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A bio-directed synthesis of gold nanoparticles (Au NPs) was developed via the reduction of hydrogen tetrachloroaurate (III) (HAuCl4·3H2O) solution by the aqueous leaf extract of Ananas comosus. The polyphenol stabilized Au NPs were characterized by UV–visible, Fourier transform infrared (FTIR), powder X-ray diffraction (PXRD)/selected area electron diffraction (SAED), high resolution transmission electron microscopy (HRTEM) and energy-dispersive X-ray spectroscopy (EDX) analyses. The HRTEM images revealed that Au NPs were well dispersed with spherical structures. The size ranges from 7.39 to 32.09 nm with average particle size of 18.85 ± 6.74 nm. The peaks of XRD analysis at (2θ) 37.96°, 44.06°, 64.54°, 77.50° and 81.73° were respectively assigned to (1 1 1), (2 0 0), (2 2 0), (3 1 1) and (2 2 2) planes of the face-centered cubic (fcc) lattice of gold. The photocatalytic potential of Au NPs was studied through the solid-phase degradation of low-density polyethylene (LDPE) film. The photoinduced degradation of LDPE@Au nanocomposite film was higher than that of the pure LDPE film. The weight loss of LDPE@Au (1.0 wt%) nanocomposite film steadily increased and reached 51.4 ± 4.8% in 240 h under solar light irradiation, compared to the photo-induced LDPE with only 8.6 ± 0.7%. However, LDPE film with 1.0% Au NPs gave a weight loss value of 4.72 ± 0.71 under the dark condition at the end of 240 h. Thus, LDPE film with 1.0% Au NPs showed a degradation efficiency of 90.8% under solar irradiation after 240 h. The sustainability of the nanoparticles was confirmed through reusability in the photocatalytic degradation reaction up to five consecutive cycles without substantial loss in its catalytic performance.

Nickel oxide nanoparticles (NiO NPs) were synthesized using Ananas comosus leaf extract, and were characterized by UV–Vis spectroscopy, Fourier transform infrared (FTIR) spectroscopy, high resolution transmission electron microscopy (HRTEM), Energy dispersive X-ray (EDX) and X-ray diffraction (XRD) techniques. The FTIR analysis confirms the formation of the NiO with appearance of Ni O band at 468 cm−1. The HRTEM analysis reveals that the NiO NPs size was in the range of 0.63–5.75 nm, with an average particle size of 1.42 ± 1.76 nm. The EDX analysis shows clear peaks of Ni (2.7%) and O (5.74%) in the spectrum. The peaks of XRD analysis at (2θ) 30°, 43.89°, 60.16°, 77.95° and 82.94° were assigned to (1 1 1), (2 0 0), (2 2 0), (3 1 1) and (2 2 2) planes of the face-centered cubic (fcc) lattice of NiO. The photocatalytic properties of the NiO NPs were studied through the solid phase degradation of low-density polyethylene (LDPE) film. We observed that polymeric nanocomposites (NCs) showed a significant weight loss of 33 ± 1.6% compared with the pure LDPE (8.6 ± 0.7%) after exposure to solar light irradiation for 240 h, while the nanocomposites under the dark condition gave a weight reduction of 1.90 ± 0.05 at the end of 240 h. The FTIR analysis also confirms the presence of carbonyl group, a degradation product of LDPE, with carbonyl index of 0.4. All these important factors showed that NiO is an effective photocatalyst. The study therefore suggests the incorporation of NiO NPs into the polymer matrix so as to enhance its photodegradation.

Coatings for corrosion protection of metallic substrates such as steel, iron, magnesium, and aluminium, and their alloys have attracted tremendous interest in the offshore industry. Offshore facilities are prone to corrosion in various zones, ranging from atmospheric, splash, submerged and mud zones. Thus, there is high demand for prevention of corrosion of offshore facilities using organic coatings as potential replacements for the traditional coatings that are inefficient and expensive. This review highlights the latest developments in the corrosion protective performance of various types of organic coating systems. These coating systems are expected to provide barrier and active protection at varying degrees to offshore metallic structures in these corrosion zones. Thus, the utilization of organic coatings in complex and aggressive environmental conditions such as offshore, for efficient control of the initiation of metallic degradation, structural failures, and resource depletion is highly desirable by offshore industry to ensure safe and productive drilling operations. The effects of various loading systems on the performance of organic coatings are also discussed.

Metal–organic frameworks (MOFs) have received special attention in recent years as a result of their attractive and unique properties such as structure flexibility, high surface area, tunable pore size and functionalizable organic linkers and metal centres which have led to vast array of promising applications. Their properties can be improved to further enhance their performance by functionalization of the organic linkers, postsyntheic modification, and doping of nanomaterials into their frameworks. In this review, some recent synthetic methods for the preparation of MOFs are discussed, especially those that are applicable to CO2 adsorption. The second part of this paper discusses the applications of MOFs as heterogeneous catalyst for various CO2 conversion processes, with a view to address some of the challenges faced by the current technology of CO2 conversion which tend to be very energy intensive processes with high level of waste emission and cost. The current state of MOF commercialization for niche markets is also discussed.

The conversion of CO2 into fuels and value-added chemicals is one the most promising and sustainable route for mitigating the atmospheric build up of CO2. However, the kinetic and thermodynamic limitations of the conversion process necessitate the need for the development of an efficient catalytic system capable of operating at favorable conditions to convert CO2 into value-added chemicals/fuel with industrial appeal. Various approaches have been implemented for the development of both homogeneous and heterogeneous catalytic systems for CO2 conversion, but unfortunately, none of the current technologies for CO2 conversion meet the safety needs, mild reaction conditions, efficiency, selectivity and cost-effectiveness. Therefore nanotechnology has been the main focus of many researchers, as the technology can provide viable catalytic materials that can address all the challenges being faced with conventional catalytic systems used for CO2 conversion process. This review highlights some recent promising research results in the area of reductive and non-reductive conversion of CO2 into fuels and value-added chemicals over nanoparticles-based catalysts, and more importantly, the reaction mechanisms of CO2 conversion over these nanocatalysts. The potential opportunities and future trends of nanotechnology application in the CO2 conversion process are also discussed.

This study describes the analysis of 16 + 1 US-EPA Priority PAHs (polycyclic aromatic hydrocarbons) occurrence in twenty-three (23) imported and locally manufactured samples of green, black and herbal tea commercially marketed and widely consumed in Nigeria. A gas chromatograph (GC) coupled with an auto-sampler in tandem with a flame ionisation detector (FID) was used for the analysis. The percentage recoveries of each individual PAH varied between 90.24 and 108.92%. The degree of contamination expressed as sum of sixteen priority PAHs (∑16PAHs) ranged between 1.63 ± 0.33–73.53 ± 6.07 μg/kg, 4.71 ± 0.23–79.61 ± 7.02 μg/kg, and 12.52 ± 0.15–26.89 ± 0.68 μg/kg, for green, herbal and black tea samples, respectively. Benzo(a)pyrene played a significant role in the carcinogenicity and mutagenicity potentials of the samples. The lifetime cancer incident risk assessments indicate higher cancer risk levels in herbal and black teas. Generally, children have higher lifetime probability of cancer risk than adults.

New indices – modified hazard quotient (m HQ) and ecological contamination index (ECI) – were developed for the evaluation of heavy metals contamination of sediment. Sequential extraction method was employed to determine the levels of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), and lead (Pb) in subtidal sediment samples from tropical ecosystems off the Gulf of Guinea. The results were used to assess the degree of contamination and estimate the extent of anthropogenic inputs from industrial activities. Results indicated that the concentrations of Cd, Cr, Cu, Ni and Pb ranged from 4.33 –5.67, 11.12–28.52, 30.26–43.72, 2.02–2.60 and 162.0–190.37 mg/kg dw, respectively. The mean metal levels did not show significant variations among study sites during the wet and dry seasons. Spatial distribution and severity of sediment-associated contamination by heavy metals based on the newly developed indices (m HQ and ECI) were in good agreement with existing pollution indices and followed the descending sequence: Cd>Pb>Cu>Cr>Ni. Contamination severity index, mean hazard quotient and modified risk assessment code were also used to evaluate the sediment-heavy metal contamination, which generally indicated medium risk contamination of the investigated ecosystems. Aquatic pollution indicators (potential contamination index, ECI, hazard quotients, m HQ) revealed significant anthropogenic contamination by Cd and Pb, while Cr, Cu and Ni showed relatively low degree of contamination. Potential contamination index (PCI) generally followed the sequence Cd>Pb>Cu>Cr>Ni. A comparison of newly proposed indices with existing pollution indices revealed very good agreement. The contamination trends derived from the new indices were consistent and took into consideration site specificity, toxicity and a three-tier effect levels (threshold, mid-range and extreme effects guideline values) that support their reliability in evaluating contaminated aquatic ecosystems.

Graphical abstract, This paper presents the assimilation of heavy metal concentration data from sequential extraction method (SEM) with metal toxicity factors to develop and propose two new sediment quality indices modified hazard quotient (mHQ) and ecological contamination index (ECI), to predict the potential ecological risks associated with sediment contamination. Chemical speciation data of five heavy metals: cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), and lead (Pb) from five coastal aquatic ecosystems of the Equatorial Atlantic Ocean were used in the assessment of the degree of heavy metal contamination. Evaluation based on ECI indicated that sediments of most aquatic ecosystems were considerably to highly contaminated. The results showed that the proposed indices are reliable, precise, and in good agreement with similar existing indices used for evaluating the severity of sediment-associated contamination by heavy metals. The principal component analysis (PCA) and factor analysis indicated that heavy metals in the benthic sediments were mostly from anthropogenic sources. • New indices – modified hazard quotient (mHQ) and ecological contamination index (ECI) - were developed for predicting sediment-associated risk adverse effects. • Newly proposed indices agree closely with the existing pollution indices. • Pollution indices reveal significant anthropogenic contamination by Cd and Pb.

Chitosan–iron@silver (CS–Fe@Ag) nanocomposite was synthesized by a simple green synthetic method. The bimetallic Fecore@Agshell nanoparticles (NPs) were synthesized through a simple reduction of equimolar amounts of their salt mixture with Alchornea laxiflora leaf extract at 100 °C. The resulting bimetallic nanoparticles and nanocomposite were characterized with Fourier transform infrared (FTIR) and UV–visible spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) techniques. The evidence for the formation of Fecore@Agshell NPs within the chitosan polymer matrix was confirmed by UV–visible, XRD and FTIR spectra where the bonding of the bimetallic shell (Agshell) with carboxyl group to form Ag–O was confirmed. The effect of dosage, pH and agitation time on turbidity reduction of wastewater was studied to determine optimum conditions for the determination of water quality parameters. The CS-Fe@Ag nanocomposite gave higher maximum removals of BOD (48.7%), COD (15.5%) and TDS (54.9%) than pure CS with BOD (25.5%), COD (3.6%) and TDS (38.9%) at optimum conditions.

Copper nanoparticles were biosynthesized using aqueous plant leaf extract of Alchornea laxiflora as reducing and capping agents. The as synthesized copper nanoparticles (CuNPs) were confirmed by the colour change after addition of the aqueous leaf extract of Alchornea laxiflora into copper sulphate solution. The CuNPs were characterized by UV–Visible spectrophotometer, high-resolution transmission electron microscopy (HRTEM), energy-dispersive x-ray spectroscopy (EDX), and Fourier transform infrared (FTIR) spectrophotometer. The result of HRTEM reveals the formation of CuNPs with an average size of 3.29 ± 0.57 nm. The biosynthesized CuNPs gave absorption at 364 nm and the FTIR spectrum shows the Cu–O stretching vibration at 590 cm−1. The synthesized CuNPs show higher catalytic activity than the conventional acetic acid catalyst used in the oxidative desulphurization of model oil. The CuNPs can, therefore, serve as an inexpensive alternative catalytic material that can be used in the oxidative desulphurization (ODS) process.

Corrosion is the destructive chemical attack, abrasive action of tidal waves, and microbial attacks upon a metallic structure by its environment, and it is the commonest electrochemical phenomenon that is experienced in day-to-day activities of offshore oil and gas production. Corrosion control of metallic structures is an important activity in technical, economic, environmental and safety terms. The negative impacts of corrosion are so enormous, and it is therefore imperative for oil and gas industry, particularly offshore industry to have corrosion awareness in their daily activities with a view to providing corrosion protection of offshore structures, and ensure safe and productive drilling operations. This review discusses extensively multi-component synthetic organic compounds and phytochemicals of green inhibitors with S, N and O functionalities in their structure, for use as corrosion inhibitors against the corrosion of offshore oil and gas production facilities such as pipelines and storage containers in corrosive media, stressing specifically their synthesis (where applicable), properties and efficiency of inhibitors. Also addressed in this review are the future challenges in flow assurance due to the formation of gas hydrates in flowline, especially for offshore oil and gas production. The corrosion performance tests are extensively discussed.

This study aims to determine the seasonal variations and composition of suspended particulate matter in different sizes PM1.0, PM2.5, PM10 and the total suspended particles (TSP) emitted at major intra-urban traffic intersections (TIs) of Ilorin metropolis. The concentration levels of PM (PM1.0, PM2.5, PM10) obtained at the TIs during the rush hours (45.1, 77.9, and 513 μg/m3) are higher than the levels obtained for the non-rush hour periods (42.3, 62.7, and 390 μg/m3). The average on-road respiratory deposition dose (RDD) rates of PM1.0, PM2.5 and PM10 during the dry period at TIs types was found to be about 24%, 9% and 25% higher than those obtained during the wet period. Based on EF values calculated, Pb and Zn were anthropogenically-derived while Fe, Mn, Cr, Cu and Mg were of crustal source. Principal component analysis (PCA) has been applied to a set of PM data in order to determine the contribution of different sources. It was found that the main principal factors extracted from particulate emission data were related to exhaust and non-exhaust emissions such as tyre wears, oil and fuel combustion sources.

This study determines the pollution, fractionation, and ecological risks of sediment-bound heavy metals from coastal ecosystems off the Equatorial Atlantic Ocean. Contamination Factor (CF), pollution load index (PLI), and geoaccumulation index (Igeo) were used to assess the extent of the heavy metal pollution, while the potential ecological risk was evaluated using the risks assessment code (RAC) and Hakanson potential ecological risk. The analysis revealed concentrations (mg/g, dw) of the cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), and lead (Pb) in sediments for wet and dry seasons vary from 4.40–5.08, 14.80–21.09, 35.03–44.8, 2.14–2.28, and 172.24–196.39, respectively. The results also showed that the metal fractionation percentages in the residual, oxidizable, and reducible fractions are the most significant, while the exchangeable and carbonate bound trace metals are relatively low. The RAC values indicate no risk for Cd and Ni and low risk for other metals at all the studied sites during both seasons. Potential ecological risk analysis of the heavy metal concentrations indicates that Cd had high individual potential ecological risk, while the other metals have low risk at all investigated sites. The multi-elemental potential ecological risk indices (R1) indicate high ecological risk in all the ecosystems.

This study reports removal of dibenzothiophene (DBT) from model oil (DBT dissolved in n-heptane) by silver nanoparticles modified activated carbon prepared from brewer’s spent grains using wet impregnation (WI) method. The removal efficiency follows the order A g N P s c w / A C > A g N P s k p / A C > ACB. The AgNPskp/AC and AgNPscw/AC exhibit higher adsorption capacities for DBT with maximum values of 25.7 and 29.8 mg DBT/gAds at 25 °C respectively, than ACB with 13.9 mg DBT/gAds. The two-fold enhancement in the DBT uptake capacities of modified ACs can be attributed to the introduction of Ag(1) ion, a weak Lewis acid as an additional adsorption site. A significant decrease from 212.9 to 136.2 m2/g in the Brunauer–Emmett–Teller surface area of AgNPscw/AC is observed following the loading of DBT. The equilibrium adsorption data is adequately represented by Freundlich isotherm. The adsorption kinetics of DBT by these adsorbents followed pseudo second-order (PSO) model and the mechanism of adsorption was controlled by film and intra-particle diffusion. The change in entropy and heat of adsorption for DBT adsorption by these adsorbents range from 0.18 to 0.19 kJ/mol K and 21.5 to 23.9 kJ/mol, respectively. The results indicate that Ag nanoparticles-modified ACs from brewer’s spent grains can be used as adsorbent for the removal of DBT from model oil.

The ever-increasing demand for nanostructured composite materials and sustainable processes for next generation CO2 capture technologies has necessitated the need to develop novel and cost-effective synthetic routes for CO2 adsorbents based on amine and ionic liquid functionalized porous adsorbent materials with improved physico-chemical properties. The most obvious option is modification of the synthesized porous adsorbent materials by the incorporation of organic functional molecules into the pore structures of support materials, giving place to hybrid materials that combine the properties of both composites. These hybrid materials will be of great potential for practical applications, especially for post-combustion CO2 capture, owing to the increase in CO2 capturing ability and selectivity to CO2 compared to other gases in the flue gas stream. This paper reviews the diverse synthesis routes of bare porous materials and rich functionalities of porous adsorbent materials which will allow further post-modification to improve their performance in CO2 capture and increase their CO2/N2 and CO2/CH4 selectivity ratios. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.

As a novel class of porous crystalline organic materials assembled from molecular building blocks, the synthetic strategies of covalent organic frameworks (COFs) allow for the design and construction of new crystalline materials since their properties can easily be tuned through appropriate selection of the building blocks and the linkage motif. Their fascinating and versatile properties have made them to emerge as a platform for functional explorations and applications in CO2 capture. This review article addresses the synthetic strategies with special emphasis on dynamic covalent chemistry and potential application of COFs for CO2 capture. Recent advancements in the synthesis of COFs, including the strategies and principles involved are discussed. Also discussed are strategies of introducing extra tools in COFs to enhance their crystallininty, porosity and chemical stability, which are important parameters in the applications of COFs for post-combustion capture of CO2 in the CCS technology.

Gas hydrate formation and deposition in deepwater subsea flowlines has been a major concern to flow assurance engineers as oil and gas exploration moves towards offshore developments in deeper water and may cause operational safety hazards in subsea and cold regions. This challenge can be addressed through adequate knowledge of the mechanisms of formation and deposition of hydrates as well as predictive tools for their deposition in flowlines. This paper reviews various predictive models to study hydrate formation and deposition mechanisms based on the current publications on the gas-dominated flowloop investigations. The review also provides an overview of various gas hydrate mitigation and management strategies used in offshore production system. Important methods such as chemical injection and depressurization that have been used for mitigating hydrate formation are reviewed in this paper. These mitigation strategies assist in avoiding any form of casualties/hazards and ensure safe production operations. This review suggests that the management of gas hydrate risk in flowlines is the best solution to maintaining hazard-free operations, prevent causes of the loss of production and derive economic benefits from the use of huge deposits of natural gas hydrate as a source of methane gas.

The brewing industry is one of the largest industrial users of water. In spite of significant technological improvements over the last 20 years, energy consumption, water consumption, wastewater, solid waste and by-products and emissions to air remain major environmental challenges in the brewing industry. This article reviews some of these challenges with a focus on key issues: water consumption and waste generation, energy efficiency, emission management, environmental impact of brewing process and best environmental management practices which do not compromise quality of beer. The review is meant to create an awareness of the impact of beer production on the environment and of, practices to reduce environmental impact.

Bimetallic core/shell palladium/gold (PdcoreAushell) nanoparticles (NPs) were synthesized from aqueous solutions of Pd(II) and Au(III) species using Ananas comosus leaf extract as a reducing agent. The as-synthesized nanoparticles (NPs) were characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible absorption (UV–Vis), high resolution transmission electron microscopy (HRTEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD). The bimetallic PdcoreAushell structure was confirmed with a UV–visible spectroscopy, and the surface Plasmon resonance (SPR) band occurred at around 517 nm, indicating the formation of Aushell layer on the surface of pre-formed Pd NPs. The sizes of the bimetallic PdcoreAushell NPs range from 2.06 to 28.59 nm with an average particle size of 13.15 ± 6.22 nm, and they crystallized in face-centred cubic (fcc) symmetry. The EDX analysis confirms the bimetallism of PdcoreAushell NPs with individual metal present in the ratio 1:2. The photocatalytic potential of the as-synthesized PdcoreAushell NPs was studied through the solid-phase degradation of low-density polyethylene (LDPE) film. We observed that the LDPE film with 1.0% PdcoreAushell NPs showed an enhanced degradation of 55.8 ± 5.9 compared with the pure LDPE with degradation of 8.6 ± 0.7 after solar light irradiation for a short period of 240 h. However, LDPE film with 1.0% PdcoreAushell NPs gave a degradation value of 1.90 ± 0.03 under the dark condition at the end of 240 h. The sustainability of the nanoparticles was confirmed through reusability in the photocatalytic degradation reaction up to five consecutive cycles without substantial loss in its catalytic performance. SEM characterization of the nanoparticles before and after degradation reaction showed the stability of the nanoparticles. The development of eco-friendly photodegradable plastic by incorporation of Pd@Au NPs into the polymer matrix is suggested in the current study for the polymer industry as a means of addressing challenges of plastic pollution.

The presence of formation water and the treatment methods (both water flooding and chemical treatments) employed during exploration and production operations have great potential for mineral scale formation. Scale deposition poses a lot of serious threat in field production and it is a menace to production flow assurance, which in turn reduces the production flow resulting in production losses. Although oilfield scale deposit is a long standing problem, oil and gas industry are facing new challenges in managing scale deposits created during offshore exploration activities in ultra-deepwater and other harsh environments. Traditional onshore chemistries for scale inhibitions are not viable under HT/HP conditions thereby making flow assurance a critical issue for deepwater project development. An ideal management program maximizes hydrocarbon production and minimizes the cost of scale deposits control, thereby maintaining the economic viability of the operations. This paper reviews various types of mineral scale deposits as well as the thermodynamics and kinetics prediction of mineral scale formation potentials. Also, the mitigation strategies of oilfield mineral scale deposits and chemical stimulation techniques used in oil industry to improve well productivity are discussed.

The adsorption characteristics of ternary dye system (TDS), comprising of a mixture of congo red, methyl orange and methylene blue, on formaldehyde-treated melon husk (FMH) were investigated with respect to the changes in initial pH of TDS, contact time, and initial TDS concentration. The surface of FMH was studied by investigation using Fourier Transform infrared (FTIR) and Scanning Electron Microscopy (SEM). The adsorption equilibrium of TDS was rapidly reached after 45 minutes of contact time and pH of 8.5. The equilibrium adsorption data were interpreted using the following isotherm models Langmuir, Freundlich, Temkin, Dubinin-Radushkevich (D-R), HarkinJura and Halsey and the goodness of fittings were monitored using linear regression analysis (R 2 ), sum-ofsquare-error (SSE) and chi-square (χ). The results indicated that the isotherm could be interpreted by Freundlich model as it was the best fitted of all the models used, (R 2 = 0.998) suggesting multilayer adsorption. The kinetics of the adsorption process were analyzed using three kinetic models; pseudo first-order, pseudo second-order and intraparticle diffusion models and the Original Research Article Giwa et al.; ACSj, 7(1): 7-25, 2015; Article no.ACSj.2015.057 8 adsorption data followed the pseudo second-order model more closely (R = 0.998 – 1). The calculated values of thermodynamic parameters such as ΔGo and ΔSo were positive, indicating the presence of an energy barrier in the adsorption process. The positive values of ΔHo for biosorbent indicated that the adsorption mechanism was endothermic. The adsorption capacity of TDS was found to be 26.42 mg/g.

Owing to the inefficiency of the conventional primary and secondary recovery methods to yield above 20–40% of the OOIP (original oil in place) as incremental oil, the need for EOR (Enhanced Oil Recovery) techniques to recover a higher proportion of the OOIP has become imperative. ASP (Alkaline/Surfactant/Polymer) is one of such techniques that has proven successful due to its ability to improve displacement and sweep efficiency. Alkaline–surfactant–polymer (ASP) flooding is a combination process in which alkali, surfactant and polymer are injected at the same slug. Because of the synergy of these three components, ASP is widely practiced in both pilot and field operations with the objective of achieving optimum chemistry at large injection volumes for minimum cost. Despite its popularity as a potentially cost-effective chemical flooding method, it is not without its limitations. This paper therefore focuses on the reviews of the application of ASP flooding process in oil recovery in the petroleum industry and its limitations in maximizing oil recovery from onshore and offshore reservoirs. Also discussed are technical solutions to some of these challenges.

Polluted water may contain more than one dye species. Consequently, the behavior of a particular dye in a water system may be affected by the presence of the others. In this study, the adsorption of methylene blue (MB) in single dye system (SDS) and in ternary dye system (TDS) comprising of MB, congo red and methyl orange onto formaldehyde-treated melon husk (FMH) was investigated as a function of pH, contact time and species concentra- tions. Surface studies of FMH were investigated by Fourier transform infrared and scanning electron microscopy. The dye species adsorption equilibria were rapidly attained after 60 (SDS) and 90 min (TDS) of contact times. The adsorption kinetics were analyzed using pseudo first-order, pseudo second-order and intraparticle diffusion models and the adsorption data were well described by the pseudo second-order model. The equilibrium adsorption data were interpreted in terms of the Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Harkin-Jura and Halsey isotherm models and the goodness of fittings were inspected using linear regression analysis (R 2 ). Our results indicated that the Langmuir model was best fitted, suggesting monolayer adsorption. Thermodynamic study showed that the adsorptions in SDS and TDS on FMH are favourable. The change in entropy (DS) and heat of adsorption (DH )o f dye species on FMH in TDS were estimated as 82.2 J/ mol K and 17.95 kJ/mol. respectively while in SDS, they were respectively -43.76 J/mol K and -21.84 kJ/mol. The sorption process in both systems was thermodynami- cally feasible with negative DG values.

This paper investigated the photocatalytic potential of biosynthesized palladium nanoparticles (Pd NPs) for the degradation of low density polyethylene (LDPE). A green route synthesis of Pd NPs was carried out using Ananas comosus leaf extract (ACLE) as the reducing and stabilizing agent. The as-synthesized Pd NPs was characterized by UV–vis spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDX). The HRTEM image revealed that Pd NPs were well dispersed with particle size range of 1.71–16.14 nm and average particle size of 4.46 ± 2.44 nm. The XRD revealed four distinct peaks at 40.26°, 47.11°, 67.56°, and 78.09° which correspond to (111), (200), (222) and (311) planes, respectively, that can be indexed to face-centered cubic (fcc) phase of Pd NPs. Films of LDPE and its Pd NPs modified form were exposed to solar light in open air at ambient condition for increasing times of up to 30 days. The degradation of LDPE and nanocomposite LDPE films (LDPE@Pd NPs) was determined in terms of photo-induced weight loss, TEM, FTIR and thermogravimetric analysis (TGA). Thus, LDPE films with 1.0% Pd NPs showed degradation of around 49% under solar light irradiation over a short period of 30 days. The study therefore suggested the development of eco-friendly degradable plastic by utilizing the photocatalytic potential of Pd NPs, and to also serve as a possible means of addressing the growing agitations of plastic pollution in marine environment.

Complete oxidation or combustion of any carbon-based organic matter produces CO 2 , which is known to cause global warming and climate changes. To mitigate the concentration of CO 2 in the atmosphere various strategies have been implemented such as separation, storage, and valorization of CO 2 . The focus of this review was on the catalytic processes of the chemistries involved in the conversion of CO 2 into value-added products. The various valorization technologies which include conversion of CO 2 into fuel, valorization of CO 2 as a feedstock for chemicals were discussed. Also, an overview regarding the challenges and opportunities for future research in CO 2 valorization was provided.

Mineral carbonation technology (MCT) is a process whereby CO2 is chemically reacted with calcium- and/or magnesium-containing minerals to form stable carbonate materials which do not incur any long-term liability or monitoring commitments. Mineral carbonation is a potentially attractive sequestration technology for the permanent and safe storage of CO2. Vast amounts of magnesium silicate minerals exist worldwide that may be carbonated, with magnesium carbonate as stable and environmentally harmless product. In this review, a number of processes under development, such as the Abo Akademi University (AA) process routes, the CO2 Energy Reactor©, and the chemical and biological catalytic enhancement as new carbon capture and sequestration (CCS) technology are discussed. The key factors of the mineral CO2 sequestration process are identified, their influence on the carbonation process and environmental impact of the reaction products with regard to their possible beneficial utilization are critically evaluated. Chemistry and comparative analysis of residues and ores carbonation processes, as well as cost and gap analyses of this technology are discussed.

Two new flavones, namely 5,7,2’,5’-tetrahydroxy-3,4’-dimethoxyflavone and 5’-acetoxy-5,7,2’-trihydroxy-3, 4’-dimethoxyflavone were successfuly isolated from the leaves of Acanthospermum hispidum DC and identified by UV-Vis, IR, 1H-NMR and EI-MS techniques. Both compounds exhibited antibacterial activity against Salmonella typii, Staphylococcus aureus, Klebsiella pneumoniae, Proteus mirabilis, Bacillus subtilis, Pseudomonas aeruginosa and Shigella dysenteriae with minimum inhibition concentration (MIC) ranging from 0.001 - 0.20 but was inactive against Escherichia coli, Corybacterium pyogenes and Proteus vulgaris.

The distribution of polycyclic aromatic hydrocarbons (PAHs) in epipelic and benthic sediments from Iko River estuary mangrove ecosystem has been investigated. Total PAHs ranged from 6.10 to 35.27 mg/kg dry weight. Quantitative difference between the total PAHs in epipelic and benthic sediments showed that the benthic sediment known for higher capability to serve as sink for chemical pollutants accumulated less PAHs. This implies that PAHs in the epipelic sediment may plausibly be from industrial sources via runoff and/or of biogenic origin. A strong pyrolytic source fingerprint has been detected with slight influence of petrogenic sources. Total organic carbon normalized PAHs (sum of 16 PAHs, 59.7 to 372.4 mg/kg OC) were under (except for ES3 and BS3) the threshold effects concentrations (TEC, 290 mg/kg OC). Total PAHs in Iko River estuary sediments were in the range between ERL and ERM.

Carbon capture from point source emissions has been recognized as one of several strategies necessary for mitigating unfettered release of greenhouse gases (GHGs) into the atmosphere. To keep GHGs at manageable levels, large decreases in CO 2 emissions through capturing and separation will be required. This article reviews the possible CO 2 capture and separation technologies for end-of-pipe applications. The three main CO 2 capture technologies discussed include post-combustion, pre-combustion and oxyfuel combustion techniques. Various separation techniques, such as chemical absorption, physical absorption, physical adsorption, cryogenics, membrane technology, membranes in conjunction with chemical absorption and chemical-looping combustion (CLC) are also thoroughly discussed. Future directions are suggested for application by oil and gas industry. Sequestration methods, such as geological, mineral carbonation techniques, and ocean dump are not covered in this review.

Soil and water samples from the vicinity of Agbabu bitumen field of Southwestern Nigeria were analysed by GC‐FID for n‐alkanes, in order to characterize their distributions and to gather information on the degree of contamination by bitumen exploration and processing and other biogenic contributions. Total concentrations of n‐alkanes in water and soil samples analysed ranged from 61.5 to 472.7 µg L−1 and 422.8 to 2289.4 ng g−1 dw, respectively. On the basis of the total n‐alkane concentrations, carbon preference index (CPI) values and the odd‐even carbon predominance, it is suggested that both natural (e.g. aquatic input) and anthropogenic (e.g. bitumen and synthetics) sources contribute to the n‐alkanes load in soil and water samples of the area studied.

The recovery of an environment polluted by petroleum and allied hydrocarbons through bioremediation is being embraced globally as the best technology of removing hydrocarbon pollutants from environment. Infrared spectral changes and gravimetric analysis from the preliminary biodegradability study carried out on Agbabu Natural Bitumen showed the vulnerability of the bitumen to some bacteria: Pseudomonas putrefaciens , Pseudomonas nigrificans, Bacillus licheniformis, Pseudomonas fragi and Achromobacter aerogenes . This study investigates the ability of P. putrefaciens , P. nigrificans, B. licheniformis, P. fragi and A. aerogenes to degrade the aliphatic and polycyclic aromatic hydrocarbon fractions of Agbabu natural bitumen. Samples of the bitumen were separately inoculated with each of the bacteria for 14 days and the hydrocarbon profiles before and after inoculation were quantified using gas chromatography technique. The total aliphatic hydrocarbon compounds (C 11 - C 29 ) in the bitumen degraded by P. putrefaciens and P. nigrificans was slightly higher than that in the undegraded bitumen, while the concentration of compounds (C 11 - C 29 ) found in samples of the bitumen degraded by B. licheniformis, P. fragi and A. aerogenes was less than what was contained in the undegraded bitumen. Also the even-odd carbon-ratios of the degraded bitumen were higher than unity while these were less than unity in the undegraded bitumen. The polycyclic aromatic hydrocarbons (PAHs) profile in the bitumen degraded samples also differed from that of undegraded bitumen. A substantial reduction in the concentration of some PAHs was found in the bitumen samples following their degradation by the bacteria strains, typically from 55.98 to 30.79%, thus suggesting the possibility of using the bacteria strains for bioremediation process. Keywords: Agbabu, bitumen, bacteria, biodegradability, hydrocarbons African Journal of Biotechnology , Vol 13(11), 1257-1264

The distribution of polycyclic aromatic hydrocarbons (PAHs) in epipelic and benthic sediments from Iko River estuary mangrove ecosystem has been investigated. Total PAHs ranged from 6.10 to 35.27 mg/kg dry weight. Quantitative difference between the total PAHs in epipelic and benthic sediments showed that the benthic sediment known for higher capability to serve as sink for chemical pollutants accumulated less PAHs. This implies that PAHs in the epipelic sediment may plausibly be from industrial sources via runoff and/or of biogenic origin. A strong pyrolytic source fingerprint has been detected with slight influence of petrogenic sources. Total organic carbon normalized PAHs (sum of 16 PAHs, 59.7 to 372.4 mg/kg OC) were under (except for ES3 and BS3) the threshold effects concentrations (TEC, 290 mg/kg OC). Total PAHs in Iko River estuary sediments were in the range between ERL and ERM.

Various sludge samples from different domestic and industrial wastewater treatment plants were analyzed by Flame Atomic Absorption Spectrometry (FAAS) to evaluate their total and available contents of heavy metals (Pb, Hg, Cd and Zn). The EDTA, pyridine and acetic acid single extraction techniques were applied to these samples with the objective of studying the leaching behavior of the metals in different sludges and also to predict their possible mobility when these wastes are disposed on the environment and landfills. In EDTA, higher extraction efficiency was observed for major part of the elements studied in the industrial sludges except for Hg and Cd, which were also considerably released from domestic sludges. Acetic acid and pyridine gave a better extraction efficiency for Zn in industrial sludge than EDTA. Moreover, the results of total digestions were compared, for total metal contents, with those obtained using pseudototal digestion procedure and a good correlation (r 2 = 0.95) was found between the two methods of digestion.

The potential risk of soil, surface and ground water contamination by trace metals leached from highway construction solid wastes is a major environmental concern. The objectives of this study were to evaluate trace metal leachability, toxicity of the leachate to aquatic organism and environmental impacts of highway construction solid waste (HCSW). Potential leachability, defined as the maximum metal pool that may become available for leaching at a constant pH 4 decreased in the following order: ZnNiAsPbCu. Potential metal leachability was controlled mainly by solid phase distribution of metals in wastes. The kinetics of metal release were determined using the cascade leaching test (CLT) with water at pH 4. With the exception of zinc in the first fraction, metal concentrations in all consecutive leaching fractions remained below the maximum permissible level in water for human consumption. The result of toxicity test showed that the leachates were in concentrations that did not exceed toxic concentrations for aquatic toxicity tests. The results indicate low risk of surface and ground water contamination resulting from highway construction solid wastes.

A knowledge of the total content of trace metals is not enoughto fully assess the environmental impact of polluted soils. Forthis reason, the determination of metal species in solution isimportant to evaluate their behaviour in the environment andtheir mobilization capacity. Sequential extraction procedure wasused to speciate five heavy metals (Cd, Pb, Cu, Ni and Zn) fromfour contaminated soils of Southern Nigeria into sixoperationally defined geochemical species: water soluble,enchangeable, carbonates, Fe-Mn oxide, organic and residual.Metal recoveries were within ± 10% of the independentlydetermined total Cd, Pb, Cu, Ni and Zn concentrations. The highest amount of Cd (avg. 30%) in the nonresidual fractionswas found in the exchangeable fraction, while Cu and Zn weresignificantly associated with the organic fraction. Thecarbonate fraction contained on average 14, 18.6, 12.6, 13 and11% and the residual fraction contained on average 47, 18, 33,50 and 25% of Cd, Pb, Cu, Ni and Zn respectively. Assuming thatmobility and bioavailability of these metals are related to thesolubility of the geochemical form of the metals, and that theydecrease in the order of extraction sequence, the apparentmobility and potential bioavailability for these five metals inthe soil were: Pb > Zn > Cu > Ni > Cd. The mobility indexes ofcopper and nickel correlated positively and significantly withthe total content of metals, while mobility indexes of cadmiumand zinc correlated negatively and significantly with the totalcontent of metals.

This article is a state–of-the-art review on the aerobic degradation of petroleum components that are commonly found in the environment. Numerous microorganisms have been isolated and their phylogeny and metabolic capacity to degrade a variety of aliphatic and aromatic hydrocarbons have been demonstrated. This review focuses on recent progress on how microbes degrade hydrocarbons and heteroaromatic components of petroleum contaminants directed towards better understanding of the aerobic degradation processes and their exploitation for bioremediation. The phylogenetic diversity of the oil-degrading microbes was also discussed.

The present investigation provides data of some ions, namely Na+, Ca2+, NH4+, Cl-, NO3-, CN- and PO4(3-) on water samples of river Osun, selected rivers in the region and groundwaters. The pH, temperature, electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH) and total carbon (IV) oxide (TCO2) have also been determined to asses the chemical status and pollution levels of these water sources. The higher values of certain parameters with respect to the acceptable standard limits for drinking water indicate the pollution in both groundwater and river water samples of the study area, and make the waters unsuitable for various applications. The high pollution river water source showed higher levels of phosphate, nitrate and ammonium ions (P < 0.05). There is no significant difference (P < 0.05) between the mean concentrations of other inorganic nutrients in the high and low pollution water source types. The correlation coefficient between quality parameter pairs of river water and groundwater samples are determined and the significance of these parameters in both types of water sources are discussed.

(Received October 27, 1999; revised March 24, 2000) The concentrations and distributions of Cd, Cu, Ni, Pb, Cr and Zn in Osun river, selected rivers in the region and groundwaters have been studied, in order to establish the current levels of pollution. The metal concentration (mean±RSD in g dm-3) in the Osun river for the sampling periods of May, June and August, respectively, were: Cd, 1.45±0.65, 1.40±0.37, 1.25±0.52; Ni,21.8±6.22, 10.6±3.68, 15.3±6.01; Pb, 7.16±3.30, 8.45±3.24, 4.86±1.98; Cu, 16.7±9.32, 11.9±4.81, 8.27±3.80; Cr, 250±118, 400±160, 150±72.9; Zn, 398±109, 289±113, 259±94.4. The correlation coefficient between metal pairs of river water and groundwater samples are calculated and possible sources of the polluting substances are discussed.Bull. Chem. Soc. Ethiop. 2000, 14(1), 1-8Bulletin of the Chemical Society of Ethiopia. ISSN: 1011-3924&nbsp

Samples of compost-amended soil from waste dumping sites in Lagos Metropolis were extracted with dichloromethane (3 × 20 cm3) and the extract was evaporated at 35 °>C. The residue was extracted with 2,2,4-trimethylpentane, and portions of the solution were applied to a column containing silica gel from which aliphatic and aromatic hydrocarbons were eluted with n-hexane and toluene respectively. Analysis of the n-hexane fraction using gas chromatography showed the presence of a mixture of aliphatic hydrocarbons, ranging from C9 to C25, while ultraviolet analysis of the toluene fraction suggested 1,2-benzanthracene; 2,3-benzphenanthrene, chrysene and pyrene as polyaromatic compounds present in samples analyzed. The crude extracts were highly coloured and viscous. Total extractable organic residues in the 2,2,4-trimethylpentane extracts ranged from 36 to 89 mg g-1 of soil.

The bioaccumulation of Sb, Sn, As, Fe, Ni, Mn, Pb, Cu, and Zn in mosses from polluted and unpolluted areas of the southern parts of Nigeria is presented. Results of the moss samples show strong variations in the concentration of metal ions with type of sampling sites. The concentration of accumulated heavy metals also differs in various moss species from the same biotope. Bryidae mnium is a better accumulator of heavy metals than Tetraphidae tetraphis, as evidenced from the interspecies calibration between the two moss samples.