Isolation and purification of high-molecular weight hemicelluloses from radiata pine wood chips prior to thermo-mechanical pulp (TMP) production

A novel thermo-mechanical pulping (TMP) process has been developed to produce a by-product rich in high-molecular weight (MW) hemicelluloses, a potential raw material for barrier coatings and films. This process uses prehydrolysis to solubilise the hemicelluloses followed by chip compression to separate the soluble material from the wood matrix. The pressate from the chip compression stage was dark-coloured and had a high content of high-MW hemicelluloses and lignin. However, isolating the high-MW material from the pressate directly by ultrafiltration was not feasible because of membrane fouling by dissolved lignin and wood extractives, while coloured impurities are undesirable for many potential applications. To solve these problems the pressate was purified using XAD adsorbent resin to remove low-MW lignin, extractives and colour. Ultrafiltration of the purified pressate yielded lightly coloured high-MW hemicellulose with a low content of lignin and well suited for barrier films and coatings

Esterification of Condensed Tannins and Their Impact on the Properties of Poly(Lactic Acid)

polymer

Release of additives and non-intentionally added substances from microplastics under environmentally relevant conditions

Microplastics and their associated plastic additives are contaminants of emerging environmental concern. The extent and rate of additive leaching affects the behaviour and fate of these contaminants, and therefore the risk they present to organisms. However, most studies examining the leaching of additives from microplastics use methods that are not environmentally relevant. We evaluated additive leaching from a range of common plastics using an environmentally relevant dynamic leaching method with additives and non-intentionally added substances quantified by liquid chromatography-mass spectrometry. The leaching method was validated to ensure sink conditions were maintained over the duration of the test. Release was not solubility limited indicating that the test conditions were representative of those occurring in the environment. Leaching profiles showed significantly different kinetics across the different types of plastic, with cumulative additive release over 64 days spanning more than five orders of magnitude. This study highlights the wide variation in additive leaching behaviour between different plastics and the importance of understanding leaching kinetics to assess the chemical impacts of microplastic pollution. Furthermore, we identify the need for environmentally relevant leaching methods and suggest the creation of standardised methods to enable robust risk assessments and regulation

Solving a microplastic dilemma? Evaluating additive release with a dynamic leaching method for microplastic assessment (DyLeMMA)

Microplastics and plastic additives are contaminants of emerging environmental concern. Static leaching methods are commonly applied to assess the rate and extent of additive release from microplastics. However, this approach may not be representative of environmental conditions where near infinite dilution or percolation commonly occur. We evaluated three different approaches for assessing additive leaching under environmentally relevant sink conditions, culminating in the refinement and validation of DyLeMMA (Dynamic Leaching Method for Microplastic Assessment). Analysis was performed using a high-resolution liquid chromatography-mass spectrometry method enabling targeted quantification of additives and screening for non-intentionally added substances. Using four different plastics, sink conditions were maintained over the duration of the test, thereby avoiding solubility limited release and ensuring environmental relevance. Background contamination from ubiquitous additive chemicals was minimised, thereby providing good sensitivity and specificity. Resulting data, in the form of additive release curves, should prove suitable for fitting to release models and derivation of parameters describing additive leaching from microplastics.Key attributes of DyLeMMA: • Environmentally relevant dynamic leaching method for microplastics, demonstrated to maintain sink conditions over the test duration, • Simple, fast, and cost-effective approach without complication of using a solid phase sink, • Provide data suitable for understanding microplastic leaching kinetics and mechanisms

Leaching and extraction of additives from plastic pollution to inform environmental risk: A multidisciplinary review of analytical approaches

Highlights • Release of additives from plastic pollution may harm wildlife. • Robust methods to characterise additives and their leaching behaviour are needed. • Extraction and leaching methods are informed from well-established industry methods. • Recommended approaches for extraction and leaching studies are presented. • The use of environmentally relevant methods and test materials is advised. Plastic pollution is prevalent worldwide and has been highlighted as an issue of global concern due to its harmful impacts on wildlife. The extent and mechanism by which plastic pollution effects organisms is poorly understood, especially for microplastics. One proposed mechanism by which plastics may exert a harmful effect is through the leaching of additives. To determine the risk to wildlife, the chemical identity and exposure to additives must be established. However, there are few reports with disparate experimental approaches. In contrast, a breadth of knowledge on additive release from plastics is held within the food, pharmaceutical and medical, construction, and waste management industries. This includes standardised methods to perform migration, extraction, and leaching studies. This review provides an overview of the approaches and methods used to characterise additives and their leaching behaviour from plastic pollution. The limitations of these methods are highlighted and compared with industry standardised approaches. Furthermore, an overview of the analytical strategies for the identification and quantification of additives is presented. This work provides a basis for refining current leaching approaches and analytical methods with a view towards understanding the risk of plastic pollution