Alkaline Degradation of Cellulose: Mechanisms and Kinetics

Cellulose powder and softwood sawdust were subjected to alkaline degradation under conditions representative of a cementitious environment for periods of 7 and 3 years, respectively. During the first 3 years, sampling was frequent, and data on the degradation of cellulose and production of isosaccharinic acid was used for establishing long-term prediction models. Samples after an additional period of 4 years were compared to the predicted values. The total rate of degradation was measured as the increase in total organic carbon (TOC) in corresponding solutions. A previously published theoretical model of degradation kinetics gave a good approximation of the present experimental data. Peeling-off, stopping, and alkaline hydrolysis reaction rate constants were obtained as model parameters, and the results suggested that the transformation of the glucose end group is the rate-limiting step in the cellulose peeling-off reaction and also determines the pH dependence of that reaction. After 3 years, isosaccharinic (ISA) acid represented 70–85% of all degradation products as quantified by capillary zone electrophoresis. The long-term prediction model indicated that all of the cellulose would be degraded after only 150–550 years. The control sampling after 7 years points toward a lower degradation of cellulose and production of ISA than predicted by the model, reflecting either a degradation of ISA that was faster than the production or a termination of the ISA production.     

Degradation of Cellulosic Materials Under the Alkaline Conditions of a Cementitious Repository for Low- and Intermediate-Level Radioactive Waste. II. Degradation Kinetics

The degradation of cellulosic materials, differing mainly in the degree of polymerization and the number of reducing end groups, was studied under the alkaline conditions similar to those existing in a cementitious repository for low- and intermediate-level radioactive waste (pH 13.3, T = 25°C). The kinetics of alkaline degradation (peeling-off reaction) were studied and the data analyzed by the model of Haas et al. [13]. The observed kinetic parameters for the propagation reaction and overall stopping reaction were compared with literature data. Although measured under different experimental conditions, literature data and data from this study show a consistent picture. Differences in the extent of degradation observed for the different cellulosic materials could be satisfactorily explained by differences in reducing end group content and, consequently, by differences in the degrees of polymerization. Besides the number of reducing end groups, the degree of amorphousness also plays an important role. The main degradation products formed under the experimental conditions used are - and -(gluco)isosaccharinic acid. This is in agreement with many other studies on alkaline degradation of cellulose. The two isomers are formed in roughly equal amounts.     

Effect of organics on selenite uptake by cementitious materials

The behaviour of three organic ligands in suspensions of fresh and degraded hydrated ordinary Portland cement pastes (HCP) has been investigated. EDTA arises as a decontamination product whilst ISA (isosaccharinic acid) is a main degradation product of cellulose. GLU (gluconic acid) is used as a retarding organic admixture in concrete. The affinity of EDTA, ISA and GLU with HCP increases with the degradation state. At long contact times, ISA and GLU desorbed from HCP, perhaps as a result of carbonation. Their influence on the uptake of selenium (as SeO3(2-)) on HCP has been studied as a function of time, addition order and HCP degradation state. The sorption study of Se(IV) also shows a positive effect of the HCP degradation with R(d)=120 mLg(-1) for fresh HCP and 1000 mLg(-1) for degraded HCP. The addition order of Se(IV) and EDTA or ISA is important as pre-equilibration of HCP with either EDTA or ISA drastically decreases the uptake of Se(IV) to 10-30 mLg(-1). Mixing of cement with GLU seems to reduce the strong competitive effect of other organic compounds on Se(IV) sorption.     

Rheology of Concentrated Cellulose Solutions in 1-Butyl-3-methylimidazolium Chloride

Rheological behavior of the concentrated cellulose/1-butyl-3-methylimidazolium chloride ([BMIM]Cl) solutions was investigated. As polymeric fluid, solutions of cellulose in [BMIM]Cl display a marked elastic behavior under shear flow. The dependence of the shear viscosity η, and of the dynamic modulus, on concentration, average degree of polymerization (DP) and temperature is discussed. At lower concentrations and degrees of polymerization (DP), cellulose solutions show viscous, inelastic behavior at low frequencies and low shear rate. At higher concentration and DP, cellulose solutions are more elastic at higher frequencies and shear rate. Such solutions also have some usual rheological properties. The dynamic rheological responses revealed that the Cox–Merz rule did not hold for these cellulose solutions at high deformation rate. Plotting storage modulus G′ against loss modulus G″ gave almost a master curve which is independent of temperature and concentration, with the slope of about 1.651 for 10 wt% cellulose solutions. This value indicates the existence of microheterogeneity in the solution system.     

Evaluation of PFAS treatment technology: Alkaline ozonation

A bench‐scale treatability study was performed to evaluate the effectiveness of alkaline ozonation on removing per‐ and polyfluoroalkyl substances (PFAS) present in groundwater at a former industrial site in Michigan. The study involved testing the PFAS‐impacted groundwater under alkaline ozonating conditions under a range of experimental conditions, including modifying pH, hydrogen peroxide‐to‐ozone molar ratio doses, length of ozonation pretreatment times, and sampling techniques. PFAS‐spiked samples were used to determine if inorganic ions such as fluoride (F^?), sulfate (SO₄^2?), formate (HCOO^?), acetate (CH₃COO^?), and trifluoroacetate (CF₃COO^?) were generated or if there were decreases in total organic fluorine resulting from PFAS treatment. The results from all tests indicate that decreases in PFAS concentrations were due to a combination of removal and destructive mechanisms with enhanced removal under acidic pH ozonation pretreatment conditions. Short‐chain PFAS concentrations increased during the experiments followed by an overall decrease in concentration under continuous alkaline ozonation conditions. Reductions in concentrations in perfluorooctane sulfonic acid of 75–97% were observed. Reductions in concentrations were also observed in other PFAS such as 6:2 FTS, PFHxS, PFOA, and PFNA. To our best knowledge, this is the first time that alkaline ozonation has been performed on PFAS‐impacted water while monitoring a larger suite of PFAS analytes in addition to destruction byproducts. Treatment of PFAS under the conditions discussed in this paper suggests that alkaline ozonation may be a viable remediation option for PFAS‐impacted waters.     

酸浸—萃取—沉淀法回收废锂离子电池中的钴

采用酸浸—萃取—沉淀法回收废锂离子电池中的钴。实验结果表明:废锂离子电池在600℃下煅烧5 h可将正极材料上的有机黏结剂与正极活性物质分离;正极活性物质在Na OH溶液浓度为2.0 mol/L、n(Na OH)∶n(铝)=2.5、碱浸温度为20℃的条件下碱浸反应1 h后,铝浸出率达99.7%;已除铝的正极活性物质在硫酸浓度为2.5 mol/L、H_2O_2质量浓度为7.25 g/L、液固比为10、酸浸温度为85℃的条件下酸浸反应120 min,钴浸出率高达98.0%;酸浸液在p H为3.5、萃取剂P507与Cyanex272体积比为1∶1的条件下,经2级萃取,钴萃取率为95.5%;采用H_2SO_4溶液反萃后在硫化钠质量浓度为8 g/L、反萃液p H为4的条件下沉淀反应10 min,钴沉淀率达99.9%。     

Effects of Temperature and Relative Humidity on Polylactic Acid Plastic Degradation

Three high molecular weight (120,000 to 200,000 g mol^–1) polylactic acid (PLA) plastic films from Chronopol (Ch-I) and Cargill Dow Polymers (GII and Ca-I) were analyzed for their degradation under various temperature and relative humidity (RH) conditions. Two sets of plastic films, each containing 11 samples, were randomly hung in a temperature/humidity-controlled chamber by means of plastic-coated paper clips. The tested conditions were 28, 40, and 55°C at 50 and 100% RH, respectively, and 55°C at 10% RH. The three tested PLA films started to lose their tensile properties when their weight-average molecular weight (M _w) was in the range of 50,000 to 75,000 g mol^–1. The average degradation rate of Ch-I, GII, and Ca-I was 28,931, 27,361, and 63,025 M _w/week, respectively. Hence, GII had a faster degradation rate than Ch-I and Ca-I under all tested conditions. The degradation rate of PLA plastics was enhanced by the increase in temperature and relative humidity. This trend was observed in all three PLA plastics (Ca-I, GII, and Ch-I). Of the three tested films, Ch-I was the first to lose its mechanical properties, whereas Ca-I demonstrated the slowest loss, with mechanical properties under all tested conditions.     

Biodegradation of Poly(Aspartic Acid-Itaconic Acid) Copolymers by Miscellaneous Microbes from Natural Water

Poly(aspartic acid-itaconic acid) copolymers (PAI) is a new scale inhibitor for water treatment. Thus, it is necessary to investigate its biodegradability. The biodegradability of PAI was investigated through CO₂ evolution tests under different conditions based on determination of carbon dioxide production. The investigation results showed that the degradation rate of PAI on day 10 and day 28 were respectively 38.7 and 79.5%, indicating that PAI was one kind of easily biodegradable scale inhibitors. With the increase in the content of itaconic acid in copolymerization process, the biodegradability of PAI was significantly reduced. In addition, the high biodegradability might be attributed to the existence of C–N bone-structure and more –COO–. Finally, Cu²⁺ could decrease the degradation percentage and the enzyme inhibition effect of Cu²⁺ was not the linear effect, but the “low-dosage effect”.     

Release Of Some Trace Elements From Sluiced Fly Ash On Acidic Soils With Particular Reference To Boron

The purpose of this study was to examine the relationship between the concentration of boron (B) and some other selected trace elements in soil solution as effected by hydrogen ion activity within the normal pH range for acidic soils commonly amended with agricultural limestone and, alternatively, alkaline fly ash. Sluiced alkaline fly ash was applied to an acidic, clay textured soil at rates equivalent to 0, 42, 84, 125 and 167 tonne ha^-1 based on the soil lime requirement. After wheat was grown and harvested the soil-ash mixtures were maintained at field capacity moisture content for an additional 4 months before pore water samples were extracted by immiscible displacement. The total concentrations of Co, Cr, Fe, V and Zn in the ash treated soils increased by < 10% at the highest application rate of ash, the content of Cu was increased by 13% and B by 38%. Only the concentration of boron increased appreciably in the pore water extracts. Release of B from the ash was correlated with the solubility behaviour of Ca and Mg, and not with the dissolution of glass phases in the ash. Speciation and adsorption calculations for the extracts were carried out using the program MINTEQ. Common Ca, Mg and Na borate minerals were undersaturated with respect to the equilibrated solutions. Application of the constant capacitance model to the adsorption of B on mineral surfaces suggested that adsorption had little effect on total dissolved B at pH values below 6.0. Predicted concentrations of B in solutions, equilibrated with calcite in a subsurface horizon, were up to 10.6 mg dm^-3; more than double the recommended maximum concentration for B (5mg dm^-3) in potable water in Ontario.     

The Effect of Extraction Conditions on the Chemical Characteristics of Pectin from Opuntia ficus indica Cladode Flour

Pectin from the cladode flour of Opuntia ficus indica was extracted at different ethylenediaminetetraacetate concentrations (10 or 20 %), temperatures (40 or 80 °C), pH values (2 or 11), and times (10, 20, 30 40, 50 or 60 min). The effects of the extraction conditions on the yield, purity, and chemical composition of pectin were assessed. The highest pectin yield was observed for pectin obtained under alkaline conditions and 20 % of EDTA. However, pectin produced from alkaline extractions had a lower content of GalA than pectin produced from acid extractions. Higher temperatures favored the extraction of pectin under acid conditions, but these conditions diminished the arabinose content of pectins in a time-dependent manner. The tested extraction conditions caused only slight changes in the molecular weight of the extracted pectin as a function of time.     

废无汞碱性电池极性材料制备锰锌铁氧体磁性纳米颗粒

以硝酸浸取废无汞碱性电池极性材料,再加入硝酸铁及蔗糖生成前驱体,最后通过焙烧制得锰锌铁氧体磁性纳米颗粒。优化了酸浸和焙烧条件,采用FTIR和DTA-TG技术研究了前驱体的形成和热解过程,采用XRD、FTIR、TEM技术和振动样品磁强计对锰锌铁氧体进行了表征。结果表明:废无汞碱性电池极性材料酸浸的最佳条件为H_2O_2加入量3%(w)、液固比10 mL/g、稀硝酸浓度4 mol/L、浸取温度40℃,该条件下浸取10 min锰和锌的浸出率均可达100%;所得前驱体为葡萄糖酸盐,其最佳焙烧条件为焙烧温度450℃、焙烧时间2 h;最佳条件下所得锰锌铁氧体为尖晶石型Mn_(0.5)Zn_(0.5)Fe_2O_4,其颗粒为球形、大小均匀,且磁性能优良。     

Chloroethene dechlorination in acidic groundwater: Implications for combining fenton's treatment with natural attenuation

A sulfuric acid leak in 1988 at a chloroethene‐contaminated groundwater site at the Naval Air Station Pensacola has resulted in a long‐term record of the behavior of chloroethene contaminants at low pH and a unique opportunity to assess the potential impact of source area treatment technologies, which involve acidification of the groundwater environment (e.g., Fenton's‐based in situ chemical oxidation), on downgradient natural attenuation processes. The greater than 75 percent decrease in trichloroethene (TCE) concentrations and the shift in contaminant composition toward predominantly reduced daughter products (dichloroethene [DCE] and vinyl chloride [VC]) that were observed along a 30‐m groundwater flow path characterized by highly acidic conditions (pH = 3.5 ± 0.4) demonstrated that chloroethene reductive dechlorination can continue to be efficient under persistent acidic conditions. The detection of Dehalococcoides‐type bacteria within the sulfuric acid/chloroethene co‐contaminant plume was consistent with biotic chloroethene reductive dechlorination. Microcosm studies conducted with ¹⁴C‐TCE and ¹⁴C‐VC confirmed biotic reductive dechlorination in sediment collected from within the sulfuric acid/chloroethene co‐contaminant plume. Microcosms prepared with sediment from two other locations within the acid plume, however, demonstrated only a limited mineralization to ¹⁴CO₂ and ¹⁴CO, which was attributed to abiotic degradation because no significant differences were observed between experimental and autoclaved control treatments. These results indicated that biotic and abiotic mechanisms contributed to chloroethene attenuation in the acid plume at NAS Pensacola and that remediation techniques involving acidification of the groundwater environment (e.g., Fenton's‐based source area treatment) do not necessarily preclude efficient chloroethene degradation. © 2007 Wiley Periodicals, Inc.     

Air Pollution Zones and Harmful Pollution Levels of Alkaline Dust for Plants

For characterisation of landscapes in north-eastern Estoniaaffected by alkaline oil shale fly ash and cement dust the zonation-method based on average annual (C _y) and short-termconcentrations of pollutants in the air was used, as well as on deposition loads of dust and Ca²⁺. In the overground layer of atmosphere the zones with different air pollution loads were distinguished. A comparative analysis of pollution zones characteristics and biomonitoring data revealed that for sensitive lichen the dangerous level of alkaline dust in the air, introducingthe degradation of Sphagnum sp. at the level of C _y of dust 10–20 g m^-3 and at 0.5–1 hr maximums 100–150 g m^-3. For Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) this limited concentration (decline of growth parameters) of cement dust is correspondingly following: 30–50 g m^-3 and 150–500 g m^-3, in case of fly ash the limit level of C _y amounting 100 g m^-3. Daily deposition load of Ca²⁺ should not exceed approximately 4.5–15 mg m^-2 for lichen; for conifers the harmful pollution load is higher – >22 mg m^-2.     

Study concerning the recovery of zinc and manganese from spent batteries by hydrometallurgical processes

Used batteries contain numerous metals in high concentrations and if not disposed of with proper care, they can negatively affect our environment. These metals represent 83% of all spent batteries and therefore it is important to recover metals such as Zn and Mn, and reuse them for the production of new batteries. The recovery of Zn and Mn from used batteries, in particular from Zn–C and alkaline ones has been researched using hydrometallurgical methods. After comminution and classification of elemental components, the electrode paste resulting from these processes was treated by chemical leaching. Prior to the leaching process the electrode paste has been subjected to two washing steps, in order to remove the potassium, which is an inconvenient element in this type of processes. To simultaneously extract Zn and Mn from this paste, the leaching method in alkaline medium (NaOH solution) and acid medium (sulphuric acid solution) was used. Also, to determine the efficiency of extraction of Zn and Mn from used batteries, the following variables were studied: reagents concentration, S/L ratio, temperature, time. The best results for extraction yield of Zn and Mn were obtained under acid leaching conditions (2 M H₂SO₄, 1 h, 80 °C).     

Rheology of Lyocell Solutions from Different Cellulose Sources

Rheological measurements were used to characterize the behavior of lyocell solutions, i.e., cellulose dissolved in N-methymorpholine-N-oxide. Cellulose sources included dissolving pulp, kraft pulp, sugar cane fibers, and kenaf fibers. The dominance of viscous behavior, G values, over elastic behavior, G values, is affected by cellulose concentration and molecular weight. At lower concentrations and degrees of polymerization (DP), dissolving pulp solutions show viscous, inelastic behavior at low frequencies. At higher concentration and DP, dissolving pulp solutions are more elastic at higher frequencies. Solutions prepared with kenaf and sugar cane fibers show similar properties to those using pure dissolving pulp, and comparisons suggest the molecular weight and/or the presence of other substances such as lignin in the cellulose from these alternative sources affect the rheology.     

Stable isotope signatures for characterising the biological stability of landfilled municipal solid waste

Stable isotopic signatures of landfill leachates are influenced by processes within municipal solid waste (MSW) landfills mainly depending on the aerobic/anaerobic phase of the landfill. We investigated the isotopic signatures of δ¹³C, δ²H and δ¹⁸O of different leachates from lab-scale experiments, lysimeter experiments and a landfill under in situ aeration. In the laboratory, columns filled with MSW of different age and reactivity were percolated under aerobic and anaerobic conditions. In landfill simulation reactors, waste of a 25 year old landfill was kept under aerobic and anaerobic conditions. The lysimeter facility was filled with mechanically shredded fresh waste. After starting of the methane production the waste in the lysimeter containments was aerated in situ. Leachate and gas composition were monitored continuously. In addition the seepage water of an old landfill was collected and analysed periodically before and during an in situ aeration.We found significant differences in the δ¹³C-value of the dissolved inorganic carbon (δ¹³C-DIC) of the leachate between aerobic and anaerobic waste material. During aerobic degradation, the signature of δ¹³C-DIC was mainly dependent on the isotopic composition of the organic matter in the waste, resulting in a δ¹³C-DIC of ?20‰ to ?25‰. The production of methane under anaerobic conditions caused an increase in δ¹³C-DIC up to values of +10‰ and higher depending on the actual reactivity of the MSW. During aeration of a landfill the aerobic degradation of the remaining organic matter caused a decrease to a δ¹³C-DIC of about ?20‰. Therefore carbon isotope analysis in leachates and groundwater can be used for tracing the oxidation–reduction status of MSW landfills.Our results indicate that monitoring of stable isotopic signatures of landfill leachates over a longer time period (e.g. during in situ aeration) is a powerful and cost-effective tool for characterising the biodegradability and stability of the organic matter in landfilled municipal solid waste and can be used for monitoring the progress of in situ aeration.     

An Effect of Salt Concentration and Inoculum Size on Poly(Vinyl Alcohol) Utilization by Two <Emphasis Type="Italic">Sphingomonas</Emphasis> Strains

Due to its widespread use and water solubility, poly(vinyl alcohol) (PVA) has the potential to find its way into various water or soil ecosystems. Despite the fact that many bacterial species with the capacity of utilizing PVA have been found and described, the influences of some environmental factors on their capabilities to biodegrade PVA have not been adequately studied. Therefore, study was made of the effects of two environmental factors on PVA degradation exhibited by two Sphingomonas strains. Both strains originated from common wastewater treatment plants, and proved to be considerably sensitive to increased inorganic salt concentrations; in brief, 13.3 mmol/l either of phosphate or chloride ions significantly delayed the degradation process or inhibited it entirely. In contrast to such halosensitivity, both strains were able to rapidly utilize PVA under suitable conditions, even when low inoculum sizes were applied. Initial cell densities, ranging from 10⁰ to 10⁷ cells/ml, were used in two series of degradation trials and PVA degradation occurred in all cases; merely delays extending over several days in the degradation process were noted when inoculum sizes of 10⁰–10³ cells/ml were applied.     

Water transport in polylactic acid (PLA), PLA/ polycaprolactone copolymers, and PLA/polyethylene glycol blends

Polylactic acid (PLA) is a hydrolytically degradable aliphatic polyester, and water vapor permeability may have a significant influence on the rate of degradation. A method is devised to use bags prepared from PLA films and filled with molecular sieves to determine the water vapor permeability in the polymer, its copolymers with caprolactone, and blends with polyethylene glycol. The “solution-diffusion” model is used to determine the permeability parameters. These include the solubility coefficient,S, a measure of the equilibrium water concentration available for hydrolysis and the diffusion coefficient,D, which characterizes the rate of water vapor diffusion into the film under specific conditions. Values ofS andD at 50‡C and 90% relative humidity ranged from 400 × 10^-6 to 1000 × 10^-6 cm³ (STP)/(cm³ Pa) and 0.20 × 10^-6 to 1.0 × 10^-6 cm²/s, respectively. TheS andD coefficients were also measured at 20 and 40‡C and compared to those of other polymers. The degree of crystallinity was found to have little influence on the measured permeability parameters. The heat of sorption, δH_S, and the activation energy of diffusion, E_D, were used to show that the permeability process is best described by the “water cluster” model for hydrophobic polymers. Finally, the diffusion coefficient is used to compare the rate of water diffusion to the rate of water consumption by ester hydrolysis. Results indicate that hydrolytic degradation of PLA is reaction-controlled.     

Sonophotocatalytic Degradation of Chitosan in the Presence of Fe(III)/H2O2 System

The degradation of chitosan by means of ultrasound irradiation and its combination with homogeneous photocatalysis (photo-Fenton) was investigated. Emphasis was given on the effect of additive on degradation rate constants. 24 kHz of ultrasound irradiation was provided by a sonicator, while an ultraviolet source of 16 W was used for UV irradiation. To increase the efficiency of degradation process, degradation system was combined with Fe(III) (2.5 × 10⁻⁴mol/L) and H₂O₂ (0.020–0.118 mol/L) in the presence of UV irradiation and the rate of degradation process change from 1.873 × 10⁻⁹−6.083 × 10⁻⁹ mol^1.7 L s⁻¹. Photo-Fenton process led to complete chitosan degradation in 60 min with the rate increasing with increasing catalyst loading. Sonophotocatalysis in the presence of Fe(III)/H₂O₂ was always faster than the respective individual processes. A synergistic effect between ultrasound and ultraviolet irradiation in the presence of Fenton reagent was calculated. The degraded chitosans were characterized by X-ray diffraction (XRD), gel permeation chromatography (GPC) and Fourier transform infrared (FT-IR) spectroscopy and average molecular weight of ultrasonicated chitosan was determined by measurements of intrinsic viscosity of samples. The results show that the total degree of deacetylation (DD) of chitosan change, partially after degradation and the decrease of molecular weight led to transformation of crystal structure. A negative order for the dependence of the reaction rate on total molar concentration of chitosan solution within the degradation process was suggested. Results of this study indicate that the presence of catalyst in the reaction medium can be utilized to reduce molecular weight of chitosan while maintaining the power of irradiated ultrasound and degree of deacetylation.     

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.