Search results for "Chemical engineering"
showing 10 items of 5892 documents
Novel pathways for the preparation of mesoporous MCM-41 materials: control of porosity and morphology
1999
Two novel synthesis routes for the preparation of mesoporous MCM-41 materials are introduced. Both methods use tetra-n-alkoxysilanes such as tetraethoxysilane (TEOS) or tetra-n-propoxysilane (TPS) as a silica source which are added to an aqueous solution of a cationic surfactant in the presence of ammonia as catalyst. In this study, n-alkyltrimethylammonium bromides and n-alkylpyridinium chlorides were employed as templates. The addition of an alcohol (e.g. ethanol or isopropanol) leads to a homogeneous system which allows the formation of spherical MCM-41 particles. The main advantages of these methods are short reaction times, excellent reproducibility and easy preparation of large batche…
Protein aggregation induced by phase separation in a pea proteins–sodium alginate–water ternary system
2012
Abstract The physicochemical properties of a native, globular plant protein–linear anionic polysaccharide aqueous system at 20 °C were investigated in conditions where biopolymers carry a net negative charge (pH 7.2, 0.1 M NaCl). The pea proteins–sodium alginate mixtures showed a phase separation mainly by thermodynamic incompatibility, characterized at both the macroscopic and microscopic scale. Phase diagram was established and confocal laser scanning microscopy (CLSM) provided accurate data on the microstructure morphology of the system, regarding its phase behavior. In admixture, sodium alginate induced a protein aggregation, certainly by a local depletion of the polysaccharide. Protein…
Removal of drugs in aqueous systens by photoassisted degradation
2005
Aqueous solutions of tetracycline, lincomycin and ranitidine were irradiated with UV light in homogeneous and heterogeneous systems. Two commercial polycrystalline TiO2 powders (Degussa P25 and Merck) were used as photocatalysts. After 5A h, an appreciable photolytic degradation of tetracycline and ranitidine was observed while the degradation of lincomycin was noticeably lower. As far as the mineralization is concerned, a small decrease of the TOC values was measured in the case of tetracycline whereas negligible variations were found for lincomycin or ranitidine. The presence of the photocatalysts greatly enhanced the degradation rates of the drugs with respect to those observed during th…
Study of separation of water + 2-propanol mixture using different ionic liquids: 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide or 1-b…
2018
Abstract The liquid–liquid equilibria data of water (1) + 2-propanol (2) + [bmim][Tf2N] (3) and water (1) + 2-propanol (2) + [bmp][Tf2N] (3) at 283.2, 303.2 and 323.2 K and atmospheric pressure were measured with the objective of understanding the behavior of these two systems and to try to improve the extraction of 2-propanol from water from economical and environmental points of view. The thermodynamic parameters were determined using the non-random two-liquid (NRTL) and universal quasichemical (UNIQUAC) models, and excellent results were achieved in both cases (the maximum root-mean-square deviation was 0.433%). Lastly, the capability of the two ionic liquids to separate 2-propanol from …
Measurement and correlation of liquid-liquid equilibria at different temperatures in water + 1-propanol + 1-ethyl-3-methylimidazolium bis(trifluorome…
2016
Abstract In order to reduce the environmental impact and the economical costs of the separation of 1-propanol from aqueous mixtures, which enables the recycling of the alcohol, the experimental liquid-liquid equilibria (LLE) data of water (1) + 1-propanol (2) + 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf2N]) (3) and water (1) + 1-propanol (2) + 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([hmim][Tf2N]) (3) systems were measured in this work at different temperatures: 283.2, 303.2 and 323.2 K at atmospheric pressure. The results were correlated by non-random two-liquid (NRTL) and universal quasichemical (UNIQUAC) models with good results in both…
Biosorption lead(II) and nikel(II) from an aqueous solution by bacterial biomass
2010
Biosorption lead(II) and nikel(II) from an aqueous solution by bacterial biomass The optimum conditions for biosorption of Pb(II) and Ni(II) from aqueous solution were investigated, by using living and nonliving Pseudomonas fluorescens and Bacillus pumilus isolated from wastewater treatment plant. It was found that the optimum pH for Pb(II) removal by living and nonliving cells was 6.0, while 7.0 for Ni(II) removal. At the optimal conditions, metal ion biosorption was increased as the initial metal concentration increased. The binding capacity by living cells is significantly higher than that of nonliving cells at tested conditions. The maximum biosorption capacities for lead and nickel by …
Arsenic(III) Removal at Low Concentrations by Biosorption usingPhanerochaete chrysosporiumPellets
2013
As(III) removal from dilute aqueous solutions by biosorption onto pellets of the white rot fungus Phanerochaete chrysosporium was investigated. The As(III) uptake capacity was evaluated at low initial concentrations (0.2–1 mg/L) which revealed that the P. chrysosporium pellets were only slightly less efficient than the well studied adsorbent granular ferric hydroxide. Moreover, its performance was much more superior compared to anaerobic granular sludge, another cheaply available bacterial biosorbent. In the studied pH (5–9) and biomass concentration (0.25–1.5 g/L wet weight basis) ranges, no large differences in As(III) removal efficiency were observed. The influence of different ions, com…
Fixed‐Bed Removal of Free and Complexed Ni from Synthetic and Industrial Aqueous Solutions
2008
Abstract This paper evaluates the application of several biosorbents for Ni removal from aqueous solutions in the absence and in the presence of EDTA. Fixed bed experiments were performed (Ni influent concentration, 2 mg dm−3; EDTA doses, 0, 5, and 10 mg dm−3; pH=7) to study the process feasibility as refining after conventional physicochemical treatment. In absence of EDTA, uptake capacity followed the order peat > Posidonia oceanica > chitosan > chitin ≫ Scharlau AC. Maximum uptakes of 8.95 mg g−1 and 5.10 mg g−1 were found for peat and Posidonia oceanica, respectively. In the presence of EDTA, removal capacity decreased for all biosorbents; Ni was detected in the effluent from the beginn…
Halogen-containing BODIPY derivatives for photodynamic therapy
2019
Abstract Two iodinated (1 and 2) and two brominated (3 and 4) BODIPY-based photosensitizers are prepared and characterized using slightly modified synthetic procedures previously described. 1–4 present intense absorption bands in the 510–540 nm interval and very weak emissions due to the presence of halogen atoms in their structure. Irradiation of aqueous solutions of 1–4 with visible light (wavelength > 475 nm) induce the generation of singlet oxygen with quantum yields of ca. 0.62–0.66 for the photosensitizers containing iodine atoms (1 and 2) and of ca. 0.16–0.21 for the brominated counterparts (3 and 4). In vitro studies carried out with HeLa, SCC-13 and HaCaT cell lines and the four ph…
Some working principles of heterogeneous photocatalysis by semiconductors
1993
The present paper outlines some of the principles which are the working base for the photocatalytic processes: we refer to those photocatalytic processes performed using irradiated semiconductors. The steps related to the photoproduction of electron-hole pairs and their separation are discussed. It is also shown how the step of pair separation induces the formation of various chemical species, some of which are useful for the oxidation reactions. It is also shown that in order to reach a detailed description of photocatalytic processes it is necessary to have the knowledge of both the electronic and the physicochemical features of the semiconductors. The paper finally reports a case study r…