Cornélio de Freitas Carvalho

Qualidade das águas do ribeirão Ubá - MG

The water quality of the Uba creek, inside and in the outskirts of the town with this name in the state of Minas Gerais, was investigated. Both physico-chemical and bacteriological analyses were performed in this investigation. Also, physico-chemical analyses of the effluents from furniture industries, the main industrial activity in that town, were also carried out. The Water Quality Index (WQI) - based on chemical and biological parameters - was used to determine the quality of the water of this creek. It has been found that inside this town as well as after leaving it, the water of the Uba creek is of bad quality, due to pollution resulting from both domestic and industrial sewage.

Manganese ore tailing : optimization of acid leaching conditions and recovery of soluble manganese.

Manganese recovery from industrial ore processing waste by means of leaching with sulfuric acid was the objective of this study. Experimental conditions were optimized by multivariate experimental design approaches. In order to study the factors affecting leaching, a screening step was used involving a full factorial design with central point for three variables in two levels (2(3)). The three variables studied were leaching time, concentration of sulfuric acid and sample amount. The three factors screened were shown to be relevant and therefore a Doehlert design was applied to determine the best working conditions for leaching and to build the response surface. By applying the best leaching conditions, the concentrations of 12.80 and 13.64 %w/w of manganese for the global sample and for the fraction -44 + 37 μm, respectively, were found. Microbeads of chitosan were tested for removal of leachate acidity and recovering of soluble manganese. Manganese recovery from the leachate was 95.4%. Upon drying the leachate, a solid containing mostly manganese sulfate was obtained, showing that the proposed optimized method is efficient for manganese recovery from ore tailings.

Rendering wastes obtained from gold analysis by the lead-fusion fire-assay method non-hazardous

The classical method of melting lead by fire-assay (Pb-FA) is the most frequently used analytical technique in gold prospection. The crucible solid waste which is generated in this process is usually characterized by chemical and mineralogical composition, granulometric size distribution, and classified according to Brazilian Environmental Regulations. This study demonstrates how acid leaching can be used to remove lead from waste originally classified as hazardous by treatment with hydrochloric and nitric acids followed by chemical precipitation in sodium metasilicate solution. It is shown that for every 1000 kg of hazardous waste, 995.6 kg of non-harzardous waste can be recovered.

Caracterização e biodegradabilidade aeróbia e anaeróbia dos esgotos produzidos em campus universitário

The aim of this study was to characterize and evaluate the tratability of wastewater produced in the campus of the Federal University of Ouro Preto (UFOP). The physical-chemical parameters showed the wastewater from the campus had characteristics of typical domestic wastewater, with average values of total BOD, total COD, Kjeldahl Nitrogen and total phosphorus of 300 mg.L-1, 670 mg.L-1, 56 mg.L-1 e 6 mg.L-1 respectively. Only the metals Fe (0,847 mg/L), Al (0,355 mg/L) and Zn (0,389 mg/L) were present in higher concentration, nonetheless, such concentrations were below the thresholds limits for microbial toxicity. The biodegradability tests showed that despite the potential presence of toxic organic compounds, the wastewater could be degraded aerobically (97% efficiency, K1app = 1,73 d-1) and anaerobically (50% efficiency, AME = 0,0579 gDQOCH4/gSSV.d).

Caracterização e tratabilidade biológica dos efluentes líquidos gerados em cabines de pintura de uma indústria moveleira

The main objective of this work was to characterize the wastewater from the dying hood of a woven furniture industry, and to assess the efficiency of biological processes (anaerobic and aerobic) for its treatment. The physical-chemical characterization of the industrial wastewater showed a high organic matter content (total COD from 634 to 2,790 mg.L-1; total BOD5 from 360 to 972 mg.L-1), low content of macronutrients (NTK of 1.9 mg.L-1 and P of 0.5 mg.L-1) and toxic metals. The anaerobic degradation tests in a bench-scale UASB reactor (25oC and hydraulic retention time - HRT = 10 hours) showed that a maximum removal efficiency of 90% was obtained when the reactor was fed with 30% raw sewage and 70% industrial wastewater. The feeding of UASB reactor with only industrial wastewater resulted in volatile fatty acids accumulation and microbial inhibition; however, the use of aerobic post-treatment (HRT = 96 hours) granted a high (~88%) organic matter removal efficiency.

Adsorção do corante têxtil amarelo remazol usando um dos rejeitos da fabricação da alumina como adsorvente

This work discusses the possibility of using one of the residues retained in electrostatic filters during alumina production, in the adsorption of the remazol yellow dye which is commonly employed in the textile industry. The results presents a removal efficiency of 95% of the dye in an aqueous solution containing 50 mg/L of this substance. The Langmuir isotherm model showed to be adequate to describe the adsorption mechanism of this dye. The ability of the dye adsorption depends on its structure and the interaction dye-adsorbent.

Recovering lead from cupel waste generated in gold analysis by Pb-Fire assay

Because of its precision and accuracy, Pb-Fire assay is the most employed method for gold analysis in geological materials. At the second stage of the method, namely cupellation, lead is oxidized to PbO which is absorbed by the cupel, leading to metallic gold as a tiny bend at the bottom of the recipient. After cupellation, cupel becomes highly contaminated with lead, making its disposal a serious risk of environmental contamination. In the present work, a leaching process for removing lead from cupel waste is proposed, which allowed for removing 96% of PbO by weight. After a precipitation step, 92.0% of lead was recovered from leachates in the form of PbSO4. Lead in the solid wastes left by the extraction was above the limit established by Brazilian legislation and these were classified as non-hazardous. Finally, secondary effluents generated after the precipitation step presented lead content more than twenty times lower than that of leachates from cupel waste. Tons of cupel waste are annually generated from gold analysis by Pb-Fire assay. Thus, the proposed method can contribute to prevent the discharge of high amounts of lead into the environment. Also, recovery of lead can help to partially meet the industrial demand for lead compounds.

Comparison between bentonite and serpentinite in the production process of iron ore pellets

Pelletizing iron ore fines is an agglomeration process that through a thermal treatment converts the ultra-fines fraction thereof into small balls ranging in size from 8mm (0.31 in.) to 18mm (0.71 in.), with adequate characteristics for feeding steel reduction works. The binder more used to make pellets is bentonite, which is an item of significant cost in the process. The present paper aims at evaluating the use of serpentinite instead of bentonite. The results obtained show that the full substitution of bentonite for serpentinite is unfeasible. However a potential does exist for using serpentinite and bentonite together in the iron ore palletizing process in the proportion of 1:1.