1,721,011 research outputs found
Antimicrobial and antioxidant amphiphilic random copolymers to address medical device-centered infections
No full textMicrobial biofilms are known to support a number of human infections, including those related to medical devices. This work is focused on the development of novel dual-function amphiphilic random copolymers to be employed as coatings for medical devices. Particularly, copolymers were obtained by polymerization of an antimicrobial cationic monomer (bearing tertiary amine) and an antioxidant and antimicrobial hydrophobic monomer (containing hydroxytyrosol, HTy). To obtain copolymers with various amphiphilic balance, different molar ratios of the two monomers were used. 1H NMR and DSC analyses evidenced that HTy aromatic rings are able to interact with each other leading to a supra-macromolecular re-arrangement and decrease the copolymer size in water. All copolymers showed good antioxidant activity and Fe2+ chelating ability. Cytotoxicity and hemolytic tests evidenced that the amphiphilic balance, cationic charge density and polymer size in solution are key determinants for polymer biocompatibility. As for the antimicrobial properties, the lowest minimal inhibitory concentration (MIC = 40 μg/mL) against Staphylococcus epidermidis was shown by the water-soluble copolymer having the highest HTy molar content (0.3). This copolymer layered onto catheter surfaces was also able to prevent staphylococcal adhesion. This approach permits not only prevention of biofilm infections but also reduction of the risk of emergence of drug-resistant bacteria. Indeed, the combination of two active compounds in the same polymer can provide a synergistic action against biofilms and suppress reactive species oxygen (ROS), known to promote the occurrence of antibiotic resistance. © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved
Raw materials recovery from spent hydrochloric acid-based galvanizing wastewater
No full textThe composition of spent hydrochloric acid-based pickling liquors, deriving from the galvanizing industry, greatly depends on how long the bath has been used for pickling. We considered solutions containing 40–50 g L−1 of iron and zinc (as FeCl2 and ZnCl2) and 130–220 g L−1 of chloride, and used tri-butyl phosphate (TBP) and di-(2-ethylhexyl) phosphoric acid (D2EHPA) in kerosene as extraction solutions. From the spent liquors, zinc was selectively extracted and then recovered from the organic phase by using water or dilute hydrochloric acid. By using the kinetic results obtained for TBP and D2EHPA, recovery selectivity of zinc over iron (αZn/Fe) was estimated to be of 16.7 and 0.5, respectively. According to the McCabe & Thiele diagram for an organic to aqueous ratio of 2, three stages of extraction are sufficient to remove about 98% of the zinc from a real solution. The remaining solution of FeCl2 can be used to recover HCl and FeSO4 through the so-called “sulphuric acid distillation”. Finally, the recovered HCl can be used as a raw material, together with limestone, to produce CaCl2. Overall, an integrated process to recover the above-mentioned raw materials (Zn salts, FeSO4·7H2O and CaCl2) is presented: all products have been obtained in a ready-to-sell form, minimizing the waste according to the strategies of the “circular economy” and the “near-zero discharge” of hazardous chemicals. © 201
Metals recovery from printed circuit boards: The pursuit of environmental and economic sustainability
No full textThe possible optimization of metal recovery from Printed Circuit Boards (PCBs) and Central Processing Units (CPUs) has been investigated. Usual practice is to primarily recover metals with the highest market price. In contrast, the present work shows how strategic considerations of the value share (%) of metals content and data regarding the environmental impact of their recovery can instruct about the best strategies to adopt, pointing at the metals to be recovered as a priority depending on the case. An accurate PCBs’ characterization carried out through microwave digestion with a mixture of HNO3, HF and HCl, is a first essential step of the procedure. Then metals are recovered through chemical leaching with different chemical substances, exploiting both chemical and physical steps. In particular, a proposal to improve environmental and economic sustainability of the PCBs’ treatment is presented, which contrary to expectations first considers the recovery of Cu, Pb and Sn by leaching with 6M HNO3, followed only later by the recovery of gold and other precious metals. Although unusual, the recovery procedure can be adapted accordingly, allowing more profits, easier management and higher metals recovery rates. Copyright © 2018, AIDIC Servizi S.r.l
Dyes Adsorption from Aqueous Solutions by Chitosan
No full textIn this study the ability of chitosan to remove acid, basic, reactive, and direct dyestuffs by adsorption was studied. The effect of several factors influencing dye adsorption such as dye concentration, grain size, pH, and temperature were investigated. Desorption of dyes at different pH was also examined. It was shown that the adsorption capacities of chitosan were comparatively high for acid and direct dyes and that the adsorption was controlled by the acidity of the solution. The kinetics of adsorption were found to be of pseudo second order. Batch isotherm studies showed that adsorption of dyes from aqueous solution by chitosan was described by the Langmuir equation. © , Copyright © Taylor & Francis Group, LLC
New trends in the synthesis of nanoparticles by green methods
No full textIn this brief survey, we deal with green processes concerning the synthesis of zerovalent nanoparticles, enlighting some aspects motivating their choice with respect to traditional techniques generally relying upon toxic or noxious reactants and stabilizing agents. After a short discussion about health and environmental safety related to the use of standard reductants, we run through several green methods for metal nanoparticle synthesis and we split them into two basic classes, according to the electropositivity of the elements which the nanoparticles are made of. This classification has been proposed in order to account for strengths and weaknesses of processes based on active substances of biological origin that, though being effective in the production of noble metal nanoparticles, proved to be much less suitable when tested in the synthesis of nanoparticles made of more electropositive elements. The goal of this work is essentially oriented to stimulating new research trends for the eco-friendly production of nanosized non-noble elements deserving more attention by current nanobiotechnology. © 2017, AIDIC Servizi S.r.l
Improved remediation processes through cost-effective estimation of soil properties from surface measurements
No full textA wide range of technologies is presently available for the remediation of contaminated soils. The optimal selection depends on a number of soil characteristics. However, if the depth of the contaminated layer is considerable, the direct measurement of these properties can be costly and sometimes outright infeasible. In this paper, a method originally developed for the early detection of leaks in landfill liners has been properly modified to accommodate the estimation of soil characteristics. In particular, while the soil properties were considered known parameters in the previous model, they are now present as non-linear parameters and their estimation constitutes the main goal of the article. The resulting algorithm consists in the optimization of a suitable objective function with respect to both linear and non-linear variables and makes it possible to estimate soil characteristics from surface measurements. In particular, it is shown that partitioning linear and non-linear variables into two different sets and regularizing the inverse problems resulting from the discretization of the Richards’ problem with unknown boundary conditions provides a robust numerical procedure. As an example, the method has been applied to the estimation of soil porosity, demonstrating its robustness and reliability potential. Including an inexpensive estimation procedure for proper soil parameters in the preliminary analysis can greatly improve the performances of remediation technologies whose convenience depends critically on the parameters selected case by case. © 2017 Elsevier Lt
Effect of MW and pH on poly(ethylene glycol) adsorption onto carbon
No full textPoly(ethylene glycol) (PEG) is a water-soluble polymer commonly found in industrial and domestic wastewaters. In this study the adsorption onto granular activated carbon (GAC) of PEG, of different molecular weights, from aqueous solutions was examined to evaluate its applicability to wastewater treatment. Batch kinetic models have been tested to predict the rate constant of adsorption. The amount of PEG adsorbed on activated carbon depends mainly on the pH, the MW and on the solution characteristics. The adsorption at fixed temperature decrease by MW (PEG-8000 < PEG-3350 < PEG-1450) a polymer chain conformation modification can explain these effect. The large values of adsorption capacity (>350 mg/g) at low and high pH values show a great potential for GAC. The adsorption process can be described well with the Langmuir and the pseudo first order equation. The effective intraparticle diffusion coefficients of PEG molecules in the GAC adsorbent varying according to the MW values in the range 8.45 × 10-3-9.71 × 10 -7. © 2013 Springer Science+Business Media New York
Antimicrobial activity of catechol functionalized-chitosan versus Staphylococcus epidermidis
No full textProtein mussel-inspired adhesive polymers, characterized by the presence of catechol groups, possess superior muco-adhesive properties and have great potentiality in wound healing. Suitable materials for wound dressing should properly combine muco-adhesiveness and antimicrobial activity. In this work, catechol-functionalized chitosan was obtained by reaction with hydrocaffeic acid (HCAF), in order to investigate how catechol introduction at different content could affect the intrinsic antimicrobial activity of the polymer itself. Unexpectedly, an enhancement of chitosan antimicrobial activity was observed after catechol functionalization, with a fourfold reduction in the polymer minimum inhibitory concentration versus Staphylococcus epidermidis. Additionally, a commercial wound dressing coated with one of the synthesized CS-HCAF derivatives showed a significant reduction in the adhesion of S. epidermidis compared to the uncoated dressing (3-log reduction). The CS-HCAF derivatives also showed an interesting antioxidant property (EC50 ranging from 20 to 60 μg/mL), which further confirms the potentiality of these materials as wound dressings. © 2017 Elsevier Lt
Antioxidant hydroxytyrosol-based polyacrylate with antimicrobial and antiadhesive activity versus Staphylococcus epidermidis
No full textThe accumulation of reactive oxygen species (ROS) in microbial biofilms has been recently recognized to play a role in promoting antibiotic resistance in biofilm-growing bacteria. ROS are also over-produced when a medical device is implanted and they can promote device susceptibility to infection or aseptic loosening. High levels of ROS seem also to be responsible for the establishment of chronic wounds. In this study, a novel antioxidant polyacrylate was synthesized and investigated in terms of antimicrobial and antibiofilm activity. The polymer possesses in side-chain hydroxytyrosol (HTy), that is a polyphenolic compound extracted from olive oil wastewaters. The obtained 60 nm in size polymer nanoparticles showed good scavenging and antibacterial activity versus a strain of Staphylococcus epidermidis. Microbial adherence assays evidenced that the hydroxytyrosol-containing polymer was able to significantly reduce bacterial adhesion compared to the control. These findings open novel perspective for a successful use of this antioxidant polymer for the prevention or treatment of biofilm-based infections as those related to medical devices or chronic wounds. © Springer International Publishing Switzerland 2015
Application of solvent extraction operation to recover rare earths from fluorescent lamps
No full textThe paper is focused on the application of solvent extraction for the recovery of rare earth elements from sulfuric leaching solutions obtained by the dissolution of fluorescent powders of lamps. The efficiency on rare earths extractions of three extractants, Cyanex 272, Cyanex 572 and D2EHPA in kerosene were investigated as a function of pH levels. Similar extraction for all the rare earths elements were observed, but the tests performed with D2EHPA showed that for pH values less than 1, yttrium and terbium could be extracted with yields higher than the other rare earths. The orders of the extraction were determined: yttrium ≥ terbium > gadolinium ≥ europium > cerium ≥ lanthanum. Further tests showed the optimal conditions, under the investigated ones, to extract yttrium with traces of terbium and cerium from sulfate leaching solutions. According to the experimental results, operating conditions of extractions were proposed in order to establish the guidelines for the following stripping and operation steps to recover rare earths selectively or at least in groups of them. A simulation of the proposed process was performed using a specific software in order to define the mass and energy balance of the entire recycling treatment of spent lamps. © 2017 Elsevier Lt
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