Kinetic and mechanism studies of the adsorption of lead onto waste cow bone powder (WCBP) surfaces

This study examines the adsorption isotherms, kinetics and mechanisms of Pb²⁺ sorption onto waste cow bone powder (WCBP) surfaces. The concentrations of Pb²⁺ in the study range from 10 to 90 mg/L. Although the sorption data follow the Langmuir and Freundlich isotherm, a detailed examination reveals that surface sorption or complexation and co-precipitation are the most important mechanisms, along with possibly ion exchange and solid diffusion also contributing to the overall sorption process. The co-precipitation of Pb²⁺ with the calcium hydroxyapatite (Ca-HAP) is implied by significant changes in Ca²⁺ and PO₄ ^3? concentrations during the metal sorption processes. The Pb²⁺ sorption onto the WCBP surface by metal complexation with surface functional groups such as ≡ POH. The major metal surface species are likely to be ≡ POPb⁺. The sorption isotherm results indicated that Pb²⁺ sorption onto the Langmuir and Freundlich constant q _max and K _F is 9.52 and 8.18 mg g^?1, respectively. Sorption kinetics results indicated that Pb²⁺ sorption onto WCBP was pseudo-second-order rate constants K ₂ was 1.12 g mg^?1 h^?1. The main mechanism is adsorption or surface complexation (≡POPb⁺: 61.6%), co-precipitation or ion exchange [Ca_3.93 Pb_1.07 (PO₄)₃ (OH): 21.4%] and other precipitation [Pb 50 mg L^?1 and natural pH: 17%). Sorption isotherms showed that WCBP has a much higher Pb²⁺ removal rate in an aqueous solution; the greater capability of WCBP to remove aqueous Pb²⁺ indicates its potential as another promising way to remediate Pb²⁺-contaminated media.     

Characterization of polychlorinated dibenzo-p-dioxins and dibenzofurans in different particle size fractions of marine sediments

The distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) was examined according to particle size in marine sediments, with a particular focus on fine particulates. Samples from different coastal sites were fractionated into five size groups (<2, 2-5, 5-10, 10-20, and 20-63 microm diameter) by gravitational split-flow thin fractionation. Despite the different size profiles and PCDD/F contents of the sediments at each site, PCDD/F levels in fractionations tended to increase as the particle size decreased; the PCDD/F levels in the finest particles were up to 16 times higher than in the coarsest particles, which was associated with their organic carbon contents. Log normalization showed high levels of PCDD/Fs in the fine silt particles (2-10 microm), which are consumable by aquatic biota. Because of the different toxicity and bioavailability of PCDD/Fs in different sediment particle sizes, it is important to study particle actions to understand their effects on the aquatic ecosystem.     

Dissolved organic matter effects on the performance of a barrier to polycyclic aromatic hydrocarbon transport by groundwater

In order to contain the movement of organic contaminants in groundwater, a subsurface sorption barrier consisting of sand or clay minerals coated with a cationic surfactant has been proposed. The effectiveness of such a sorption barrier might be affected by the presence of dissolved organic matter (DOM) in the groundwater. To study the impact of DOM on barrier performance, a series of batch experiments were performed by measuring naphthalene and phenanthrene sorption onto sand coated with cetylpyridinium chloride (CPC) and bentonite coated with hexadecyltrimethylammonium bromide (HDTMA) in the presence of various concentrations of DOM. The overall soil-water distribution coefficient (K*) of naphthalene and phenanthrene onto CPC-coated sand decreased with increasing DOM concentration, whereas the K* of the compounds onto HDTMA-coated bentonite slightly increased with increasing DOM concentration. To describe the overall distribution of polycyclic aromatic hydrocarbons (PAHs) in the systems, a competitive multiphase sorption (CMS) model was developed and compared with an overall mechanistic sorption (OMS) model. The modeling studies showed that while the OMS model did not explain the CPC-coated sand experimental results, a model that included competitive sorption between DOM and PAH did. The experimental results and the modeling study indicated that there was no apparent competition between DOM and PAH in the HDTMA-coated bentonite system, and indicated that in groundwater systems with high DOM, a barrier using HDTMA-coated bentonite might be more effective.     

A kinetic study on oxidation of pentachlorophenol by ozone

The kinetics of pentachlorophenol (PCP) ozonation in terms of the gaseous O3 and dissolved PCP concentrations has been investigated. When the O3 concentration in the gas phase was in the range of 10 to 40 g O3/m3, the O3 dissolved for a short time period was proportional to the gaseous O3 concentration. In this range, the ozonation reaction was first order for each reactant and the overall reaction was second order. At 25 degrees C, in an aqueous solution, the reaction rate constant was estimated to be 10.048 L/mol.sec. The reaction rate was much greater than the mass-transfer rate, indicating that the reaction of O3 and PCP was an interface reaction on the surface of gaseous O3 bubbles. The final product of the PCP ozonation was oxalic acid, with the carbon yield of the reaction being 59.4%. The ozonation of PCP in the aqueous solution was not a radical reaction but a direct reaction between O3 and PCP molecules under the conditions investigated in this study, since O3 has a high selectivity toward PCP. The reaction rate increased with the reaction temperature up to 35 degrees C but decreased at temperatures greater than 35 degrees C due to the decreased solubility of O3. The addition of H2O2 did not increase the reaction rate significantly.     

Atmospheric deposition of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) in urban and suburban areas of Korea

Bulk atmospheric samples (wet and dry) were collected monthly throughout a year at urban and suburban areas of Korea to assess the deposition flux and seasonal variations of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs). The PCDDs/DFs deposition fluxes ranged from 1.0 to 3.7 ng TEQ/m²/year in the urban area and from 0.5 to 4.6 ng TEQ/m²/year in the suburban area. The deposition fluxes of PCDDs/DFs in this study were comparable to or lower than those previously reported at different locations. The atmospheric deposition fluxes of particles and PCDDs/DFs in winter tended to be higher than those in summer. However, monthly variations between particle and PCDDs/DFs deposition fluxes were small, and the correlation coefficients between the deposition fluxes of air particles and each homologue group of PCDDs/DFs varied according to the degree of chlorination of the homologue group. The deposition velocity of PCDDs/DFs in the urban area was estimated at 0.04 cm/s, which is a lower value than those found in other studies. The two most likely factors affecting the monthly variation of deposition fluxes are the ambient temperature and the amount of precipitation. In particular, the ambient temperature had an influence on the lower chlorinated homologues of PCDDs/DFs while precipitation had an influence on the higher chlorinated PCDDs/DFs. The PCDDs/DFs profiles in atmospheric deposition bulk samples showed a similar pattern at the urban and suburban sites. The possibility of the loading of PCDDs/DFs by Asian dust events could be partly confirmed by investigation of homologue profiles.     

Biodegradation and detoxification of organophosphate insecticide, malathion by Fusarium oxysporum f. sp. pisi cutinase

Efficiencies of two lypolytic enzymes (fungal cutinase and yeast esterase) in malathion degradation were investigated. Surprisingly, degradation rate of malathion by fungal cutinase was very high, i.e. almost 60% of initial malathion (500 mg l(-1)) was decomposed within 0.5 h, and nearly 50% of the degraded malathion disappeared within initial 15 min. With the yeast esterase, despite the same concentration, more than 65% of malathion remained even after 2-day treatment. During enzymatic degradation of malathion, two malathion-derived compounds were detected, and time-course changes in composition were also monitored. In the degradation by both fungal cutinase and yeast esterase, two additional organic chemicals were produced from malathion: malathion monoacid (MMA) and malathion diacid (MDA) by ester hydrolysis. Final chemical composition after 2 d was significantly dependent on the enzyme used. Fungal cutinase produced MDA as a major degradation compound. However in the malathion degradation by yeast esterase, an isomer of MMA was produced in abundance in addition to MDA. Toxic effects of malathion and its final degradation products were investigated using various recombinant bioluminescent bacteria. As a result, the degradation products (including MMA) by esterase severely caused membrane damage and inhibition of protein synthesis in bacterial cells, while in the fungal cutinase processes, malathion was significantly degraded to non-toxic MDA after the extended period (2 days).     

Optimum Dose Of Lime And Fly Ash For Treatment Of Hexavalent Chromium–Contaminated Soil

The presence of hexavalent chromium, Cr(VI), in soil is an environmental concern due to its effect on human health. The concern arises from the leaching and the seepage of Cr(VI) from soil to groundwater. In this paper, a stabilization technology to prevent this problem was simulated on an artificial soil contaminated with hexavalent chromium. The process is a physico-chemical treatment in which the toxic pollutant is physically entrapped within a solid matrix formed by the pozzolanic reactions of lime and fly ash to reduce its leachability and, therefore, its toxicity. This paper presents the optimum ratio of fly ash and lime in order to stabilize artificial soils contaminated with 0.4 wt.% of Cr (VI) in a brief term process. The degree of chromium released from the soil was evaluated using a modified Toxicity Characteristic Leaching Procedure (TCLP) by US Environmental Protection Agency (EPA). Overall, experimental results showed reduced leachability of total and hexavalent chromium from soils treated with both fly ash and quicklime, and that leachability reduction was more effective with increasing amount of fly ash and quicklime. Stabilization percentages between 97.3% and 99.7% of the initial chromium content were achieved, with Cr(VI) concentration in the TCLP leachates below the US EPA limit for chromium of 5 mg/l. Adequate treatment was obtained after 1 day of curing with just 25% fly ash and 10% quicklime.     

Hepatopancreas mitochondria from Mytilus edulis:

A method for the isolation of intact coupled mitochondria from the hepatopancreas of Mytilus edulis has been developed. These mitochondria prefer lipid substrates and accept a range of fatty acid chain lengths. Acetyl carnitine is also oxidized at high rates. Evidence for the presence of the tricarboxylate and the dicarboxylate transporters is presented. The absence of the pyruvate transporter or inhibition of pyruvate dehydrogenase is indicated by the absence of pyruvate oxidation. Glutamate is oxidized at high rates with a pH optimum of 7.5 based on the RCR. Cysteine oxidation may indicate the presence of the enzymes involved in the synthesis of taurine. Ornithine transport is also indicated, implying the existence of the urea cycle. Alanine, glycine, proline, asparagine, arginine, aspartate and citrulline were not oxidized at detectable levels. The osmotic optimum for the oxidation of glutamate extends from 600 to 1000 mOsm l^-1. The state 3 rate is more profoundly affected by the osmolarity than the state 4 rate. The role of osmolarity in the control of oxidation of amino acids during volume regulation of osmotically stressed M. edulis is suggested. Mitochondrial volume changes correlate with the optimal range of osmolarity for glutamate oxidation based on the RCR.     

Chemical composition of major VOC emission sources in the Seoul atmosphere

This paper describes a chemical analysis of volatile organic compounds (VOCs) for five emission sources in Seoul. The source categories included motor vehicle exhaust, gasoline evaporation, paint solvents, natural gas and liquefied petroleum gas (LPG). These sources were selected because they have been known to emit significant quantities of VOCs in the Seoul area (more than 5% of the total emission inventory). Chemical compositions of the five emission sources are presented for a group of 45 C2-C9 VOCs. Motor vehicle exhaust profiles were developed by conducting an urban tunnel study. These emissions profiles were distinguished from the other emission profiles by a high weight percentage of butanes over seasons and propane in the wintertime. It was found that this is due to the wide use of butane-fueled vehicles. To obtain gasoline vapor profiles, gasoline samples from five major brands for each season were selected. The brands were blended on the basis of the marketshare of these brands in Seoul area. Raoult's law was used to calculate gasoline evaporative compositions based on the liquid gasoline compositions. The measured and estimated gasoline vapor compositions were found to be in good agreement. Vehicle and gasoline evaporation profiles were made over seasons because of the seasonal change in their compositions. Paint solvent emissions profiles were produced based on a product-use survey and sales figures. These profiles are a composite of four major oil-based paints and thinning solvent. The source profile of natural gas was made on a methane-free basis. It was found that Ethane and propane were the most abundant compounds accounting for 95% of the natural gas composition. LPG was largely composed of propane and ethane and the remaining components were minor contributors.