Andrea Miskufova

Leaching of copper and tin from used printed circuit boards after thermal treatment

The hydrometallurgical route of copper and tin extraction from printed circuit boards (PCBs) of used personal computers after thermal pretreatment is discussed. The samples were thermally pretreated within temperature range of 300-900°C during 15, 30 and 60 min. Two methods of the thermal pretreatment were studied: burning and pyrolysis. The leaching solution of 1 M HCl at 80°C was used. The original as well as thermally pretreated samples were leached. The weight losses within the range from 5 to 35% were achieved. The increase of burning temperature causes the copper extraction into solution up to 98%, while copper extraction into solution from non-burned samples was up to 6%. In the case of the tin leaching the highest extraction was achieved when the original sample was leached. The increase of the burning temperature caused the lowering of the copper extraction. The increase of the pyrolysis temperature enhances copper and tin extraction.

Acidic leaching both of zinc and iron from basic oxygen furnace sludge.

During the steel production in the basic oxygen furnace (BOF), approximately 7-15 kg of dust per tonne of produced steel is generated. This dust contains approximately 1.4-3.2% Zn and 54-70% Fe. Regarding the zinc content, the BOF dust is considered to be highly problematic, and therefore new technological processes for recycling dusts and sludge from metallurgical production are still searched for. In this study the hydrometallurgical processing of BOF sludge in the sulphuric acid solutions under atmospheric pressure and temperatures up to 100 °C is investigated on laboratory scale. The influence of sulphuric acid concentration, temperature, time and liquid to solid ratio (L:S) on the leaching process was studied. The main aim of this study was to determine optimal conditions when the maximum amount of zinc passes into the solution whilst iron remains in a solid residue.

Hydrometallurgical treatment of used printed circuit boards after thermal treatment.

The hydrometallurgical route of copper and tin extraction from printed circuit boards (PCB) of used personal computers after thermal pretreatment is discussed. The PCB fractions crushed and sorted into -8+0, -8+3 and -3+0 mm were used for the experiments. The samples were thermally pretreated at temperatures of 300, 500, 700 and 900 °C during 15, 30 and 60 min with the presence of air (burning) before the leaching process. The leaching solution of 1M HCl and temperature of 80 °C was used for the leaching. The original as well as thermally pretreated samples were leached under these conditions. The weight losses within the range from 5% to 35% were achieved by burning depending on the burning temperature. The increase of burning temperature causes the copper extraction into solution up to 98%, while copper extraction into solution from non-burned samples was up to 6%. The opposite effect was observed in the case of the tin leaching, where the highest extraction was achieved when the original sample was leached. The increase of the burning temperature caused the lowering of the copper extraction.

Submerged-arc welding slags: Characterization and leaching strategies for the removal of aluminum and titanium

In the present study, submerged-arc welding slags were characterized by applying a variety of methods, including X-ray fluorescence, X-ray diffraction, particle size, Raman spectroscopy, and scanning electron microscope with energy dispersive X-ray analysis. The content of Al proved to be quite similar within neutral and acid slags (10-14%), while that of Ti proved to be much higher in acid slags (approximately 10%) than in neutral slags (<1%). The presence of spinel structures associated with Al species could also be identified in the analyzed samples. This characterization study was accompanied by leaching tests performed under changing operating conditions in an attempt to evaluate to what extent the Al and Ti bearing components could be removed from the slags. The leaching work involved three distinct strategies: (i) NaOH leaching followed by H(2)SO(4) leaching, (ii) acid leaching (HCl and H(2)SO(4)) using oxidizing/reducing agents, and (iii) slag calcination followed by H(2)SO(4) leaching. In the best result, 80% of Al was extracted in one single leaching stage after calcination of the acid slag with NaCl+C at 900 °C. By contrast, the removal of Ti proved to be unsatisfactory.

Recovery of Copper and Tin from Used Printed Circuit Boards

This work focuses on possibilities to recover tin and copper by hydrometallurgical processes from printed circuit boards (PCBs) of discarded personal computers after thermal treatment. For experimental work crushed and sorted printed circuit boards with various granularity /-8 +0 mm, -8 +3 mm, -3 +0 mm/ were used. They were exposed to thermal treatment at temperatures 300 °C, 500 °C, 700 °C and 900 °C before leaching for 15, 30 and 60 minutes. The two thermal treatments were studied: in air flow, i.e. burning, and pyrolysis (without air flow). For leaching experiments 1M solution of HCl at 80 °C was used. Under the mentioned conditions both samples, the thermally treated sample of PCB as well as the original untreated printed circuit board, were leached with the aim to compare the experimental results. Weight losses during burning accounted for 5 to 35 %, while pyrolysis caused weight losses from 10 to 30 %, depending on the thermal treatment temperature. The higher the burning temperature, the higher the extraction of copper into the solution with up to 98%.However, extraction of copper from non-burned samples does not exceeded 6 %. An opposite effect has been observed during leaching of tin, where the highest extraction was reached using thermally untreated samples, and extraction decreased with an increasing burning temperature. With increasing pyrolysis temperature a higher extraction level was observed during leaching of copper and tin into the solution. The maximal extraction was reached with the leaching of thermally untreated samples, namely 6 % for copper and about 68 % for tin whereas the extraction of copper and tin achieved with thermally treated samples was 63 % and 98 %, respectively.

Problems with Solidification of Fly Ashes from the Municipal Solid Waste Incineration

One of the negative aspects of MSW (municipal solid waste) incineration is production of hazardous fly ashes. MSW fly ash usually contains heavy metals like for example chromium, lead, cadmium and organic substances (dioxins, furans), soluble compounds (salts) and other harmful substances. According to environmental legislative and with respect to the environment fly ash as a hazardous waste should be stabilized before landfilling. This work deals with certain problems occurring at solidification process of MSW fly ash by cementation. This work also describes efficiency of stabilization by two different binders (slag cement and waste containing alumina and silica). Leachability tests by TCLP (toxicity characteristic leaching procedure) and compressive strength of original and solidified samples by use of uniaxial pressing were studied in order to find suitable parameters for effective stabilization.