Adsorption of Cr(VI) onto crosslinked chitosan microbeads - new kinetic and thermodynamic correlations using continuous isothermal microcalorimetry

The synthesis and characterization of crosslinked chitosan microbeads and their application in the removal of Cr(VI) are described. New kinetic and thermodynamic parameters of Cr(VI) adsorptions processes were found using continuous isothermal calorimetry. All adsorption processes are exothermic in nature. However, a multivariate statistical analysis have pointed out that adsorption enthalpies were affected by important binary interactions of the initial Cr(VI) in solution and temperature. The adsorption energetic data were well fitted to a kinetic exponential model, which have indicated fractionary adsorption kinetic orders

The interaction of a naturally occurring membranous collagen with high-saline dye solutions – mechanistic features from unusual multi-step biosorption

It is known that wastewaters containing dyes are very difficult to treat, since many dyes are stable and recalcitrantmolecules. In this way, sorption may suitable for effectively remove dyes in this specific application field.In this work, a first approach for using polymeric membranous collagen of fish scales for sorption of salinemethylene blue dye (MB) solution found in subsurface procedures of oil well industry. From structural characterization,the sorbent was found to be a composite of fibrillar type I collagen and apatites. The MB sorptionamounts decreased with temperature increasing, with maximum MB sorbed of 2.18 mmol g-1 at 25 0C. In mostsorption tests, residual MB in saline water was undetectable within 200 min of contact time. The sorption kineticdata were well adjusted to a three-parameter multi-step exponential function. The good fitting of such functionwere only obtained taking into account the presence of time-dependent kinetic parameters. The proposed multistepsorption mechanism involved surface interaction and diffusion of MB into the membranous collagen. Theinteraction of positively charged MB ions with the collagenous adsorbent occurred through electrostatic forces.The results point out the collagenous adsorbent for effective procedures of sorption of MB dyes from high-salinewastewaters.Keywords: Biosorption; membranous adsorbents; high-saline water; multi-step kinetics; oil well

Chemical modification of in natura collagen by acidic catalysis – structural characterization and mechanistic features of Cd(II) sorption by solution microcalorimetry

Chemically-modified in natura collage was prepared under acidic catalysis for using in sorption of Cd(II)from aqueous solutions. Simultaneous determination of the quantity and energetic parameters of Cd(II) sorptionon PGA-scale at pH 8.0 were determined using solution microcalorimetry (SM). The calorimetric enthalpiesof Cd(II) sorption on PGA-scale are all exothermic, and Cd(II) adsorption energies decrease as temperatureincreases. The maximum sorption capacity of PGA-scale for Cd(II) (438 μmol g-1) is superior withmany sorption data reported in the literature. Characterization and SM indicate that the main sites for Cd(II)sorption are located in the collagen structure of PGA-scale. It was found that the interactions PGAscale/Cd(II) are mainly due to chemisorption and diffusion may occur at the PGA-scale/Cd(II) interface. Theresults of this study underline the good features of PGA-scale as a promising material for sorption of Cd(II)from aqueous media.Keywords: Cadmium; biosorbents; fish scales; acidic catalysis; solution microcalorimetry; thermodynamics

A new cement slurry modified with chitosan/alginate interpenetrating networks and hydroxyapatite -- structural characteristics after long-term contact with hyper-saline produced water from oil well operations

Oil is an important source of energy, mainly in developing countries. Important research has been conductedto find cementing procedures that guarantee safe and cost-effective oil exploration below pre-salt layers. Thiswork aimed to make a new cement paste with cement, seawater, silica, biopolymers (chitosan and sodiumalginate) and hydroxyapatite (HA), found in nature. For comparison purposes, slurry without additives wasprepared and characterized. The HA used was extracted from fish scales (Cynoscion acoupa) in optimizedcondition NaOH concentration, temperature and reaction time. Both slurry were prepared with ratioswater/cement (w/c) and silica/cement (s/c) equal to 0.50 and 0.35, respectively. The new cement slurry wasobtained with proportions of 5% of each biopolymer and HA with respect to the total weight of the cement.In the immersion tests, specimens were immersed in samples of hyper production of saline water by 35°C for15 days. Thereafter, they were washed, dried and its surface layers were scraped. Before, the resultingmaterials were characterized. The values of the ratios Ca/Si of new cement slurry (3.38 À 0.06) were superiorcompared to standard (2.58 À 0.05). The new slurry had high thermal stability and low amounts of smallcrystallite-type portlandite (35.70 nm). Conversely, a slurry standard formed larger crystals of about 50.3 nm.Significantly, after continuous long-term contact of both slurries with hyper-saline produced water from oilwell fields operations, in comparison with standard slurry structural characteristics, the new slurry haspractically maintained its pristine chemical structure, as well as has shown crystallite-type particles of NaCland Friedel's/Kuzel's salts with lower proportion. The presence of the biopolymers and HA has driven theimproved the self-healing properties observed in the new cement slurry. In this first study, the new slurry hasshown adequate characteristics to contribute to cost effective and environmental-friendly oil well operations

The influence of low amounts on in situ-polymerized bisphenol-diamine net in cement slurries prepared in seawater – structural analysis after long-term contact with in situ-generated mud-acid fracturing fluid

Inadequate zonal isolation in oil wells can provoke safety and environmental problems. New cement slurries can avoid such problems. In this work, novel cement slurries were prepared in the presence of seawater with in situ-formed epoxy resin–ethylenediamine. The new slurries were tested in relation to their mechanical properties and characterized by FTIR, XRD, TG/DTG, porosimetry by N2 adsorption-desorption and solidstate 29Si and 27Al NMR. Some kinetic features of long-term contact of the slurries with in situ-generated mud-acid were performed to evaluate the performances of the new slurries in routine acidizing procedures in oil well industry. The experimental kinetic data were well fitted to order-variable exponential kinetic model and a factorial design of four variables (24). In these studies, it was possible to evaluate in detail how some important experimental factors act on the quantities of acid that interact with the pastes, as well as to verify how these factors affect the speed with which the mud-acid interacts with the slurries. The results strongly suggest that the interactions occurred at epoxy/ethylenediamine cement slurry/mud-acid interfaces are due to surface reactions with preservation of the chemical structures of the cement slurries, even after long-term contact with mud-acid. The new cement slurry present good features to be used in environmental-friendly procedures in oil well field. Keywords: Epoxidized bisphenols; cement slurries; characterization of oil well materials; kinetic modeling; Multivariate analysi

Sintese e caracterização de silica mercapto e mercapto oxidado : quimissorção de cations divalentes e aminas primarias

Orientador : Claudio AiroldiDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de QuimicaMestrad

Imobilização de diaminas com cadeias longas pelo processo sol-gel e estudos de suas interações com cations metalicos

Orientador: Claudio AiroldiTese (doutorado) - Universidade Estadual de Campinas, Instituto de QuimicaDoutorad

Influência de pequenas quantidades do bisfenol-diamina polimerizado in situ em pastas de cimento preparadas com água do mar-análise estrutural após longo tempo de contato com fluído de fraturamento mud acid gerado in situ

International audienceInadequate zonal isolation in oil wells can provoke safety and environmental problems. New cement slurries can avoid such problems. In this work, novel cement slurries were prepared in the presence of seawater with in situ-formed epoxy resin–ethylenediamine. The new slurries were tested in relation to their mechanical properties and characterized by FTIR, XRD, TG/DTG, porosimetry by N2 adsorption-desorption and solid-state 29Si and 27Al NMR. Some kinetic features of long-term contact of the slurries with in situ-generated mud-acid were performed to evaluate the performances of the new slurries in routine acidizing procedures in oil well industry. The experimental kinetic data were well fitted to order-variable exponential kinetic model and a factorial design of four variables (24). In these studies, it was possible to evaluate in detail how some important experimental factors act on the quantities of acid that interact with the pastes, as well as to verify how these factors affect the speed with which the mud-acid interacts with the slurries. The results strongly suggest that the interactions occurred at epoxy/ethylenediamine cement slurry/mud-acid interfaces are due to surface reactions with preservation of the chemical structures of the cement slurries, even after long-term contact with mud-acid. The new cement slurry present good features to be used in environmental-friendly procedures in oil well field.O isolamento zonal inadequado em poços de petróleo pode provocar problemas de segurança e ambientais. Novas pastas de cimento podem evitar esses problemas. Neste trabalho, novas pastas de cimento foram pre-paradas na presença de água do mar com resina epóxi-etilenodiamina formada in situ. As novas pastas foram testadas em relação às suas propriedades mecânicas e caracterizadas por FTIR, DRX, TG / DTG, porosime-tria por adsorção-dessorção de N2e RMN de 29Si e de 27Al no estado sólido. Algumas características cinéticas do longo tempo de contato das pastas com o mud acidgerado in situforam realizadas para avaliar o desempenho das novas pastas nos procedimentos rotineiros de acidificação na indústria de poços de petróleo. Os dados cinéticos experimentais foram bem ajustados ao modelo cinético exponencial de ordem variável e ao planejamento fatorial de quatro variáveis (24). Nesses estudos, foi possível avaliar detalhadamente como al-guns fatores experimentais importantes atuam sobre asquantidades de ácido que interagem com as pastas, bem como verificar como esses fatores afetam a velocidade com a qual o mud acidinterage com as pastas. Os resultados sugerem fortemente que as interações ocorridas nas interfaces da pasta de cimento epoxi/ eti-lenodiamina / mud acid são devidas a reações de superfície com preservação das estruturas químicas das pas-tas de cimento, mesmo após contato prolongado com mud acid. A nova pasta de cimento apresenta boas características para ser usada em procedimentos nos poços de petróleo