Luciane Pimenta Cruz Romão

Biosorption of Cr(III) using in natura and chemically treated tropical peats

The physicochemical characteristics of three Brazilian peats were investigated using elemental analysis, scanning electron microscopy (SEM), X-ray diffractometry (XRD) and studies of Cr(III) biosorption based on adsorption isotherms. Adsorption of Cr(III) by in natura peat from Santo Amaro das Brotas (Sergipe State) was much greater than by peats from either Ribeirão Preto (São Paulo State) or Itabaiana (Sergipe State), with adsorption capacities (q) of 4.90+/-0.01, 1.70+/-0.01 and 1.40+/-0.01 mg g(-1), respectively. Pre-treatments with HCl and NaOH+HCl reduced adsorption by the Santo Amaro das Brotas peat, showing that adsorption efficiency was associated with the amount of organic matter present. Conversely, increase in the mineral content following pre-treatment increased adsorption of Cr(III) by the Ribeirão Preto and Itabaiana peats. Highest adsorption (retention >95.0%) was achieved at equilibrium pH 4.0 using the Santo Amaro das Brotas peat. Experimental data for the adsorption of Cr(III) from aqueous solution onto this peat were fitted to the Langmuir equation, from which an equilibrium adsorption capacity, q(max), of 5.60 mg g(-1) was obtained, which was close to the experimentally determined value.

Environmental strategies to remove volatile aromatic fractions (BTEX) from petroleum industry wastewater using biomass.

This work investigates the potentials of peat and angico hardwood sawdust to remove BTEX (benzene, toluene, ethylbenzene, and isomers of xylene) from the produced water discharged into aquatic systems during petroleum extraction. Peat and angico sawdust samples were pyrolyzed at 500°C, and found to contain n-alkenes, n-alkanes and pentacyclic triterpenes (peat), and 4-methoxyphenol, 1,4-dimethoxyphenol and 1,3,4-trimethoxyphenol (angico sawdust). In batch experiments, the removal capacities using peat were 32.4%, 50.0%, 63.0%, 67.8%, and 61.8% for benzene, toluene, ethylbenzene, m,p-xylenes and o-xylene, respectively. This compared with removal capacities using angico sawdust of 20.2%, 36.4%, 52.8%, 57.8%, and 53.7% for these compounds respectively, demonstrating the superior performance of the peat.

Structure and properties of brazilian peat: analysis by spectroscopy and microscopy

Amostras de turfa (SAO e ITA) coletadas no Estado de Sergipe, Brasil, foram caracterizadas por diferentes tecnicas: analise termica e elementar, infravermelho, espectroscopia de ressonância magnetica nuclear de 13C (NMR), microscopia eletronica de varredura (SEM), microscopia eletronica de varredura ambiental (ESEM), difratometria de raios X (XRD) e comparadas com outras amostras de turfa (SAP) coletadas no Estado de Sao Paulo, Brasil. As razoes mais baixas O/C, E4/E6 e as curvas de analise termica diferencial (DTA) da amostra de Santo Amaro (SAO) indicaram que esta possui o mais alto grau de decomposicao. Resultados da espectroscopia na regiao do infravermelho mostraram que as amostras de Itabaiana (ITA) e Sao Paulo (SAP) apresentam pico predominante a 1086 cm-1 atribuidos a presenca de Si-O diferente da amostra de Santo Amaro (SAO). Esta mostrou dois picos intensos a 2920 cm-1 e 2850 cm-1 corroborando com dados de RMN 13C e analise termogravimetrica em que houve maior abundância dos grupos C-alquila. A difratometria de raios X (XRD) da amostra de SAO apresentou caracteristicas de material amorfo. Entretanto, as amostras de SAP e ITA revelam maior presenca de quartzo mineral. A microscopia eletronica de varredura (SEM) e a microscopia eletronica de varredura ambiental (ESEM) mostraram que a superficie das amostras de turfa possui grânulos porosos de materia orgânica. As amostras de turfa de ITA e SAP sao semelhantes enquanto a de SAO possui alto teor de materia orgânica. Apenas a amostra de SAO apresenta caracteristicas de turfa. Os resultados deste estudo mostraram que as amostras sao muito diferentes devido aos teores variaveis de material orgânico e inorgânico.

Adsorption of trihalomethanes by humin: Batch and fixed bed column studies.

The objective of the present work was to assess the performance of batch and fixed bed column systems, using humin in natura and immobilized on sodium silicate, respectively, for the adsorption of the principal trihalomethanes (THMs) found in water supply systems. Kinetically, adsorption of THMs by humin follows a pseudo-second order reaction, with more than 50% removal in the first 5min for all compounds studied, and equilibrium described by the Freundlich model reached in 240min. The THM adsorption results were significant at p<0.05 for both batch (74.6-83.2% removal) and column (99.7% removal in optimized tests) experiments, and were significantly (p<0.05) influenced by flow rate and bed height. The work demonstrates the potential of humin for removal of THMs.

Distribuição de metais e caracterização das constantes de troca entre espécies metálicas e frações húmicas aquáticas de diferentes tamanhos moleculares

In this work the metal distribution and exchange constants between metal species and aquatic humic fractions with different molecular sizes were studied. The aquatic humic substances (AHS) were extracted by XAD-8 resin from water sample collected from Itapitangui river, Sao Paulo State, Brazil. The AHS were fractionated in six fractions with different molecular sizes (>100 - <5 kDa) and characterized by several techniques. Molar ratios H/C suggested higher aromaticity for fractions F1 and F6 whereas molar ratios C/N didn´t show any differences regarding the humification degree between the fractions. The UV-Vis absorbance a254/a436 ratio showed higher results for F4 and F5, probably by less condensed features. FTIR studies showed high similarity in the functional groups in the fractions. The highest percentage of traces of Co, Al, Fe, Mn, Cu, Zn and Ni (determined by ICP-AES) was preferably complexed by fractions F3 and F4 with a greater amount of dissolved organic carbon (DOC). In addition, the exchange constants, determined by ultrafiltration method, showed complexes AHS-Fe and AHS-Al with higher stability than complexes AHS-Co in all fractions.

A new functionalized MCM-41 mesoporous material for use in environmental applications

Este trabalho descreve a sintese e caracterizacao de um novo adsorvente mesoporoso que consiste o MCM-41 funcionalizado com o acido p-aminobenzoico modificado (PABA-Si). A sintese foi realizada pelo metodo hidrotermal/co-condensacao. O PABA-MCM-41 foi caracterizado usando FTIR, SAXS, adsorcao/desorcao de N2, MEV e TG. Os experimentos em batelada foram utilizados para determinar os efeitos da concentracao inicial do adsorbato, tempo de contato e temperatura. A adsorcao do benzo[a]pireno (B[a]P) alcancou o equilibrio depois de 90 min (qe = 27,2 µg g-1) e concentracoes mais altas do adsorbato foram associadas com o aumento, em ambos, da percentagem de remocao (71,0-95,7%) e no valor de qe (20,1-27,1 µg g-1). A adsorcao seguiu o modelo cinetico de pseudo-segunda ordem, e se ajustou ao modelo de isoterma de Langmuir. Foi verificado em temperaturas mais altas um aumento na taxa inicial de adsorcao e na constante cinetica. Os parâmetros termodinâmicos indicaram que o processo foi espontâneo, endotermico e com uma tendencia para desordem.

Recycling of chromium wastes from the tanning industry to produce ceramic nanopigments

Growth in the use of colored ceramics and the demand for better quality have stimulated research into the development of new classes of pigments with superior durability and color reproducibility, which can be produced using inexpensive, straightforward, and eco-friendly synthesis procedures. The present work proposes a modified sol–gel route for the production of green and pink Cr–Al2O3 nanoparticles, employing solid and liquid tannery wastes together with NOM-rich water. The synthesis involved preparing a solution of Al2Cl3 and the wastes in NOM-rich water. The solution was kept under stirring to form a gel that was then heated to 100 °C in order to eliminate water. This material was subsequently homogenized and calcined. The results indicated that single phase chromium-doped α-alumina could be obtained using an initial solution pH of 4.0 and calcination at 1100 °C for 4 h. Colorimetric analysis of the pigments was performed according to the CIE 1976 L*a*b* norm. The results revealed a strong dependence of pigment color on the dopant concentration and pH used in the synthesis. The presence of the Cr3+ oxidation state in all the samples studied was confirmed using X-ray absorption near-edge structure (XANES) spectroscopy. The particle size of the samples was 39 ± 1 nm, as determined by FEG-SEM measurements. The catalytic tests demonstrated the potential of tannery wastes for use in the catalytic reduction of nitrophenol, with conversion rates between 49 and 98%. It could be concluded that the proposed route was effective for the production of α-alumina pigments and catalysts using tannery wastes, offering important technological and environmental advantages.

Green synthesis of a magnetic hybrid adsorbent (CoFe2O4/NOM): Removal of chromium from industrial effluent and evaluation of the catalytic potential of recovered chromium ions

This work describes the removal of chromium ions from industrial effluent using a hybrid magnetic adsorbent, CoFe2O4/NOM, synthesized using water rich in natural organic matter. The hybrid obtained at ambient temperature (HbAmb) was calcined at 200, 400, and 800°C for 2h, and formation of the cobalt ferrite phase was confirmed by XRD, which indicated the presence of NOM in the structure of the material. Removal tests showed that HbAmb provided efficient removal of chromium at the natural pH of the effluent, while the other materials were effective at pH 6. Evaluation of the kinetics showed excellent performance of the process, with 70-87% removal in 20min, which provided a high degree of flexibility. The hybrid showed high removal during five reuse cycles, ranging from 96% in the first cycle to 82% in the final. The matrices containing the saturated adsorbent (HbAmb_Sat) and recovered chromium ions (CrD) showed high performance in the catalytic reduction of 4-nitrophenol, with conversion rates of 99.9% in short periods of time, as well as excellent potential for reuse in three cycles. The results demonstrated that the production of a technological material and its use for remediation could be achieved in an ecologically sustainable manner.

A green strategy for desorption of trihalomethanes adsorbed by humin and reuse of the fixed bed column

The objective of the present work was to develop a thermal desorption method for the removal of trihalomethanes (THM) adsorbed by humin, followed by multiple recycling of the fixed bed column in order to avoid excessive consumption of materials and reduce operating costs. The results obtained for adsorption on a fixed bed column confirmed the effectiveness of humin as an adsorbent, extracting between 45.9% and 90.1% of the total THM (TTHM). In none of the tests was the column fully saturated after 10h. Experiments involving thermal desorption were used to evaluate the potential of the technique for column regeneration. The adsorptive capacity of the humin bed increased significantly (p<0.05) between the first and fifth desorption cycle, by 18.9%, 18.1%, 24.2%, 20.2% and 24.2% for CHBr(3), CHBr(2)Cl, CHBrCl(2), CHCl(3) and TTHM, respectively.

Thermal decomposition kinetics of humic substances extracted from mid-Rio Negro (Amazon Basin) soil samples

In this work humic substances (HS) extracted from non-flooded (Araca) and flooded (Iara) soils were characterized through the calculation of stability and activation energies associated with the dehydration and thermal decomposition of HS using TGA and DTA, electronic paramagnetic resonance and C/H, C/N and C/O atomic ratios. For HS extracted from flooded soils, there was evidence for the influence of humidity on the organic matter humification process. Observations of thermal behaviour, with elemental analysis, indicated the presence of fossilized organic carbon within clay particles, which only decomposed above 800 oC. This characteristic could explain the different thermal stability and pyrolysis activation energies for Iara HS compared to Araca HS.