Extractive decontamination of heavy metals from CCA contaminated soil using organic acids

In this paper, the mobilization and extraction of As, Cr and Cu from chromated copper arsenate (CCA) contaminated soil obtained from a wood treatment factory site by four organic acids are presented and discussed. The CCA contaminated soil (pH = 5.91, carbon = 0.32, CEC = 47.84 meq/100 g) was found to contain 39.55 mg/kg As, 313.97 mg/kg Cr and 200.00 mg/kg Cu with a contamination factor greater than 6 for As, 3.14 for Cr and 4 for Cu; thus classifying the soil as very highly contaminated for As and considerably contaminated with Cr and Cu. However, speciation studies on the contaminated soil sample showed that 59% As, 19% Cr and 5% Cu were potentially bio-available and mobile. Chemical wash test using four chelating agents: oxalic, malonic, succinic and citric acid were performed at 1:10 solid/liquid ratio, 0.05M chelant concentration and at 2, 4 and 6 h contact time, respectively. At the investigated operating conditions, oxalic acid extracted the lowest amount of As, Cr and Cu from the contaminated soil and the extraction efficiency depended on the solid/liquid contact time. The amount of metal extracted at the contact time of 6 h were 10.41, 12.50, 17.71 and 18.75 mg/kg As using oxalic, malonic, citric and succinic acid, respectively; 97.05, 123.69, 140.05 and 147.28 mg/kg Cr using oxalic, malonic, citric and succinic acid, respectively; 64.00, 94.10, 106.00 and 118.00 mg/kg Cu using oxalic, malonic, citric and succinic acid, respectively. Chromium (47%) was the least to be removed of the three metals after 6 h of washing. The contamination factor of the contaminated soil was affected by the extraction test. Levels of the metals in the decontaminated soil after 6 h of washing were found to be below the target value for all metals, which is somewhat higher for Sparks in respect of As and higher than the control values for As, Cr and Cu. After the 6 h extraction test, 15.84 – 16.62 mg/kg (60 - 63%) As, 59.35 - 65.04 mg/kg (32 - 38%) Cr and 37.10 - 49.53 mg/kg (38 - 50%) Cu was found in the bioavailable fraction of the soil treated with the four different organic acid chelants.Key words: CCA contaminated soil, decontamination, organic acids, extraction

Removal of heavy metals from aqueous media using native cassava starch hydrogel

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. Grafting was confirmed by Fourier transform infrared spectroscopy (FTIR). The grafted copolymer and the hydrolyzed graft copolymer (hydrogel) were used as sorbent for the uptake of heavy metals from the aqueous media. The sorption capacity was evaluated by measuring the extent of sorption of nickel, copper, and leads metals ions, under equilibrium conditions. Using the sorption isotherm models, the Freundlich model was found suitable because of good fitness and equilibrium data yielded the following ultimate capacity values for the sorbent of the grafted copolymer: 54 mgPb/g, 64.5 mgCu/g and 71.1 mgNi/g and for the hydrogel: 72 mgPb/g, 76.6 mgCu/g and 86.5 mgNi/g. Hydrolysis increases the sorption affinity of grafted copolymer toward metal ions. Acid stripping with 2% HCl resulted in 99.6% metal recovery for the hydrogel and 52.2% for the grafted copolymer. This shows the ability of the product to be reused, upon drying between treatments.Key words: Acrylonitrile, cassava starch, grafted copolymer, heavy metals, hydrogel, sorption

Preliminary investigation of chemical fractionation and heavy metal accumulation in plant maize (Zea mays) grown on chromated copper arsenate (CCA) contaminated soil amended with poultry droppings

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 forchromium 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

Sublethal effects of industrial chemicals on fish fingerlings (Tilapia guineensis)

Tilapia guineensis commonly found in the Niger Delta ecological zone of Nigeria was exposed to sublethal concentrations (1.56, 3.13 mg/l) of neatex (industrial detergent) and norust CR 486 (corrosion inhibitor) using the Organisation for Economic Cooperation and Development (OECD) # 203 protocol. At test termination on the 28th day, the rate of bioaccumulation of surfactants in the fish gills, gut and muscle tissues were measured. The levels of surfactant in the gills, gut and muscle tissues were significantly different at levels of p < 0.05 in fish exposed to neatex and norust CR 486. Surfactant levels in the fish also increased significantly with increase in concentrations. Surfactant accumulation in the test treatments may be an indication that the observed effects on the exposed fish may have been due to the chemicals. This study demonstrates the sublethal effects of surfactant-containing industrial chemicals on T. guineensis, an economic and ecologically important sentinel

The Synergy between Meteorological Parameters and the Total Suspended Particles in the Atmosphere using Polynomial as Model

Pollutants in the atmosphere are influenced by weather and chemistry thus making it difficult to know when they will concentrate and cause poor air quality. The only way to be sure of this is to monitor the air pollution at as many sites as possible and very often as well. In this study, particulate matter was captured at ten locations using SKC Air check XR5000 High volume Gravimetric sampler. The meteorological parameter was captured by LM-8000 Anemometer and with hydro thermograph -RS humidity /temperature meter. This study was conducted from May to October, 2010 in Sapele, Nigeria. The mean concentration range from156.25-850.70μg/m3 while the correlation of suspended particulate matter with wind speed and temperature were both positive and the correlation of suspended particulate matter with relative humidity was negative. It was observed that the total suspended particulate matter correlated well with relative humidity and poorly with wind speed and temperature.Keywords: Spatial Variation; Meteorological; Urban area; Suspended Particulate matter, polynomial mode

Short-term phyto-toxicity consequences of a nonselective herbicide glyphosate (Roundup™) on the growth of onions (Allium cepa Linn.)

This study examined the phyto-toxic effects of a commonly named non-selective herbicide glyphosate (Roundup™) on onions (Allium cepa Linn.). The study was necessitated due to the indiscriminate use and release of Roundup™ for weed control in the Niger Delta soils of Nigeria. The Organisation for Economic Co-operation and Development (OECD) standard protocol # 208 was adopted. The   short-term phyto-toxic consequence on onion (A. cepa L.) was determined after a 4-day exposure to varying concentrations of the test chemical at 0.625, 1.25, 2.5, 5 and 10 mg/L, respectively. The percentage growth rate decreased as percentage growth rate inhibition efficiency increased, which implies that the effect of the herbicide was concentration dependent. The mean percentage growth rate inhibition efficiency relative to the control was 28, 47, 61, 73 and 96%, respectively. The effective concentration (EC50) for % Inhibition efficiency was 1.550 mg/L with a 95% confidence interval of 1.269 to 1.848 mg/L. The biological alterations on the onions in the test solutions varied in order of increasing concentrations. Some observations made include decolouration of the test solutions and stunted growth especially at the highest concentration of 10 mg/L. Other effects include: bulb  deformation, tissue and root damage. There was significant difference between the exposed species and the control at P < 0.05. The use of the herbicide Roundup™ with such hazardous effects can harm plants especially onion which is a very viable food product of man. This could lead to likely distortion on the ecosystem balance of onions (A. cepa) and similar plants and subsequent effect on human, the major end user.Key words: Herbicide, glyphosate (roundup), onion (Allium cepa Linn.), phytotoxicity

Elemental Concentration of Inhalable and Respirable Particulate Matter in Urban Area During Wet Season

Previously, the capture of suspended particulate matter focused on the total suspended particulate matter, until recent research into the health impacts of suspended particulate matter suggests that minute particles that have toxic substances adsorbed onto their surface are insidious and deleterious for human health and vegetation. The Inhalable fraction and respirable fraction were captured between the month of May 2009 to October 2009 using SKC Air Check Gravimetric Sampler- Model 210-5000 serial No. 20537 and respirable foam for I.O.M sampler. The elemental composition (Co, Ni, Zn, Cu, Fe, Pb, Cr, Mn and Cd) were analyzed by using Atomic Absorption Spectrophotometric (AAS). The data generated were subjected to descriptive analysis. In inhalable fraction,the enrichment factor ranged from 1-73.3 while in respirable ,it was 1- 72.9.Lead had the highest mean concentration in both inhalable and respirable fraction. From the enrichment factor Cd was highly enriched while Pb was moderately enriched. Co and Ni were below detection limit in both inhalable and respirable suspended particulate matter

UV-induced electrical and optical changes in PVC blends

2-Chloro-polyaniline (2-Cl-PANI) in its non-conducting (emeraldine base, EB) form, prepared by a chemical route, was dissolved together with poly-(vinylchloride) (PVC) in THF for casting into thin (10-50 μm) films. Upon exposure to UV radiation, the electrical conductivity of these films increased by more than 4 orders of magnitude (from 10-6 to 10-2 S/cm). This is attributed to the dehydrochlorination of PVC by exposure to energetic photons and subsequent doping of 2-Cl-PANI (i.e. conversion to emeraldine salt, ES) by in situ created HCl. The doped films could be returned to their undoped form by exposure to NH3 vapours. The UV-induced doping/NH3 undoping cycles could be repeated several times. Various spectroscopic techniques were employed to follow the changes in the films upon exposure to UV radiation. The same photo-dehydrochlorination process has also been utilized for optical and/or lithographic purposes by preparing PVC blends containing methyl violet, and acid-base indicator dye. The photo-dehydrochlorination can be effectively sensitized by incorporating hydroquinone into the PVC blends containing methyl violet

Mixed contaminant interactions in soil: Implications for bioavailability, risk assessment and remediation

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