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The removal of Cr(III) present in spent leather tanning baths by precipitation with acetylene production sludge (APS) is studied. The hydroxide and carbonate contents in APS were 1.05 and 0.10 g of CaCO3/g of dry sludge, respectively, and the Cr concentration in the tanning bath was 2467 mg/L. The experimental work was carried out at 15, 20, 25, 30, and 35 degrees C using APS samples of different grain size (89, 178, and 356 microm). Percent removals after 180-min reaction time using 356-microm APS particles range from 99.0 to 99.9 as temperature increased from 15 to 35 degrees C. Similar or higher removal rates are obtained when using smaller APS particles. Chromium removal efficiencies using APS as precipitant are comparable with those obtained with NaOH, CaO, or MgO. The Cr conversion X increases with time t and is related to the particle radius and the absolute temperature T by the expression X/1 - X= r0(-0.22) exp(45.45-13401/T)t. The average activation energy for the reaction is 111.4 kJ mol(-1). Despite some deviations observed for the finer particles and the lower temperature (15 degrees C), the model describes adequately the results obtained for all APS particle sizes at 20 degrees C.

This paper presents a Web-based graphical tool that makes it possible to view and simulate a working circuit at the layout level. This tool allows one to observe changes in logical levels with a dynamic alteration of the color properties of the graphical elements that characterize the circuit at layout level. The layout view changes colors in function of logic level changes. Two aspects of the circuit simulation are presented: taking into account the gates delay or not.

In this work, samples of components usually present in healthcare waste, such as cotton, diapers, transfusion tubes, surgical gloves, examination gloves, adhesives, surgical masks, urine bag collectors, serum bottles and syringes, were subjected to alkaline hydrolysis or autoclaving and the effects of these treatments were assessed. Both treatments were carried out at 135 ºC, and the weight loss and the carbon loss of the components as well as the total organic carbon and the chemical oxygen demand in the effluents were determined. The biodegradability of effluents was assessed by measuring the bio-chemical oxygen demand after 5 days. Alkaline hydrolysis caused appreciable degradation in most of the components, with the adhesives and the diapers having the highest weight losses and carbon losses. Components made with low-density polyethylene, highdensity polyethylene and polypropylene showed good chemical resistance with 2 M NaOH solution. The effluents obtained after alkaline treatment of healthcare waste are hazardous due to their very high alkalinity. The effluent obtained after treatment of a mixture of all components using a 2 M NaOH solution was biodegradable with the following parameters: 6.5 g C/l of total organic carbon, 29.8 g O2/l of chemical oxygen demand and 14.9 g O2/l of biochemical oxygen demand after 5 days. Although the autoclaving treatment degraded the components much less than alkaline hydrolysis, the effluents obtained from some components showed an appreciable organic load.

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