Tomasz Wiltowski

Removal of hexavalent chromium and metal cations by a selective and novel carbon adsorbent

Carbon produced by the contact arc method (whereby graphite electrodes are arced in an inert atmosphere) was employed for the removal of hexavalent and trivalent chromium ions as well as other metal cations from aqueous solutions. It is known that hexavalent chromium is present as an anionic species in the solution. The carbon adsorbent used in this study selectively removed the anions of hexavalent chromium from the solution, whereas, depending upon the solution pH, no or very small uptake of metal cations was observed. On the other hand, commercial activated carbon showed great affinity for cations of lead, zinc, and trivalent chromium but none for the anion of hexavalent chromium.

Chromium adsorption by lignin

Hexavalent chromium is a known carcinogen, and its maximum contamination level in drinking water is determined by the U.S. Environmental Protection Agency (EPA). Chromium in the wastewaters from plating and metal finishing, tanning, and photographic industries poses environmental problems. A commercially available lignin was used for the removal of hexavalent as well as trivalent chromium from aqueous solution. It is known that hexavalent chromium is present as an anionic species in the solution. It was found that lignin can remove up to 63% hexavalent and 100% trivalent chromium from aqueous solutions. The removal of chromium ions was also investigated using a commercially available activated carbon. This absorbent facilitated very little hexavalent and almost complete trivalent chromium removal. Adsorption isotherms and kinetics data on the metal removal by lignin and activated carbon are presented and discussed.Hexavalent chromium is a known carcinogen, and its maximum contamination level in drinking water is determined by the U.S. Environmental Protection Agency (EPA). Chromium in the wastewaters from plating and metal finishing, tanning, and photographic industries poses environmental problems. A commercially available lignin was used for the removal of hexavalent as well as trivalent chromium from aqueous solution. It is known that hexavalent chromium is present as an anionic species in the solution. It was found that lignin can remove up to 63% hexavalent and 100% trivalent chromium from aqueous solutions. The removal of chromium ions was also investigated using a commercially available activated carbon. This absorbent facilitated very little hexavalent and almost complete trivalent chromium removal. Adsorption isotherms and kinetics data on the metal removal by lignin and activated carbon are presented and discussed.

FUEL-FLEXIBLE GASIFICATION-COMBUSTION TECHNOLOGY FOR PRODUCTION OF H2 AND SEQUESTRATION-READY CO2

GE Global Research is developing an innovative energy technology for coal gasification with high efficiency and near-zero pollution. This Unmixed Fuel Processor (UFP) technology simultaneously converts coal, steam and air into three separate streams of hydrogen-rich gas, sequestration-ready CO{sub 2}, and high-temperature, high-pressure vitiated air to produce electricity in gas turbines. This is the draft final report for the first stage of the DOE-funded Vision 21 program. The UFP technology development program encompassed lab-, bench- and pilot-scale studies to demonstrate the UFP concept. Modeling and economic assessments were also key parts of this program. The chemical and mechanical feasibility were established via lab and bench-scale testing, and a pilot plant was designed, constructed and operated, demonstrating the major UFP features. Experimental and preliminary modeling results showed that 80% H{sub 2} purity could be achieved, and that a UFP-based energy plant is projected to meet DOE efficiency targets. Future work will include additional pilot plant testing to optimize performance and reduce environmental, operability and combined cycle integration risks. Results obtained to date have confirmed that this technology has the potential to economically meet future efficiency and environmental performance goals.

Conditions for energy generation as an alternative approach to compost utilization

Very strict limits constrain the current possibilities for compost utilization in agriculture and for land reclamation, thus creating a need for other compost utilization practices. A favourable alternative can be compost utilization as a renewable heat source – alternative fuel. The changes of the basic physical–chemical parameters during the composting process are evaluated. During the composting process, energy losses of 920 kJ/kg occur, caused by carbohydrate decomposition (loss of 12.64% TOC). The net calorific value for mature compost was 11.169 kJ/kg dry matter. The grain size of compost below 0.045 mm has the highest ash content. The energetic utilization of compost depended on moisture, which can be influenced by paper addition or by prolonging the time of maturation to six months.

Kinetics and mechanisms of iron sulfide reductions in hydrogen and in carbon monoxide

The reduction of iron sulfides by hydrogen and by carbon monoxide has been studied using plug flow and thermogravimetric methods. The reactions were studied in the 523-723/sup 0/K temperature range and were found to be first-order processes. Plug flow studies were used to correlate reactions rates between pyrite and the gases as a function of the surface area of the pyrite. The rate of H/sub 2/S formation increases with the surface area of the pyrite sample. The results of thermogravimetric experiments indicate that the reactions consist of several steps. Rate constants for the pyrite reduction by H/sub 2/ and by CO were obtained. The activation energies increased with degree of reduction. Value of E/sub a/ were 113.2 (step I) and 122.5 kJ/mole (step II) for pyrite reduction with CO and 99.4 (step I), 122.4 (step II), 125.2 (step III), and 142.6 kJ/mole (step IV) for pyrite reduction with hydrogen.

Recovery of metallic impurities from chromium plating solutions by electromigration

Conclusion The porous pot method appears to be a viable and a most cost-effective technique for the simultaneous regeneration and purification of the spent chromium plating solutions. The purification of the solution is brought about by the process of electromigration of metallic impurities to the cathode compartment where they are either deposited or precipitated de pending on the pH of the catholyte. Oxidation of trivalent chromium at the lead cathode results in further regeneration of the solution. The experiments strongly suggest that the chromic-oxide-containing solution serves as a most effective catholyte, since it prevents sludge formation, allows for metal electrodeposition, serves as a source for the makeup of hexavalent chromium needed in a spent plating solutions, in addition to being inexpensive and readily available to electroplaters. Work is in progress to use mathematical modeling to investigate the kinetics of the removal of metallic impurities and the reoxidation rate.

Photocatalytic oxidation of trichloroethylene and carbon tetrachloride using titanium dioxide filter as a catalyst

Destruction of trichloroethylene (TCE) and carbon tetrachloride by using TiO2 photocatalyst supported on an alumina filter prepared for this investigation was carried out using UV light. The kinetics of the rate of reaction were studied. The complete destruction of TCE and CCl4 occurred in 26 and 30 min, respectively, at room temperature and atmospheric pressure. The Langmuir?Hinshelwood rate expression was used to evaluate the rate constants from the experimental data.Destruction of trichloroethylene (TCE) and carbon tetrachloride by using TiO2 photocatalyst supported on an alumina filter prepared for this investigation was carried out using UV light. The kinetics of the rate of reaction were studied. The complete destruction of TCE and CCl4 occurred in 26 and 30 min, respectively, at room temperature and atmospheric pressure. The Langmuir?Hinshelwood rate expression was used to evaluate the rate constants from the experimental data.

Catalytic reduction of SO2 with methane over molybdenum catalyst

This paper deals with catalytic reduction of SO 2 with methane using molybdenum sulfide catalyst supported on two different activated carbons (Darco TRS and Norit ROZ-3). The experiments evaluated the effects of MoS 2 catalyst loading (10, 15, and 20% Mo, by weight), gas feed-rate concentration ratios of CH 4 to SO 2 (CH 4 :SO 2 ratios of 2:1, 1:1, and 1:2) and reaction temperatures (450, 500, and 600°C). The reactivity of each catalyst was evaluated by three different parameters: (a) SO 2 conversion, (b) CH 4 conversion and (c) the yield of elemental sulfur. The results show that the catalytic activity of MoS 2 supported on activated carbons is strongly related to the reaction temperature and the CH 4 :SO 2 feed ratio, with a secondary dependency on the loading of the MoS 2 . The 20% MoS 2 catalyst supported on Darco TRS in a reactor stream with CH 4 :SO 2 =1:1 demonstrated the highest activity of all the catalysts tested, having an SO 2 conversion of 99.8%. At 600°C and with a CH 4 :SO 2 =1:1, the catalysts with 20% loading supported on both Dacro TRS and Norit ROZ-3 exhibited comparable SO 2 conversion, both above 90%.

Simultaneous influence of gas mixture composition and process temperature on Fe2O3->FeO reduction kinetics: neural network modeling

The kinetics of Fe2O3®FeO reaction was investigated. The thermogravimetric (TGA) data covered the reduction of hematite both by pure species (nitrogen diluted CO or H2) and by their mixture. The conventional analysis has indicated that initially the reduction of hematite is a complex, surface controlled process, however once a thin layer of lower oxidation state iron oxides (magnetite, wustite) is formed on the surface, it changes to diffusion control. Artificial Neural Network (ANN) has proved to be a convenient tool for modeling of this complex, heterogeneous reaction runs within the both (kinetic and diffusion) regions, correctly considering influence of temperature and gas composition effects and their complex interactions. ANNs model shows the capability to mimic some extreme (minimum) of the reaction rate within the determined temperature window, while the Arrhenius dependency is of limited use.

Removal of Iron and Nickel from Solutions by Application of Electrical Fields

Metallic impurities such as Ni Fe, Cu ions in chromium plating solutions can be removed by electromigration followed by electrodeposition or coagulatiion using a porous pot, suspended in the bath and containing a lead cathode. In the same process, Cr(III) is oxidized to Cr (VI) at the insoluble lead anode leading to regeneration of the plating solution. Previous research and data from industrial operations have indicated the “porous pot” method could be a cost-effective and environmentally friendly method to continuously separate impurities and recycle spent chromium solutions. However, no data are available that relate the various concentrations of impurities to the extent and the rate of their removal. This investigation focused on the use of five suitable catholytes for the removal of impurities. Up to 60% nickel and 52% iron removal were observed in orthophosphoric acid and sodium monophosphate catholytes respectively. In addition to these two electrolytes, chromic acid appears to be a most suitable c...