Equilibrium, Kinetic and Thermodynamic Studies of Dyes in Aqueous Solution onto Iron Nanocomposite Stabilized by Irvingia gabonensis Leaf Extract

Elimination of dyes in contaminated water or wastewater has become a universal challenge because of their colouration, toxicity, mutagenicity and carcinogenicity when discharged into the recipient environment without treatment and several technologies have been developed to deal with this problem. This paper reports the potential of exploring the use and comparison of conventional iron zero-valent (nZVI) nanoparticle and Irvingia gabonensis stabilized iron nanocomposite (Ig-nZVI) for the elimination of methyl red (MR) and methyl orange (MO) dyes in aqueous solution under effect of different experimental conditions of adsorbent dosage, initial dye concentrations, pH, contact time and temperature. Data obtained show an increase in percent dye elimination as the amount of adsorbent increased. The optimal removal of MR and MO occurred in ˂ 60 min of the start of each experimentation, obtained at a maximum pH of 5.1 at 98.5% and 80.6% for adsorbent dosage of 0.3g/50 mL and 20 mg/L initial dye concentration at temperature of 27oC. The experimental data fitted the Lamgmuir isotherm with maximum adsorption capacity (qmax) of 166.7mg/g (Ig-nZVI) and 83.35 mg/g (nZVI) for MR while 128.21 mg/g (Ig-nZVI) and 40.02.5 mg/g (nZVI) were obtained for MO. Kinetics studies showed that the removal of MR and MO fitted the pseudo second-order model. The adsorption of MR and MO were endothermic and spontaneous with enthalpy values of 3.39kJ/mol (Ig-nZVI) and 776.26kJ/mol (nZVI) and standard Gibbs free energy values of -5.95kJ/mol (Ig-nZVI) and -12.00kJ/mol (nZVI). Thermodynamic studies (ΔG < 0, ΔH < 0, ΔS > 0) implied a spontaneous and exothermic process in nature. The adsorption of MO was endothermic and spontaneous with enthalpy values of 31.70kJ/mol (Ig-nZVI) and 20.91kJ/mol (nZVI) and standard Gibbs free energy values of -5.92kJ/mol and -7.07kJ/mol for Ig-nZVI and nZVI respectively. Adsorbent produced from leaf extracts of African mango tree (Irvingia gabonensis) and stabilized by iron oxide could be an attractive option for elimination of dye from industrial effluents

Identification and quantification of Polycyclic Aromatic Hydrocarbons (PAHs) and trace metal analyses in soils around the Donald Ekong Library Car Park, University of Port Harcourt

The outcome of analysis of the levels of PAHs and trace metal in soils around Donald Ekong library car park at University of Port Harcourt shows that its heavy metal contents is high relative to the DPR standard in soils. With the exception of Vanadium, all other selected heavy metal in mg/kg was detected in the soil samples. The selected trace metals and concentration in mg/kg are Cd (0.15), Pb (13.10), Zn (34.75), Fe (30.73), Cr (5.73), and Ni (9.45) relative to their respective Department of petroleum resources standards (mg/kg) which are 0.01, 0.05, 1.0, 1.0, 0.03 and 0.10 respectively. Twelve PAHs were detected while four PAHs were not detected. The carcinogenic and high molecular weight PAHs were all detected while some of the low molecular weight PAHs were not detected or were detected at very small concentration. The higher solubility and volatility of the lower molecular weight PAHs are responsible for this trend of PAHs distribution. There is need to use proper soil remediation strategy for restoration of the soil in line with the appropriate permissible limits for heavy metal and PAHs in soil, which are both (as they are) above their respective permissible limit.Keywords: PAHs, Soil, Heavy Metal, Quantificatio