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Formation of hexavalent chromium in Cr-containing steelmaking slag

Sato Y., Ijima K., Shibayama A., Inoue R.

Archives of Materials Science and Engineering

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2018

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Vol. 94, nr 1

5--10

EN

Purpose: In present work, the mineral phases in chromium-containing slags were identified, and the formation mechanisms of Cr(VI) in Cr2O3-containing mineral phases were discussed. Design/methodology/approach: In steelmaking slag containing chromium, chromium is mainly present as spinel phases such as MgCr2O4 and (Mg,Fe)Cr2O4. When these Cr(III) oxides are oxidized to Cr(VI) oxide, the Cr(VI) is easily eluted from the slag due to its high solubility in water. Findings: The Cr (VI) adversely affects the human health and the environment. In this study, the influence of cooling rate, quenching temperature and oxidation/reduction condition during cooling on the Cr(VI) amount eluted from synthesized MgCr2O4, (Mg,Fe)Cr2O4 and CaCr2O4 were investigated. Research limitations/implications: The formation of Cr(VI) oxide in MgCr2O4 and CaCr2O4 compounds during heating under air was considered to be indispensable. The amounts of Cr(III) and Cr(VI) dissolved from MgCr2O4 were smaller than those from CaCr2O4. Since the formation of CrO3 in MgCr2O4 started at around 1400 K during cooling, slag should be cooled rapidly from the high temperature above 1400 K, or cooled in inert atmosphere in order to minimize Cr(VI) formation. FeO in (Mg,Fe)Cr2O4 solid solution suppressed Cr(VI), Cr(III) and Mg elution. Originality/value: The development of prevention method of Cr(VI) formation in the slags containing chromium is urgent in order to utilize the slags to land-fill and civil engineering works.

2

Oznaczenie stężeń miedzi i ołowiu w eluatach uzyskanych z odpadu hutniczego za pomocą podstawowego i kolumnowego testu wymywania

Mizerna K.

Zeszyty Naukowe. Inżynieria Środowiska / Politechnika Opolska

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2016

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nr 359, z. 9

47--50

EN

The paper presents the results of copper and lead leaching from smelter slag obtained by testing using the column and basic (compliance) leaching tests. Concentrations of heavy metals are presented as a function of L/S ratio. Higher leaching of copper and lead in eluates in the basic test was determined.

3

Elution of heavy metals from granulates produced from municipal sewage deposits and fly-ash of hard and brown coal in the aspect of recycling for fertilization purposes

Rosik-Dulewska Cz., Głowala K., Karwaczyńska U., Robak J.

Archives of Environmental Protection

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2008

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Vol. 34, no. 2

63-71

EN

Deposits used as fertilizer bring to soil both biogens necessary for plant growth and other ingredients such as metals, including heavy metals. Knowledge of quantities and rate in which heavy metals are to be released to soil from granulates is important because of their toxic influence on plants (in the case of high metals concentration). This paper presents results of investigation of elution of Cu, Zn, Ni, Cd, Pb, and Cr from granulates prepared from municipal sewage sludge, hard coal ash and brown coal ash. Elution to water solution was carried out in static conditions with single-stage and tree-stage extraction. Heavy metal a component of sludge-ash granulates eluted in various quantities, i.e. from trace for cadmium to 9.26-9.53 mg/kg of dm. for zinc. Among the soluble forms of metals the most mobile are (in decreasing sequence): Cu > Pb > Zn > Ni in granulates containing brown coal ash and Cu >Pb > Ni > Zn in granulates contain hard coal ash.

PL

Wykorzystywanie odpadów w celach nawozowych wiąże się z wprowadzaniem do środowiska glebowego poza niezbędnymi do wzrostu i rozwoju roślin biogenami, również innych zawartych w nich składników min. metali (w tym ciężkich). Z uwagi na toksyczne oddziaływanie metali ciężkich na rośliny (w przypadku nadmiernego stężenia) istotna jest wiedza na temat ilości i tempa uwalniania poszczególnych metali z takich odpadów. W pracy przedstawiono wyniki badań wymywania Cu, Zn, Ni, Cd, Pb i Cr z granulatów przygotowanych w oparciu o komunalne osady ściekowe i popioły lotne ze spalania węgla kamiennego i brunatnego Wymywanie do roztworu wodnego prowadzono w układzie statycznym: jednoetapowo i trójetapowo. Melale ciężkie były wymywane w zróżnicowanych ilościach tj. od śladowych dla kadmu do 9,5 mg/kg s.m dla cynku. Spośród rozpuszczalnych form metali najbardziej mobilnymi były, w sekwencji malejącej, Ni > Cu > Pb > Zn zarówno dla granulatów zawierających popiół z węgla brunatnego jak i kamiennego.