Retention Of Heavy Metals Research Articles

Removal of Cadmium (II) Ions from Aqueous Phase by Biosorption on Biological Activated Dates' Pedicels (Kinetic, Equilibrium and Thermodynamic Study)

The preparation of biological activated dates’ pedicels (ADP) adsorbents and its biosorption behaviour of cadmium (II) was the topic of this study. The raw (RDP) and activated (ADP) dates’ pedicels were characterized by SEM, XRF, FTIR and surface area analysis. SEM analysis revealed a heterogeneous structure for ADP and a cellular aspect different from that of RDP, due to the deposit of the bacterial film which has been constituted during the biological treatment of the material. The XRF results show the presence of potassium, calcium in RPD, and sodium in APD which could favour the retention of heavy metals in aqueous solutions by ions exchange. The FT-IR spectra showed that there are different functional groups in adsorbents, which are able to react with metal ions in aqueous solution. Biological pretreatment was carried out in nitrate enriched solution; allowing to enhance the development of denitrifying micro-organisms already existing on the organic support without the need for biomass inoculation. Biological pretreatment allowed the appearance of a bacterial film at the surface of the date pedicel particles, which improved their biosorption capacity. Indeed, the biosorption yields of cadmium (II) ions obtained at equilibrium (60 min) were 70.4 and 57.4% for ADP and RDP, respectively. The experimental data were analyzed by the Langmuir and Freundlich isotherm models and the model constants were evaluated. The maximum biosorption capacity as calculated using the Langmuir isotherm model was 10.75 mg g-1 which is greater than that of commercial and granular activated carbon. The kinetic data obtained at different initial cadmium concentrations and different temperatures were analyzed using pseudo-second-order and intra-particle diffusion models. The biosorption kinetics followed a pseudo-second-order kinetic model. The biosorption of cadmium ion was endothermic and spontaneous. Elution efficiencies with different concentrations of CaCl2, KCl and NaCl were evaluated. The desorption studies showed the reversibility of biosorption and CaCl2 was the most efficient desorbent for elution and desorption of cadmium from the biosorbant.

Time of flight secondary ion mass spectrometry and high-resolution transmission electron microscopy/energy dispersive spectroscopy: A preliminary study of the distribution of Cu 2+ and Cu 2+/Pb 2+ on a Bt horizon surfaces

Relatively new techniques can help in determining the occurrence of mineral species and the distribution of contaminants on soil surfaces such as natural minerals and organic matter. The Bt horizon from an Endoleptic Luvisol was chosen because of its well-known sorption capability. The samples were contaminated with Cu 2+ and/or Pb 2+ and both sorption and desorption experiments were performed. The preferential distribution of the contaminant species ( 63Cu and 208Pb) to the main soil components and their associations were studied together with the effectiveness of the surface sorption and desorption processes. The results obtained were compared with non-contaminated samples as well as with previous results obtained by different analytical techniques and advanced statistical analysis. Pb 2+ competes favorably for the sorption sites in this soil, mainly in oxides and the clay fraction. Cu 2+ and Pb 2+ were mainly associated with hematite, gibbsite, vermiculite and chlorite. This study will serve as a basis for further scientific research on the soil retention of heavy metals. New techniques such as spectroscopic imaging and transmission electron microscopy make it possible to check which soil components retain heavy metals, thereby contributing to propose effective measures for the remediation of contaminated soil.

Forest soils adjacent to urban interstates: Soil physical and chemical properties, heavy metals, disturbance legacies, and relationships with woody vegetation

While urban ecology is an expanding field of study, some natural areas within the urban environment remain under-examined. These include naturally regenerating forest communities adjacent to urban interstates. In addition, the status of interstate soils and their relationships with the community composition of forested interstate verges has received little ecological study. The purpose of this study was to examine variation in soil conditions along forested interstate corridors in Louisville, KY and to explore the extent to which soil characteristics (e.g., bulk density, pH) and heavy metals (e.g., Pb, Zn) vary with respect to three factors: interstate (e.g., traffic density), surrounding urban environment (e.g., industrial land use), and interstate construction legacies. Additionally, we explored the relationships between several edaphic factors and woody vegetation structure in these forested verges. We found that the degree and direction of the slope of land towards the interstate and the distance to the interstate pavement were strong determinants of soil characteristics and heavy metal concentrations, suggesting that the movement of de-icing salts, heavy metals, and other pollutants from the interstate was important in determining forest soil conditions along urban interstates. Since within our study area these highways did not extend into rural lands, variation in urban land uses and cover within 26 km of the city center was not large enough to explain variation in soil characteristics or heavy metals, except for a positive correlation between chromium and surrounding industrial land use. We did find that past physical soil disturbance caused by interstate construction (e.g., imported fill) left an important legacy on soil characteristics, heavy metal retention, and woody plant growth patterns in forests adjacent to urban interstates. The legacy of interstate construction on the current forest community structure (e.g., lower species richness) and the future forest (e.g., reduced tree regeneration) may further alter ecosystem productivity and ecosystem services provided by these forests and their soils.

Screening biochars for heavy metal retention in soil: Role of oxygen functional groups

Oxygen-containing carboxyl, hydroxyl, and phenolic surface functional groups of soil organic and mineral components play central roles in binding metal ions, and biochar amendment can provide means of increasing these surface ligands in soil. In this study, positive matrix factorization (PMF) was first employed to fingerprint the principal components responsible for the stabilization of heavy metals (Cu, Ni, Cd, Pb) and the release of selected elements (Na, Ca, K, Mg, S, Al, P, Zn) and the pH change in biochar amended soils. The PMF analysis indicated that effective heavy metal stabilization occurred concurrently with the release of Na, Ca, S, K, and Mg originating from soil and biochar, resulting in as much as an order or magnitude greater equilibrium concentrations relative to the soil-only control. In weathered acidic soil, the heavy metal (especially Pb and Cu) stabilization ability of biochar directly correlated with the amount of oxygen functional groups revealed by the O/C ratio, pH pzc, total acidity, and by the 1H NMR analysis. Equilibrium speciation calculation showed minor influence of hydrolysis on the total soluble metal concentration, further suggesting the importance of binding by surface ligands of biochar that is likely to be promoted by biochar-induced pH increase.

Influence of Pyrolysis Temperature on Biochar Property and Function as a Heavy Metal Sorbent in Soil

While a large-scale soil amendment of biochars continues to receive interest for enhancing crop yields and to remediate contaminated sites, systematic study is lacking in how biochar properties translate into purported functions such as heavy metal sequestration. In this study, cottonseed hulls were pyrolyzed at five temperatures (200, 350, 500, 650, and 800 °C) and characterized for the yield, moisture, ash, volatile matter, and fixed carbon contents, elemental composition (CHNSO), BET surface area, pH, pHpzc, and by ATR-FTIR. The characterization results were compared with the literature values for additional source materials: grass, wood, pine needle, and broiler litter-derived biochars with and without post-treatments. At respective pyrolysis temperatures, cottonseed hull chars had ash content in between grass and wood chars, and significantly lower BET surface area in comparison to other plant source materials considered. The N:C ratio reached a maximum between 300 and 400 °C for all biomass sources considered, while the following trend in N:C ratio was maintained at each pyrolysis temperature: wood≪cottonseed hull≈grass≈pine needle≪broiler litter. To examine how biochar properties translate into its function as a heavy metal (NiII, CuII, PbII, and CdII) sorbent, a soil amendment study was conducted for acidic sandy loam Norfolk soil previously shown to have low heavy metal retention capacity. The results suggest that the properties attributable to the surface functional groups of biochars (volatile matter and oxygen contents and pHpzc) control the heavy metal sequestration ability in Norfolk soil, and biochar selection for soil amendment must be made case-by-case based on the biochar characteristics, soil property, and the target function.

Impactos potenciais das alterações do Código Florestal nos recursos hídricos

Florestas ripárias, mosaicos de vegetação e áreas alagadas têm papel fundamental na proteção dos recursos hídricos mantendo a qualidade da água em excelentes condições para abastecimento e recarregado aquíferos repondo, portanto, volumes substanciais de águas para o componente subterrâneo. A remoção de florestas ripárias e áreas alagadas têm um efeito extremamente negativo degradando a qualidade das águas superficiais e subterrâneas, acelerando a sedimentação de lagoas, represas e rios, e diminuindo o estoque de água nas nascentes e aquíferos. Todos os serviços ambientais dos ecossistemas aquáticos ficam comprometidos com o desmatamento e remoção de áreas naturalmente alagadas, portanto a preservação destas áreas é essencial para regular tanto o ciclo hidrológicos como os ciclos biogeoquímicos. A remoção destas áreas torna insustentável a agricultura em curto prazo.

Micellar-enhanced ultrafiltration for the removal of cadmium and zinc: Use of response surface methodology to improve understanding of process performance and optimisation

In this study, removal of cadmium and zinc from their respective water samples was conducted by micellar-enhanced ultrafiltration (MEUF), using sodium dodecyl sulfate (SDS) as the surfactant. Response surface methodology (RSM) was used for modelling and optimising the process, and to gain a better understanding of the process performance. Face Centred Composite (CCF) Design was used as the experimental design. The factors studied were pressure ( P), nominal molecular weight limit (NMWL), heavy metal feed concentration ( C Zn, C Cd) and SDS feed concentration ( C SDS). Using RSM the retention of heavy metals was maximized while optimising the surfactant to metal ratio (S/M). Response surface plots improved the understanding the effect of the factors on permeate flux. Concentration polarisation was negligible and therefore, high NMWL membranes with high pressure provided high flux with negligible effect on the retention of heavy metals. The optimal conditions of zinc removal were C SDS = 13.9 mM, C Zn = 0.5 mM, NMWL = 10 kDa and P = 3.0 bar, and for cadmium removal C SDS = 14.2 mM, C Cd = 0.5 mM, NMWL = 10 kDa and P = 3.0 bar. The retentions achieved were 98.0 ± 0.4% for zinc and 99.0 ± 0.4% for cadmium. To improve resource efficiency, the surfactant was reclaimed after use; 84% of the initial SDS was recovered by precipitation.

Evaluation of Ecological Function of Mangrove Soil on Absorbing Heavy Metals: A Case Study from the Dongzhaigang Mangrove in China

ABSTRACT: Mangroves are special plant communities that live along intertidal zones in tropical and subtropical areas. They are regarded as one of the most important types of natural ecosystem in the world because of the many ecosystem functions that they perform, of which water purification is the most complex. Mangrove ecosystems are conducive to the deposition and retention of heavy metals. So it is important to understand the impact of heavy metals on mangrove ecosystems, and especially on soil subsystems. We examined the levels of heavy metals in the soil of mangroves in the Dongzhaigang Mangrove National Nature Reserve. Dongzhaigang, the first mangrove nature reserve established in China, is located south of Haikou in Hainan Island and encompasses 33.37 km 2 , of which mangroves comprise 20.56 km 2 . To assess the impact of human activities, we collected a large number of soil samples in four sampling areas (the protection station, the harbor, a tour area, and Yeboluo island) in the study area. We measured the concentrations of Cu, Pb, Zn and Cd in the soil samples using the spectra of polyatomic molecules. The average concentrations of Cu, Pb, Zn and Cd were 5.04 μg/g, 10.36 μg/g, 20.06 μg/g and 0.06 μg/g, respectively, and the heavy metal concentrations were lowest in the protected area, highest in the harbor, and intermediate in Yeboluo Island and the tour area. The heavy metal concentrations in the soil collected from different sample plots are related not only to the physical and chemical properties of the soil, but also to the heavy metal emitted by nearby pollution sources. Our analysis indicates that tourist boats are the main pollution sources in the study area. Key words: ecological function, heavy metal, mangrove soil

Spatial and temporal variation of the nutrients in the sediment and leaves of two Brazilian mangrove species and their role in the retention of environmental heavy metals

Spatial and temporal variation of the nutrient concentrations in leaves and sediment between the roots of Laguncularia racemosa (L.) Gaertn. f and Rhizophora mangle L. was analyzed in the mangrove forest of the estuary of São Mateus River, Espírito Santo, Brazil. In leaves, the nutrients followed the sequence: N> Ca> K> Mg> S> P> Fe> Mn> Zn> Cu, and there were significant differences between species and sites studied. In general, the levels of K were higher in the dry season compared to the rainy season for both species analyzed while Ca and Cu showed higher concentrations in the rainy season for Laguncularia racemosa. In the sediment, the nutrients followed the sequence: Mg> Ca> Fe> K> Mn> P> Zn> Cu, in general, with lower concentrations at the site where the sediment was sandier. We observed a significant variation of nutrient concentrations in the sediment between the periods analyzed, but the seasonal pattern was not clear for all nutrients. Nutrient concentration profile found in leaves of both plant species was not correlated with concentrations found in the respective sediments. The concentration factor was less than 1.0 for Fe and between 1.0 and 3.7 for Mn, Zn and Cu. These results provide physiological evidences about the relevance of these tree species for the role of mangroves as biogeochemical barriers to the transit of heavy metals.

The effects of artificial ageing on the leaching behaviour of heavy metals in stabilized/solidified industrial sludge

The use of a hydraulic binder for the treatment of mineral‐based industrial wastes, containing heavy metals, by the chemical fixation and solidification (CFS) technique has raised serious questions regarding the prediction of the behaviour of these pollutants in the obtained solid matrix. It seems necessary, for this reason, to study the behaviour of these metals in response to leaching in order to evaluate their chemical speciation within the solidified sludge over the medium and long‐terms. Within the framework of the current research, we applied the CFS technique to metallic hydroxide sludge, produced by the electrotyping surface treatment industry, by using Portland artificial cement (PAC). Compaction at the paste phase of this treated sludge resulted in up to 35% enhancement of the retention of pollutants, mainly trivalent chromium, in a cementing matrix, as compared with the classical technique that uses a simple vibration of sludge at the paste phase. The implemented process led to an improvement in the compactness of the sludge, and thus assured a better retention of heavy metals in response to the leaching of this treated sludge. The evaluation of the chemical properties of the materials obtained after an artificial ageing process using humidity variation cycles and thermal chocks also revealed a significant improvement in the retention capacity of heavy metals in the solidified sludge, which was mainly favoured by the development of carbonation. In fact, the release of the heavy metals from the above mentioned treated sludge was reduced by 58% for zinc and 51% for trivalent chromium after the artificial ageing process.

Use of Sphagnum peat moss and crushed mollusk shells in fixed-bed columns for the treatment of synthetic landfill leachate

A laboratory bench-scale fixed-bed column study operated as a down-flow configuration was conducted to evaluate Sphagnum peat moss and crushed mollusk shells as natural low-cost adsorbents for the removal of heavy metals from aerated and unaerated synthetic landfill leachate. Columns were packed with 15 cm of prepared peat moss, or 15 cm adsorbent mixtures made up of peat moss and crushed mollusk shells (4.0–4.75 mm) from Lake Ontario at different bed depth ratios. Peat was found to have the best adsorption capacities in columns treating aerated synthetic leachate for cadmium and nickel with 78.6% and 83.8% removal efficiencies, respectively. The removal of chemical oxygen demand (COD) and total nitrogen from the synthetic leachate was also monitored to evaluate the potential effects of biological activity on heavy metal adsorption. Columns receiving unaerated raw synthetic leachates did not show any significant removal of COD and total nitrogen, whereas some reduction in COD and total nitrogen was noted in the columns treating aerated synthetic landfill leachate. The results suggested that biological activity and biofilm growth could positively contribute to heavy metal retention within the fixed-media biosorption columns.

Competitive Sorption of Nickel and Cadmium in Different Soils

Competing ions strongly affect heavy-metal retention and release in soils. In this study, we evaluated the sorption of Ni and Cd in single and binary Ni-Cd systems for one neutral and 2 acidic soils. Ni and Cd sorption isotherms were obtained using batch techniques over a wide range of concentrations. Both Ni and Cd adsorption isotherms exhibited strong nonlinear behavior with similar overall patterns for all soils. Sorption of Ni and Cd correlated well the cation exchange capacity for all soils. Moreover, Cd sorption by the two acidic soils was greater than Ni, whereas for the neutral soil, Ni sorption was greater than Cd. The Freundlich model was utilized to describe the family of Ni and Cd isotherms in the presence of competing ions. For both Ni and Cd isotherms, the Freundlich distribution coefficient K decreased with increasing concentration of the competing ion. The dimensionless parameter n was within a narrow range of 0.50 to 0.64 for both Ni and Cd and was not affected by the competing ion. Competitive sorption was described using the Sheindorf-Rebhun-Sheintuch (SRS) equation, which is based on multicomponent Freundlich-type models. Estimates of SRS competitive sorption coefficients indicated that for the neutral soil, Ni sorption was least affected by Cd. The SRS equation was also capable of describing the overall competitive Ni and Cd sorption patterns for all soils. However, SRS model modifications are needed to improve sorption prediction for the highest competing concentrations.

The biomass and nutrient and heavy metal content of cattails and reeds in wastewater treatment wetlands for the production of construction material in Estonia

Cattails and reeds are the most common plants in constructed and semi-natural wetlands for wastewater treatment, and can play an important role in both nutrient and heavy metal retention. On the other hand, both plants are highly valued in ecologically oriented construction. The aim of this chapter is to measure common cattail (Typha latifolia) and reed (Phragmites australis) biomass production and the annual assimilation of nutrients (N, P) and heavy metals (Cd, Zn, Cu, Pb) in the phytomass of common cattail (T. latifolia) in two free-water surface flow constructed wetlands (FWSF CWs) and in one semi-natural treatment wetland in Estonia. The phytomass measurements were performed after the vegetation period in autumn and winter from 2002 to 2006. The average aboveground biomass of T. latifolia varied from 0.30 to 1.76 kg dry weight (DW) m−2, and the corresponding values for P. australis were from 0.61 to 1.32 kgDWm−2. Average N, P and heavy metal concentrations showed that the harvesting of aboveground biomass does not have much of an effect on the removal of heavy metals from wetlands.

Feasibility study on solidification of municipal solid waste incinerator fly ash with circulating fluidized bed combustion coal fly ash

The objective of this study was to assess the feasibility of solidification of municipal solid waste incinerator (MSWI) fly ash with circulation fluidized bed combustion (CFBC) fly ash, which is unsuitable as a cement replacement due to its high amounts of carbon, lime and anhydrite. The solidification process was conducted on samples prepared from MSWI fly ash, binders (cement clinkers and CFBC fly ash were mixed at two replacement ratios) and water (water/solid weight ratio = 0.4), among which the MSWI fly ash replaced each binder at the ratio of 0, 20, 40, 60 and 80% by dry weight. The samples were subjected to compressive strength tests and Toxicity Characteristic Leaching Procedure and the results showed that all solidified MSWI fly ash can meet the landfill standard imposed by US EPA after 28 days of curing. Micro-analysis (X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectrophotometry) revealed that the main hydrate products were C-S-H gel and ettringite, which have a positive effect on heavy metals retention. Therefore, this method provides a possibility to achieve a cheap and effective solution for MSWI fly ash management and use for CFBC fly ash.

Avaliação da integridade e da retenção de metais pesados em materiais estabilizados por solidificação

A quantidade de resíduos sólidos industriais tem aumentado significativamente em decorrência da industrialização, e o seu gerenciamento adequado é necessário para reduzir o impacto ao meio ambiente e aos ecossistemas. Neste trabalho, foram avaliadas a integridade e a retenção de metais pesados em materiais estabilizados por solidificação. Foi adotado o planejamento completamente aleatorizado com um único fator, ou seja, foram comparadas as médias de quatro tratamentos (A, B, C e D) com 0, 40, 50 e 60% respectivamente de contaminantes e três repetições. Cimento Portland comum, bentonita sódica e hidróxido de cálcio foram usados para estabilizar por solidificação o resíduo sólido sintético contendo óxido de Cd2+, Pb2+ e Cu2+. Pode-se concluir que os tratamentos influenciaram no resultado de lixiviação do cádmio, chumbo e cobre. Os tratamentos mostraram que as concentrações do extrato solubilizado e lixiviado aumentam em função da quantidade de cádmio, chumbo e cobre adicionada. O maior valor encontrado foi para o material proveniente do tratamento D, que apresentou lixiviação igual a 32,815 mg.kg-1 para o cádmio e 29,769 mg.kg-1 para o chumbo. Para os ensaios de integridade/durabilidade, constatou-se que o aumento da absorção de água fez com que a resistência à compressão diminuísse. O uso de cimento, de hidróxido de cálcio e de bentonita sódica se mostrou ideal para retenção de metais pesados, evitando a sua lixiviação e a solubilização para o meio ambiente.

Storm-Water Filter Media Pollutant Retention under Aerobic versus Anaerobic Conditions

Storm-water runoff entering filters is usually aerobic and therefore the removal processes in the filter normally occur under oxidizing and aerobic conditions. However, storm-water filters differ from water and wastewater treatment filters because there are quiescent times when no influent enters the filter and the pore water stagnates. During this stagnation period, anaerobic conditions on a macro- or microscale could develop. This note presents the results of experiments conducted to determine if four potential filter media (sand, activated carbon, peat moss, and compost) could retain previously trapped pollutants when anaerobic conditions develop during interevent periods. The results indicated that permanent retention of heavy metals may occur even in an anaerobic environment (for the media and metals investigated). However, retention of some nutrients may not occur under these conditions, particularly for the organic media. This is an area of concern when the design of filters and bioretention devices includes an internal water storage zone where, between events, anaerobic conditions for nitrate removal are encouraged.

Heavy metal retention and microbial activities in geochemical barriers formed in glacial sediments subjacent to a former uranium mining leaching heap

Understanding the co-precipitation and sorption of metals and radionuclides in minerals and the biologically induced release of metals is important for predicting the future contaminant mobility in sediments affected by groundwater flow. This study aims to determine the retention of heavy metals in local epigenetic zones, termed geochemical barriers, in sediments of a former uranium mining district (Ronneburg, Germany) and to evaluate the potential microbial impact on the formation and stability of these barriers. Accumulation of heavy metals occurred in two distinct geochemical barriers. Cd, Ni, and Co accumulated in a greyish, manganese-rich layer, whereas the metalloid As and the metals U, Ni, and Co accumulated in a reddish-brown, iron-rich layer. Crystalline iron oxides, mainly goethite, served as important heavy metal sorbents in the reddish-brown, iron-rich layer. Iron and manganese oxides occurred mainly as a cover on quartz grains and as cement between the quartz grains, which might further close the porous sandy sediment matrix. On a molar basis, the manganese oxide barrier appeared to be more effective in metal retention than the iron oxide barrier. The presence of nitrate and Fe(III) in the porewater indicated oxic conditions throughout the sediment profile. Microbial abundances and activities in the sediment profile were low, apparently due to the low organic carbon content of the sediment but not due to toxic effects of heavy metals. Nitrate- and Fe(III)-reducing activities could be detected only after the addition of a carbon source. Collectively, these results demonstrated that both barriers prevent contaminant mobility in the aquifer and that reductive microbial processes did not have a major impact on metal retention at this site.

Classification and regression trees (CARTs) for modelling the sorption and retention of heavy metals by soil

The sorption and retention of mixtures of heavy metals by soil is a complex process that depends on both soil properties and competition between metals for sorption sites. In this study, the sorption and retention of mixtures of Cd, Cr, Pb, Cu, Zn and Ni by a representative sample of soils from Galicia (N.W. Spain) was reproduced considerably more precisely by binary decision-tree regression models constructed using the CART algorithm than by linear regression models. Of the six metals competing for sorption sites in these experiments, Pb, Cu and Cr were sorbed and retained to a greater extent than Cd, Ni and Zn. Non-linear tree regression models constructed with CART fitted the data better than linear models, especially for Cd, Ni and Zn; and with both kinds of model the data for Pb, Cu and Cr were fitted better than those for Cd, Ni and Zn (the difference being much more marked for linear models), suggesting that the influence of soil properties on the sorption and retention of the latter three metals was limited by the preferential binding of the former three.

Heavy metals retention capacity of a non-conventional sorbent developed from a mixture of industrial and agricultural wastes

Zinc and copper removal from aqueous solutions using brine sediments (industrial residue), sawdust (agricultural residue) and the mixture of both materials has been researched through batch and column tests. Brine sediments were found to be mainly constituted by halite and calcite, while its main cations exchangeable were sodium, calcium, magnesium and potassium. In sawdust the main exchangeable cations detected were calcium, magnesium, sodium and potassium. FT-IR spectra of sawdust and brine sediment–sawdust mixture showed that brine sediments produced important changes in carboxylic, alcoholic and phenolic groups present in the sawdust. The maximum zinc adsorption capacity was found to be 4.85, 2.58 and 5.59 mg/g using an adsorbent/solution ratio of 1/40, for brine sediments, sawdust and the mixture, respectively. For copper, the maximum adsorption capacity was found to be 4.69, 2.31 and 4.33 mg/g, using adsorbent/solution ratios of 1/40, for brine sediments, sawdust and the mixture, respectively. Maximum copper adsorption capacity of the mixture, on the contrary to zinc adsorption, was lightly inferior to maximum adsorption capacity obtained in brine sediments. Adsorption isotherms data adjusted better to the Langmuir model. Additionally, columns reached the saturation point at 690 min for zinc and 360 min for copper. The main mechanism involved in the removal of both metals may be the ionic exchange between sodium and calcium ions present in brine sediments and H + present in functional groups of sawdust. The use of brine sediments, sawdust and their mixture, presents an interesting option both, for wastewater decontamination (as a possible non-conventional sorbent for the removal of heavy metals) and as a waste recycling option.

Fate of Heavy Metal Contaminants in a Former Sewage Treatment Lagoon, Hancock County, Ohio

A Former sewage sludge lagoon, thoroughly mixed and abandoned in 1999, was analyzed to determine the subsequent mobility of heavy metals and their relationship to the dominant plant species at the site. ICP analyses of soils taken with respect to depth relative to the root zone and association with either common ragweed or stinging nettles revealed noticeable differences. In the five years since abandonment, the heavy metals have been stratified due to leaching and plant uptake, with the majority of metals showing higher concentrations at more shallow depths. Although stinging nettles can uptake higher concentrations of heavy metals into their plant parts, the soils do not have an associated reduction in heavy metal content. As the plants die in the fall, the heavy metals are returning to the soil as vegetation decays. Ragweed is less capable of incorporating the heavy metals into its biomass and is found associated with overall higher heavy metal concentrations in the soil around its roots. Thus, some other process is causing the retention of heavy metals in these soils. The lower concentrations in the soils beneath the root zones, which were reported to have been initially identical in composition to the shallower soils, are likely due to leaching.