Search results for "Polymers."
showing 10 items of 3543 documents
Microbial production and recovery of hybrid biopolymers from wastes for industrial applications- a review
2021
Abstract Agro-industrial wastes to be a global concern since agriculture and industrial processes are growing exponentially with the fast increase of the world population. Biopolymers are complex molecules produced by living organisms, but also found in many wastes or derived from wastes. The main drawbacks for the use of polymers are the high costs of the polymer purification processes from waste and the scale-up in the case of biopolymer production by microorganisms. However, the use of biopolymers at industrial scale for the development of products with high added value, such as food or biomedical products, not only can compensate the primary costs of biopolymer production, but also impr…
Strawberry fields forever: That is, how many grams of plastics are used to grow a strawberry?
2020
Abstract In important areas of the agricultural sector, plastic is one of the most important tools for improving the managerial and economic performance of companies. Horticultural production under protected cultivation, in particular, makes abundant use of plastic polymers—polymers that mostly turn into waste. This study aims to identify similar organisational models among farmers operating in the strawberry production sector in relation to their intention to recycle plastic material and which factors characterize these models (attitudes, subjective norms, perceived behavioural control, and socio-demographic characteristics) and to quantify the plastic used in relation to the different typ…
Effect of chemical and biological surfactants on activated sludge of MBR system: Microscopic analysis and foam test
2015
Abstract A bench-scale MBR unit was operated, under stressing condition, with the aim of stimulating the onset of foaming in the activated sludge. Possible synergies between synthetic surfactants in the wastewater and biological surfactants (Extra-Cellular Polymeric Substances, EPSs) were investigated by changing C/N ratio. The growth of filamentous bacteria was also discussed. The MBR unit provided satisfactory overall carbon removal overall efficiencies: in particular, synthetic surfactants were removed with efficiency higher than 90% and 95% for non-ionic and ionic surfactants, respectively. Lab investigation suggested also the importance to reduce synthetic surfactants presence entering…
The role of EPS in fouling and foaming phenomena for a membrane bioreactor
2013
In contraposition to conventional activated sludge processes, the foaming phenomenon in membrane bioreactor (MBR) is still in its infancy. On the other hand, although several studies have been carried out for better understanding the fouling phenomenon in MBR there are still some gaps in the up-to-date knowledge. The extracellular polymeric substances (EPSs) may have a primary role in fouling and foaming phenomena which in turn can be crucial for MBRs. The aim of this study is to detect a possible relationship that EPSs may have with fouling and foaming in an MBR for wastewater treatment. Foaming phenomenon is monitored by performing specific foam-tests: Foam Power, Scum Index, Foam Rating …
The preparation and evaluation of core-shell magnetic dummy-template molecularly imprinted polymers for preliminary recognition of the low-mass polyb…
2020
Abstract The design, preparation process, binding abilities, morphological characteristic and prospective field of application of dummy-template magnetic molecularly imprinted polymer (DMMIP) for preliminary recognition of the selected low-mass polybrominated diphenyl ethers (PBDE-47 and PBDE-99) from aquatic environment were investigated. The surface of iron oxide (Fe3O4) nanopowder (50–100 nm particles size) was modified with tetraethoxysilane and next prepared Fe3O4@SiO2 particles were dispersed in anhydrous toluene functionalized by (3-aminopropyl)triethoxysilane. Finally, MIPs' thin film layer on the surface of Fe3O4@SiO2@NH2 was formed in acetonitrile as a solvent solution, using ethy…
Remediation of Solutions Containing Oxyanions of Selenium by Ultrafiltration: Study of Rejection Performances with and without Chitosan Addition
2017
Among the various technical options for removing ionic contaminants from wastewaters, membrane processes and especially their coupling with polymer addition have been proven to provide worthwhile prospects for the removal of metal cations. Nevertheless, their use for the removal of anionic pollutants such as oxyanions has been little studied in the literature. In the present work, the rejection of oxyanions forms of Se(IV) and Se(VI) by tight ultrafiltration membranes was deeply investigated under various experimental conditions. This paper aims at understanding the mechanisms governing oxyanion rejection and determining the potential ways to improve performances. It is first shown that sel…
On the equation of state for thermal polymer solutions and melts with attractive interaction
1996
We perform Monte Carlo simulations of a lattice model for polymer melts, i. e., the bond fluctuation model in three dimensions. By using an energy parameter that prefers relatively long bonds, the model exhibits a glass transition at low temperatures, in close qualitative similarity to experiment. We modify this model by adding an attractive interaction of variable strength. We demonstrate that a small interaction strength has only a very small effect on the static properties of the melt. For a fixed strength of the potential, the chemical potential is measured by a modified particle-insertion method over a large range of temperatures and densities. The osmotic pressure is obtained by therm…
Novel Biocompatible Cationic Copolymers Based on Polyaspartylhydrazide Being Potent as Gene Vector on Tumor Cells
2007
Introduction. The reaction between !,"-poly(aspartylhydrazide) (PAHy), a water soluble synthetic polymer and 3-(carboxypropyl)trimethyl-ammonium chloride (CPTACl) produced copolymers bearing permanent positive charges (PAHy–CPTA) with molecular weight of 10 kDa and PAHy–CPTA copolymers differing in positive charge amount (18–58%) were chosen for biological investigations. Materials and methods. Biophysical properties of DNA/PAHy–CPTA polyplexes were evaluated in terms of DNA condensation, zeta potential and size distribution. Cytotoxicity studies on Neuro2A murine neuroblastoma cells evidenced absence of toxicity of these copolymers up to 300 2g/ml unlike linear polyethylenimine (LPEI) that…
Microwave-assisted synthesis of PHEA-oligoamine copolymers as potential gene delivery systems
2009
Aims - Copolymers bearing oligoamines and having buffering capacity in the endosomal pH range seems very promising as non viral vectors in gene delivery, due to the great importance of endosomal escaping for an efficient endocellular DNA release. Aim of this paper was to prepare new copolymers based on α,β-poly-(N-2-hydroxyethyl)-D,L-aspartamide (PHEA) as polymeric backbone and bearing an oligoamine, such as diethylentriamine (DETA) in the side chain and useful for gene delivery. Moreover in order to reduce solvent volume and to make faster the reaction, microwave-assisted has been used. Materials and methods - PHEA copolymers bearing different amount of DETA were prepared by using bis(4-ni…
Cysteine-Specific Radioiodination of Proteins with Fluorescein Maleimide
1997
A protocol is described for coupling of carrier-free iodine to protein sulfhydryl groups via fluorescein maleimide. 125I is first coupled to fluorescein maleimide in the presence of chloramine T. Iodination is stopped with sodium thiosulfate, and the iodine-substituted fluorescein maleimide is reacted with free cysteines of the protein. Excess label is then removed by gel-permeation chromatography. The procedure avoids exposition of the protein to oxidative conditions and does not require purification of the labeled carrier reagent. Suitability of the method for a given protein can be evaluated spectrophotometrically without employing radioactivity. It can be applied under denaturing condit…