Remediation of poly-and perfluoroalkyl substances (PFAS) contaminated soil using gas fractionation enhanced technology.

This study investigated a gas fractionation enhanced soil washing method for poly-and perfluoroalkyl substances (PFAS) removal from contaminated soil. With the assistance of gas fractionation, PFAS removal was increased by a factor of 9, compared to the conventional soil washing method. Pre-extraction (pre-treatment) of the soil with water before gas fractionation enhanced PFAS removal from soil. The optimum extraction time varied based on the soil particle size, since it will change the swelling time of the soil. The influence of various operational conditions such as water to soil mass ratio (W:S ratio), gas type in fractionation, gas flowrate, fractionation time and soil pre-treatment condition have been studied to identify the critical influencing factors. Among various W:S ratios (2, 4, 5, 6, 8, and 10) studied, higher W:S ratio resulted in better PFAS removals, but PFAS removal began to plateau as the W:S ratio increased. PFAS removal could be improved by repeated treatment with low water consumption. Air, oxygen, and ozone generated by air and oxygen were used, in which ozone generated by oxygen achieved the highest PFAS removals of 55.9%. Among different fractionation times (10 min, 20 min and 30 min), a fractionation time of 20 min achieved better total PFAS removal for studied soil, because PFOS was the dominant species in the total PFAS. However, the removal of some PFAS species, such as PFHxS, would be increased with extended fractionation time. With constant fractionation time (10 min), PFAS removal performance improved with the increasing gas flowrate.

Mass Transfer and Optical Properties of Active PET/PP Food-Grade Films Impregnated with Olive Leaf Extract.

A supercritical solvent impregnation (SSI) technique was employed to incorporate, by batch- and semicontinuous-modes, bioactive olive leaf extract (OLE) into a food-grade multilayer polyethylene terephthalate/polypropylene (PET/PP) film for active food packaging applications. The inclusion of OLE in the polymer surfaces significantly modified the colour properties of the film. A correlation of 87.06% between the CIELAB colour parameters and the amount of the OLE impregnated in the film was obtained which suggests that colour determination can be used as a rapid, non-destructive technique to estimate the OLE loading in the impregnated matrices. The UV barrier and water permeability properties of the films were not significantly modified by the incorporation of OLE. The migration of OLE into a 50% (v/v) ethanol food simulant demonstrated faster release of OLE from the PP surface than from the PET surface which may be due to the different interactions between OLE and each polymer.

Functionalized Carbon Nanotube-Mediated Transport in Membranes Containing Fixed-Site Carriers for Fast Pervaporation Desalination.

Facilitated transport membranes (FTMs) comprising fixed carrier agents hold considerable potential for obtaining selective and fast separation of mixed molecules in either gas or liquid state. However, diffusion through the membrane is inevitably affected by the resistance from the polymer matrix, where the carrier is absent. Herein, a poly(vinyl alcohol) (PVA)-based separating layer combining the merits of fixed-site transport agents and inorganic nanofillers was developed to reduce the transport resistance. Carbon nanotubes (CNTs) with different degrees of oxidation were prepared and incorporated into the sulfonic acid (-SO3H)-modified PVA matrix. The resultant composite membrane consisting of a microporous polytetrafluoroethylene substrate and a thin PVA-based separating layer (∼700 nm thick) was subject to pervaporation desalination of sodium chloride solution (35,000 ppm) at 30 °C. The effect of -SO3H as a fixed transport agent in the PVA matrix was first investigated experimentally, showing an increase of water flux by 21.8% compared with a control membrane without the transport agent. Subsequently, the CNT-incorporated FTM exhibited good stability (50 h) and improvement in water transport, which was ∼161% of the control FTM (PVA with -SO3H) without loss of selectivity. Such high and stable performance achieved in the CNT-incorporated FTM originated from the construction of low-resistance transport pathways by CNTs between -SO3H groups as well as their uniform dispersion in the polymer matrix.

Dimensional Nanofillers in Mixed Matrix Membranes for Pervaporation Separations: A Review.

Pervaporation (PV) has been an intriguing membrane technology for separating liquid mixtures since its commercialization in the 1980s. The design of highly permselective materials used in this respect has made significant improvements in separation properties, such as selectivity, permeability, and long-term stability. Mixed-matrix membranes (MMMs), featuring inorganic fillers dispersed in a polymer matrix to form an organic-inorganic hybrid, have opened up a new avenue to facilely obtain high-performance PV membranes. The combination of inorganic fillers in a polymer matrix endows high flexibility in designing the required separation properties of the membranes, in which various fillers provide specific functions correlated to the separation process. This review discusses recent advances in the use of nanofillers in PV MMMs categorized by dimensions including zero-, one-, two- and three-dimensional nanomaterials. Furthermore, the impact of the nanofillers on the polymer matrix is described to provide in-depth understanding of the structure-performance relationship. Finally, the applications of nanofillers in MMMs for PV separation are summarized.

Reinforcement of Refined and Semi-Refined Carrageenan Film with Nanocellulose.

Carrageenans obtained from seaweeds can be processed into films for a range of applications including food packaging. The level of carrageenan refinement during extraction can influence the key properties, with semi-refined carrageenan (SRC) containing more impurities than the more refined carrageenan (RC). Further refinement steps, however, result in higher costs associated with the production of RC. In order to obtain a lower cost and more ecofriendly, bio-based material for food packaging applications, SRC was used in this investigation to produce a thin film reinforced with nanocellulose fibrils (NCF). Films derived from RC containing NCF were also investigated with water sensitivity and physico-mechanical and thermal properties among the properties tested. Levels of NCF were varied from 1% to 7% (w/w), and in general, the NCF reinforcement improved the overall properties of both the SRC and RC films, including the water sensitivity and moisture barrier. However, NCF inclusion in SRC film was less effective with regard to the mechanical and thermal properties compared with NCF inclusion in RC film. The enhancement in properties was attributed to the greater cohesiveness of the reinforced polymer structure and the crystalline regions formed in the structures of SRC and RC films by NCF incorporation.

A Review of Property Enhancement Techniques for Carrageenan-based Films and Coatings.

Carrageenan, a polysaccharide extracted from marine algae, is becoming increasingly regarded as a promising renewable biomaterial that has strong potential as a substitute for conventional synthetic plastics. Materials derived from carrageenans have been widely investigated over the recent decades for use in pharmaceutical and biomedical applications through to edible films and coatings. In the area of flexible films, carrageenans suffer from limitations that are primarily a result of their inherent hydrophilicity. Considerable research efforts have been devoted to the improvement of the properties of carrageenan films in order to extend the range of suitable applications. These include blending with other polymers, the use of plasticizers, and reinforcements with nanomaterials. This review comprehensively assesses the current status of carrageenan-based film development including material characteristics and strategies to obtain desirable film properties with particular regard to real applications.

Current and Emerging Techniques for High-Pressure Membrane Integrity Testing.

Ideally, pressure driven membrane processes used in wastewater treatment such as reverse osmosis and nanofiltration should provide a complete physical barrier to the passage of pathogens such as enteric viruses. In reality, manufacturing imperfections combined with membrane ageing and damage can result in breaches as small as 20 to 30 nm in diameter, sufficient to allow enteric viruses to contaminate the treated water and compromise public health. In addition to continuous monitoring, frequent demonstration of the integrity of membranes is required to provide assurance that the barrier to the passage of such contaminants is intact. Existing membrane integrity monitoring systems, however, are limited and health regulators typically credit high-pressure membrane systems with only 2 log10 virus rejection, well below their capability. A reliable real-time method that can recognize the true rejection potential of membrane systems greater than 4 log10 has not yet been established. This review provides a critical evaluation of the current methods of integrity monitoring and identifies novel approaches that have the potential to provide accurate, representative virus removal efficiency estimates.

Influence of acid hydrolysis, saponification and sample clean-up on the measurement of phytosterols in dairy cattle feed using GC-MS and GC with flame ionization detection.

The fortification of processed foods including dairy products is increasingly commonplace with phytosterols among many compounds used to improve the nutritional value of food products. It is also increasingly common practice for some dairy cattle feeds to be fortified for their potential to increase phytosterol levels in milk. In this study, a combined, streamlined protocol using acid hydrolysis, saponification and sample clean-up was developed to enable the rapid and reliable measurement of phytosterols. The method was developed with focus on streamlining the overall technique to make it suitable for commercial laboratories, to reduce labor and consumable costs, while maintaining accuracy. A total of 12 different feed types commonly used in the dairy industry were analyzed with the highest and lowest sterol contents found in cotton seed oil and tannin with average phytosterol contents of 256 and <30 mg per 100 g, respectively. With a limit of reporting of 30 mg/kg for individual sterols and a correlation coefficient > 0.99, the method was validated for milk to enable feed comparison studies with respect to the total phytosterol content in raw milk.

Optimisation of ß-cyclodextrin inclusion complexes with natural antimicrobial agents: thymol, carvacrol and linalool.

Beta-cyclodextrin (ß-CD) inclusion complexes with naturally derived antimicrobial (AM) agents: thymol, carvacrol and linalool were prepared using a co-precipitation technique. Conditions including solvent composition, temperature, reaction time and total solvent volume were investigated to optimise the inclusion efficiency (IE) and yield. Electrospray ionisation mass spectrometry was used to confirm the formation of the thymol/ß-CD complex and gas chromatography was used to quantify the amount AM agent that was encapsulated, absorbed onto the surface, or remaining in the filtered solvent. The systematic optimisation of the conditions improved both the yield of the complex and the IE of the AM agents compared to previously reported methods that have been applied to other agents. Using a 1:1 mole ratio of the AM agent to ß-CD, the optimised parameters resulted in maximum yields of 87, 84 and 86% (w/w) for thymol, carvacrol and linalool, respectively, with IE's close to 100% (w/w) for each agent.

Membrane Distillation of Meat Industry Effluent with Hydrophilic Polyurethane Coated Polytetrafluoroethylene Membranes.

Meat rendering operations produce stick water waste which is rich in proteins, fats, and minerals. Membrane distillation (MD) may further recover water and valuable solids, but hydrophobic membranes are contaminated by the fats. Here, commercial hydrophobic polytetrafluorethylene (PTFE) membranes with a hydrophilic polyurethane surface layer (PU-PTFE) are used for the first time for direct contact MD (DCMD) on real poultry, fish, and bovine stick waters. Metal membrane microfiltration (MMF) was also used to capture fats prior to MD. Although the standard hydrophobic PTFE membranes failed rapidly, PU-PTFE membranes effectively processed all stick water samples to colourless permeate with sodium rejections >99%. Initial clean solution fluxes 5-6 L/m²/h declined to less than half during short 40% water recovery tests for all stick water samples. Fish stick water uniquely showed reduced fouling and up to 78% water recovery. Lost flux was easily restored by rinsing the membrane with clean water. MMF prior to MD removed 92% of fats, facilitating superior MD performance. Differences in fouling between stick waters were attributed to temperature polarisation from higher melt temperature fats and relative proportions to proteins. Hydrophilic coated MD membranes are applicable to stick water processing but further studies should consider membrane cleaning and longer-term stability.

Development and characterisation of HPMC films containing PLA nanoparticles loaded with green tea extract for food packaging applications.

A novel active film material based on hydroxypropyl-methylcellulose (HPMC) containing poly(lactic acid) (PLA) nanoparticles (NPs) loaded with antioxidant (AO) green tea extract (GTE) was successfully developed. The PLA NPs were fabricated using an emulsification-solvent evaporation technique and the sizes were varied to enable a controlled release of the AO from the HPMC matrix. A statistical experimental design was used to optimise the synthesis of the NPs in order to obtain different sizes of nanoparticles and the loading of these into the HPMC matrix was also varied. The physico-chemical properties of the composite films were investigated and the release of the AO was confirmed by migration studies in 50% v/v ethanol/water food simulant. The AO capacity of the GTE released from the active films was studied using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical method and the results suggest that the material could potentially be used for extending the shelf-life of food products with high fat content.

Rapid measurement of phytosterols in fortified food using gas chromatography with flame ionization detection.

A novel method for the measurement of total phytosterols in fortified food was developed and tested using gas chromatography with flame ionization detection. Unlike existing methods, this technique is capable of simultaneously extracting sterols during saponification thus significantly reducing extraction time and cost. The rapid method is suitable for sterol determination in a range of complex fortified foods including milk, cheese, fat spreads, oils and meat. The main enhancements of this new method include accuracy and precision, robustness, cost effectiveness and labour/time efficiencies. To achieve these advantages, quantification and the critical aspects of saponification were investigated and optimised. The final method demonstrated spiked recoveries in multiple matrices at 85-110% with a relative standard deviation of 1.9% and measurement uncertainty value of 10%.

A review of poly(lactic acid)-based materials for antimicrobial packaging.

Poly(lactic acid) (PLA) can be synthesized from renewable bio-derived monomers and, as such, it is an alternative to conventional petroleum-based polymers. Since PLA is a relatively new polymer, much effort has been directed toward its development in order to make it an acceptable and effective option to the more traditional petroleum-based polymers. Commercially, PLA has received considerable attention in food packaging applications with a focus on films and coatings that are suitable for short shelf life and ready-to-eat food products. The potential for PLA to be used in active packaging has also been recognized by a number of researchers. This review focuses on the use of PLA in antimicrobial systems for food packaging applications and explores the engineering characteristics and antimicrobial activity of PLA films incorporated and/or coated with antimicrobial agents.

Physical, mechanical and barrier properties of corn starch films incorporated with plant essential oils.

Corn starch-based films are inherently brittle and lack the necessary mechanical integrity for conventional packaging. However, the incorporation of additives can potentially improve the mechanical properties and processability of starch films. In this work two essential oils, Zataria multiflora Boiss (ZEO) or Mentha pulegium (MEO) at three levels (1%, 2% and 3% (v/v)), were incorporated into starch films using a solution casting method to improve the mechanical and water vapor permeability (WVP) properties and to impart antimicrobial activity. Increasing the content of ZEO or MEO from 2% to 3% (v/v) increased values for elongation at break from 94.38% to 162.45% and from 53.34% to 107.71% respectively, but did not significantly change tensile strength values of the films. The WVP properties of the films decreased from 7.79 to 3.37 or 3.19 g mm m(-2) d(-1) kPa(-1) after 3% (v/v) ZEO or MEO incorporation respectively. The oxygen barrier properties were unaffected at the 1% and 2% (v/v) oil concentration used but oxygen transmission increased with 3% (v/v) for both formulations. The films' color became slightly yellow as the levels of ZEO or MEO were increased although transparency was maintained. Both films demonstrated antimicrobial activity with films containing ZEO more effective against Escherichia coli and Staphylococcus aureus than those containing MEO. These results suggest that ZEO and MEO have the potential to be directly incorporated into corn starch to prepare antimicrobial biodegradable films for various food packaging applications.

Antimicrobial activity of biodegradable polysaccharide and protein-based films containing active agents.

Significant interest has emerged in the introduction of food packaging materials manufactured from biodegradable polymers that have the potential to reduce the environmental impacts associated with conventional packaging materials. Current technologies in active packaging enable effective antimicrobial (AM) packaging films to be prepared from biodegradable materials that have been modified and/or blended with different compatible materials and/or plasticisers. A wide range of AM films prepared from modified biodegradable materials have the potential to be used for packaging of various food products. This review examines biodegradable polymers derived from polysaccharides and protein-based materials for their potential use in packaging systems designed for the protection of food products from microbial contamination. A comprehensive table that systematically analyses and categorizes much of the current literature in this area is included in the review.

Essential oils and their principal constituents as antimicrobial agents for synthetic packaging films.

Spices and herbal plant species have been recognized to possess a broad spectrum of active constituents that exhibit antimicrobial (AM) activity. These active compounds are produced as secondary metabolites associated with the volatile essential oil (EO) fraction of these plants. A wide range of AM agents derived from EOs have the potential to be used in AM packaging systems which is one of the promising forms of active packaging systems aimed at protecting food products from microbial contamination. Many studies have evaluated the AM activity of synthetic AM and/or natural AM agents incorporated into packaging materials and have demonstrated effective AM activity by controlling the growth of microorganisms. This review examines the more common synthetic and natural AM agents incorporated into or coated onto synthetic packaging films for AM packaging applications. The focus is on the widely studied herb varieties including basil, oregano, and thyme and their EOs.

Antimicrobial activity of natural agents coated on starch-based films against Staphylococcus aureus.

This study investigated the antimicrobial (AM) activity of starch-based films coated with linalool, carvacrol, or thymol against Staphylococcus aureus in vitro or inoculated on the surface of Cheddar cheese. In solid media using the agar diffusion method, the inhibitory effect of linalool, carvacrol, or thymol coated onto the films increased significantly (P≤ 0.05) with the increase in concentration of each AM agent. All the coated films effectively inhibited the growth of S. aureus on the surface of Cheddar cheese. The sensitivity of S. aureus to the AM agents tested in the concentration range of the study is in the order of thymol > carvacrol > linalool.

Release of naturally derived antimicrobial agents from LDPE films.

The migration of the naturally derived antimicrobial (AM) agents, linalool, carvacrol, and thymol, from low-density polyethylene (LDPE) films containing ethylene vinyl acetate (EVA) copolymer into the food simulants, isooctane and various ethanol/water mixtures, was studied with a view towards examining the applicability of a first-order kinetic approach as well as a diffusion model approach for describing these systems. The results suggest that the proposed models adequately describe the release of AM agents. The combination of kinetic and diffusion analyses can provide additional information about the release process using the same data set. The analyses suggest that the release of linalool from LDPE/EVA depends on the EVA content in the formulation and that an optimum level of EVA is required to minimize the rate of release. A modification of the existing "idealized diffusion" model is proposed that enables the model to be applied to systems that demonstrate a departure from linearity when subjected to conventional analysis. The applicability of the idealized diffusion model was compared with the "simulant-limited" model and the results suggest that the former model is appropriate for describing most real systems when the simulant (or foodstuff) is favored in the partitioning of the AM agent between the film and the simulant.

Quantitative analysis of polyethylene blends by Fourier transform infrared spectroscopy.

The quantitative analysis of binary polyethylene (PE) blends by Fourier transform infrared (FT-IR) spectroscopy has been achieved based on the ratio of two absorbance peaks in an FT-IR spectrum. The frequencies for the absorbance ratio are selected based on structural entities of the PE components in the blend. A linear relationship between the absorbance ratio and the blend composition was found to exist if one of the absorbance peaks is distinct to one of the components and the other peak is common to both components. It was also found that any peak resulting from short-chain branching in copolymers (such as linear low-density polyethylene (LLDPE) or metallocene-catalyzed LLDPE (mLLDPE)), is suitable for use as the peak that is designated as being distinct to that component. In order to optimize the linearity of the equation, however, the selection of the second common peak is the most important and depends on the blend system studied. Indeed, under certain circumstances peaks that are not spectrally distinct can be used successfully to apply the method. The method exhibits potential for the routine analysis of PE blends that have been calibrated prior to its application.