Process Optimization for the Remediation of P.M.S Contaminated Soil using Enhanced Fenton Oxidation Technique: A Remediation approach for Hydrocarbon Polluted Soils In Nigeria
The optimization of Fenton oxidation remediation technique for effective and efficient remediation of P.M.S contaminated soil for possible application in real field challenges in Nigeria was carried out in situ by laboratory simulation.
Soil contaminated with 15% P.M.S by laboratory simulation was characterized for its physicochemical properties and heavy metal contents using standard methods, while total petroleum hydrocarbon (TPH) content was determined by molecular spectroscopy. The treatment technique was optimized for Fenton reactant concentration, temperature and time. An investigation of the soil physicochemical properties shows severe impact of the contaminant on pH (6.70 mg/kg from uncontaminated to 5.40 mg/kg in contaminated soil), conductivity (262 μS/cm from uncontaminated to 137 μS/cm in contaminated soil), phosphorus (8.30 mg/kg from uncontaminated to 6.20 mg/kg in contaminated soil) and TPH content (25.0 mg/kg from uncontaminated to 1400 mg/kg in contaminated soil). Soil texture (sand fraction: 84.60 to 82.0 %, silt fraction: 2.40 to 2.90 %, clay fraction: 13.9 to 15.10 %) and heavy metal levels (Pb: 0.3 to 0.4 mg/kg; Cd: 0.7 to 0.4 mg/kg, Ni: 0.78 to 0.69 mg/kg; V: 0.94 to 0.91mg/kg; Cr: 0.21 to 0.21 mg/kg) were not significantly affected from the result, as their values were all in the same range. pH (5.6 mg/kg from contaminated to 6.3 mg/kg in treated soil), conductivity (137 μS/cm from contaminated to 210 μS/cm in treated soil), TPH (1400.0 mg/kg from contaminated to 105.9 mg/kg in treated soil) and metal concentrations (cadmium: 0.04 ppm to 0.02 ppm; vanadium: 0.91ppm to 0.18 ppm) were improved after Fenton oxidation treatment, which indicates the ability of the technique to improve the physicochemical quality of the contaminated soil. The optimum concentrations of Fenton reactants were found as 500,000 ppm H2O 2;and 250 ppm FeSO4, while temperature of 300 0 C and pH of 4 were found as the optimum temperature and pH respectively from the process optimization. P.M.S contaminated soil treatment with Fenton reactants using these optimum conditions yielded excellent and impressive result, with significant decrease in TPH content by 92.44 % after nine hours of periodic monitoring; breaking down the hydrocarbons into non-toxic environmental friendly products (CO 2and H 2O) from the degradation process. Kinetics analysis and evaluation shows pseudo - first order mechanism for the Fenton treatment with a calculated rate constant of 0.236 hour -1and a calculated half-life of 2 hrs, 56 minutes. The Fenton method is found to be very effective and efficient not only for the removal of the P.M.S contaminant, but also for the restoration of lost physicochemical properties occasioned by the effect of the contaminant. The environmental friendliness and fast response time towards effective clean up gives the technique a cutting edge advantage over other conventional methods. It therefore presents potentials for remediation experts in outright applications on real field challenges in Nigeria, especially the abandoned polluted Ogoni area in the Niger Delta region that has since been receiving global outcry for attention.
Keywords: Soil, Process optimization, Remediation, P.M.S, Pseudo-first order, Fenton oxidation, T.P.H