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Hexavalent chromium was adsorbed from aqueous solution with three prepared and characterized adsorbents, namely goethite (G), activated carbon (AC) and their composite (GAC). The goethite particle was synthesized using the precipitation methods, and activated carbon was prepared from the stem bark of Daniellia oliveri tree and composite in a ratio of 1:5 goethite–activated carbon. The adsorption capacities of G, AC and GAC for Cr(VI) are 6.627, 5.455 and 6.354 mg/g with 0.02 g adsorbent within contact time of 60, 180 and 30 min for G, AC and GAC, respectively, for Cr(VI) adsorption at optimum pH of 3. The isotherm studied was best explained by Langmuir adsorption isotherm and fitted with the pseudo-second-order kinetic model. Desorption studies showed that 1.0 M HNO3 was a better desorbing agent than 0.1 M HNO3, 0.1 M HCl and 1.0 M HCl. Chromium was most desorbed (94.60% in Cr//G using 1 M HNO3). The result obtained revealed that goethite and activated carbon produced are favourable adsorbents and the composite of the two adsorbents gives a more favourable, economical and affordable adsorbent for the clean-up of heavy metal contamination.

Bisphenol A (BPA) is an organic compound which is often used as plasticizer and has been reported to be hazardous to man. In this research the efficiency of removal of BPA from water by magnetite through adsorption process was studied. The magnetite was synthesized using reverse co-precipitation method and fully characterized. Various physicochemical parameters affecting the adsorption of BPA using magnetite were studied as well. The optimum time for the adsorption process was found to be 60 min at pH of 6, adsorbent dose of 0.2 g and 50 ppm of BPA. The adsorption data were fitted by the Langmuir adsorption isotherm best with a regression value of 0.957. The R L value was 0.179 which revealed that the process is favorable. The Freundlich constant n which was 1.901 also revealed that the adsorption is normal and favorable. The data were in agreement with the pseudo-second-order kinetics with regression value of 0.98. From the thermodynamic studies, the process was found to be exothermic and the Gibb's free energy value which was negative showed that the adsorption was spontaneous. The synthesized magnetite therefore offers great potential for the remediation of bisphenol A-contaminated media.

The oil and biodiesel produced from Nigerian and Indian Jatropha curcas seeds were evaluated using a parametric Student's t-test model. The characteristics assessed include oil yield, specific gravity, density, acid value, free fatty acid, iodine value, saponification value, peroxide value, viscosity and flash point. The results revealed significant differences (p < 0.05) between the yield of the Nigerian and Indian Jatropha oils (80% vs 56%). The acid value, free fatty acid, iodine value, peroxide and viscosity values were significantly higher in the Nigerian Jatropha oil compared to the Indian Jatropha oil. There was no significant difference in the density and moisture content between the two Jatropha oils. A higher flash point was recorded for the Nigerian Jatropha diesel. The calorific value was 48.31 MJ/kg in the Nigerian Jatropha diesel as against 47.50 MJ/k Indian Jatropha diesel. Most of the properties of the Nigerian Jatropha diesel evaluated compared favourably with the ATM and EN (for biodiesel) standard values. It could be concluded from this study that, Jatropha curcas plant found in Nigeria has the potential of boosting the economy in term of biodiesel production.

ABSTRACT:The adsorption of Mn(II) and Co(II) ions from aqueous solution was investigated using batch adsorption experiment at room temperature. The effect of pH, contact time, metal ion concentration and temperature were evaluated. The residual concentrations of the metal ions were determined by atomic absorption spectrophotometer. The results showed that maximum removal of Mn(II) and Co(II) ions occurred at pH 9. Some physico-chemical and spectroscopic characterization of the adsorbents were done such as moisture content, ash content, bulk density, volatile matter, iodine number, point of zero charge (PZC), XRF, and FTIR. The moisture and ash content of MCAC adsorbent were found to be 9.85±0.06 and 5.5±0.1% respectively. The bulk density was found to be 0.37±0.01g/m 3 , iodine number of 367.66±30 mg/g and PZC of 6.8. The SEM micrograph shows particle grains and jelly like rough surfaces, FTIR analysis results show different functional group in the MCAB adsorbent such as O-H, C=O, and C=C stretching. Kinetic study shows that the pseudo-second order kinetic model best described the adsorption of metal ions. The equilibrium data fitted Langmuir, Freundlich and Temkin adsorption isotherms, in each case, the Langmuir model appears to have better regression coefficients than the Freundlich and Temkin. Thermodynamics investigation showed that Gibb's free energy change ( ) was negative indicating that the adsorption of Mn(II) and Co(II) ions by maize cob activated carbon were feasible and spontaneous. The positive value of enthalpy change ( ) implies that the reaction was endothermic while positive value of entropy change ( ) implies an irregular increase in the randomness at the solid/solution interface of the adsorbent during the adsorption process. © JASEM http://dx.doi.org/10.4314/jasem.v19i4.22

This study focused on the liquid phase sorption of methylene blue (MB) using low cost agro-waste from moringa pod husks. Moringa pod husk was carbonized at 450°C for 30 min, which was later activated with 0.1 M phosphoric acid. The physico-chemical properties of moringa pod activated carbon (AMP) were determined. The results of the physicochemical parameters are: moisture content (13.6 ± 0.02), ash content (2.61 ± 0.11), point of zero charge (pH ZPC) (7.2) and bulk density (0.6 g L-1). The sample was also characterized using Brunaeur Emmett Teller (BET), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Fourier-transform infrared spectroscopy (FTIR). The BET surface area obtained for AMP is 1340.234 m 2 g-1. The effect of optimized parameters such as initial concentration, contact time, pH, adsorbent dosage, and temperature on methylene blue removal was investigated. The obtained maximum monolayer adsorption capacity value (q max) is 9.5785 mg g-1. The three adsorption isotherm models, namely Langmuir, Freundlich and Temkin, were employed to describe the fitness of equilibrium data. The Langmuir equation fitted the adsorbent system better with a R 2 value of 0.9958. The pseudosecond-order kinetic equation also fitted the data well. Thermodynamic studies showed that the AMP-MB adsorption system is spontaneous and endothermic as a negative and positive value was obtained for G 0 (-0.460 KJ mol-1) and H 0 (4.482 KJ mol-1), respectively.

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