An evaluation into the potential of biological processing for the removal of metals from sewage sludges

The use of sewage sludge in agricultural land as a means of sludge disposal and recycling has been shown to be economical and suitable because of the presence of nutrients such as nitrogen and phosphorus. However, municipal sludges often contain high quantities of toxic metals and other compounds that must be removed for its safe use in agricultural soils. The biological leaching of metals from sewage sludges has been shown to be a promising technique for metal detoxifying in such complex matrix. The process efficiency is dependent on several physico-chemical parameters, such as total solids concentration, metal forms, pH-ORP, and temperature. Scale-up of the process has not yet been defined and is still pursuing the correct operational design. Current research involving the bioleaching of metals from sewage sludge and its application to land, which affects soil physical properties, are presented and discussed.

Small-angle X-ray and nuclear-magnetic resonance study of siloxane-PMMA hybrids prepared by the sol-gel process

Transparent siloxane-polymethylmethacrylate (PMMA) hybrids were synthesized by the sol-gel process through hydrolysis of methacryloxyproyltrimethoxysilane (TMSM), tetramethoxysilane (TMOS) and polymerization of methylmethacrylate (MMA) using benzol peroxide (BPO) as catalyst. These composites have a good chemical stability due to the presence of covalent bonds between the inorganic (siloxane) and organic (PMMA) phases. The effects of siloxane content, pH of the initial sol and BPO content on the structure of the dried gels were analyzed by small-angle X-ray scattering (SAXS). SAXS results revealed the presence of an interference (or correlation) peak at medium q-range for all compositions, suggesting that siloxane groups located at the ends of PMMA chains form isolated clusters that are spatially correlated. The average intercluster distance - estimated from the q-value corresponding to the maximum in SAXS spectra - decreases for samples prepared with increasing amount of TMSM-TMOS. This effect was assigned to the expected increase in the number density of siloxane groups for progressively higher siloxane content. The increase of BPO content promotes a more efficient polymerization of MMA monomers but has no noticeable effect on the average intercluster distance. High pH favors polycondensation reactions between silicon species of both TMOS and TMSM silicon alcoxides, leading to a structure in which all siloxane clusters are bonded to PMMA chains. This effect was confirmed by Si-29 nuclear-magnetic resonance (NMR) measurements.

Simultaneous solidification of two catalyst wastes and their effect on the early stages of cement hydration

Two catalyst wastes (RNi and RAI) from polyol production were considered as hazardous, due to their respective high concentration of nickel and aluminum contents. This article presents the study, done to avoid environmental impacts, of the simultaneous solidification/stabilization of both catalyst wastes with type II Portland cement (CP) by non-conventional differential thermal analysis (NCDTA). This technique allows one to monitor the initial stages of cement hydration to evaluate the accelerating and/or retarding effects on the process due to the presence of the wastes and to identify the steps where the changes occur. Pastes with water/cement ratio equal to 0.5 were prepared, into which different amounts of each waste were added. NCDTA has the same basic principle of Differential Thermal Analysis (DTA), but differs in the fact that there is no external heating or cooling system as in the case of DTA. The thermal effects of the cement paste hydration with and without waste presence were evaluated from the energy released during the process in real time by acquiring the temperature data of the sample and reference using thermistors with 0.03 A degrees C resolution, coupled to an analog-digital interface. In the early stages of cement hydration retarding and accelerating effects occur, respectively due to RNi and RAl presence, with significant thermal effects. During the simultaneous use of the two waste catalysts for their stabilization process by solidification in cement, there is a synergic resulting effect, which allows better hydration operating conditions than when each waste is solidified separately. Thermogravimetric (TG) and derivative thermogravimetric analysis (DTG) of 4 and 24 h pastes allow a quantitative information about the main cement hydrated phases and confirm the same accelerating or retarding effects due to the presence of wastes indicated from respective NCDTA curves.

Structural refinement, growth process, photoluminescence and photocatalytic properties of (Ba1-xPr2x/3)WO4 crystals synthesized by the coprecipitation method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cinética da remoção dos extrativos da madeira de Eucalyptus grandis durante polpação Kraft

Kinetics of the removal of Eucalyptus grandis wood extractives during Kraft pulping. The objective of this work was to study the kinetics of the removal of Eucalyptus grandis wood extractives during Kraft pulping. The pulping was done in steel tubular reactors using wood saw under the following conditions: active alkali = 14%, sulfidity = 25%; liquor-to-wood ratio = 10 L kg(-1) of dry wood; and temperatures of 130, 150, 160 and 180 C during 30, 60, 90, 120, 150 and 180 minutes. After pulping, analyses were conducted of the yield and extractives in residue (pulp and reject). Total extractives (ethyl alcohol-toluene (1:2), ethyl alcohol and hot water, respectively) and soluble extractives in acetone were analyzed. The results showed that most extractives are degraded in the first 30 minutes of the pulping process. It was observed that the removal occurs in two different stages: the first is rapid, where the majority of the extractives are removed, and the last is slow, where few extractives are removed.

Degradation of the antibiotic amoxicillin by photo-Fenton process - Chemical and toxicological assessment

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Advanced ceramics: Evaluation of the mechanism of stock removal and ground surface quality

The aim of this work is to evaluate the mechanism of stock removal and the ground surface quality of advanced ceramics grounded by a plane tangential grinding process with diamond grinding wheels. The analysis of the grinding performance was done regarding the cutting surface wear behavior of the grinding wheel for ceramic workpieces. The discussion about the results emphasized the wear mechanism of the grinding wheel cutting surface and the cutting phenomenology of the grinding process. The grounded surface was evaluated using Scanning Electron Microscopy (SEM). © 1999 Society of Automotive Engineers, Inc.

Advanced ceramics: Evaluation of the mechanism of stock removal and ground surface quality

The aim of this work is to evaluate the mechanism of stock removal and the ground surface quality of advanced ceramics machined by a surface grinding process using diamond grinding wheels. The analysis of the grinding performance was done regarding the cutting surface wear behavior of the grinding wheel for ceramic workpieces. The ground surface was evaluated using Scanning Electron Microscopy (SEM). As a result it can be said that the mechanism of material removal in the grinding of ceramic is largely one of brittle fracture. The increase of the hmax can reduce the tangential force required by the process. Although, it results in an increase in the surface damage, reducing the mechanical properties of the ground component.

Solar photodegradation of dichloroacetic acid and 2,4-dichlorophenol using an enhanced photo-Fenton process

The photo-Fenton process using potassium ferrioxalate as a mediator was investigated for the photodegradation of dichloracetic acid (DCA) and 2,4-dichlorophenol (DCP) in aqueous medium using solar light as source of irradiation. The influence of the solution depth, the light intensity and the effect of stirring the solution during irradiation process were evaluated using DCA as a model compound. A negligible influence of stirring the solution was observed when the concentration of ferrioxalate (FeOx) was 0.8 mM and solution depth was 4.5 or 14 cm. The optimum FeOx concentration determined for solution depths between 4.5 and 14 cm was 0.8 mM considering total organic carbon (TOC) removal during DCA irradiation. The high efficiency of the photo-Fenton process was demonstrated on summer days, when only 10 min of exposition (around noon) were sufficient to completely destroy the organic carbon of a 1.0 mM DCA solution in the presence of 0.8 mM FeOx and 6.0 mM H2O2 using a solution depth of 4.5 cm. It was observed that the photodegradation efficiency increases linearly with the solar light intensity up to values around 15 Wm-2 but this linear relationship does not hold above this value showing a square root dependence. The photodegradation of a solution of DCP/FeOx showed a lower TOC removal rate than that observed for DCA/FeOx, achieving ∼90% after 35 min irradiation under 19 Wm-2, while under this light intensity, the same TOC removal of DCA/FeOx was achieved in only 10 min irradiation. © 2002 Elsevier Science Ltd. All rights reserved.

Behavior of bromide in the photoelectrocatalytic process and bromine generation using nanoporous titanium dioxide thin-film electrodes

In this study, the photoelectrocatalytic behavior of bromide and generation of bromine using TiO2 was investigated in the separate anode and cathode reaction chambers. Our results show that the generation of bromine begins around a flatband potential of -0.34 V vs. standard calomel electrode (SCE) at pH 3.0 under UV illumination and increases with an increase in positive potential, finally reaching a steady-state concentration at 1.0 V vs. SCE. Maximum bromine formation occurs over the range of pH 4-6, decreasing sharply at conditions where the pH > 7. © 2003 Elsevier Ltd. All rights reserved.

Polishing of water treated by a biological process with heterogeneous photocatalysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A photoelectrocatalytic process that disinfects water contaminated with Mycobacterium kansasii and Mycobacterium avium

Nontuberculous mycobacteria are resistant to conventional water treatment; indeed, they have been recovered from a wide variety of environmental sources. Here, we applied the photoelectrocatalytic technique using a Ti/TiO2-Ag photoanode to inactivate mycobacteria. For a mycobacteria population of 5 × 108 CFU mL-1, we achieved 99.9 and 99.8% inactivation of Mycobacterium kansasii and Mycobacterium avium with rate constant of 6.2 × 10-3 and 4.2 × 10-3 min-1, respectively, after 240 min. We compared the proposed method with the photolytic and photocatalytic methods. Using a mycobacteria population of 7.5 × 104 CFU mL-1, the proposed Ti/TiO2-Ag photoanode elicited total mycobacteria inactivation within 3 min of treatment; the presence of Ag nanoparticles in the electrode provided 1.5 larger degradation rate constant as compared with the Ti/TiO2 anode (1.75 × 10-2 for M. kansassi and 1.98 × 10-2 for M. avium). We monitored the degradation of the metabolites released during cellular lysis by TOC removal, sugar release, chromatography, and mass spectrometry measurements; photoelectrocatalysis and Ti/TiO2-Ag photoanodes furnished the best results. © 2013 Elsevier Ltd. All rights reserved.

Decoration of Ti/TiO2 Nanotubes with Pt Nanoparticles for Enhanced UV-Vis Light Absorption in Photoelectrocatalytic Process

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Monitoring scaling and dental calculus removal with an optical fluorescence system

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Multi-scale structural and chemical analysis of sugarcane bagasse in the process of sequential acid-base pretreatment and ethanol production by Scheffersomyces shehatae and Saccharomyces cerevisiae

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)