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Developing an effective cleaner process technology for maize-cob biomass wastes is of utmost importance. This work involved the comparison of products yield (bio-oil, biogas, and biochar) from the fast, slow, and flash pyrolysis of maize-cob biomass wastes using a fixed-bed reactor; evaluation of the individual and combined influences of pyrolysis temperature, biomass particle size, and residence time on the yield of product, and the determination of the optimum pyrolysis conditions/products yield of fast pyrolyzed maize-cob. The fast pyrolysis was performed according to the Box-Behnken Design of Experiment with three variables and three levels of the response surface methodology. The bio-oil fuel properties were determined utilizing ASTM methods and chemically characterized using CHNS elemental analyzer, GC/MS, and FTIR. The performance of the three pyrolysis techniques in terms of their product yield is in the following order: Flash pyrolysis > Fast pyrolysis > Slow pyrolysis (for bio-oil); Slow pyrolysis > Fast pyrolysis > Flash pyrolysis (for biochar and biogas). An optimum bio-oil yield of 43.13% with a high heating value (HHV) of 30.59 MJ/kg, biochar yield of 37.18% with HHV of 20.41 MJ/kg, and biogas yield of 26.05% (HHV = 13.19 MJ/kg) was respectively obtained at an optimum temperature of 567.72, 463.71, and 593.17 °C; biomass particle size of 0.51, 3.83, and 2.58 mm; and residence time of 10.01, 15.28, and 18.92 min. The determined physicochemical characterized properties of the maize-cob-derived-bio-oil revealed that the bio-oil can potentially be valued as a biofuel and as a more promising feedstock for value-added chemical production. [ABSTRACT FROM AUTHOR]

This study was carried out to optimize the batch adsorption of a polycyclic aromatic dye from a simulated textile wastewater onto Delonix regia-derived activated carbon (DRP-AC) under the influence of contact time, agitation rate, and initial dye concentration as process variables. Congo red (CR) dye was used as the model pollutant. Response Surface Methodology (RSM) with a D-Optimal experimental design was employed for this study having three factors and three levels as independent variables and percentage dye removal as the dependent variable (response). The kinetics and CR adsorption equilibrium were investigated and modeled. The CR adsorption data fitted well to a second-order quadratic regression model with a high coefficient of determination ( R 2 = 0.9999) using Design-Expert Statistical program (v. 6.0.8). The regression model indicated that the percentage dye removal was significantly (p < 0.05) impacted upon by the linear, quadratic, and interactive effects of contact time, agitation rate, and initial dye concentration. The optimum values for the dye adsorption process conditions to elicit a maximum percentage dye removal of 79.7% were found to be: 140 min (contact time), 165 rpm (agitation rate), and 300 mg/L (initial dye concentration). The CR dye adsorption kinetics followed pseudo-first-order kinetics while the mechanism of adsorption was controlled by intraparticle diffusion. The CR equilibrium adsorption can well be described by the Langmuir isotherm model (R2 = 0.9951). The maximum monolayer adsorption capacity ( Q max ) was found to be 17.12 mg/g. Therefore, DRP-AC has the potential for polycyclic aromatic dye adsorption from wastewaters. [ABSTRACT FROM AUTHOR]

Biocorrosion inhibition of mild steel in the crude oil-water environment was investigated in the absence and presence of Carica papaya peel extract, Musa paradisiaca peel extract, and Moringa oleifera leaf extract as potential biocidal-green inhibitors using gravimetric, polarization, and surface analysis (Inverted metallurgical microscope and Fourier transform infra-red spectroscopy) methods. Kinetics and adsorption behaviors of the extracts were determined and evaluated. Results revealed that each of the extracts functioned as biocidal-green inhibitors in the crude oil-water environment and that biocorrosion inhibition efficiency (IE%) of each extract increased with increase in extract concentration and exposure time. Maximum IE% of 97.7, 96.5, and 99.2% was achieved with Musa paradisiaca peel extract, Moringa oleifera leaf extract, and Carica papaya peel extract, respectively, at 4000 mg/l extract concentration and 35 d exposure time. Polarization studies indicated that each of the extracts acts as a mixed-type inhibitor. Mild steel susceptibility to biocorrosion was significantly reduced by each of the extracts through biofilm development suppression and extract adsorption onto the mild steel surface which obeyed Langmuir, Freundlich, Temkin, and Flory-Huggins isotherm models. Kinetics of mild steel biocorrosion inhibition followed a Monod form of kinetics (Type A). Gibbs free energy of adsorption values for Musa paradisiaca peel extract (−9.65 kJ/mol), Moringa oleifera leaf extract (−9.57 kJ/mol), and Carica papaya peel extract (−9.71 kJ/mol) showed that each extract adsorption was spontaneous and of physical adsorption. [ABSTRACT FROM AUTHOR]

This study evaluated the bioremediation of atrazine herbicide contaminated agricultural soil under different bioremediation strategies using indigenous Pseudomonas aeruginosa, Bacillus subtilis and Aspergillus niger as bioaugmentation agents and poultry droppings as biostimulation agent. The results showed that bioaugmentation with Pseudomonas aeruginosa, bioaugmentation with Bacillus subtilis, bioaugmentation with Aspergillus niger, bioaugmentation with bacterial-fungal consortium (Pseudomonas aeruginosa, Bacillus subtilis and Aspergillus niger), biostimulation with poultry droppings, and combined biougmentation and biostimulation (Pseudomonas aeruginosa, Bacillus subtilis, Aspergillus niger and poultry droppings) resulted in maximum atrazine biodegradation of about 97%, 95%, 84%, 99%, 100% and 100%, respectively. The kinetics of atrazine biodegradation in the soil were modelled using first-order kinetic model and the biodegradation half-life estimated. The first order kinetic model adequately described the kinetics of atrazine biodegradation in soil under the different bioremediation strategies. The rate constants (k1) of atrazine biodegradation in soil subjected to bioaugmentations with Pseudomonas aeruginosa, Bacillus subtilis, Aspergillus niger, and bacterial-fungal consortium ranges between 0.059 day-1 and 0.191 day-1 while for that subjected to natural bioattenuation, biostimulation and combined bioaugmentation and biostimulation are 0.026 day-1, 0.164 day-1 and 0.279 day-1, respectively. The half-life (t1/2) of atrazine biodegradation in soil under natural bioattenuation was obtained to be 26.7 days. This was reduced to between 2.5 and 11.7 days under the application of bioaugmentation, biostimulation and combined bioaugmentation and biostimulation strategies. The bioremediation efficiencies of the different bioremediation strategies in influencing atrazine biodegradation or removal is of the following order: Combined bioaugmentation and biostimulation > Bioaugmentation with bacterial-fungal consortium > Biostimulation with poultry droppings > Bioaugmentation with Pseudomonas aeruginosa > Bioaugmentation with Bacillus subtilis > Bioaugmentation with Aspergillus niger > Natural bioattenuation. [ABSTRACT FROM AUTHOR]

The objective of this study was designed to evaluate the effects of nutrients (inorganic NPK fertilizer and organic fertilizer) and adsorptive amendment agents (activated carbon) as well as their interactions on bioremediation of soil contaminated with Weathered Crude Oil (WECO). The organic fertilizer was made up of cattle dungs, pig dungs and poultry droppings mixtures. Box Behnken Design (BBD) of Response Surface Methodology (RSM) with three levels and three factors was used having inorganic NPK fertilizer (3 - 5 g), activated carbon (20 - 40g) and organic fertilizer (30 - 50 g) as independent variables and percentage WECO degradation as dependent variable (response) in a four weeks remediation period. Results of the study showed that WECO removal rate in soil is invariably dependent on the amount of nutrient and adsorptive agents. The optimum amount of nutrient and adsorptive amendment agents obtained to achieve a predicted maximum WECO removal of 66.24% are: inorganic NPK fertilizer, 4.19 g; activated carbon, 35.42 g and organic fertilizer, 48.94 g. At this predicted optimum amount, validation experiment revealed that 65.55% of WECO removal was achieved. Statistical analyses revealed the closeness of the experimental results to model predictions which thus show the reliability of the quadratic regression model. Therefore, organic and inorganic nutrients as well as adsorptive amendment alone and/or in combination enhances soil indigenous microbial density and activity which thereby accentuates petroleum hydrocarbons biodegradation and subsequently reduces the period of bioremediation and remediation cost. [ABSTRACT FROM AUTHOR]

A Microbial Fuel Cell (MFC) is a biochemical-catalyzed system that generates electricity by oxidation of biodegradable organic substance in the presence of microorganisms or enzymes. Microbial fuel cell technology is a new form of renewable and sustainable technology for electricity generation as it recovers energy from renewable materials such as organic wastes and wastewaters that can constitute environmental pollution if not disposed without proper treatment. This work therefore investigated the possibility of electricity generation from cassava mill effluent using MFC. The cassava mill effluent was found to generate voltage and current to the maximum of 275 mV and 2.75 mA, respectively, corresponding to a maximum power density of 189 mW/m². The voltage and current generation was respectively and significantly influenced with change in temperature, pH, concentration (strength) of effluent and addition of nutrient. Thus, it can be concluded that bioelectricity can directly be generated from cassava mill effluent using the MFC technology. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the potential of green seaweed biomass to remove heavy metals such as iron (Fe), calcium (Ca), magnesium (Mg), potassium (K), silver (Ag) and chromium (Cr) present in textile wastewater. The wastewater sample was treated with the biomass at different contact time ranging from 10 to 90 minutes. The result showed that there was 87.5%, 99.9 %, 59.7 %, 57.2 %, 100% and 86.8% corresponding maximum reduction in the concentration of Fe, Ca, Mg, K, Ag and Cr at 60 min contact time, respectively. The experimental biosorption data fitted very well to both pseudo first-order and pseudo second-order kinetic models, however, the biosorpton kinetics of Fe, Ca, Mg, K, Ag and Cr followed a pseudo first-order kinetic model and the biosorption mechanisms were controlled by boundary layer surface diffusion. Thus green seaweed biomass has the potential to be used as a low cost biosorbent for the treatment of industrial wastewater that contains the presence of heavy metals. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the potential use of cassava steep liquor (CSL) alone and in combination with potassium phosphate and ammonium sulphate (inorganic nutrients) as biostimulation bioaugmentation agent in the bioremediation of crude oil contaminated waters. Bioremediation was carried out for six weeks at ambient temperature in plastic bucket bioreactors containing water artificially contaminated with 10% (v/v) Bonny light crude oil. CSL alone and in combination with potassium phosphate and/or ammonium sulphate was added to each bioreactor. Similar contaminated water without CSL and potassium phosphate/ammonium addition served as control designated as natural bioattenuation. The results revealed that natural bioattenuation, CSL supplementation, CSL + potassium phosphate, CSL + ammonium sulphate, and combined CSL + potassium + ammonium sulphate remediation systems elicited 40%, 58.5%, 67.7%, 64.1% and 77.4% total petroleum hydrocarbon degradation and a corresponding biochemical oxygen demand (BOD) reduction of 52%, 62.7%, 71%, 66.7% and 81.7%, respectively. The microbial load in the contaminated water increased rapidly between days 0 and 7 and decreased between days 14 and 42 in all the remediation systems. A first-order kinetic model fitted well to the biodegradation data and the corresponding half-life time was also estimated. The model revealed that crude oil contaminated water under combined CSL + potassium + ammonium sulphate treatment strategy had higher biodegradation rate constants, k as well as lower half-life times, t1/2 than other remediation systems. Thus, the results suggest that CSL and in combination with inorganic nutrient could be an indispensable tool in bioremediation of petroleum hydrocarbons contaminated environment. [ABSTRACT FROM AUTHOR]

The adsorption of naphthalene from aqueous solution onto unripe orange peel has been investigated. The experiments were conducted using a batch reactor system. The influence of different experimental parameters such as pH, initial naphthalene concentration, particle size, adsorbent dosage and contact time on naphthalene removal was considered. Results of the batch adsorption experiment showed that equilibrium adsorption was attained in 180 min. The removal efficiency increased with an increase in adsorbent dosage, contact time and concentration but decreased with an increase in the particle size. The adsorption capacity of the unripe orange peel for an initial 100 mg/l of naphthalene was maximum at an optimum pH of 6, with an orange peel loading of 7.5 g. This study satisfactorily demonstrated that unripe orange peel which is an environmental pollutant could be used to adsorb polycyclic aromatic hydrocarbons and achieve environmental cleanliness. [ABSTRACT FROM AUTHOR]

The heaps of solid waste found along the streets of major cities in Nigeria are worrisome. Apart from aesthetic considerations, the waste heaps serve as breeding grounds for disease carriers like rodents and flies. This work looks at the functional elements in an ISWM (integrated solid waste management). A three-way approach for successful handling of the problem is suggested. Problems identified include inadequate enforcement of existing legislations, poor funding, lack of private participation, and poor facilities for proper waste management. The integrated model proposed emphasizes proper policy formulation as a preventive tool to waste generation, reuse and recycling of waste, decentralization and private sector participation in waste management activities, as well as reorientation of all stakeholders in the sector. With proper implementation by the federal and state governments, the aims for a hazard-free environment will be realized. The government Was advised to introduce the concept of cleaner production and its benefits to industries. [ABSTRACT FROM AUTHOR]

The microbial degradation of phenols has been reviewed including the phenol-degrading microbes, factors affecting degradability, and the use of biotechnology with emphasis on degradation mechanisms and their kinetics. The mechanism of microbial degradation depends on aerobic and anaerobic conditions. Under aerobic conditions, degradation of phenol was shown to be initiated by oxygenation into catechols as intermediates followed by a ring cleavage at either the ortho or meta position, depending on the type of strain. Anaerobic biodegradation of phenol occurs by carboxylation followed by dehydroxylation (reducing reaction) and dearomatisation. It was also clear that the parameters used in the Haldane model are not constants but vary, hence it may never be possible to describe the kinetic properties of a microbial cell with a single set of constants. [ABSTRACT FROM AUTHOR]

The potential of microorganisms to catabolise and metabolise xenobiotic compounds has been recognised as a potentially effective means of toxic and hazardous wastes disposal. Phenol and its derivatives have long been recognised as some of the most persistent chemicals in petroleum refinery wastewaters, with high toxicity even at low concentrations. Biodegradation of these compounds has been recognised as a potential solution for their disposal owing to its cost effectiveness and simplicity. Two species of pseudomonas, P. aeruginosa and P. fluorescence, were studied for their biodegradation potential on phenol present in a refinery wastewater under a batch fermentation process. Phenol was successfully degraded by both species, and there was high positive correlation between phenol biodegradation and microbial growth. The maximum specific growth rate were obtained for both species from the Haldane model. The study revealed the high potential of these local strains, with P. aeruginosa being more effective, and the possibility of using them in bioremediation of petroleum refinery wastewaters. [ABSTRACT FROM AUTHOR]

This study investigated the use of coconut shell as a non-conventional and low-cost adsorbent for the removal of naphthalene and pyrene from synthetic waste water. Coconut shells were used to adsorb naphthalene and pyrene at varying initial naphthalene and pyrene concentrations, adsorbent dosage, particle size and agitation time. The results of the batch equilibrium adsorption studies revealed that adsorption capacity decreased with increase in particle size and increased with increase in adsorbent dosage. The equilibrium adsorption data were analysed by two-parameter models of Langmuir and Freundlich and three-parameter models of Redlich-Peterson, Sips and Toth isotherms. The results showed that the equilibrium adsorption data for naphthalene and pyrene sorbent systems fitted well with all the tested adsorption isotherm models which can adequately describe the adsorption behaviour of naphthalene and pyrene onto coconut shell. The adsorption kinetic data obtained at 100 mg/l initial naphthalene and pyrene concentrations were analysed using Lagergren pseudo-first order, Elovich and intraparticle diffusion rate equations. The rate equations fitting showed that the adsorption kinetic data generally fit the three rate equations tested from which the rate constants and diffusion rate constants were estimated. However, the Lagergren pseudo first-order rate equation gave the best fit and, thus the process followed the first-order rate kinetics. Therefore, coconut shells being an agricultural waste product have the potential to be used as a low-cost adsorbent for the removal of organic pollutant from waste water. [ABSTRACT FROM AUTHOR]