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Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Geotechnical Journal is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aluminium plant production wastes are contaminated by fluoride according to TCLP (toxicity characteristics leaching procedure) and Quebec legislation (>150 mg F-/L). Those wastes contain 2-323 g F-/kg. The extraction of fluoride by acid leaching (H2SO4, pH 1.5) at total solids content between 1% and 16% allows the removal of approximately 33% of F- but does not respect the TCLP regulation. However, the chemical stabilization of aluminium wastes by use of calcium hydroxide (Ca(OH)2) at a concentration varying from 10 to 12 g/L in the suspension of EC (100 g/L) allowed us to record lower concentrations of fluoride ions (110-115 mg F-/L) in the leachate from the TCLP test. The subsequent treatment of the dehydration filtrate of stabilized residues by decreasing the pH from the initial value (pH 11.9 or 12.0) to pH values between 7.0 and 8.5 by addition of an inorganic acid (H2SO4, 10 mol/L) removed up to 98% of fluoride ions by precipitation. [ABSTRACT FROM AUTHOR]

The objective of this research was to evaluate the effects of sewage sludge storage on biological and physico-chemical parameters of sludge treated by different stabilization and decontamination processes. Three sludge storage methods were tested: inside at stable temperature (21 ± 2 °C), outside during summer (May-October), and inside at different temperatures to simulate the winter season. An increase of the sludge pH (approximately 8.0-8.5) and an odour removal process were measured following a 5-month storage period, and this, for all conditions of sludge treatments and storage options. The sanitary conditions of the sludge improved, because the fecal coliforms were completely eliminated, and fecal streptococci and salmonella were significantly reduced. The results also revealed that the pH adjustment, near neutrality, of sludge treated by acid processes (Stabiox and Metix-AC) is preferable before a long storage period. This allows a better biodegradation of the organic matter and the production of less odorous sludge. Sludge neutralization also decreases phosphorus and metals concentrations in drainage waters. The preservation of the acid conditions remains however useful during a short storage period, by allowing to avoid a fast resumption of the nauseous odours. Overall, the different temperatures had few effects on sludge characteristics after the 5-month storage period. [ABSTRACT FROM AUTHOR]

Environmental contamination produced by acid generating mines currently represents the largest environmental liability of the mining industry and necessitates the development of novel techniques for its mitigation. This paper reviews existing literature on stabilization of sulphidic mine tailings and prevention of acid mine drainage (AMD). It is shown that stabilization using ordinary portland cement in combination with pozzolanic and cementitious materials could be a viable option. However, variation of mine waste constituents and their interactions with different binders thwart the formulation of a generalized recipe for stabilization and further necessitate research to explore the optimal waste-binder proportions of the stabilized system components for the particular mine tailings under consideration. The demonstrated effective utilization of industrial by-products (fly ash, slag, cement kiln dust, etc.) in the preparation of modified cementitious materials for stabilization of sulphidic mining waste reinforces further interest in this area, not only to cope with acid mine drainage, but also to utilize abundant discarded industrial by-products for various beneficial considerations. This paper critically examines various mine tailings stabilization techniques in the literature, identifies the fundamental mechanisms controlling their performance and the intrinsic parameters of stabilization systems, along with the tailings-binder interaction mechanisms and performance assessment tools for stabilized tailings. [ABSTRACT FROM AUTHOR]

Air pollution control residues (APCR) from municipal waste incinerators are usually considered as hazardous wastes because of their high contents in easily soluble Pb and other toxic metal contaminants. The objective of this research was to compare various techniques using Pb adsorption on Sphagnum peat moss (MT) for the treatment of alkaline leachates produced during the decontamination of various types of APCR including used lime (CU), electrofilter ashes (CE), and boiler ashes (CC). Regeneration tests of saturated MT using hydrochloric and sulphuric acids have revealed that excessive acid consumption (>250 kg acid/metric ton of treated APCR) are necessary for the elution of metals. However, the incineration of the saturated MT and its possible valorization represents an interesting way to explore for the management of the adsorbent. This method allows to reduce by a factor of 3 or 4 the mass of residues and increases in the same proportion the Pb content in the incinerated MT. Finally, the present study has highlighted that ion exchange on the anionic functional groups of MT would be one of the most important mechanisms implied in the Pb fixation on this natural sorbent during the treatment of very alkaline leachates (pH > 11) of APCR. [ABSTRACT FROM AUTHOR]

A detailed characterization of the different types of air pollution control residues (APCR) produced in municipal waste incinerators has been performed. The analysis of the Pb distribution in boiler and electrofilter ashes has shown that the separation of these ashes in two fractions (<125 µm and >125 µm) allows to get a coarse fraction slightly contaminated and a finer fraction more heavily contaminated, which can be treated by chemical means. Scanning electron microscope – energy-dispersive spectrometry (SEM-EDS) techniques have been used to identify the most dominant forms of the lead particles. Lead present in used lime is principally associated with oxides in a carrying phase of calcium chloride or phosphate. Lead present in boiler and electrofilter ashes is principally associated with silicates and phosphates. Finally, only one leaching step in alkaline aqueous solution is required to remove a large proportion of the leachable lead in APCR and to reach the allowed level by the toxicity characteristic leaching procedure test (TCLP) and neutral water test. [ABSTRACT FROM AUTHOR]

The mobility of Cu alone and in the presence of Cd (compatible) and Pb (incompatible) was studied using laboratory columns packed with a 95 wt.% sand and 5 wt.% bentonite mixture. The liner material was subjected to one of four heavy metal solutions using a pressure head of 7 kPa: 2.0 cmol(+) Cu/L solution; 1.0 cmol(+) Cu and 1.0 cmol(+) Cd/L solution for a total of 2.0 cmol(+)/L solution; and 1.0 cmol(+) Cu and 1.0 cmol(+) Pb/L solution for a total of 2.0 cmol(+)/L solution. The effluents and the liner samples were analyzed for Cu, Pb, and Cd. The breakthrough curves indicated that Cd was the most mobile of the metal cations, whereas Pb was the least. Total metal adsorption was greatest for Cu with Pb, followed by that of Cu with Cd, and then that of Cu alone, showing that Cu is compatible with Cd but not Pb. The selective sequential extraction analysis indicated that most of the Cu was precipitated by the carbonate and hydroxide fractions. Key words:Cd, Pb, Cu, sand–bentonite liners, adsorption, leaching. [ABSTRACT FROM AUTHOR]

Fly ashes produced by the incineration of municipal solid wastes are usually considered as hazardous wastes. The objective of the present study was to demonstrate the feasibility of a closed circuit decontamination process. The latter includes the reuse of treated process effluents and leads to the production of treated ashes that respect the toxicity characteristic leaching procedure (TCLP). The process should also reduce the production of metallic hazardous wastes and the operating costs. The results show that the process removes 70 ± 3% Cd and 18 ± 4% Pb from fly ashes during the chemical leaching (alkaline and acid) steps. The optimized process generates two types of metallic wastes. The first, representing 13 kg/tct (tons of treated ashes), is a nonhazardous waste produced during the nucleation–precipitation step at pH = 5. The second is classified as hazardous waste and is produced subsequently by precipitation at pH = 7. The production of this metallic hazardous waste is estimated at 29 kg/tct. The treated fly ashes respect the three leaching tests performed in this study, including the TCLP. Significant decreases in the water consumption (91%) and of chemicals used (12%) have been realized, in comparison with a reference decontamination process. These improvements result in a 36% decrease of the operating costs. [ABSTRACT FROM AUTHOR]

This work estimated the leaching behavior of metolachlor from montmorillonite-based and commercial emulsifiable concentrate (EC) formulations in soil columns and field plots by using bioassay and chemical techniques. A montmorillonite-based formulation of metolachlor was prepared by adsorbing metolachlor to montmorillonite–benzyltrimethylammonium (BTMA) complex from aqueous solution. Bioassay and gas chromatography (GC) techniques detected high metolachlor concentrations in the top soil layers (0–9 cm) in soil columns and field plots sprayed with montmorillonite–BTMA–metolachlor complex. These results were also evident by severe growth inhibition restricted to the top soil layers (0–9 cm) and normal growth at deeper layers in soil columns and field plots. A wider range of metolachlor concentrations were detected in soil layers in columns treated with EC formulation in both soil columns and field plots. Relatively higher metolachlor concentrations were detected in the soil layers in field plots than in soil columns. A bioassay technique was a more sensitive tool than chemical technique and detected diluted concentration of metolachlor at deeper layers. The different leaching behavior of metolachlor applied as montmorillonite–BTMA complex is due to the adsorption capacity of montmorillonite–BTMA complex. [ABSTRACT FROM AUTHOR]

Enhancing the value of the cement kiln dust so as to use it as an environmental barrier requires, amongst other things, the addition of fly ashes in order to improve the different properties needed to insure a better placing and a long term efficiency. Taking advantage of different experimental techniques, particular attention was devoted to the physicochemical behaviour of different kiln dusts associated with the fly ashes. Depending on the nature of the added compound, a different behaviour may condition the evolution of the mixtures with an effect on their stability. Indeed, this study has confirmed the improvement of the physicochemical properties of the dusts interacting with the fly ashes rich in silica and poor in lime, which argues well for their use as an environmental barrier. Moreover, the follow up has led to a better understanding of certain mechanisms generated by the systems dealt with. Hence, after hydration and different chemical transformations, some expansive phases as the ettringite, gypsum, syngenite, and portlandite develop in the paste, and therefore condition the behaviour of the mixtures worked out.Key words: cement kiln dusts, fly ashes, stabilization, physicochemistry, environmental barrier, lixiviation.[Journal translation]La valorisation des poussières de four de cimenterie en vue de leur exploitation en tant que barrière environnementale requiert, entre autres, l'ajout de cendres volantes afin d'améliorer les différentes propriétés nécessaires à une meilleure mise en place et assurer leur efficacité à long terme. En mettant à profit différentes techniques expérimentales, une attention particulière est accordée au comportement physico-chimique de différentes poussières de four associées aux cendres volantes. Selon la nature des ajouts considérés, un comportement différent peut conditionner l'évolution des mélanges avec une incidence sur leur stabilité. En effet, cette étude a confirmé l'amélioration des propriétés physico-chimiques des poussières mises en interaction avec les cendres volantes riches en silices, et pauvres en chaux, ce qui laisse de bons augures quant à leur utilisation en tant que barrière environnementale. Par ailleurs, le suivi a permis une meilleure compréhension de certains mécanismes générés par les systèmes abordés. Ainsi, après hydratation et différentes transformations chimiques, des phases à caractère expansif tels que l'ettringite, le gypse, la syngénite et la portlandite, prennent naissance dans la pâte et conditionnent, par conséquent, le comportement des mélanges élaborés.Mots clés : poussières de four de cimenterie, cendres volantes, stabilisation, physico-chimie, barrière environnementale, lixiviation. [ABSTRACT FROM AUTHOR]

The objective of this research was to compare the efficiency of different natural adsorbents for lead recovery from basic leachate produced during municipal incinerator used lime decontamination. Shake flasks adsorption tests have shown that cedar barks, pine barks, cocoa shells, and peat moss are efficient and cheap adsorbents for lead removal from this type of leachate. Peanut skins are less efficient than other tested natural materials. The use of a hot-acid treatment (H[sub 2] SO[sub 4] 0.75 M) allows to slightly increase lead removal performance of the adsorbents. However, this gain does not justify, from an economical point of view, the utilization of the chemical treatment. Tests done with different cedar and pine bark concentrations (2–30 g/L) have revealed that heavily lead-contaminated (approximately 130–140 mg/L) used lime leachate can be efficiently treated by addition of a small adsorbent concentration (e.g. 2 g/L). Finally, elution tests (HCl 0.5 M) with reuse of adsorbents have demonstrated that some natural materials, like cedar barks and cocoa shells, can be used for many adsorption–elution cycles without loss of lead removal efficiency. Key words: lead, adsorption, used lime, leaching, peat, bark.[Journal translation]Cette recherche visait à comparer l'efficacité de divers adsorbants naturels pour la récupération du plomb extrait par lessivage basique de chaux usées d'incinérateur de déchets municipaux. Les tests d'adsorption effectués en fioles agitées ont montré que les écorces de cèdre, les écorces de pin gris, les écailles de cacao, ainsi que la tourbe de sphaigne sont des adsorbants efficaces et peu coûteux pour l'enlèvement du plomb de ce type d'effluent très basique. Les écailles d'arachides se sont avérées moins efficaces que les autres adsorbants testés. L'application d'un pré-traitement acide (H[sub 2] SO[sub 4] 0,75 M) à chaud permet d'accroître légèrement les rendements d'élimination du plomb des adsorbants. Les gains obtenus ne justifient toutefois pas l'utilisation de ce traitement chimique. Les tests effectués avec diverses concentrations (2 à 30 g/L) d'écorces de pin gris et de cèdre ont montré qu'il est possible de traiter efficacement les lixiviats de chaux usées chargés en plomb (environ 130 à 140 mg/L) par un apport de faibles quantités d'adsorbants, soit de l'ordre de 2 g/L. Finalement, des essais d'élution (HCl 0,5 M) et de réutilisation des adsorbants ont démontré que certains adsorbants, tels que les écorces de cèdre et les écailles de cacao, peuvent être employés pour plusieurs cycles d'adsorption–élution sans perdre leur capacité d'enlèvement du plomb. Mots clés : plomb, adsorption, chaux usées, lixiviation, tourbe, écorce. [ABSTRACT FROM AUTHOR]