Adsorption of Rhodamine B Dye from Aqueous Solution on Irvingia gabonensis Biomass: Kinetics and Thermodynamics Studies

Raw Irvingia gabonenses (dika nut) (DN) and its acid-treated form(ADN) were used for the uptake of rhodamineB(RhB) dye from aqueous solution. The adsorbents were characterized by Fourier transform infrared (FTIR) spectroscopy, Brunauer–Emmett– Teller (BET) surface area analysis and scanning electron microscopy (SEM). The adsorbents were found to have characteristic functional groups such as –OH, C-N and C=O. SEM revealed that acid treatment resulted in the development of several pore sizes. Sorption data fitted the Freundlich adsorption isothermbetter than the Langmuir isotherm.The maximum sorption capacities, qmax, obtained from the Langmuir adsorption isotherm were 212.77 and 232 mg g–1 for DN and ADN, respectively. The pseudosecond- order kinetics model was observed to fit the adsorption data. Solution pH and temperature significantly influenced the adsorption process and negative values of ΔG° suggest that the sorption process was spontaneous and feasible. Intraparticle diffusion mainly controlled the uptake of RhB onto DN and ADN; however, boundary layer diffusion also occurred in the RhB-ADN system. The desorption efficiency of RhB from the adsorbents was tested with a number of eluents. The eluents were found to follow the order: H2O>CH3COOH>HCl and CH3COOH>HCl>H2O for DN and ADN, respectively.KEYWORDS Irvingia gabonenses, adsorption, rhodamine B, thermodynamics, kinetics, biomass

Heavy Metals Distribution and Speciation in Soils around a Mega Cement Factory in North-Central Nigeria

Surface and sub-surface soils were sampled in the neighbourhood environment of an ultra-modern and largest cement factory in Nigeria. The five geochemical fractions investigated were exchangeable, carbonate, Fe-Mn oxide, organic matter and residual. All fractions were subsequently analyzed for lead (Pb), copper (Cu), zinc (Zn), manganese (Mn) and iron (Fe) using atomic absorption spectrophotometer. The average total metals concentrations (mg/Kg) in the surface soil were 1063.8± 261 for Fe, 30.29 ± 19.25 for Mn, 24.15 ± 21.69 for Cu, 15.08 ± 11.95 for Pb and 8.54 ± 3.18 for Zn. Relatively lower mean concentrations were measured in the sub-surface soil samples. The percent distribution concentration of the various metals in the residual fraction ranged from 0.23 to 69.48% for Pb, 0.85 to 75.30% for Cu, 36.02 to 83.86% for Zn, 12.97 to 44.04% for Mn and 18.11 to 57.25% for Fe. Factor analysis revealed that while Pb, Cu and Zn would majorly be of anthropogenic origin, Mn and Fe are mainly of natural origin. Pb was found to be the most mobile with mobility factor of 71.8% while Fe has the least mobility factor of 3.62%. Regression analysis (r2 = 0.71) further showed that Cu is correlated with Pb. Soil pollution indices revealed that the surface soil is slightly contaminated in lead and zinc, and moderately contaminated in copper.Key words: Heavy metals speciation, Mobility factor, Soil pollution, Cement industr