Topic
Calcium oxide
About: Calcium oxide is a research topic. Over the lifetime, 7600 publications have been published within this topic receiving 66104 citations. The topic is also known as: caustic lime & quicklime.
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08 Oct 2002
TL;DR: In this article, a new composition and process for lanthanum oxide concentrate that is used to significantly reduce arsenic and/or selenium concentration levels in aqueous solutions is described.
Abstract: The invention is a new composition and process for lanthanum oxide concentrate that is used to significantly reduce arsenic and/or selenium concentration levels in aqueous solutions. The lanthanum oxide concentrate is a mixture of lanthanum oxide and one or more oxides from the following group: neodymium oxide, cerium oxide, parseodymiun oxide, strontium oxide, calcium oxide and sodium oxide. The process of manufacture comprises the steps of sintering the lanthanum oxide concentrate, then washing the resultant media. The process of use is the contact of the lanthanum oxide concentrate with an aqueous solution containing arsenic and/or selenium whereby the lanthanum oxide concentrate removes at least a portion of the arsenic and/or selenium from the aqueous solution.
20 citations
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TL;DR: Experimental laboratory investigation was carried out on sediments carefully collected from the Mar Piccolo of Taranto in Southern Italy, contaminated by heavy metals, polycyclic aromatic hydrocarbons and polychlorinated biphenyls, indicating that the addition of binders increased the pH of the mixtures with a consequent leachability of different metals.
Abstract: Among ex situ remediation technologies, stabilization/solidification (S/S) provides for the addition of a binder to dredged materials in order to chemically immobilise the contaminants and improve mechanical behaviour of sediments. The simplest form of treatment is obtained by the addition of Portland cement or lime (calcium oxide), although other additives such as adsorbents may be added. Nevertheless, the success of the S/S treatment may be affected by the contaminants present or by the salt content in the water. In this study, experimental laboratory investigation was carried out on sediments carefully collected from the Mar Piccolo of Taranto in Southern Italy, contaminated by heavy metals, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs); the goal was to explore the effectiveness of S/S treatment by using Portland cement/lime as binders, monitoring over time (28 days) the leaching of the different mixtures of treated sediment. It is noted that the Mar Piccolo of Taranto is one of the sites of national interest subject to remediation by the Italian government. Once taken within the first meter under the sea floor by a team of experienced divers, the samples were stored at a controlled temperature, characterised in terms of grain size and physical-chemical characteristics and treated by S/S laboratory tests. The results indicate that the addition of binders increased the pH of the mixtures with a consequent leachability of different metals. The mobility of the metals appeared to be governed also by the curing time. The performance of the mixtures in terms of immobilised metals was influenced by the presence of organic contaminants (e.g. organic matter, PAHs and PCBs). As a lesson, high organic matter and fine-grained particles can negatively affect the effectiveness of the S/S treatment in terms of metal immobilisation.
20 citations
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TL;DR: In this article, the ability of calcite (CaCO 3 ) and quicklime (GaO), two common amendments, to establish and maintain pH conditions and dissolved metal concentrations within environmentally acceptable ranges over long time periods was compared.
Abstract: Flooding partially oxidized mine tailings for the purpose of mitigating further oxidation of sulfide minerals and generation of acid drainage is generally preceded by treatment with alkaline amendments to prevent releasing previously accumulated acidity to the water cover. This work compares the ability of calcite (CaCO 3 ) and quicklime (GaO), two common amendments, to establish and maintain pH conditions and dissolved metal concentrations within environmentally acceptable ranges over long time periods. Although higher initial pH values were obtained with quicklime, the pH of quicklime treated tailings decreased over time. This was attributed to the low buffering capacity of quicklime treated tailings and to the consumption of hydroxide ions by incongruent dissolution of water-insoluble iron oxyhydroxysulfate minerals. In contrast, the pH of tailings treated with calcite increased initially and then remained stable at pH 6.7. This pH behavior was due to the lower reactivity of iron oxyhydroxysulfates with calcite, the increased buffering capacity provided by bicarbonate ions, and the incomplete dissolution of calcite. Overall, calcite was found preferable to quicklime for maintaining long-term neutral pH conditions in the treated tailings. With the exception of zinc, acceptable dissolved metal concentrations were achieved with calcite treated tailings.
20 citations
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28 Nov 2011
TL;DR: In this paper, the authors proposed a method for increasing the rate of recovery of valuable metals when waste batteries batteries are treated by a dry process, where the valuable metal recovery method in the dry step S20 includes a melting step ST21 including melting waste batteries to form a melt, a slag separation step ST22 including separating slag from the melt, and an alloy separation step S23 including separating an alloy of valuable metal from the melting, wherein the slag has an aluminium oxide content of 20% by weight to less than 75% by value and an iron content of 5
Abstract: Provided is a method for increasing the rate of recovery of valuable metals when waste batteries batteries are treated by a dry process. The valuable metal recovery method in the dry step S20 includes a melting step ST21 including melting waste batteries to form a melt, a slag separation step ST22 including separating slag from the melt, and an alloy separation step ST23 including separating an alloy of valuable metals from the melt, wherein the slag has an aluminium oxide content of 20% by weight to less than 75% by weight and an iron content of 5% by weight to 40% by weight, calculated as metallic iron, and silicon oxide and calcium oxide are added as fluxes in the melting step ST21 so that the slag can have a melting point of at least 1,500°C, preferably at most 1,650°C.
20 citations
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TL;DR: In this paper, two Strategic Highway Research Program asphalts were aged in a pressure oxygen vessel (POV) with and without admixture of CaO and Ca(OH)2 at several concentrations.
Abstract: Two Strategic Highway Research Program asphalts were aged in a pressure oxygen vessel (POV) with and without admixture of CaO and Ca(OH)2 at several concentrations These same asphalts were then aged by low-temperature air blowing, and the resulting materials were softened by mixing with three recycling agents obtained by supercritical extraction of asphalts These rejuvenated asphalts were mixed with varying amounts of CaO and aged in the POV Oxidation rates and hardening were measured at various temperatures, and the resulting kinetic parameters were used to estimate hardening at road conditions The hardening rate was always reduced by lime addition The oxidation rate was sometimes reduced The recycling agents alone reduced the hardening rates relative to those of the original asphalts, but the effect was further enhanced by CaO additions
20 citations