Oladipupo O. Ogunleye

Biosorption equilibrium, kinetic and thermodynamic modelling of naphthalene removal from aqueous solution onto modified spent tea leaves

The object of this study was to investigate the feasibility of using modified spent tea leaves to remove naphthalene from its aqueous solution under batch mode. The effects on the removal process of physical factors, such as initial naphthalene concentration, contact time, biosorbent dosage, pH and temperature, have been evaluated. The equilibrium biosorption data were analyzed by the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D–R) adsorption isotherm models. These models provided a good fit to the experimental data, but the Langmuir isotherm model provided the best correlation (R 2=0.993) to the experimental data. The biosorption kinetic data of naphthalene were analyzed by pseudo-first-order, pseudo-second-order and intra-particle diffusion and surface mass transfer kinetic models. These four kinetic models fitted the biosorption kinetic data well, but the pseudo-first-order kinetic model gave the best fit. The activation energy (E a ) was found to be 15.89 kJ per mole and the thermodynamic properties of the biosorption process, such as the Gibbs free energy, enthalpy and the entropic change of biosorption, were also evaluated. It was established that the biosorption process was spontaneous, feasible and endothermic in nature.

Box-Behnken design application to study enhanced bioremediation of soil artificially contaminated with spent engine oil using biostimulation strategy

This work studies the biodegradation of spent engine oil in soil using Box-Behnken design under response surface methodology. NPK fertilizer (inorganic nutrient), Tween 80 (nonionic surfactant), and pig manure (organic nutrient) concentrations were used as independent biostimulant variables, while total petroleum hydrocarbon (TPH) and hexavalent chromium (Cr (VI)) reductions as dependent variables (response) in a 42-day remediation period. A statistically significant second-order quadratic regression model for TPH and Cr (VI) removal was obtained. The coefficient of determination (R2 = 0.9995 for TPH and 0.9988 for Cr (VI)) and probability value (P < 0.0001) demonstrated significance for the regression model. Numerical optimization technique based on desirability function was carried out for initial spent engine oil concentration of 10% w/w to optimize the biodegradation process. The optimum values for biostimulation agents to achieve a predicted maximum TPH and Cr (VI) removal of 67.20% and 53.20%, respectively, were found to be as follows: NPK fertilizer, 4.22 g; Tween 80, 10.69 mg/l; and pig manure, 47.76 g. At this optimum point, the observed TPH and Cr (VI) reductions were found to be 66.47% and 52.33%, respectively. The statistical analyses and the closeness of the experimental results and model predictions show the reliability of the regression model, and thus, biostimulation of indigenous microbial density and activity can reduce remediation period of petroleum hydrocarbon and heavy metal-contaminated environment and subsequently the cost of remediation.

Enhancement of animal waste biomethanation using fruit waste as co-substrate and chicken rumen as inoculums

ABSTRACT This work investigated the effects of co-substrates (orange, mango, and pineapple wastes) and inoculums (chicken rumen), pH, and total solid (TS) content on animal waste (cow dung, pig dung, poultry droppings) for efficient and high biomethane production. The biomethanation experiments were carried out in five different 1.5 L anaerobic digesters and incubated for 10 weeks. The results showed that co-digestion of animal wastes with fruit wastes and inoculums (additives) increased biomethane yield and reduced the startup time for biomethane generation as compared to animal wastes alone. In addition, cumulative biomethane yield increased with increase in pH while it decreased with increase in TS content.

OPTIMIZATION OF POTASSIUM NITRATE BASED SOLID PROPELLANT GRAINS FORMULATION USING RESPONSE SURFACE METHODOLOGY

This study was designed to evaluate the effect of propellant formulation and geometry on the solid propellant grains internal ballistic performance using core, bates, rod and tubular and end-burn geometries. Response Surface Methodology (RSM) was used to analyze and optimize the effect of sucrose, potassium nitrate and carbon on the chamber pressure, temperature, thrust and specific impulse of the solid propellant grains through Central Composite Design (CCD) of the experiment. An increase in potassium nitrate increased the specific impulse while an increase in sucrose and carbon decreased specific impulse. The coefficient of determination (R2) for models of chamber pressure, temperature, thrust and specific impulse in terms of composition and geometry were 0.9737, 0.9984, 0.9745 and 0.9589, respectively. The optimum specific impulse of 127.89 s, pressure (462201 Pa), temperature (1618.3 K) and thrust (834.83 N) were obtained using 0.584 kg of sucrose, 1.364 kg of potassium nitrate and 0.052 kg of carbon as well as bate geometry. There was no significant difference between the calculated and experimented ballistic properties at p < 0.05. The bate grain geometry is more efficient for minimizing the oscillatory pressure in the combustion chamber.

OPTIMIZATION OF PROCESS PARAMETERS FOR ENHANCED MECHANICAL PROPERTIES OF POLYPROPYLENE TERNARY NANOCOMPOSITES

Preparation of Polypropylene ternary nanocomposites (PPTN) was accomplished by blending multiwall carbon nanotube (MWCNT) in polypropylene/clay binary system using a melt intercalation method. The effects of MWCNT loadings (A), melting temperature (B) and mixing speed (C) were investigated and optimized using central composite design. The analysis of the fitted cubic model clearly indicated that A and B were the main factors influencing the tensile properties at a fixed value of C. However, the analysis of variance showed that the interactions between the process parameters, such as; AB, AC, AB 2 , A 2 B and ABC, were highly significant on both tensile strength and Young’s modulus enhancement, while no interaction is significant in all models considered for elongation. The established optimal conditions gave 0.17%, 165 °C, and 120 rpm for A, B and C, respectively. These conditions yielded a percentage increase of 57 and 63% for tensile strength and Young’s modulus respectively compared to the virgin Polypropylene used.