Raimundo N. Damasceno

The chemistry of Co2+ interaction with calcite and aragonite surfaces☆

Abstract Co2+ adsorbs on both calcite and aragonite surfaces, but has a much higher affinity for calcite. The adsorption of Co2+ from dilute solutions onto calcite indicates that after extended periods (> 500 min.) of reaction a near-surface coprecipitate may form, but no evidence was observed for the formation of a distinct CoCO3 surface phase, even at Co2+ concentrations to ∼ 100 times supersaturation for CoCO3. This behavior is similar to that observed in dilute solutions for Cu2+, but differs from that of Mn2+ and Cd2+ where distinct MnCO3 and CdCO3 phases have been observed. Ca2+ and Mg2+ compete with Co2+ for calcite adsorption sites. Also, the ratio of dissolved to adsorbed Co2+ changes in a nonlinear manner over a wide range of concentrations for adsorption on both calcite and aragonite. Thus, carbonate mineralogy, Co2+ concentration, and solution composition all can influence the adsorption of Co2+ on CaCO3.

Low temperature conversion of some Brazilian municipal and industrial sludges

Abstract Three Brazilian municipal and industrial sludges were subjected to the Low Temperature Conversion (LTC) process. They include activated, digested and lacquer sludges. The activated sludge recorded the highest yield of LTC oil (31.4%), followed by lacquer sludge (14.0%) and the digested sludge 11%. 1 H-NMR studies of the oils indicated that they consisted mainly of aliphatic and olefinic compounds, while the concentration of aromatics was below 2.5%. The major hydrocarbons in the oils were pentadecane and heptadecane. The distribution pattern of hydrocarbons present in the oils was similar to what is known from the conversion of other sludges. In addition the LTC oil from activated sludge contained 26% fatty acids, while the oils from digested and lacquer sludge contained only about 3% fatty acids. Recovery studies on the fate of heavy metals in the sludges indicated that they were accumulated in the char. Partial gasification studies of the LTC chars resulted in active carbons with quite low iodine and methylene blue numbers. However, even if their use is limited the production of active carbon together with the recovery of LTC oil constitutes a complete disposal of the sludges.

Low temperature conversion (LTC)--an alternative method to treat sludge generated in an industrial wastewater treatment station--batch and continuous process comparison.

In this work low temperature conversion (LTC) process was applied in a dried sludge from a petrochemical industry wastewater treatment station located in Rio de Janeiro, Brazil. The process was performed in two modes: continuous and batch-scale. This process produced a pyrolysis oil (continuous 14%; batch-scale 40% yield); pyrolytic char (continuous 46%; batch-scale 56% yield); gas and water. Pyrolysis oil fraction was analyzed by gas chromatographic mass spectrometry (GCMS) and the main components identified were toluene, ethylbenzene, styrene, isopropyl benzene, alpha-methylstyrene, butanenitrile and 1,3- biphenyl propane. Metals content, sulfur content and calorific value have been determined for the pyrolysis oil fraction. The results showed that the pyrolysis oil obtained could be used for industrial purposes and/or as energetic matrix.

Fractions composition study of the pyrolysis oil obtained from sewage sludge treatment plant

In this work the parameters of Low Temperature Conversion--LTC were applied in a centrifuged sludge from a sewage treatment plant located in Rio de Janeiro, Brazil. Before the conversion, the sludge was dried and analyzed by TGA to observe its behavior with increasing temperature. The chemical composition of the crude pyrolysis oil was analyzed by FTIR, 1H NMR and GC-MS. The results showed that the oil is a mixture of hydrocarbons, oxygenated and nitrogenated compounds. Using a catalytic treatment it was possible to fractionate the oil where the predominant constituents were hydrocarbons showing that the cracking was effective. An important result was the difference between the calorific value of dry sludge (10 MJ kg(-1)), the pyrolysis oil (36 MJ kg(-1)) and one of the fractions separated by catalytic cracking (40 MJ kg(-1)) when compared with commercial diesel (45 MJ kg(-1)).