Journal of Polymers and the Environment

In this study, a novel polyurethane foam (PU) nanocomposite adsorbent based on silane-modified magnetic iron-oxide nanoparticles (Fe3O4@APTES) is synthesized via a low cost and simple in situ polymerization method for the removal of arsenic ions from aqueous solutions. The chemical structure and surface morphology of the prepared nanoparticles and adsorbent were characterized using Fourier transform infrared spectroscopy, attenuated total reflection, scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Inductively coupled plasma mass spectrometry was used to measure the arsenic concentration of the treated solutions. Sorption isotherms models were applied to determine the adsorption mechanism and modeling parameters. The removal capacity of the modified PU foam was at its highest during a contact time of four hours which resulted in a removal capacity of 95%. Kinetic studies were conducted to determine the adsorption capacity and the uptake rate of arsenic. A Pseudo-order model was found to be the best fit model for adsorption. The prepared adsorbent can be separated from the solution by using an external magnet field.

Cellulose acetate (CA) films with degree of substitution (d.s.) values of 1.7 and 2.5 were exposed to biologically active in-laboratory composting test vessels maintained at approximately 53 °C. The CA 1.7- and 2.5-d.s. films (thickness values of ∼0.5–1.0 and 2.0 mil, respectively) had completely disappeared by the end of 7- and 18-day exposure time periods in the biologically active bioreactors, respectively. The relatively small CA film weight loss observed in the poisoned control test vessels allows the conclusion that CA film erosion during the composting exposures resulted, at least in part, from biologically mediated processes. Under strictly anaerobic conditions, an active methanogenic inoculum was developed by acclimation of a sewage sludge to a synthetic municipal solid waste (SMSW) mixture at 42°C. The CA 1.7-d.s. film samples (0.5- to 1.0-mil thickness) were exposed in anaerobic serum bottles containing a 25% solids loading of SMSW in which methanogenic activity was rapidly established after introducing of the developed inoculum. For exposures of 30 days only small visually distinguishable fragments of the CA 1.7-d.s. films were recovered. In contrast, exposure of the CA 1.7-d.s. film to a poisoned control test vessel resulted in negligible weight loss. Therefore, degradation of the CA 1.7-d.s. films upon exposure to the anaerobic bioreactors was due, at least in part, to biologically mediated processes.

Bionanocomposites of poly(lactic acid) (PLA) and chemically modified, nanofibrillated cellulose (NFC) powders were prepared by extrusion, followed by injection molding. The chemically modified NFC powders were prepared by carboxymethylation and mechanical disintegration of refined, bleached beech pulp (c-NFC), and subsequent esterification with 1-hexanol (c-NFC-hex). A solvent mix was then prepared by precipitating a suspension of c-NFC-hex and acetone-dissolved PLA in ice-cold isopropanol (c-NFC-hexsm), extruded with PLA into pellets at different polymer/fiber ratios, and finally injection molded. Dynamic mechanical analysis and tensile tests were performed to study the reinforcing potential of dried and chemically modified NFC powders for PLA composite applications. The results showed a faint increase in modulus of elasticity of 10 % for composites with a loading of 7.5 % w/w of fibrils, irrespective of the type of chemically modified NFC powder. The increase in stiffness was accompanied by a slight decrease in tensile strength for all samples, as compared with neat PLA. The viscoelastic properties of the composites were essentially identical to neat PLA. The absence of a clear reinforcement of the polymer matrix was attributed to poor interactions with PLA and insufficient dispersion of the chemically modified NFC powders in the composite, as observed from scanning electron microscope images. Further explanation was found in the decrease of the thermal stability and crystallinity of the cellulose upon carboxymethylation.

The use of biodegradable polymers applied in active packaging systems, where additives are incorporated that aim to extend the shelf life of foods, is a promising topic in the search for ecologically correct materials. However, it is not known whether in these systems, the presence of the antimicrobials additive, will exert a negative influence on the biodegradation process of this polymeric material. Thus, in this work, the biodegradation process of poly (butylene adipate-co-terephthalate) (PBAT) films additive with orange essential oil in anaerobic biodigesters was monitored, as well as the growth of microorganisms involved during the process, and the production of methane gas that is the main metabolite in this type of biodegradation. PBAT films were produced through the extrusion process and added orange essential oil at concentrations of 0 and 15% wt. were used. The films before and after the 90-day biodegradation were macroscopically evaluated by medium infrared, exploratory differential calorimetry, and thermogravimetric analysis. The results showed that the evaluated period was not sufficient to mineralize the polymer and that orange essential oil had no influence on the biodegradation process. The PBAT and PBAT/EO films were stable when submitted to biodegradation in sludge for 90 days.

Clean water is a prerequisite for health living and smooth eco-fundamental networking. However, the dye industry which is contributing remarkably to the world economic growth is equally contributing to the drastic reduction in the availability of clean water and this has become a global challenge. Notably, conventional methods and materials have been used to remove dye pollutants, but they encountered criticism due to harmful chemical employment and the inability to completely mineralize stubborn dyes. Interestingly, the photocatalytic degradation method using cheap biopolymeric metallic nanoparticles (BMNPs) is a trendy cutting-edge practice and have demonstrated to be an eco-economical approach that can completely mineralize dye pollutants into non-toxic molecules. This paper is a review of original research work that photocatalytically used BMNPs for the remediation of dye pollutants. From the study, it was observed that the highest reported dye degradation efficiency was 100% and the shortest degradation time was < 1 min. Various BMNPs can be reused for up to 7 cycles with over 85% recovery of dye and over 75% efficiency was recorded for spent BMNPs after the nth cycle in most cases. It was also observed that chitosan is the most commonly employed biopolymer for BMNPs. In the end, this study provides innovative frontiers and future research hotspots that can spur the application of BMNPs to a new level in real-life scenarios for sustainable water security and effluent treatment schemes.

Due to the ubiquity and single-use character of plastic products, their production represents a burden to the environment. Therefore, an increasing interest in biodegradable and bio-compostable materials has been observed in the recent years. Bio-based materials are becoming more and more popular, especially in applications where biodegradability provides an advantage for customers and environment. However, biodegradable materials are more expensive compared with durable plastic materials, so to reduce costs and in order to improve their mechanical properties, biocomposites are created by reinforcement with natural fibers: cellulose, hemp, jute, cotton, etc. This paper is focused on the investigation of the selected group of biocomposites based on poly (3-hydroxybutyrate-co-3-hydroxyvalerate) with the addition of 15 wt% of various fillers (nanocellulose, walnut shell flour, eggshell flour, and tuff). Thus far, there is limited information concerning comparison of the different natural fillers introduced into the poly(3-hydroxybutyrate-co-3-hydroxyvalerate) matrix. Here, the following mechanical properties were evaluated: the tensile strength, modulus of elasticity, strain at break, flexural modulus, and flexural stress at 3.5% strain. The tensile test was performed at various temperatures (− 24, + 23, and + 60 °C), followed by samples conditioning in water and compost. Thermal behavior of the biocomposites was studied by means of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The study showed that the value of the elasticity modulus of each composite was higher in comparison with neat poly (3-hydroxybutyrate-co-3-hydroxyvalerate), at each of the above temperatures. The factor responsible for the enhancement of the mechanical properties of composites (enhancement of the stiffness of the material) was the increase in crystalline phase content in composites. Interestingly, at − 24 °C, all of the analyzed composites exhibited over twofold increase in tensile strength which was accompanied by an almost 30% increase in elastic modulus. This phenomenon likely resulted from an increase in tensile strength and an increase in internal stress at interfaces within the components of the composites during tests. It was also observed that both conditioning in water and degradation in the compost heap led to a considerable decrease in mechanical properties of the examined composites. The scanning electron microscopy analysis, carried out to assess the distribution of particles and the adhesion of fillers to the matrix, revealed that the size and the shape of the particles affected the mechanical properties of the composites.

Recently, biopolymers have become a resource for the biomedical material field due to its biocompatibility and biodegradability. In this work, Aloe vera-loaded bacterial cellulose- and polycaprolactone -based composites were successfully prepared for wound dressing applications. The structural, morphological, thermal, swelling, and degradation properties were investigated. Result showed that the addition of Aloe vera resulted in a strong peak characteristic of hydroxyl groups and amide I by attenuated total reflectance-Fourier transform infrared analysis. Pores were present inside the composite structure and varied with the Aloe vera content. No crystallinity peak of Aloe vera was observed. Thermogravimetric analysis indicated a slight change in the thermal decomposition temperature and a loss of water molecules below 100 °C. The swelling and weight loss behaviour were remarkably changed when only 5% Aloe vera was loaded into the composite. Moreover, Aloe vera enhanced the toughness and elongation of the composite. All the composites exhibited a burst release profiles within 60 min. The MTT assay showed a concerningly low cell viability concerning the amount of Aloe vera loaded into the composite. Therefore, Aloe vera-loaded BC and PCL composites could be developed for wound dressing applications.

Candida antarctica: lipase B (CALB) is the most widely studied enzyme, due to its high selectivity and catalytic activity in organic and polymer synthesis. To avoid organometallic catalysts in the synthesis of biodegradable polyesters, the enzymatic ring-opening polymerization of cyclic esters can be carried out with CALB as a biocatalyst. This paper reviews selected examples of the application of lipases in polymer chemistry covering the synthesis of cyclic ester monomers, linear and star oligomers, as well as well-defined high molar mass polymers with improved mechanical properties. It is shown that by the selection of appropriate conditions of temperature and solvent assortment, CALB effectively catalyzes the polymerization of large size lactones obtaining polyesters with Mn up to 80 kg mol−1. The chemical structure and main applications of described materials are also discussed. As the polymer recycling is an important topic from environmental point of view, we also described the potential applications of CALB in degradation process of aliphatic polyesters.