Polyurethane foams, are highly demanded in many applications and their use is increasing incessantly. Besides these traditional applications, recently polyurethane foams with different morphologies ...have been used in environmentally-oriented applications as biofilters for waste air and water treatments, microporous sorption materials, carriers of bio-catalyst (enzyme) in biotechnologies and lightweight packing materials with high surface area for cell attachment and biofilm development, etc. For these applications it is important that polyurethane foams are not toxic, bio-based and capable of decomposing in the environment. Therefore, there is a huge potential for conducting research focused on biodegradation of newly developed bio-foams and their ecotoxicological impacts and thus to make valuable contribution in solving environmental and resource depletion problems of the world. This review gives an overview about environmental degradation of polyurethane foams with special accent to their biodegradation behavior and ecotoxicity. The paper is organized as follows: (1) polyurethane foams are shortly introduced together with their current recycling options, (2) innovative approaches in producing of bio-based and biodegradable polyurethane foams are mentioned, (3) possible ways of environmental degradations of polyurethane foams are present, (4) aspects of polyurethane foam biodegradation are discussed in details and finally (5) ecotoxicity of polyurethane foams is also mentioned.
Objective
Marine actinomycetes from the genus
Salinispora
have an unexploited biotechnological potential. To accurately estimate their application potential however, data on their cultivation, ...including biomass growth kinetics, are needed but only incomplete information is currently available.
Results
This work provides some insight into the effect of temperature, salinity, nitrogen source, glucose concentration and oxygen supply on growth rate, biomass productivity and yield of
Salinispora tropica
CBN-440
T
. The experiments were carried out in unbaffled shake flasks and agitated laboratory-scale bioreactors. The results show that the optimum growth temperature lies within the range 28–30 °C, salinity is close to sea water and the initial glucose concentration is around 10 g/L. Among tested nitrogen sources, yeast extract and soy peptone proved to be the most suitable. The change from unbaffled to baffled flasks increased the volumetric oxygen transfer coefficient (k
L
a) as did the use of agitated bioreactors. The highest specific growth rate (0.0986 h
−1
) and biomass productivity (1.11 g/L/day) were obtained at k
L
a = 28.3 h
−1
. A further increase in k
L
a was achieved by increasing stirrer speed, but this led to a deterioration in kinetic parameters.
Conclusions
Improvement of
S. tropica
biomass growth kinetics of was achieved mainly by identifying the most suitable nitrogen sources and optimizing k
L
a in baffled flasks and agitated bioreactors.
Water-blown fully aliphatic polyurethane foam was prepared at room temperature from trimer of hexamethylene diisocyanate and poly(diethylene glycol adipate) diol and post cured at 55 °C. In contrast ...to aromatic-based PUR foam analog, the produced flexible PUR foam exhibited highly porous structure with open cell content of 94% and average cell size of 700 μm. Therefore, it was subsequently tested as biodegradable cellular carrier of microorganisms (fungus Fusarium solani and bacterium Pseudomonas sp.) for biofiltration. Firstly, tests on enzyme activities (lipase, protease and urease) and utilization of PUR foam as the sole carbon and nitrogen source and determination of degradation products were carried out. Fusarium solani shown much higher both enzyme and degradation activities and higher spectrum of degradation products. Finally, the performance of a biofilter packed with the developed cellular carrier was investigated for removal of a mixture of acetone, propionic acid, ethyl acetate, toluene and α-pinene. Proven sorption properties of PUR foam against all pollutants and a high maximum elimination capacity of 218 ± 33 g m−3 h−1 make the new lightweight biofilm PU carrier suitable for this application due to their multi-functionality.
•Preparation of fully aliphatic polyurethane foam with open cells.•More efficient degradation of polyurethane foam by Fungus Fusarium solani than by bacterium Pseudomonas sp.•High sorption capacity of polyurethane foam during biofiltration.•Polyurethane foam serves as sole carbon and energy source for microorganisms, biofilm carrier and sorption material.
•Environmentally-friendly microwave in-situ synthesis of biodegradable nanocomposite films based on polycaprolactone matrix and ZnO nanoparticles.•Modification of ZnO nanoparticles with phosphonium ...ionic liquid leads to homogeneous structure of nanocomposites.•Enhanced biodegradation of nanocomposite films induced by nanoparticle addition.•Suppressed growth of food-born pathogenic bacteria E. coli on film surface.•High application potential of nanocomposite films as active bio-packaging films for food storage.
Sustainable nanocomposites based on biodegradable polycaprolactone (PCL) matrix and ZnO nanoparticles (ZnONPs) functionalized with ionic liquid (IL) were prepared via bulk in-situ ring opening polymerization of ε-caprolactone (εCL). PCL-ZnONPs nanocomposite films were examined in terms of mechanical, thermal and barrier properties. The influence of ZnONPs on the potential antimicrobial effect and biodegradation of PCL-ZnONPs films was investigated. Introduction of IL-ZnONPs NPs (3.0 wt%) into PCL matrix resulted in significant decrease of water vapor permeation (46%), induced bactericidal effect against food-born pathogenic bacterium E.coli and enhanced biodegradation rate of the prepared nanocomposite film. Therefore, these materials present high application potential as active bio-packaging films, e.g. for food storage.
Two cost-effective packing materials were used for n-butyl acetate removal in lab-scale biofilters, namely waste spruce root wood chips and biochar obtained as a byproduct from a wood gasifier. Three ...biofilters packed with spruce root wood chips: without biochar (SRWC), a similar one with 10% of biochar (SRWC-B) and that with 10% of biochar impregnated with a nitrogen fertilizer (SRWC-IB) showed similar yet differing maximum elimination capacities of 206 ± 27, 275 ± 21 and 294 ± 20 g m
−3
h
−1
, respectively, enabling high pollutant removal efficiency (>95% at moderate loads) and stable performance. The original biochar adsorption capacity was high (208 ± 6 mg
toluene
g
−1
), but near 70% of it was lost after a 300-day biofilter operation. By contrast, the exposed impregnated biochar drastically increased its adsorption capacity in 300 days (149 ± 7 vs. 17 ± 5 mg
toluene
g
−1
). Colony forming unit (CFU) and microscopic analyses revealed significant packing material colonization by microorganisms and grazing fauna in all three biofilters with an acceptable pressure drop, up to 1020 Pa m
−1
, at the end of biofilter operation. Despite a higher price (14 vs. 123 €m
−3
), the application of the best performing SRWC-IB packing can reduce the total investment costs by 9% due to biofilter volume reduction.
Polyurethane (PU) foams are classified as physically nonrecyclable thermosets. The current effort of sustainable and eco-friendly production makes it essential to explore methods of better waste ...management, for instance by modifying the structure of these frequently used polymers to enhance their microbial degradability. The presence of ester links is known to be a crucial prerequisite for the biodegradability of PU foams. However, the impact of other hydrolysable groups (urethane, urea and amide) occurred in PU materials, as well as the supramolecular structure of the PU network and the cellular morphology of PU foams, is still relatively unexplored.
In this work, fully aliphatic PU foams with and without hydrolyzable amide linkages were prepared and their aerobic biodegradation was investigated using a six-month soil burial test. Besides the variable chemical composition of the PU foams, the influence of their different supramolecular arrangement and cellular morphologies on the extent of biodegradation was also evaluated. Throughout the soil burial test, the release of carbon dioxide, and enzyme activities of proteases, esterases, and ureases were measured. At the same time, phospho-lipid fatty acids (PLFA) analysis was conducted together with an assessment of microbial community composition achieved by analysing the genetic information from the 16S rRNA gene and ITS2 region sequencing.
The results revealed a mineralization rate of 30–50 % for the PU foams, indicating a significant level of degradation as well as indicating that PU foams can be utilized by soil microorganisms as a source of both energy and nutrients. Importantly, microbial biomass remained unaffected, suggesting that there was no toxicity associated with the degradation products of the PU foams. It was further confirmed that ester linkages in PU foam structure were easily enzymatically cleavable, while amide linkages were not prone to degradation by soil microorganisms. In addition, it was shown that the presence of amide linkages in PU foam leads to a change in the supramolecular network arrangement due to increased content of hard segments, which in turn reduces the biodegradability of PU foam. These findings show that it is important to consider both chemical composition and supramolecular/macroscopic structure when designing new PU materials in an effort to develop environmentally friendly alternatives.
Display omitted
•Aliphatic polyurethane foams with/without amide linkages were successfully prepared.•Mineralization of polyurethane foams during 6-month soil burial reached 30–50 %.•Contrary to ester bonds, amide linkages are not prone to soil biodegradation.•Supramolecular structure of polyurethane foams affects biodegradation.•No ecotoxicological response of degraded polyurethane foams in soil was found.
•Complete cleavage of ester linkages during abiotic hydrolysis of polyurethane foam.•Partial hydrolysis of isocyanurate rings of polyurethane foam.•Proved metabolic activity of fungus Fusarium solani ...and bacterium Pseudomonas sp.•Final mineralization of 43% during biodegradation of polyurethane foam in soil.
Polyurethane (PUR) foams are due to their versatility highly demanded not only in traditional applications but also in biotechnological and environmentally-oriented processes in which they can reach the open environment. Therefore, new PUR foams with degradation-on-demand features are highly desirable and their (bio)degradation behavior has to be understood. Herein, we have studied abiotic and microbial degradation of fully aliphatic PUR foam, developed as a biomass carrier for biofiltration. The progress of abiotic hydrolysis shows complete degradation of soft polyol segments and partial cleavage of hard isocyanate-derived segments. Microbial in-vitro degradations showed much higher activity of fungus Fusarium solani than bacterium Pseudomonas sp. Biodegradation of the PUR foam in soil reveals that 77% of the soft segments are mineralized after 6 months reaching the final mineralization of 43%. The results demonstrate that a non-hazardous and sustainable PUR foam can be successfully prepared for applications requiring material bioactivity (biorecycling, etc.).
Fully aliphatic (isocyanurate ring-based) polyester-ether polyurethane (PUR) foams have been developed, and the influence of starch and 2-hydroxyethyl cellulose (HEC) additives on their structure, ...properties, ecotoxicity, and (abiotic and biotic) degradation has been studied. These PUR foams designed as hydrophilic open-porous materials are predisposed to enzymatic hydrolysis with potential application as cellular carriers and an alternative nutrient source for activated sludge in wastewater treatment plants. In comparison to the neat (nonmodified) PUR foam, the PUR foams with incorporated starch and HEC modifiers exhibited a tougher character and a slightly increased open-cell content but on the other hand a significantly coarser cellular structure with much larger cell sizes and reduced water absorption. The progress of 6-week abiotic hydrolysis was characterized in detail, showing almost a complete decomposition of ester groups, a partial degradation of urethane linkages, and a fully intact isocyanurate ring. The extent of biodegradation by means of bacteria was similar for all tested PUR foams, while fungus biodegradation was more efficient in starch and HEC-modified PUR foams. The leachates from both starch- and HEC-modified foams exhibited somewhat higher ecotoxicity for higher organisms, here represented by Daphnia magna, due to higher contents of leached substances.
In situ remediation is usually restricted by temperature, lack of substrate for reductive dechlorination (anaerobic respiration), the presence of dehalogenating microorganisms, and specific bedrock ...conditions. In this work, trichloroethene (TCE) degradation was studied by a number of methods, from physical–chemical analyses to molecular biological tools. The abundance changes in dechlorinating bacteria were monitored using real-time PCR. The functional genes vcrA and bvcA as well as the 16S rRNA specific for representatives of genera Dehalococcoides, Dehalobacter, and Desulfitobacterium were monitored. Furthermore, the sulfate-reducing bacteria and denitrifying bacteria were observed by amplifying the functional genes apsA and nirK. The elevated temperature and the substrate (whey) addition significantly affected TCE dechlorination. The chlorine index decreased after nine weeks from 2.5 to 0.1 at 22 °C, to 1.1 at 17 °C and 1.7 at 12 °C and complete dechlorination was achieved at 22 °C with whey addition. The achieved results of this work show the feasibility and effectiveness of biological dechlorination of TCE enhanced with elevated temperature and whey addition.
