A central composite design (CCD) under the response surface methodology (RSM)was used to study the effect of three adsorption variables (pH, initial concentration, and adsorbent dosage) in order to determine the optimum process conditions for the adsorptions of Ni (II) and Cr (III) onto sulphuric acid modified sorghum bicolor activated carbon (SBAC).This study yielded removal efficiency of 98.89 % for Ni (II) and 94.27 % for Cr (III) ion under optimal conditions of pH (8), initial metal ion concentration (25 mg/L), adsorbent dosage (10 mg) and pH (7), initial metal ion concentration (5 mg/L), dosage (15 mg);respectively. Statistical analysis of variance results showed a good correlation existed between the experimental and predicted data with R2 values of 0.99 for Ni and 0.98 for Cr. The equilibrium data for Ni (II) adsorption was best described using Freundlich model while Langmuir model best fit Cr (III) adsorption. The mechanism of adsorption for both Ni and Cr adsorptions on SBAC followed Pseudo second order kinetic model.  http://dx.doi.org/10.4314/njt.v36i3.41

ABSTRACT:The study focused on assessment of removal of cypermethrin and chloropyriphos in aqueous solution using activated carbon made from Jatropha Curcas. Batch adsorption experiments were carried out under different conditions of parameters such as pH, contact time, adsorbent dosage, and initial concentration of the adsorbate on pesticide adsorption. The adsorption data were described by Langmuir and Freundlich adsorption model. Adsorption capacity of 92.73% and 92.26% of chloropyriphos and cypermetrin respectively were removed by 2g of the adsorbent per 50 cm 3 of initial concentration of 0.78 mg/l and 1.50 mg/l chloropyriphos and cypermetrin respectively .This was achieved at 90 min of the contact time and at optimum pH of 6.3.The study demonstrates that the activated carbon made from Jatropha Curcas can be effective in the adsorption of these two pesticides from water bodies. Equilibrium experiment results show that adsorption isotherms of cypermethrin and fit better to Freundlich adsorption isotherm while chloropyriphos fit better on the Langmuir adsorption isotherm © JASEM http://dx.doi.org/10.4314/jasem.v21i1.5

The study was carried out to describe the kinetics and thermodynamics of hydrogen peroxide oxidation of a typical food dye (Tartrazine). The effect of different operational factors were investigated spectrophotometricallyat wavelength460 nm under pseudo first order reaction.These included concentration of the oxidant and the dye, the pH, ionic strength and temperature of the reacting medium and the presence of transition metal ion as homogenous catalyst. A complete and smooth decolourisation was observed. The results showed that the rate of oxidation of dye increased with increasing in concentration of substrate and oxidant. Increasing in temperature, ionic strength and pH of the basic reaction medium also raised the reaction rate. The rate of oxidation also increased with increasing in the concentration of Fe (III) ion. Pseudo second order rate constant (k2) obtained was 1.95 x 10-3 M-1s-1 and 3.8 x10-3M-1s-1 in the absence and presence of Fe (III) ion respectively. The Arrhenius activation energy for the oxidation in the absence and presence of Fe (III) ion were 47.23 kJmol-1 and 42kJmol-1 respectively. Other thermodynamic parameters showed entropy of activation (ΔS#), free energy of activation (ΔG#) and Enthalpy of activation of the reaction (ΔH#) in the presence of Fe (III) as -34.7  JK-1mol-1, 48.4 kJmol-1 and 40.30 kJmol-1 respectively. The results in the absence of Fe (III) ion were -24.6 JK-1mol-1, 51.2 kJmol-1 and 44.0 kJmol-1respectively. The relative lower activation energy (Ea),fairly higher negative value of (ΔS#) and higher (ΔG#) , with higher rate constant in the presence of Fe(III) ion showed Fe(III) ion enhancement of rate of decolourisation. Keywords: Tartrazine Food dye, Kinetics, Thermodynamics, Hydrogen Peroxidede colourisation,