<p>The production of ferrochromium alloys at Vargön Alloys AB contributes to formation of unwanted ferrochromium dust, which contains toxic Cr(VI). The dust is since summer 2005 treated with an iron-sulphate solution to reduce Cr(VI) to the non-toxic Cr(III). A year later the treatment technique was improved and disposal occurs in cells on the landfill. The cells can be up to 300 m3 and the edges can be made out of fro example concrete. Tests are conducted on the treated dust when it is disposed. The analyses show low contents of Cr(VI), which indicates that the reduction is successful. Analyses of leakage water from a small scale cell however showed an increasing content of Cr(VI) and pH under the first two months.</p><p>This thesis has evaluated the new treatment method. An investigation was conducted to determine if the same changes have occurred in the full scale cells. Half of the 18 collected samples from the disposed dust showed high or very high contents of Cr(VI). The other half had a almost no detectable content. pH was over 12. No correlation between Cr(VI)-content and pH, conductivity, age or water content in the disposed dust could be shown.</p><p>An experiment was also performed in small scale to reduce the number of influencing parameters. The results showed that if the dust has access to oxygen the Cr(VI) content increases during the first days from a few mg/kg dry substance to over 20 mg/kg dry substance, a level which was maintained during the rest of the experiment period. The content of Cr(VI) was almost constant at 4 mg/kg dry substance when oxygen was eliminated during the whole experiment period. When the water content was below 5 %, the content of chromium did not increase more.</p><p>Since almost all newly created Cr(VI) is reduced to Cr(III) by the addition of ferrous sulphate, recreation of Cr(VI) occurs. Today there is now possibility to follow the changes in the dust from untreated to after disposed. The addition of iron-sulphate is based upon an average Cr(VI) content in the dust and the variation of disposal occasions can be significant. To determine if the increase in Cr(VI) is caused of an incorrect addition of solution a smaller disposal cell can be constructed. The initial content of Cr(VI) can be controlled and the dust can be examined during the time it ages. If the dosage could be improved the addition can be optimized. It is also important to minimize the infiltration and accelerate the drying of the slurry since the Cr(VI) content can increase the as long as the water content is high the Cr(VI) content can increase.</p> / <p>Vid produktionen av ferrolegeringar på Vargön Alloys AB bildas ferrokromstoft som en oönskad biprodukt, vilken innehåller hälsofarligt sexvärt krom. Sedan sommaren 2005 behandlas stoftet med järnsulfatlösning för att reducera Cr(VI) till mindre hälsofarliga Cr(III). Ett år senare förbättrades tekniken och deponering sker sedan dess i iordningställda celler på deponin. Cellerna rymmer cirka 300 m3 och har kanter av bland annat betongstöd. Provtagning sker på det behandlade stoftet i samband med deponeringen. Analyserna visar mycket låga halter av Cr(VI), vilket tyder på att reduktionen lyckas. Analyser av lakvatten från en småskalig provcell visade däremot att Cr(VI)-halter och pH ökade under de två första månaderna.</p><p>Detta arbete har utvärderat den nya behandlingsmetoden. Undersökning huruvida samma förändring har skett i fullskaliga celler har utförts. Utav de 18 prov som inhämtades från det deponerade stoftet visade hälften på höga eller mycket höga Cr(VI)-halter och resterande hade nästan omätbara halter. I det deponerade stoftet var pH genomgående drygt 12. Inget samband mellan Cr(VI)-halt och pH, konduktivitet, ålder eller vatteninnehåll i deponerat stoft erhölls.</p><p>Försök utfördes även i liten skala i för att minska antalet påverkande parametrar. Utan tillgång till syre var Cr(VI)-halten cirka 4 mg/kg torrsubstans under hela försöksperioden. Försöken visade att om stoftet har tillgång till syre ökar Cr(VI) från några mg/kg torrsubstans till dryga 20 mg/kg torrsubstans efter bara några dagar. Halten förblev konstant under resten av försökstiden. Ett samband som sågs var att när Cr(VI)- halten har stagnerat är vatteninnehållet i provet under 5 %.</p><p>Eftersom nästan allt krom reduceras till Cr(III) vid tillsatsen av järnsulfatlösning har det nyreducerade Cr(VI) återbildats. I nuläget går det inte att följa hur stoftet förändras från obehandlat och vad som händer när det åldras efter att det har behandlats och deponerats. Tillsatsen av järnsulfat doseras efter en medelhalt Cr(VI)-innehåll i stoftet och variationen i Cr(VI)-halt mellan deponeringstillfällen kan vara stor. För att avgöra om ökningen av Cr(VI) beror på felaktig tillsatts av järnsulfatlösning kan en mindre deponeringscell anläggas. Ingående Cr(VI)-halter kan kontrolleras och stoftet kan undersökas medan det åldras på deponin. Visar det sig att dosering behöver förbättras kan tillsatsen optimeras. Det är även viktigt att minska infiltrationen samt påskynda torkningen av slurryn eftersom så länge vattenhalten är hög kan Cr(VI)-halterna öka.</p>

Objective was to assess the toxicity of chromium (Cr) contaminated soil (CS) using the earthworm Lumbricus terrestris. Specific aims were to determine: (1) survival (LC50); .(2) immunotoxicity as indicated by lysozyme activity, coelomocyte counts, secretory (SR) and erythrocyte rosette (ER) formation, and phagocytosis; and (3) compare effects of CS exposure with those of Cr spiked artificial soil (AS) . CS Cr concentration was 8.78 mg/g with 98.2% being Cr^3+ and 1.8% being Cr^6+. Using 14 d AS protocol the LC50 was 6.49% CS: AS mixture. CS concentrations of 0.5, 1.0, 2.5 and 5.0% were sublethal, whereas 6.25, 12.5, 25, 50 and 100% CS were lethal. Sublethal exposure caused no immuno- modulation. Exposure to 50% CS: AS mixture for 5 d caused reduced SR and ER formation. Exposure to AS spiked with 0.27% Cr for 5 d resulted in immunomodulation equivalent to 50% CS: AS mixtures. Results indicated the CS to be acutely toxic.

Chromium hydroxide sludge is the end product of the aluminum phosphate coating process used by a truck manufacturer in the Pacific Northwest. This sludge is listed as an (F019) hazardous waste by the Environmental Protection Agency, and must be landfilled in a hazardous waste landfill site. The purpose of this thesis is to evaluate the characteristics of this sludge, and to then recommend suitable methods for handling and disposal. The chemical analysis of the sludge found total chromium to be 5.4% by weight. Industrial hygiene monitoring found the highest concentrations of 0.002 mg/m3 total chromium and 0.00006 mg/m3 hexavalent chromium at the waste treatment plant. The eight hour permissible exposure limit for total chromium is 0.5 mg/m3 and 0.05 mg/m3 for hexavalent chromium. Given the chemical analysis and industrial hygiene monitoring, a management plan is proposed for this truck manufacturer that discusses possible options for handling the (F019) waste, and provides a cost analysis for each of the options. The options that were investigated were onsite treatment, recycling, no change, and delisting. Onsite treatment was not required since the sludge passed the TCLP extraction test. Recycling costs were determined by contacting four recycling firms. Costs were found to be $600/ton and above, which exceeded the current disposal costs of $466/ton. Delisting the sludge from the hazardous waste listing was determined to be the most feasible from a management, cost, and environmental standpoint. Delisting would reduce the costs of handling the waste, would allow a reduction in landfilling costs, and reduce recycling costs. A literature survey provides background information on industrial uses of chromium, health problems associated with chromium, and discusses the regulations that govern disposal of these chromium sludges. / Graduation date: 1991

The production of ferrochromium alloys at Vargön Alloys AB contributes to formation of unwanted ferrochromium dust, which contains toxic Cr(VI). The dust is since summer 2005 treated with an iron-sulphate solution to reduce Cr(VI) to the non-toxic Cr(III). A year later the treatment technique was improved and disposal occurs in cells on the landfill. The cells can be up to 300 m3 and the edges can be made out of fro example concrete. Tests are conducted on the treated dust when it is disposed. The analyses show low contents of Cr(VI), which indicates that the reduction is successful. Analyses of leakage water from a small scale cell however showed an increasing content of Cr(VI) and pH under the first two months. This thesis has evaluated the new treatment method. An investigation was conducted to determine if the same changes have occurred in the full scale cells. Half of the 18 collected samples from the disposed dust showed high or very high contents of Cr(VI). The other half had a almost no detectable content. pH was over 12. No correlation between Cr(VI)-content and pH, conductivity, age or water content in the disposed dust could be shown. An experiment was also performed in small scale to reduce the number of influencing parameters. The results showed that if the dust has access to oxygen the Cr(VI) content increases during the first days from a few mg/kg dry substance to over 20 mg/kg dry substance, a level which was maintained during the rest of the experiment period. The content of Cr(VI) was almost constant at 4 mg/kg dry substance when oxygen was eliminated during the whole experiment period. When the water content was below 5 %, the content of chromium did not increase more. Since almost all newly created Cr(VI) is reduced to Cr(III) by the addition of ferrous sulphate, recreation of Cr(VI) occurs. Today there is now possibility to follow the changes in the dust from untreated to after disposed. The addition of iron-sulphate is based upon an average Cr(VI) content in the dust and the variation of disposal occasions can be significant. To determine if the increase in Cr(VI) is caused of an incorrect addition of solution a smaller disposal cell can be constructed. The initial content of Cr(VI) can be controlled and the dust can be examined during the time it ages. If the dosage could be improved the addition can be optimized. It is also important to minimize the infiltration and accelerate the drying of the slurry since the Cr(VI) content can increase the as long as the water content is high the Cr(VI) content can increase. / Vid produktionen av ferrolegeringar på Vargön Alloys AB bildas ferrokromstoft som en oönskad biprodukt, vilken innehåller hälsofarligt sexvärt krom. Sedan sommaren 2005 behandlas stoftet med järnsulfatlösning för att reducera Cr(VI) till mindre hälsofarliga Cr(III). Ett år senare förbättrades tekniken och deponering sker sedan dess i iordningställda celler på deponin. Cellerna rymmer cirka 300 m3 och har kanter av bland annat betongstöd. Provtagning sker på det behandlade stoftet i samband med deponeringen. Analyserna visar mycket låga halter av Cr(VI), vilket tyder på att reduktionen lyckas. Analyser av lakvatten från en småskalig provcell visade däremot att Cr(VI)-halter och pH ökade under de två första månaderna. Detta arbete har utvärderat den nya behandlingsmetoden. Undersökning huruvida samma förändring har skett i fullskaliga celler har utförts. Utav de 18 prov som inhämtades från det deponerade stoftet visade hälften på höga eller mycket höga Cr(VI)-halter och resterande hade nästan omätbara halter. I det deponerade stoftet var pH genomgående drygt 12. Inget samband mellan Cr(VI)-halt och pH, konduktivitet, ålder eller vatteninnehåll i deponerat stoft erhölls. Försök utfördes även i liten skala i för att minska antalet påverkande parametrar. Utan tillgång till syre var Cr(VI)-halten cirka 4 mg/kg torrsubstans under hela försöksperioden. Försöken visade att om stoftet har tillgång till syre ökar Cr(VI) från några mg/kg torrsubstans till dryga 20 mg/kg torrsubstans efter bara några dagar. Halten förblev konstant under resten av försökstiden. Ett samband som sågs var att när Cr(VI)- halten har stagnerat är vatteninnehållet i provet under 5 %. Eftersom nästan allt krom reduceras till Cr(III) vid tillsatsen av järnsulfatlösning har det nyreducerade Cr(VI) återbildats. I nuläget går det inte att följa hur stoftet förändras från obehandlat och vad som händer när det åldras efter att det har behandlats och deponerats. Tillsatsen av järnsulfat doseras efter en medelhalt Cr(VI)-innehåll i stoftet och variationen i Cr(VI)-halt mellan deponeringstillfällen kan vara stor. För att avgöra om ökningen av Cr(VI) beror på felaktig tillsatts av järnsulfatlösning kan en mindre deponeringscell anläggas. Ingående Cr(VI)-halter kan kontrolleras och stoftet kan undersökas medan det åldras på deponin. Visar det sig att dosering behöver förbättras kan tillsatsen optimeras. Det är även viktigt att minska infiltrationen samt påskynda torkningen av slurryn eftersom så länge vattenhalten är hög kan Cr(VI)-halterna öka.

In this thesis work, a high grade chromite concentrate obtained from PinarbaSi, Kayseri region of Turkey was reacted with sulfuric acid solution to determine the optimum conditions of leaching of chromite ores. Conventional methods for producing chromium are still valid in industry. The main process in production includes soda melting and taking it into solution in the form of chemical compounds such as sodium dichromate. Three and six valence states of chromium have importance in production. Trivalent chromium, chrome ore or chromite have no harmful effects. However, compounds of hexavalent chromium show toxic, irritating and corrosive action to people and environment. In the mentioned conventional method, main products consist of hexavalent chromium compounds. In this study, only trivalent chromium remained in the leach solution and did not change to hexavalent state. Obtained product after leaching was chromium(III) sulfate. The maximum extraction of chromium in the absence of perchloric acid was 94.1 % under the conditions of 175 &deg / C, 6 hours and 84.6 wt % sulfuric acid. The maximum extraction of chromium in the presence of perchloric acid was 98.7 % under the conditions of 175 &deg / C, 2 hours, 84.6 wt % sulfuric acid and &frac12 / perchloric acid / chromite ratio. The latter one was also the highest recovery value obtained during the experiments. Moreover, in none of the analyzed samples, appreciable amounts of hexavalent chromium was found during analyses.

Thesis (Ph. D.)--West Virginia University, 2002. / Title from document title page. Document formatted into pages; contains xi, 148 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains viii, 124 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 160-164).

Thesis (Ph. D.)--University of Alabama at Birmingham, 1999. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Alabama at Birmingham, 1999. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.