Pyritic Material Research Articles

The Preliminary Study for Increasing the Productivity of Unit Tamban Lowland Irrigation Area based on Fact Findings of Observations

Unit Tamban is a fork system of lowland irrigation areas in Kapuas District. It has three primary canals, and each of them has a settling pond at the end. Most of the 3,506 ha planting area still apply once a year cropping patterns. A quick assessment based on field observations is carried out to determine the existing problems, including water management, water quality, and soil quality. The problem in the water management system is silting in the primary and secondary canals. The settling pond at the primary canal was no longer functioning, and it makes the silting worse because the water flow became uncontrolled. Water quality is measured with pH and TDS, the average pH at canal water was 4,22, and TDS was 71 mg/l. The soil type is mainly acid sulphate with pyritic materials, mostly 70 cm below the surface. Increasing cropping patterns twice a year requires improving the water circulations and increasing the soil pH higher than five. The problem in the secondary canal is expected to solve by changing the flow pattern from two way to 1-way flow is needed to avoid dead spots of water so that the leaching processes can work well.

Mineralogical Characteristics and in-situ Sulfur Isotopic Analysis of Gold-Bearing Sulfides from the Qilishan Gold Deposit in the Jiaodong Peninsula, China

Large-scale gold mineralization during the Early Cretaceous is identified in the Jiaodong Peninsula of China. Sources of ore-forming fluids remain debated. We study the Qilishan gold deposit in the northwestern Jiaodong Peninsula with detailed mineralogical observation and in-situ sulfur isotope analyses, in order to reveal the gold occurrence and the origin of ore-forming fluids. The Qilishan gold deposit is mainly clastic altered rock-type in mineralization, and ore minerals are visible native gold, electrum, pyrite, chalcopyrite and galena, gangue minerals as quartz, sericite and calcite. The gold occurrence includes inclusion and intergranular types, formed within pyrites and chalcopyrites and along their fissures. In-situ sulfur isotope analysis of gold-bearing sulfides suggests that the Qilishan deposit is enriched in heavy sulfur, with δ34S values mainly from +8.0‰ to +12.0‰. δ34S values increase gradually with the fluid evolution from the early to late stages, which is interpreted to be related to the loss of sulfur via sulfide precipitation. The crystallization of sulfides from hydrothermal fluids may have triggered the instability of Au(HS)2, and finally led to gold precipitation. Combined with sulfur isotope compositions of other gold deposits (n=43) and wall-rocks in the Jiaodong Peninsula, it is proposed that the ore-forming fluids were probably not directly originated from metamorphic wall-rocks (e.g., Jiaodong Group). Moreover, the relatively long time interval rules out the possibility that the gold mineralization (ca. 120 Ma) was associated with granitic magma activities (mostly 160–150 Ma). Possible ore genesis scenario is that, long-term subduction of slabs (e.g., the Paleo-Pacific) with gold-enriched pyritic materials and crustal sedimentary rocks resulted in both high Au contents and positive δ34S values of sulfur in the lithospheric mantle below the North China Craton. Subsequently, devolatilization of the metasomatized mantle produced auriferous fluids that migrated upward along translithospheric fault systems, and gold finally precipitated in favorable structural positions, generating the world-class Jiaodong deposits in the Early Cretaceous.

Chromium VI and Fluoride Competitive Adsorption on Different Soils and By-Products

Chromium (as Cr(VI)) and fluoride (F−) are frequently found in effluents from different industrial activities. In cases where these effluents reach soil, it can play an important role in retaining those pollutants. Similarly, different byproducts could act as bio-adsorbents to directly treat polluted waters or to enhance the purging potential of soil. In this work, we used batch-type experiments to study competitive Cr(VI) and F− adsorption in two different soils and several kinds of byproducts. Both soils, as well as mussel shell, oak ash, and hemp waste showed higher adsorption for F−, while pyritic material, pine bark, and sawdust had a higher affinity for Cr(VI). Considering the binary competitive system, a clear competition between both elements in anionic form is shown, with decreases in adsorption of up to 90% for Cr(VI), and of up to 30% for F−. Adsorption results showed better fitting to Freundlich’s than to Langmuir’s model. None of the individual soils or byproducts were able to adsorbing high percentages of both pollutants simultaneously, but it could be highly improved by adding pine bark to increase Cr(VI) adsorption in soils, thus drastically reducing the risks of pollution and deleterious effects on the environment and on public health.

MINE WASTE: SOURCES, PROBLEMS AND MITIGATIONS.

Mine wastes are unwanted, currently uneconomic, solid and liquid materials found at or near mine sites. Mining waste originates from the processes of excavation, dressing and further physical and chemical processing of wide range of metalliferous and non-metalliferous minerals by opencast and deep shaft methods. It comprises overburden, run-of-mine rock as well as discard, slurry and tailings from the preparation/beneficiation or extraction plants. The major problem is Acid Mine Drainage (AMD) which can lead to poor water quality, soil contamination and air pollution when the wastes are dry in the summers. The conventional method of treatment has been through methods such as lime neutralization, ion exchange, calcium silicate neutralization and carbonate neutralization; but the best way to treat AMD is prevention which can be done by using proper reclamation methods, which prevents air and/or water from reaching the pyritic materials. Generally, conventional technologies for remediation of mine tailings have focused on physical and chemical stabilization. Physical stabilization entails covering mine waste with an innocuous material, waste rock from mining operations, gravel, topsoil from an adjacent site, or a clay capping, to reduce wind and water erosion. Presently, alternative methods for the remediation of mine waste have been prescribed and adopted in various countries. Such methods includes bioremediations and phytoremediations.

Soil Microbiome Dynamics During Pyritic Mine Tailing Phytostabilization: Understanding Microbial Bioindicators of Soil Acidification

Challenges to the reclamation of pyritic mine tailings arise from in situ acid generation that severely constrains the growth of natural revegetation. While acid mine drainage (AMD) microbial communities are well-studied under highly acidic conditions, fewer studies document the dynamics of microbial communities that generate acid from pyritic material under less acidic conditions that can allow establishment and support of plant growth. This research characterizes the taxonomic composition dynamics of microbial communities present during a 6-year compost-assisted phytostabilization field study in extremely acidic pyritic mine tailings. A complementary microcosm experiment was performed to identify successional community populations that enable the acidification process across a pH gradient. Taxonomic profiles of the microbial populations in both the field study and microcosms reveal shifts in microbial communities that play pivotal roles in facilitating acidification during the transition between moderately and highly acidic conditions. The potential co-occurrence of organoheterotrophic and lithoautotrophic energy metabolisms during acid generation suggests the importance of both groups in facilitating acidification. Taken together, this research suggests that key microbial populations associated with pH transitions could be used as bioindicators for either sustained future plant growth or for acid generation conditions that inhibit further plant growth.

Pyrite oxidation: a history of treatments at the Natural History Museum, London

Whilst surveying the palaeontology collections at the Natural History Museum London (NHM), a team of Conservation Technicians working on 'Project Airless' (a re-storage project for actively deteriorating pyritic specimens) kept a record of specimen labels describing past methods for treating pyrite oxidation, ranging from 'boiling in common soda' to treating with 'Savlon'. This prompted further research into the thinking behind these approaches, and resulted in a historical review of treatments used at the NHM and how they compare to current methods. The oxidisation of unstable pyritic material became a prominent issue during the development of geological collections in the 19th Century, when early collectors provided most insight into best practice storage of affected specimens, although it was not until the 20th century when more intensive research was conducted and recommended treatments for deteriorating pyritic material began to circulate. Regardless of the treatment, however, once specimens were returned to storage conditions of high relative humidity (RH) the reaction would often recur; this instigated the need for a more preventative approach focussing on reducing, if not eliminating, the key agents involved in the oxidation process: oxygen and high RH. Project Airless is the latest attempt at the NHM to combat pyrite oxidation on a large scale by storing affected specimens in anoxic microenvironments to prevent further deterioration. Severely affected specimens are also exposed to ammonia vapour in a method which has evolved from earlier treatments. Although commonly referred to as The Natural History Museum London, the museum was officially known as The British Museum (Natural History) until 1992, so for the purposes of this article the 'BM(NH)' will be referred to until this date, and the 'NHM' thereafter.

Efficacy of two different reclamation strategies to improve chemical properties and to reduce Al toxicity in a lignite mine dump during a 20‐year period

AbstractIn this work, the efficacy of two different strategies, used for 20 years (1992–2012) to restore a lignite mine dump, was investigated. The reclamation strategies were selection of the sterile materials, avoiding surface placement of pyritic materials, or surface application of topsoil material. Representative plots corresponding to each of both strategies were selected, as well as a control plot where reclamation techniques were not applied. An increase in total C, soluble Al, and exchangeable Al, as well as a decrease in pH, electrical conductivity, sulfate, and exchangeable cations concentrations took place during the study period. Avoiding pyritic materials on surface was the strategy giving the best acid–base conditions in the whole period, showing higher pH values (6.1–6.7) than application of topsoil (4.7–5.3), as well as the highest exchangeable Ca values (0.71–6.83 vs. 0.55–3.00 cmol(+) kg−1), and less exchange Al (0.22–2.80 vs. 0.99–3.72 cmol(+) kg−1) and soluble Al (0.04–0.60 vs. 0.19–37.47 mg L−1). Regarding fractionation of Al in soil solution, labile forms predominated throughout the study period, although organic forms (nonlabile Al and acid‐soluble Al) showed an increase over time, which was in accordance with an increase in C concentration. The most toxic Al species (Al3+ and Al‐OH) were less abundant where pyritic materials were not placed on surface, compared with plots treated with topsoil (which did not differ from control plot for most parameters). The results of the study indicate that surface application of topsoil would not be justified as strategy to effectively restore lignite mine dump areas.

Pyrite Oxidation Drives Exceptionally High Weathering Rates and Geologic CO2 Release in Mountaintop‐Mined Landscapes

AbstractWeathering is the ultimate source of solutes for ecosystems, controls chemical denudation of landscapes, and drives the geologic carbon cycle. Mining and other land‐moving operations enhance physical weathering by bringing large volumes of shattered bedrock to the surface. Yet, the relative influence of these activities on chemical weathering remains poorly constrained. Here we show that catchments impacted by mountaintop removal coal mining have among the highest rates of chemical weathering ever reported. Mined catchments deliver more than 7,600 kg·ha−1·year−1 of dissolved solids downstream. The chemical signatures of these exceptionally high weathering rates reflect the product of sulfuric acid weathering of carbonate‐bearing rock, driven by the oxidation of pyritic materials. As this strong acid rapidly weathers surrounding carbonate materials, H+ ions are consumed and Ca2+, Mg2+, and HCO3− ions are exported to balance the elevated SO42− exports, generating alkaline mine drainage. The sulfate exports from pyrite oxidation in mountaintop‐mined catchments account for ~5–7% of global sulfate derived from pyrite, despite occupying less than 0.006% of total land area. Further, the suite of weathering reactions liberate 100–450 kg of rock‐derived C·ha−1·year−1 as CO2, with an additional 90–150 kg C·ha−1·year−1 of C released when HCO3− reaches the ocean. This rock C release contributes to the high carbon costs of coal combustion.

Chromium and fluoride sorption/desorption on un-amended and waste-amended forest and vineyard soils and pyritic material

Using batch-type experiments, chromium (Cr(VI)) and fluoride (F−) sorption/desorption were studied in forest and vineyard soil samples, pyritic material, pine bark, oak ash, hemp waste and mussel shell, as well as on samples of forest and vineyard soil, and of pyritic material, individually treated with 48 t ha−1 of pine bark, oak ash, and mussel shell. Pine bark showed the highest Cr(VI) sorption (always > 97% of the concentration added) and low desorption (<1.5%). Pyritic material sorbed between 55 and 98%, and desorbed between 0.6 and 9%. Forest and vineyard soils, oak ash, mussel shell and hemp waste showed Cr(VI) sorption always < 32%, and desorption between 22 and 100%. Pine bark also showed the highest F− retention (sorption between 62 and 73%, desorption between 10 and 15%), followed by oak ash (sorption 60–69%, desorption 11–14%), forest soil (sorption 60–73%, desorption 19–36%), and pyritic material (sorption 60–67%, desorption 13–15%), whereas in vineyard sorption was 49–64%, and desorption 24–27%, and in hemp waste sorption was 26–36%, and desorption 41–59%. Sorption data showed better fitting to the Freundlich than to the Langmuir model, especially in the case of Cr(VI), indicating that multilayer sorption dominated. The addition of by-products to the forest and vineyard soils, and to the pyritic material, caused an overall increase in F− sorption, and decreased desorption. Furthermore, the pine bark amendment resulted in increases in Cr(VI) retention by both soils and the pyritic material. These results could be useful to favor the recycling of the by-products studied, aiding in the management of soils and degraded areas affected by Cr(VI) and F− pollution, and in the removal of both anions from polluted waters.

Controlling risks of P water pollution by sorption on soils, pyritic material, granitic material, and different by-products: effects of pH and incubation time.

Batch experiments were used to test P sorbent potential of soil samples, pyritic and granitic materials, mussel shell, mussel shell ash, sawdust, and slate waste fines for different pH and incubation times. Maximum P sorption varied in a wide range of pH: < 4 for pyritic material, 4-6 for forest soil, > 5 for slate fines, > 6 for shell ash, and pH6-8 for mussel shell. P sorption was rapid (< 24h) for forest soil, shell ash, pyritic material, and fine shell. On the opposite side, it was clearly slower for vineyard soil, granitic material, slate fines, pine sawdust, and coarse shell, with increased P sorption even 1month later. For any incubation time, P sorption was > 90% in shell ash, whereas forest soil, pyritic material, and fine shell showed sorption rates approaching 100% within 24h of incubation. These results could be useful to manage and/or recycle the sorbents tested when focusing on P immobilization or removal, in circumstances where pH changes and where contact time may vary from hours to days, thus aiding to diminish P pollution and subsequent eutrophication risks, promoting conservation and sustainability.

Effects of Changing pH, Incubation Time, and As(V) Competition, on F- Retention on Soils, Natural Adsorbents, By-Products, and Waste Materials.

The purpose of this work was to elucidate the repercussion of changing pH, incubation time and As(V) competition on fluoride (F−) sorption on forest and vineyard soil samples, pyritic, and granitic materials, as well as on the by-products pine sawdust, oak wood ash, mussel shell ash, fine and coarse mussel shell, and slate processing waste fines. To reach this end, the methodological approach was based on batch-type experiments. The results indicate that, for most materials, F− sorption was very high at the start, but was clearly diminished when the pH value increased. However, oak wood ash and shell ash showed high F− sorption even at alkaline pH, and pine sawdust showed low F− sorption for any pH value. Specifically, F− sorption was close to 100% for both ashes at pH < 6, and around 70% at pH 10, while for forest soil it was close to 90% at pH < 2, and around 60% at pH values near 8. Regarding the effect of incubation time on F− sorption, it was very low for both soils, pyritic material, granitic material, and both kinds of ashes, as all of them showed very rapid F− sorption from the start, with differences being lesser than 10% between sorption at 30 min and 1 month of incubation. However, sawdust and slate fines sorbed 20% of added F− in 30 min, remaining constant up to 12 h, and doubling after 30 days. And finally, mussel shell sorbed 20% at 30 min, increasing to close to 60% when incubation time was 30 days. This means that some of the materials showed a first sorption phase characterized by rapid F− sorption, and a slower sorption in a second phase. As regards the effect of the presence of As(V) on F− sorption, it was almost negligible, indicating the absence of competition for sorption sites. In view of that all, these results could aid to appropriately manage soils and by-products when focusing on F− removal, in circumstances where pH value changes, contact time vary from hours to days, and potential competition between F− and As(V) could take place.

Subsurface Submergence of Mine Waste Materials as a Remediation Strategy to Reduce Metal Mobility: an Overview

The most common lead (Pb) and zinc (Zn) ore minerals are galena (PbS) and sphalerite (ZnS). Milling and mining operations of these ores produce huge amounts of waste known as chat and tailings. Chat is composed of gravel, sand, and silt-sized rock materials, whereas tailings are often fine-grained and silt-sized particles with higher toxic element concentrations. Upon oxidation, tailings with high pyritic materials release Pb, Zn, Cadmium (Cd), and other elements associated with ores affecting plant productivity, the ecosystem, and human health. This article is an overview on utilizing the subsurface submergence technique for mitigating environmental impacts from abandoned mine waste materials. In the past, researchers have studied the influence of submergence on these elements; however, an emphasis on gathering a detailed understanding of such redox-based remediation processes is not that common. We reviewed literature that evaluated water chemistry, solid phases, and association of trace elements, and addressed utilization of surface amendments of mine tailings for predicting their interactions within sediments and overlying waters. Case studies specifically focused on mining of Pb and Zn, including a recent study conducted in the Tri-State mining district (Kansas, Missouri, and Oklahoma), are presented to add a more comprehensive understanding of biogeochemical transformations of trace elements present in mine waste materials under a long-term submergence. The purpose of this article is to present evidence on the viability of subsurface disposal of mine waste materials, in order to design effective remediation and mitigation strategies to protect human and environmental health in the global dimension.

Cadmium and Lead Sorption/Desorption on Non-Amended and By-Product-Amended Soil Samples and Pyritic Material

Batch-type experiments were used to study cadmium (Cd) and lead (Pb) sorption/desorption on forest soil, vineyard soil and pyritic material samples, on the by-products mussel shell, oak ash, pine bark and hemp waste, and on forest soil, vineyard soil and pyritic material amended with 48 t ha−1 of oak ash, mussel shell, and hemp waste. The main results were that the forest soil showed higher Cd and Pb retention than the vineyard soil and the pyritic material. Regarding the byproducts, sorption was in the following order: oak ash &gt; mussel shell &gt; hemp waste &gt; pine bark, with desorption following an inverse sequence. The pH was the parameter that most influenced Cd and Pb sorption. Cd and Pb sorption curves showed better fitting to the Freundlich than to the Langmuir model, indicating the dominance of multilayer interactions. Oak ash and mussel shell were the amendments causing higher increase in Cd and Pb sorption on both soils and the pyritic material (close to 100% with the oak ash amendment), as well as more a pronounced decrease in desorption. These results could be used to favor an effective management of the by-products studied, which could retain Cd and Pb in soils and degraded areas, preventing water pollution.

Mineralogy and Geochemistry of Biologically-Mediated Gold Mobilisation and Redeposition in a Semiarid Climate, Southern New Zealand

Detrital gold in Late Pleistocene-Holocene placers has been chemically mobilised and redeposited at the micron scale by biologically-mediated reactions in groundwater. These processes have been occurring in a tectonically active semiarid rain shadow zone of southern New Zealand and are probably typical for this type of environment elsewhere in the world. The chemical system is dominated by sulfur, which has been derived from basement pyrite and marine aerosols in rain. Detrital and authigenic pyrite is common below the water table, and evaporative sulfate minerals are common above the fluctuating water table. Pyrite oxidation was common but any acid generated was neutralised on the large scale (tens of metres) by calcite, and pH remained circumneutral except on the small scale (centimetres) around pyritic material. Metastable thiosulfate ions were a temporary product of pyrite oxidation, enhanced by bacterial mediation, and similar bacterial mediation enhanced sulfate reduction to form authigenic pyrite below the water table. Deposition of mobilised gold resulted from localised variations in redox and/or pH, and this formed overgrowths on detrital gold of microparticulate and nanoparticulate gold that is locally crystalline. The redeposited gold is an incidental byproduct of the bacterially-enhanced sulfur reactions that have occurred near to the fluctuating sulfide-sulfate redox boundary.

As(V) Sorption/Desorption on Different Waste Materials and Soil Samples.

Aiming to investigate the efficacy of different materials as bio-sorbents for the purification of As-polluted waters, batch-type experiments were employed to study As(V) sorption and desorption on oak ash, pine bark, hemp waste, mussel shell, pyritic material, and soil samples, as a function of the As(V) concentration added. Pyritic material and oak ash showed high sorption (90% and >87%) and low desorption (<2% and <7%). Alternatively, hemp waste showed low retention (16% sorption and 100% desorption of the amount previously sorbed), fine shell and pine bark sorbed <3% and desorbed 100%, the vineyard soil sample sorbed 8% and released 85%, and the forest soil sample sorbed 32% and desorbed 38%. Sorption data fitted well to the Langmuir and Freundlich models in the case of both soil samples and the pyritic material, but only to the Freundlich equation in the case of the various by-products. These results indicate that the pyritic material and oak ash can be considered efficient As(V) sorbents (thus, useful in remediation of contaminated sites and removal of that pollutant), even when As(V) concentrations up to 6 mmol L−1 are added, while the other materials that were tested cannot retain or remove As(V) from polluted media.

Risk of acidification of the organic shrimp model at Tam Giang commune, Nam Can district, Ca Mau province

This paper assesses the risk of acidification of the organic shrimp model certified by Naturland at Tam Giang commune, Nam Can district, Camau province. Pond water and sediment was sampled in 8 ponds in March, July and November 2015, dike soil and mangrove soils were sampled in March 2015. Pond sediment and mangrove soils are highly reduced (Eh of top sediment and soils to 60 cm depth range respectively from -299 – -1mV and -321 – -52mV). Pond water ranges from neutral to slightly alkaline (pH of pond water 7.01-8.82) and sediment from slightly acidic to slightly alkaline (pH of fresh sediment 6.05-7.64, pHH2O 6.63-7.78, pHKCl 6.35-7.43). Mangrove soils show a large pH range with very low minimums (pHH2O 3.72, pHKCl 3.05), reconfirming the presence of pyrite mineral in the soil profile. Mangrove soils deposited on the dikes (partly oxidized) are very acidic (pHH2O 2.51±0.72, pHKCl 1.81-2.14, exchange acidity 11.56±2.69 meq/100g). At the start of the wet season, pH of pond water reduces sharply as a result of reception of acidic components from the oxidized pyritic material (FeS2) on the dikes. The exchange acidity in pond sediment and mangrove soils are negatively correlated with organic matter, indicating that the decomposition of organic matter under reduced conditions contributes to exchange acidity in pond environment. Risk of acidification of the organic shrimp model is high due to managerial activities (mostly channel digging and disposal of pyrite-containing mangrove soils on the dikes).

As(V)/Cr(VI) retention on un-amended and waste-amended soil samples: competitive experiments.

Focusing on simultaneous arsenic and chromium pollution, we used batch-type experiments to study As(V)/Cr (VI) competitive sorption on soil samples, pyritic material, mussel shell, oak ash, pine bark and hemp waste, as well as on binary mixtures (50% mussel shell and 50% another material-oak ash, pine bark, or hemp waste), and on forest and vineyard soil samples and pyritic material amended with 48tha-1 of mussel shell, oak ash, pine bark, or hemp waste. Equal As(V) and Cr(VI) concentrations (0 to 6mmolL-1) were added to the individual materials, binary mixtures, and 48tha-1 amended materials. The individual forest soil sample, pyritic material, and oak ash showed clearly higher As(V) sorption, whereas Cr(VI) sorption was higher on pine bark. Sorption was up to 50% higher for As(V) than for Cr(VI) on the forest soil sample, oak ash, and pyritic material, while pine bark sorbed 95% more Cr(VI). Regarding binary mixtures, the presence of mussel shell increased As(V) sorption on pine bark and Cr(VI) sorption on hemp waste. As regards the amendments, in the case of the forest soil sample, the amendments with oak ash and mussel shell increased As(V) sorption, while pine bark amendment increased Cr(VI) sorption; in the vineyard soil sample, the mussel shell amendment increased As(V) sorption; in the pyritic material, pine bark amendment increased Cr(VI) sorption. These results could be useful to appropriately manage the soils and individual or mixed by-products assayed when As(V) and Cr(VI) pollution occurs.

As(V)/Cr(VI) pollution control in soils, hemp waste, and other by-products: competitive sorption trials.

We study As(V)/Cr(VI) competitive sorption on a forest soil, a vineyard soil, pyritic material, mussel shell, pine bark, oak ash, and hemp waste, adding variable As(V) and Cr(VI) concentrations or displacing each pollutant with the same concentration of the other. When using variable concentrations, As(V) showed more affinity than Cr(VI) for sorption sites on most materials (sorption up to >84% on oak ash and pyritic material). The only exception was pine bark, with clearly higher Cr(VI) sorption (>90%) for any Cr(VI)/As(V) concentration added. Regarding the displacement experiments, when As(V) was added and reached sorption equilibrium, the subsequent addition of equal Cr(VI) concentration did not cause relevant As displacement from oak ash and pyritic material, indicating strong As bindings, and/or low competitive effects. When Cr(VI) was added and reached sorption equilibrium, the subsequent addition of equal As(V) concentration caused Cr(VI) displacement from all materials except pine bark, indicating weak Cr bindings. In view of these results, oak ash and the pyritic material could be used to remove As(V) in concentrations as high as 6mmolL(-1), even in the presence of a wide range of Cr(VI) concentrations, whereas pine bark could be used to remove Cr(VI) concentrations as high as 6mmolL(-1). The other materials assayed (including hemp waste, studied for the first time as As(V) and Cr(VI) bio-sorbent) cannot be considered appropriate to remove As(V) and/or Cr(VI) from polluted media.

Phosphorus retention on forest and vineyard soil samples, mussel shell, pine-sawdust, and on pyritic, granitic and waste materials

Focusing on P, we used batch-type experiments to study P retention on various materials: a forest soil sample, a vineyard soil sample, finely and coarsely ground mussel shell, pine-sawdust, pyritic material, granitic material, mussel shell calcination ash, slate processing fines, and three different mixtures that included three components: sewage sludge, mussel shell ash, and calcined mussel shell or pine wood ash. The pyritic material and the mussel shell ash showed the highest P retention capacity, reaching >95%. The lowest P retention (<60%) corresponded to the pine-sawdust and slate processing fines. Data fitted satisfactorily to the Freundlich model, unless in the case of pine-sawdust and slate fines; however, only forest and vineyard soil samples can be satisfactorily adjusted to the Langmuir model. These results could be useful to program appropriate management practices, especially when focusing on controlling P concentrations in different environmental compartments, as well as to correctly recycle the by-products and waste materials assayed.

F sorption/desorption on two soils and on different by-products and waste materials.

We used batch-type experiments to study F sorption/desorption on a forest soil, a vineyard soil, pyritic material, granitic material, finely and coarsely ground mussel shell, mussel shell calcination ash, oak wood ash, pine-sawdust, slate processing fines, and three different mixtures that included three components: sewage sludge, mussel shell ash, and calcined mussel shell or pine wood ash. The three waste mixtures, forest soil, pyritic material, and shell ash showed high sorption capacity (73-91% of added F) and low desorption, even when 100mgFL(-1) was added. All these materials (and to a lower extent wood ash) could be useful to remove F from polluted media (as certain soils, dumping sites, and contaminated waters). The vineyard soil, the granitic material, mussel shell, slate fines, and pine-sawdust were less effective in F removal. In most cases, sorption data fitted better to the Freundlich than to the Langmuir equation. These results can be useful to program the correct management of the soils, by-products, and waste materials assayed, mostly in situations where F concentrations are excessive and F removal should be promoted.