Thermal Degradation and Kinetics of Alginate Polyurethane Hybrid Material Prepared from Alginic Acid as a Polyol

Alginate polyurethane hybrid materials are prepared by varying mole ratio of 2, 4-TDI as a di-isocyanate and alginic acid as a polyol in presence of dimethyl sulfoxide (DMSO) as a solvent. FT-IR and ¹³C one-dimensional (1D) solid state NMR (SSNMR) spectroscopy indicates that alginic acid is converted into alginate-polyurethane hybrid material via urethane linkage. Surface morphology of alginate-polyurethane hybrids changes by varying alginic acid: TDI ratio. The peak at near 221 °C in DSC thermogram of alginic acid (Alg) is shifted to higher temperature in alginate-polyurethane hybrid (Algpu1 and Algpu2). TGA study shows that alginate-polyurethane hybrid prepared using alginic acid: TDI = 1:1 (Algpu2) is more stable than alginic acid: TDI = 1:0.5 (Algpu1) at 300 °C. Kinetic analysis was performed to fit with TGA data, where the entire degradation process has been considered as three consecutive 1st order reactions. This study shows that thermal stability of alginate-polyurethane hybrid material was increased by adjusting mole ratio of 2, 4-TDI and alginic acid.     

Effect of Solvent Composition on Porosity,Surface Morphology and Thermal Behavior of Metal Alginate Prepared from Algae (<Emphasis Type="Italic">Undaria pinnatifida</Emphasis>)

Alginates, extracted from algae are linear unbranched polymers containing β-(1→4)-linked d-mannuronic acid (M) and α-(1→4)-linked l-guluronic acid (G) residues. The conversion of alginic acid into the metal alginate is confirmed using FTIR spectroscopy. Asymmetric and symmetric stretching of free carboxyl group present in metal alginate occurs almost at the same position in various solvent compositions. Total intrusion volume of metal alginate prepared in propanol (0.0742 mL/g) is greater compared to those in ethanol (0.0648 mL/g) and methanol (0.0393 mL/g) as solvent. Surface morphology as well as porosity and pore size distribution of metal alginate are greatly influenced by solvent. It can be seen from thermal analysis results that calcium alginate prepared using different solvent compositions started decomposing at 100 °C, but rapid degradation started around 200 °C. The results showed a stepwise weight loss during thermal sweep, indicating different types of reactions during degradation. First and second step of rapid degradation was situated around 200–300 and 300–550 °C, respectively; whereas the final step is situated around 550–650 °C. The trend of degradation was similar for all the solvents, although the amount of final residue varied from one solvent to another. At the same time, lower thermal stability was also observed with higher heating rates. Additionally, a kinetic analysis was performed to fit with TGA data, where the entire degradation process has been considered as three consecutive first order reactions.     

Removal of Oil from Water by Calcium Alginate Hydrogel Modified with Maleic Anhydride

Calcium alginate hydrogel was prepared and used as a biosorbent for the removal of oil from aqueous solutions. Calcium alginate hydrogel was further chemically modified by esterification with maleic anhydride. The changes in the physicochemical properties of maleic anhydride modified calcium alginate were investigated via multiple techniques (FTIR, SEM, BET and DSC/TGA). Adsorption batch experiments were carried out to compare the oil adsorption capacities of native and modified calcium alginates. Adsorption experiments were carried out as a function of solution pH, temperature and ionic strength to determine the optimal conditions for the adsorption of oil. Equilibrium and kinetic studies were conducted for the modified alginate. Results revealed that the maleic anhydride modification of calcium alginate improved its adsorption capacity towards oil. Higher adsorption capacities of modified alginate were attained at lower temperatures (20 °C), higher ionic strengths (1.0 M NaCl) and within the pH range of 5–9. The oil adsorption data obtained for modified alginate could be better described by the first order kinetic model (R²?=?0.981) and the BET equilibrium isotherm (R²?=?0.984). The maximum monolayer adsorption capacity predicted by the BET model for the modified calcium alginate was found to be 143.0 mg/g.     

Tannic acid as a novel and green leaching reagent for cobalt and lithium recycling from spent lithium-ion batteries

Tannic acid–acetic acid is proposed as novel and green chemicals for cobalt and lithium recycling from spent lithium-ion batteries through a leaching process. The synergism of both acids was documented through batch and continuous studies. Tannic acid promotes cobalt dissolution by reducing insoluble Co³⁺ into soluble Co²⁺, while acetic acid is critical to improve the dissolution and stabilize the metals in the pregnant leach solution. Based on batch studies, the optimum conditions for metal recovery at room temperature are acetic acid 1 M, tannic acid 20 g/L, pulp density 20 g/L, and stirring speed 250 rpm (94% cobalt and 99% lithium recovery). The kinetic study shows that increasing temperature to 80 °C improves cobalt and lithium recovery from 65 to 90% (cobalt) and from 80 to 99% (lithium) within 4 h at sub-optimum condition (tannic acid 10 g/L). Kinetic modeling suggests the leaching process was endothermic, and high activation energy indicates a surface chemical process. For other metals, the pattern of manganese and nickel recovery trend follows the cobalt recovery trend. Copper recovery was negatively affected by tannic acid. Iron recovery was limited due to the weak acidic condition of pregnant leach solution, which is beneficial to improve leaching selectivity.

     

Biodegradability,hydrolytic degradability,and builder performance in detergent formulations of partially dicarboxylated alginic acid

Partially dicarboxylated alginic acids with degree of dicarboxylations from 13 to 61 mol% were prepared and their biodegradability, hydrolytic degradability, and builder performances in detergent formulations were measured. Also, the correlations between biodegradability and hydrolytic degradability were examined with respect to the degree of dicarboxylation. The biodegradability of dicarboxylated alginic acid sodium salt (DCAa), evaluated by biochemical oxygen demand with activated sludge, depended on the degree of dicarboxylation. DCAa containing more than 75 mol% remaining uronide residues in the polymer chain showed excellent biodegradation. Hydrolytic degradation of DCAa depended on the degree of dicarboxylation and the pH of the incubation media. After 30-day incubation at 30°C at pH 4–6, a significant molecular weight reduction by hydrolytic degradation was observed for highly dicarboxylated alginic acid. DCAa with a high degree of dicarboxylation showed excellent builder performance in detergent formulations based on the detergency and calcium sequestration capacity.     

Effect of Hydrothermal Polylactic Acid Degradation on Polymer Molecular Weight and Surface Properties

In the present work, polylactic acid, PLA, samples were degraded by hydrothermal treatment, and then their molecular weights, crystallinity, surface charges and compositions, were determined, respectively, by using viscometry, ¹H NMR, Differential Scanning Calorimetry (DSC), microelectrophoresis and Infra Red spectroscopy methods. The viscometry and ¹H NMR data indicate that the molecular weight, of the polymer, decreases after the hydrothermal treatment. However, the crystalline fractions of the PLA samples, as obtained from the DSC and X-ray data, were not altered after the hydrothermal treatment. Furthermore, the zeta potential data, as determined by microelectrophoresis, show for both non-degraded and degraded PLA, an increase of the polymer surface charge density with the pH of the aqueous phase. However, at acidic pH values, the surface charge density for the degraded PLA was higher as compared to the non degraded one. These differences in surface charge densities of the PLA samples were confirmed by Infrared study, according to which the spectra of degraded polymer show the appearance of carboxyl groups occurring at 1,600 cm⁻¹ at the polymer surface.     

Polychloroprene Degradation by Photo-Fenton. Conductivity Measures as New Approach for Detecting/Evaluation of Degradation Products

In the present work the photo-degradation of polychloroprene (PCP) in toluene solution catalyzed by FeCl₃·6H₂O and polychromatic light was investigated based on FTIR and ¹³C NMR spectroscopies, on conductivity measurements and DSC technique. The band in the 1700–1790 cm⁻¹ range in the FTIR spectrum characterized the presence of carbonyl products due to the degradation of the PCP on the solution exposed to polychromatic light. The formation of carbonyl on degraded PCP was confirmed by the presence of signal on ¹³C NMR at δ 203.5. Products of PCP degradation, such as acid chlorides, generated in the toluene solution migrate to the aqueous phase (in contact with toluene phase) and the conductivity of aqueous phase increased as the time is elapsed. The area related to the PCP melting-peak on the DSC (film casted after the PCP-FeCl₃·6H₂O toluene solution has been exposed to polychromatic light) significantly decreased in comparison to that in the DSC of the raw PCP cast film.     

Biodegradable Polyesters and Polyamides From Difunctionalized Lauric and Coconut Fatty Acids

In this work, a major fatty acid from coconut oil was used as starting material in preparing biodegradable polymers. Thus, polyesters and polyamides from varying proportions of monomers, hydroxy- and amino- derivatives of lauric acid were synthesized. Initially, the derivatives were prepared by regioselective chlorination of lauric acid, in the presence of ferrous ions in strong acid medium. Subsequent hydroxylation and amination procedures yielded the hydroxy- and amino- derivatives of lauric acid. These monomers were polymerized in a reaction tube by simple polycondensation method at 220–230 °C for 6–8 h without catalyst. Molecular weight determination using –COOH by end group titration and gel permeation chromatography (GPC) gave an average molar mass of 3,000–5,000 g mol⁻¹ with n = 15–25 monomer units. Thermal properties such as glass transition (T_g) and decomposition (T_d) temperatures were obtained using differential scanning calorimetry (DSC). The same processes of synthesis and determinations above were applied to coconut fatty acids, derived from saponification of coconut oil, and resulted to very similar conclusions. A quick biodegradation assay against fungus Aspergillus niger UPCC 4219 showed that the polymers prepared are more biodegradable than conventional plastics such as polypropylene, poly(ethyleneterepthalate) and poly(tetrafluoroethylene) but not as biodegradable as cellulosic (newsprint) paper.     

Morphological and Thermal Characterization of Linseed-Oil Based Polymers from Cationic and Thermal Polymerization

Linseed oil-based polymers have been synthesized via cationic and thermal polymerization and characterized through various techniques, such as SEM, DMA, DSC and TGA. The morphology of the polymer samples after extraction reveals the smooth structure of the polymer matrix. With an increase in oil content, the morphology is observed to be more loosely bound. With an increase in linseed oil content in the samples, the room temperature storage modulus (E′) varies from 10.4 × 10⁷ to 1.8 × 10⁷ Pa. The glass transition temperatures measured through DMA of the cationic samples ranges from 70 to −6 °C and the crosslink densities range from 18.4 × 10³ to 3.4 × 10³ mol/m³. The glass transition temperatures of the thermal samples range from 106 to −4 °C and the crosslink densities range from 7.7 × 10³ to 2.4 × 10³ mol/m³. The TGA results show three stages of degradation of the polymer samples and it is also revealed that these polymers are stable up to 200 °C, showing negligible decomposition.     

Biodegradation of Poly(3-Hydroxybutyrate) Produced from Cupriavidus necator with Different Concentrations of Oleic Acid as Nutritional Supplement

The environmental impact caused by the disposal of plastics has motivated the development of biodegradable materials. Recent studies showed that supplementation with oleic acid (OA) in cultures producing poly(3-hydroxybutyrate), P(3HB), increased the polymer productivity. However only few studies have shown the properties and biodegradation profile of the polymer obtained. This research investigated the influence of OA concentration on the biodegradation of the P(3HB) obtained from cultures of Cupriavidus necator. The crystallinity of the casting films determined by differential scanning calorimetry (DSC) was reduced from 70% (0 g L⁻¹ of OA) to 52% (3.0 g L⁻¹ of OA). A reduction of 11 °C in the melting temperature was observed with 3.0 g L⁻¹ of OA. The kinetic of biodegradation was: 3.0 > 1.5 > 0.9 > 0.3 > 0 g L⁻¹ of OA.     

Utilization of Natural Oils for Decomposition of Polyurethanes

The model polyurethane foam and model compact polyurethane material were prepared and then decomposed by means of natural oils. Castor oil and fish oil based polyol were used in this study. Optimal conditions for the polyurethane decomposition were found. Temperature 250 °C was necessary for efficient polyurethane decomposition by castor oil whereas 200 °C is sufficient in the case of fish oil based polyol. Prepared products have hydroxyl number in the range of 95–168 mg KOH g⁻¹. During the polyurethane decomposition no cleavage of double bonds in the fatty acid chains of castor oil and fish oil based polyol was observed.     

Remediation of acid mine drainage leachate by a physicochemical and biological treatment‐train approach

Biological and physicochemical approaches were utilized in a treatment train for acid mine dis charge (AMD) waters. Anaerobic bioreactors, chemical precipitation reactors, and biopolymer chelation reactors, operated in static, semicontinuous, and continuous flow modes, removed significant quantities of metals and sulfates associated with AMD water. Static tests indicated accept able copper removal via precipitation by generation of hydrogen sulfide in anaerobic reactors. However, low pH affected the biopolymer coating in the chelation reactor, resulting in loss of bed surface. Corrections of AMD to pH > 7 resulted in some metal precipitationprior to biopolymer treatment. A series of static semicontinuous tests at pH 5.0 provided improved metal and sulfate removal. Copper (Cu⁺) was reduced to trace concentrations, while manganese (Mn⁺), although reduced, proved to be the most recalcitrant of the metals. © 2006 Wiley Periodicals, Inc.     

Biodegradation of Epoxy and MF Modified Polyurethane Films Derived from a Sustainable Resource

Mesua ferrea L. seed oil (MFLSO) modified polyurethanes blends with epoxy and melamine formaldehyde (MF) resins have been studied for biodegradation with two techniques, namely microbial degradation (broth culture technique) and natural soil burial degradation. In the former technique, rate of increase in bacterial growth in polymer matrix was monitored for 12 days via a visible spectrophotometer at the wavelength of 600 nm using McFarland turbidity as the standard. The soil burial method was performed using three different soils under ambient conditions over a period of 6 months to correlate with natural degradation. Microorganism attack after the soil burial biodegradation of 180 days was realized by the measurement of loss of weight and mechanical properties. Biodegradation of the films was also evidenced by SEM, TGA and FTIR spectroscopic studies. The loss in intensity of the bands at ca. 1735 cm⁻¹ and ca. 1050 cm⁻¹ for ester linkages indicates biodegradation of the blends through degradation of ester group. Both microbial and soil burial studies showed polyurethane/epoxy blends to be more biodegradable than polyurethane/MF blends. Further almost one step degradation in TG analysis suggests degradation for both the blends to occur by breakage of ester links. The biodegradation of the blends were further confirmed by SEM analyses. The study reveals that the modified MFLSO based polyurethane blends deserve the potential to be applicable as “green binders” for polymer composite and surface coating applications.     

Influence of Carbonyl Fe on Degradation of Epoxy in Ozone Environment

Carbonyl iron/epoxy coatings are widely used in military as a radar absorbing coating (RAC). The behaviors of RACs under working environments are very important, especially in the new environments such as ozone appeared with widening of the application fields. The effects of ozone degradation on pure epoxy cured with anhydride and the influence of carbonyl Fe on the degradation of epoxy are studied. The results indicate that if the peak at 1,510 cm⁻¹ was used as the inner standard, the intensity of absorption peaks at 1,738, 1,247 and 1,182 cm⁻¹ increases with exposure time for pure epoxy resin, while for the carbonyl iron/epoxy coatings, the three peaks changes insignificantly with the exposure time. The results indicates the oxidation process begins at the hydroxyl and methyl groups, and finally ozonide and carbonyl are formed on the surface for pure epoxy, and epoxy is eroded gradually in depth by ozone. Carbonyl iron could hinder the meeting of ozone with epoxy with dilution or hindrance effect and could protect epoxy resin from ozone and thus delay the deterioration of the coating performance.     

Heterotrophic Biological Denitrification Using Microbial Cellulose as Carbon Source

The objective of this study was to investigate the feasibility of using a microbial biopolymer produced by Acetobacter xylinum as a carbon source for heterotrophic biological denitrification. The denitrification rate, COD availability and nitrite concentration were response parameters. Under the experimental conditions, a denitrification rate of about 0.74 kg NO₃ ⁻N/m³d at 6 h retention time was achieved with microbial cellulose (MC). The reactor effluent contained significantly COD concentrations (20–86 mg/L) so it was not carbon limited, and was receiving enough carbon to facilitate the denitrification process. The maximum nitrite concentration in the effluent was found to be 0.4 mg/L. However, decreasing the retention time to 3 h significantly reduced the efficiency. It can be concluded that the MC is a suitable carbon source for nitrate removal in a heterotrophic biological denitrification process.     

Chemical Recycling of Polyamide Waste at Various Temperatures and Pressures Using High Pressure Autoclave Technique

Chemical recycling of polyamide waste in water was studied using 0.5 L high pressure autoclave at temperatures of 150, 200, 210, 220,230 and 240 °C and at various pressures of 100, 200, 300, 400, 500, 600 and 700 psi (pound per square inch). Viscosity average molecular weight of the polyamide waste sample was determined by Ostwald method and recorded as 1.928 × 10³. The reaction was found to be first order with velocity constant in order of 10⁻² min⁻¹. The velocity constant and percent conversion of depolymerization reaction at 240 °C and 700 psi pressure were recorded as 2.936 × 10⁻² min⁻¹ and 99.99% respectively. The velocity constant was obtained on the basis of measurement of amine value. Kinetic and thermodynamic parameters such as energy of activation, frequency factor, enthalpy of activation were found to be 10.6 kJ mole⁻¹, 0.3719 min⁻¹ and 6.3 kJ mole⁻¹ respectively, at the optimum conditions for maximum depolymerization of polyamide waste.     

Field testing of conversion of sewage sludge to daily landfill cover material

Solidification of sewage sludge has been actively investigated in Japan and Europe since the 1970s. Most previous studies have focused on only the mechanical aspects of potential alternative cover soil made using sewage. Most solidification processes, however, suffer from severe odor problems because of the high alkalinity of the material. The objectives of this study are to develop a cost-effective solidifying agent for conversion of sewage sludge in order to reduce the odor generation, as an alternative to the conventional cement lime-based solidifying agent, and to demonstrate its applicability in the field experimentally. Field test results showed compressive strength well above the 1.0 kg/cm² criterion for landfill cover soil in Korea. Also, the permeability coefficient was far below the 5 × 10⁻⁵ cm/s design criterion for landfill cover soil. Even in harsh weather conditions, such as in winter and summer, the compressive strength was increased. In addition, the permeability was decreased from 3.45 × 10⁻⁶ cm/s to 4.78 × 10⁻⁷ cm/s, and from 2.27 × 10⁻⁶ cm/s to 3.62 × 10⁻⁷ cm/s, at 7 days after placement in January and August, respectively. It can therefore be postulated that the proposed solidification process is an appropriate alternative for production of daily landfill cover material. Concerning the odor problem, 5 min of mixing of sewage with TS103, one of the proprietary agents used in this work, was sufficient to suppress the concentration of ammonia emitted to below 10 ppm. Considering all of these experimental field test results, it is expected that the proposed method could be a competitive approach for manufacture of alternative landfill cover material.     

Palm Oleic Acid Based Alkyds: Effect of the Fatty Acid Content on the Polyesterification Kinetics

The kinetic behavior of polyesterification of the alkyd resins synthesized using glycerol and phthalic anhydride modified with oleic acid from the palm oil at temperatures between 120 and 240 °C was studied. Three alkyds having oleic acid contents of 28, 40, and 65% were prepared by employing fatty acid method. The extent of the polyesterification reaction and average degree of polymerization were monitored by determining the acid number of the aliquot of the reaction mixture at various intervals of time and by measuring the volume of water evolved. Kinetic studies revealed that initial reaction rates followed a second-order kinetics up to certain limit and thereafter deviations were observed. The extent of reaction varied from 77.4 to 86.3% before deviation for all the three samples and exhibited a considerable degree of conversion. The second-order rate constants calculated from the linear part were found to be of the order of 10⁻⁵ g (mg KOH)⁻¹ min⁻¹. Molecular weight of the alkyd samples was determined by GPC; number average molecular weight of the alkyds ranged from 980 to 2,070.     

Formation and decomposition of tetrafluoroborate ions in the presence of aluminum

The formation and decomposition of tetrafluoroborate ions (BF₄⁻) in H₃BO₃-Al³⁺-F⁻ solutions were investigated via experiments and thermodynamic calculations. The concentration of the formed BF₄⁻ increased with decreasing pH, raising the total fluoride concentration and lowering the total aluminum ion concentration. Once formed, BF₄⁻ was stable under neutral and alkaline conditions. Fluoride in the form of BF₄⁻ was converted to fluoroaluminate ions by adding an aluminum compound under acidic conditions. A method for removing fluoride in the form of BF₄⁻ is proposed whereby fluoroaluminate ions formed by the reaction of BF₄⁻ with aluminum are decomposed with calcium ions. This process was applied to the treatment of wastewater from flue gas desulfurization plants, and resulted in a satisfying level of reduction in the range of the fluoride emission limit of 8 mg/l.     

Kinetics and Thermodynamics of Hydrolytic Depolymerization of Polyamide Waste at Various Temperature and Autogenious Pressure by High-Pressure Autoclave

Hydrolytic depolymerization of polyamide waste in water was studied using 0.5 L high pressure autoclave at temperatures of 235, 240, 245, 250 °C and at autogenious pressure 480, 500, 520, and 600 psi (pound per square inch).The reaction rate constant, energy of activation, enthalpy of activation, entropy of activation and equilibrium constant were calculated from the experimental data obtained. The maximum depolymerization (59.2%) of polyamide waste into monomer caprolactum was obtained at 250 °C and 600 psi pressure. The reaction rate constant was obtained on basis of measurement of amine value and residual weight. The depolymerization reaction was found to be pseudo first order with reaction rate constant of the order of 10⁻³ min⁻¹. The enthalpy, entropy and free energy of activation were recorded as 85.75, −0.1354 and 156.59 kJ mol⁻¹ respectively at the experimental conditions for maximum depolymerization of polyamide waste. The thermodynamic equilibrium constant for this hydrolysis reaction was found to be 2.3 × 10⁻¹⁶.