg); Cr: 50.70 – 57.40 mg/kg (control sample 48.60 mg/kg); Zn: 10.90 – 20.10 mg/kg (control sample 17.50 mg/kg); after treatment with pulverized snail shell D1, E1 and F1 showed results as Ni: 1.05 – 3.59 mg/kg; Cr: 35.80 – 53.91 mg/kg; Zn: 8.43 – 16.44 mg/kg. However, the concentrations of Cadmium, Copper, Lead and Vanadium in the contaminated soil samples were below the equipment detection limit. The percentage reduction of metals in samples A, B and C treated with pulverized Oyster shells were: Ni: 42.29%, 33.55%, 21.85%; Cr: 37.52%, 19.06%, 5.47%; Zinc: 49.12%, 23.88%, 18.18% respectively. While the percentage reduction in concentration of metals in soil treated with pulverized snail shell D, E, F were: Ni: 38.24%, 21.11%, 9.57%; Cr: 29.39%, 12.72%, 6.08%, Zn: 31.84%, 22.66%, 15.69% respectively. Generally, the pulverized oyster shells showed a better percentage reduction than pulverized snail shells. The results also confirmed that both the pulverized oyster and snail shells can be employed for remediation of heavy metals in hydrocarbon contaminated soils.