[Show abstract][Hide abstract] ABSTRACT: Graft copolymers of cassava starch and acrylonitrile were synthesized in aqueous solution using
ceric ammonium ion as the initiator. Saponification of grafted copolymer was done by reaction
with sodium hydroxide and precipitated with methanol. The grafting was confirmed using FTIR
and SEM. The hydrolyzed graft copolymer was used as sorbent for the uptake of copper ions (Cu)
from the aqueous media. The sorption capacity was optimized using response surface
methodology (RSM) while the effects of the concentration copper ions, contact time, temperature
and pH on the extent of adsorption of Cu was assessed using a four variable central composite
design. The regression model developed to represent the adsorption of copper was statistical
significant, with a small standard deviation (5.17) and did not show lack of fit (R2=0.701). High
levels of contact time and pH were favourable to the adsorption process while the reverse was the
case for concentration and temperature. The optimal conditions of sorption as obtained from the
RSM were as follows: initial concentration 20g/L, contact time 18.25hr, temperature 27.5oC, pH
7.85. Under these conditions, the maximum removal of Cu was obtained to be 93.92%. Validation
of the model indicated no significant difference between predicted and experimental values.
[Show abstract][Hide abstract] ABSTRACT: Majority of contaminated sites in the world contain complex mixtures of heavy metals and organic contaminants from diverse natural processes and anthropogenic activities. Mixed interactions of heavy metals and organic contaminants may affect their bioavailability and accumulation in soil and biota through synergistic or antagonistic processes. Evaluation of contaminant bioavailability is a necessary component of the overall site assessment process for establishing either bioavailability-based or risk-based, site-specific remedial options. However, contemporary approaches aimed at the effective characterisation of contaminated soils for risk assessment, remedial and regulatory purposes are frequently challenged by knowledge gaps in contaminant bioavailability, mixed contaminant effects and emerging contaminants. Understanding mixed contaminant interactions at the elemental and molecular levels is, therefore, imperative not only to explain the underlying mechanisms controlling the fate and transport of these contaminants in soils, but also predict their bioavailability, ecotoxicological effects on natural communities under realistic exposure conditions and remediation endpoints. In this paper, scattered literature is harnessed to review specific soil-contaminant interactions, inter-contaminant (metal-metal, organic-organic, metal-organic) interactions and their implications for bioavailability, risk assessment and soil remediation.
[Show abstract][Hide abstract] ABSTRACT: Chemical fractionation patterns and plant tissue concentrations were used to assess nickel, copper, zinc, cadmium, and lead phytoavailability to maize in a soil amended with metal salts or poultry manure. A sandy loam was treated with 80–400 mg kg−1 doses of a quinternary mixture of the metal nitrates either directly or as spiked poultry manure. The European Communities Bureau of Reference sequential extraction procedure partitioned the metals among three operationally defined pools in the soil. Metal mobilities were lower in the poultry manure–amended than the metal salt–treated soil, indicating the manure's ability to fix the metals in soil. Pot experiments revealed high metal transferabilities with no apparent phytotoxic symptoms in maize at the doses applied, suggesting some degree of tolerance to the metals. Heavy-metal concentrations in maize increased linearly with metal doses in metal salt–treated soil, but were less phytoavailable in soil amended with poultry manure. Heavy-metal concentrations in maize were reasonably predicted from soil parameters using stepwise multivariate regression models. The findings are useful in the assessment and remediation of heavy metal–contaminated soils.
Full-text · Article · Nov 2012 · Communications in Soil Science and Plant Analysis
[Show abstract][Hide abstract] ABSTRACT: The effect of carbonization on the processing characteristics of rubber seed shell powder was studied. Rubber seed shells were carbonized at different temperatures and then ground into fine powder. The various powders obtained were then characterized by pH, bulk density, moisture content, iodine adsorption value, yield%, conductivity and loss on ignition. The results show that there was a significant change in the pH as the heating temperature increases. The bulk density and moisture content decrease with increasing heating temperature while the iodine adsorption number and the loss on ignition increase with increasing heating temperature thus showing that carbonization has a significant influence on the processing characteristics of rubber seed shell.
Full-text · Article · Aug 2012 · Arabian Journal of Chemistry
[Show abstract][Hide abstract] ABSTRACT: Scattered literature is harnessed to critically review the possible sources, chemistry, potential biohazards and best available remedial strategies for a number of heavy metals (lead, chromium, arsenic, zinc, cadmium, copper, mercury and nickel) commonly found in contaminated soils. The principles, advantages and disadvantages of immobilization, soil washing and phytoremediation techniques which are frequently listed among the best demonstrated available technologies for cleaning up heavy metal contaminated sites are presented. Remediation of heavy metal contaminated soils is necessary to reduce the associated risks, make the land resource available for agricultural production, enhance food security and scale down land tenure problems arising from changes in the land use pattern.
[Show abstract][Hide abstract] ABSTRACT: The impact of storm water run-off from a location of intensive application of CCA in wood treatment on the quality of sediment of the receiving water body was examined. Sediment samples were collected along Ogba River. Physico-chemical characteristics as well as total levels of As, Cr and Cu in sediment samples were determined. Physico-chemical analysis of composite sediment samples upstream and downstream showed pH of sediments to be neutral (6.95 upstream and 6.90 downstream). The sand content for downstream sediment was 90.52 and 87.52% for upstream sediment sample. Total levels of 3.3-14.9 mg kg-1 As, 3.1-116.6 mg kg-1 Cr, and 13.7-16.4 mg kg-1 Cu were obtained for downstream sediment samples and 2.2-2.3 mg kg-1 As, 8.1-13.1 mg kg-1 Cr, and 6.0-7.4 mg kg-1 Cu were obtained for upstream samples. Sequential extraction procedure involving six steps was used to evaluate the partitioning of As, Cr and Cu in the sediments. The results showed that the bioavailable fraction of sediment 20 m downstream was 10%, 100% and 20% of the total levels of As, Cr and Cu respectively in the sediment.
No preview · Article · Apr 2011 · Chemical Speciation and Bioavailability
[Show abstract][Hide abstract] ABSTRACT: Rubber seed oil alkyd was post-polymerized with styrene monomer at ratios of 1:2, 1:4, 1:6, 1:8, and 1:10 at 100°C for 3 h (samples i - v) and 6 h (samples A - B), to obtain two sets of styrenated alkyds. The styrenated alkyds and the rubber seed oil alkyd were all characterized and evaluated by standard methods, for their physico-chemical properties, drying schedule and chemical resistance. All the resins showed good properties. However, the styrenated alkyds gave a faster drying time, even in the absence of a drier. Unlike the unstyrenated alkyd which is only resistance to water, brine and acidic media, the styrenated alkyds were also resistant to alkali. The styrenated alkyds prepared over a period of 6 h gave shorter drying time than those prepared in 3 h, irrespective of the alkyd - styrene ratios.
No preview · Article · Mar 2011 · AFRICAN JOURNAL OF BIOTECHNOLOGY
[Show abstract][Hide abstract] ABSTRACT: The lethal effects resulting from incessant release of toxic surfactant-containing industrial chemicals into the Niger Delta Ecological Zone of Nigeria was studied using a laboratory toxicity test. The study employed the Organisation for Economic Development and Cooperation (OECD) 203 protocol. The test organism (Tilapia guineensis [fish]) was obtained from a brackish water environment and exposed to Neatex (industrial detergent) and Norust CR 486 (corrosion inhibitor) at concentrations of 6.25, 12.5, 25, 50, and 100 mg/L for 96 h. The ecological endpoint considered was mortality at 96 h, and the results obtained indicate that concentration and duration of exposure influenced the effects of the test chemicals. The 96-h lethal concentration (LC(50)) values for the industrial detergent and corrosion inhibitor were 46.52 +/- 2.16 and 13.95 +/- 0.80 mg/L, respectively. Differential toxicity was observed between the industrial detergent and corrosion inhibitor at the level of F (1,28) = 8.22, P < 0.05, with the corrosion inhibitor exhibiting a higher toxicity level. The brackish water fish were more sensitive to Norust CR 486 than to the industrial detergent. The mean mortality rate in response to the test chemicals was significantly higher than that to the control treatment at F (2,42) = 42.07, P < 0.05. The observed concentrations are indicative of early warning signs of water quality deterioration, as well as ecological effects on aquatic organisms.
Full-text · Article · Jan 2011 · Turkish Journal of Biology
[Show abstract][Hide abstract] ABSTRACT: The use of polymer in agriculture is gaining popularity in science, particularly in the field of polymer chemistry. This has provided solutions to the problems of the present day agriculture which is to maximize land and water productivity without threatening the environment and the natural resources. Superabsorbent polymer hydrogels potentially influence soil permeability, density, structure, texture, evaporation and infiltration rates of water through the soils. Functionalized polymers were used to increase the efficiency of pesticides and herbicides, allowing lower doses to be used and to indirectly protect the environment by reducing pollution and clean-up existing pollutants. This account; a detailed review study, has been put together as an expose on the myriad application of polymer in the field of agriculture, highlighting present research trend , impact on food security and future outlook.
[Show abstract][Hide abstract] ABSTRACT: The development of high-performance composite materials from locally sourced and renewable materials was investigated. Rubber seed oil polyurethane resin synthesized using rubber seed monoglyceride derived from glycerolysis of the oil was used as matrix in the composite samples. Rubber seed oil-based polyurethane composite reinforced with unidirectional sisal fibers were prepared and characterized. Results showed that the properties of unidirectional fiber-reinforced rubber seed oil-based polyurethane composites gave good thermal and mechanical properties. Also, the values of tensile strengths and flexural moduli of the polyurethane composites were more than tenfold and about twofold higher than un-reinforced rubber seed oil-based polyurethane. The improved thermal stability and the scanning electron micrographs of the fracture surface of the composites were attributed to good fiber–matrix interaction. These results indicate that high-performance “all natural products” composite materials can be developed from resources that are readily available locally.
No preview · Article · Oct 2010 · Materials and Design
[Show abstract][Hide abstract] ABSTRACT: Cow dung used as soil amendments and a sequential chemical speciation (six steps) procedure were used to predict the uptake of Cr, Cu and As by maize (Zea mays) plant in chromated copper arsenate (CCA) contaminated soil. A pot experiment containing the contaminated soil samples with different percentage levels of amendments and control (no amendment) was set up. The relative concentrations of the metals in the CCA contaminated soil were established as Cr 265.84 mg/kg, Cu 155.82 mg/kg and As 33.09 mg/kg. However, with the use of speciation and calculations based on mobility factor (M f), the relative toxicity of the metals in the soil was established as As (60%) > Cr (19%) > Cu (8%). The amendment, rich in organic matter raised the pH level of the soil, demobilized the metals rendering them unavailable through bounding resulting into relatively lower uptake by plants in soils with amendment when compared with plants in the control pots.
[Show abstract][Hide abstract] ABSTRACT: Soaps are a class of surface active compounds derived from natural oils and fats. Double decomposition reactions permit the
synthesis of metallic soaps, which are long-chain carboxylates of metal ions, from alkaline ones such as sodium, potassium
or ammonium soaps. Metallic soaps are commercially important as they find use in diverse applications such as driers in paints
or inks, components of lubricating greases, heat stabilizers for plastics (especially PVC), catalysts and water proofing agents,
fuel additives and cosmetic products amongst others. Many of these applications are related to the thermal properties of these
compounds and the thermal behaviour of metal soaps in terms of decomposition processes is of great importance. Rubber seed
oil (RSO) which is an unsaturated triglyceride abundantly available in Nigeria, India and Australia is an excellent starting
material for metal soaps. In this study rubber seed oil having 2.2% myristic acid, 7.6% palmitic acid, 10.7% stearic acid,
20.61% oleic acid, 36.62% linoleic acid, 22.5% linolenic acid was used in making barium, calcium, cadmium and zinc soaps.
The thermal behaviour of soaps (Ba, Ca, Cd and Zn) of rubber seed oil for use as additives in the processing of poly(vinyl
chloride) (PVC) was investigated by thermal gravimetry and differential scanning calorimetry. The stability of the soaps was
examined by thermogravimetry up to 873 K at a constant heating rate of 10 °C min−1. The soaps were found to be thermally stable up to 473 K as they recorded less than 5% mass loss at this temperature with
values of apparent activation energy for decomposition varying from 52 to 96 kJ mol−1. Differential scanning calorimetric studies of the soaps revealed melting and decomposition behaviour of metal soaps.
No preview · Article · Aug 2010 · Journal of Thermal Analysis and Calorimetry
[Show abstract][Hide abstract] ABSTRACT: Changes in heavy metal speciation and uptake by maize in a soil before and after washing with chelating organic acids, citric acid, tartaric acid and ethylenediaminetetraacetic acid were assessed. A sandy loam was collected from the vicinity of the Benue industrial layout, Makurdi, Nigeria and spiked with a quinternary mixture of nickel, copper, zinc, cadmium and lead nitrates to achieve higher levels of contamination. Batch soil washing experiments performed on 1.0 g portions of the spiked soil using 0.05 M chelating agents at a solid:liquid ratio of 1:25 showed that washing efficiencies varied in the order: ethylenediaminetetraacetic acid> citric acid> tartaric acid with metal extraction yields typically following the sequence, copper> nickel> zinc> cadmium> lead. Sequential extractions proposed by the European Communities Bureau of Reference method used to assess the redistribution of heavy metal forms in the soil showed that apparent metal mobilities were reduced upon soil washing. Citric acid removed most of the metals hitherto associated with the exchangeable and reducible fractions; tartaric acid, the exchangeable metal pools; and ethylenediaminetetraacetic acid, the non-residual metal pools. Heavy metal assay of harvested biomass of maize grown on unwashed and washed soil samples indicated that metal transfer coefficients, decreased in the order of treatment: ethylenediaminetetraacetic acid <citric acid <tartaric acid <unwashed soil. Ethylenediaminetetraacetic acid and citric acid appeared to offer greater potentials as chelating agents to use in remediating the high permeability soil. Tartaric acid, however, is recommended in events of moderate contamination.
Full-text · Article · Jun 2010 · International journal of Environmental Science and Technology
[Show abstract][Hide abstract] ABSTRACT: Poultry droppings used as soil amendments and a sequential chemical speciation (six steps) procedure were used to predict the uptake of Cr, Cu and As by maize (Zea mays) plant in chromated copper arsenate (CCA) contaminated soil. A pot experiment containing contaminated soil samples to different percentage levels of amendments and control (no amendment) was set up. The initial concentration of Cr, Cu and As in the contaminated soil sample were established. The six fractions based on sequential extractions were also established. The distribution patterns of the metals based on their mobility factor Mf showed values high enough to predict high lability and bioavailability for arsenic, moderate for chromium and low for copper. The amendment, an energy-rich source substance enhanced mobility and bioavailability of the metals and their subsequent uptake and accumulation in the maize plant. This led to a cleanup at 20% amendment of As (20.6%), Cr (2%), and Cu (17.1%) after a period of twenty days. These figures are impressive considering the fact that the increase in pH occasioned by the poultry dropping amendment must have bound the metals.
No preview · Article · May 2010 · AFRICAN JOURNAL OF BIOTECHNOLOGY
[Show abstract][Hide abstract] ABSTRACT: Graft copolymers of starch and acrylonitrile were synthesized in aqueous solution. Ceric ammonium ion was used to initiate the graft copolymerization. Ten grades of graft copolymers were synthesized-five by varying the initial concentration of the monomer and the other five by varying the initial concentration of the initiator. Evidence of graft copolymerization of the hydrolyzed products was obtained from the IR analyses. Some grafting parameters such as % grafting ratio and % conversion were favoured by initial increase in the monomer concentration. However, these parameters were observed to decrease at much higher concentrations (>3 M). Evidence of hydrolysis shows that the grafted copolymers could be used as flocculants.
[Show abstract][Hide abstract] ABSTRACT: Samples of rubber seed shells were carbonized at varying temperatures (100, 200, 300, 400, 500, 600, 700 and 800 °C) for three hours each and sieved through a 150 μm screen. The portion of the rubber seed shell carbon that passed through the screen was characterized in terms of loss on ignition, surface area, moisture content, pH, bulk density, and metal content and used in compounding natural rubber. The characterization shows that the pH, conductivity, loss on ignition and the surface area increases with the increases of the heating temperature, unlike the bulk density which decreases. The compound mixes were cured using the efficient vulcanization system. Cure characteristics of compounds and physico-mechanical properties of the vulcanisates were measured as a function of filler loading along with that of N330 carbon-black filled natural rubbers. The results showed that the cure times, scorch times and the torque gradually increased, with increasing the filler content for rubber seed shell carbon-filled natural rubber, with the filler obtained at carbonizing temperature of 600 °C tending to show optimum cure indices. The physicomechanical properties of the vulcanisates increase with filler loading. The reinforcing potential of the carbonized rubber seed shell carbon was found to increase markedly for the filler obtained at the temperature range of 500-600 °C and then decreases with further increase in temperature.
Preview · Article · Apr 2010 · Chemical Industry and Chemical Engineering Quarterly
[Show abstract][Hide abstract] ABSTRACT: Novel biobased additives prepared from rubber seed oil were evaluated as thermal stabilizer for PVC. Divalent metal (barium and cadmium) soaps of rubber seed oil were prepared by metathesis in aqueous alcohol and characterized by thermal methods (differential scanning calorimetry and thermogravimetry). The stabilizing effect of the soaps and their admixtures on the thermal degradation of PVC powder and plasticized PVC was examined by dynamic thermogravimetry and dehydrochlorination studies at 160°C using the Thermomat equipment. The metal soaps showed multiple decomposition endotherms but were generally stable (with weight loss less than 5%) within the temperature range (180-220°C) frequently used in the processing of PVC. Using the Broido model, values of apparent activation energy of decomposition of between 50 and 200 kJmol-1 were obtained for the soaps. The biobased additives were found to be relatively effective in stabilizing PVC in powder and plasticized forms against thermal degradation. Using inhibition/retardation time, temperature of incipient decomposition, and temperature at which various extents of decomposition was attained as indices of thermal stabilization, the results from this study indicate a potential for the application of the biobased additives as thermal stabilizer for PVC in rigid and flexible formulations.