Wet oxidation of recalcitrant lignin water solutions: experimental and reaction kinetics

The purpose of the research was to study the behavior of lignin degradation under different conditions (T 110–190°C, pO₂ 0.5–1.5 MPa, pH 5, 9 and 12) and to develop a predictive model. Temperature increase improved lignin removal from 75% at 110°C to 100% at 190°C (experimental). Increasing the pH enhanced the lignin removal efficiency from 30 to 97% (experimental). The developed model predicted the lignin degradation and changes in COD, BOD and TOC. The model agreed well with the experimental data (R ² = 0.93 at pH 5 and 12).     

Sources and concentrations of vascular plant material in sediments of Buzzards Bay,Massachusetts, USA

Samples of surface sediment from Buzzards Bay and creek sediment from Great Sippewissett Marsh were analyzed for lignin and stable carbon isotope composition in 1984. The lack of change in composition of lignins in detritus of Spartina alterniflora over two years of decomposition and similar aldehyde/acid ratios of lignin oxidation products of plant and sediment samples indicated minimal diagenesis of lignins in sediments. Remains of non-woody angiosperm tissues made up the bulk of the vascular plant debris in Great Sippewissett Marsh and Buzzards Bay sediments. These plant remains were evenly distributed over the sampling area in Buzzards Bay. Based on model calculations, salt marshes potentially contributed a significant fraction of the total amount of vascular plant debris in coastal marine sediments. The bulk of the organic matter in Buzzards Bay sediments, however, was derived from phytoplankton; vascular plant remains made up only 5 to 7% of the total amount of organic carbon in these sediments.     

Miscanthus × Giganteus straw and pellets as sustainable fuels and raw material for activated carbon

Miscanthus × Giganteus is an excellent candidate for energy cultivation. Here we report, for the first time, the results of the pyrolysis of Miscanthus × Giganteus straw or pellets both in tubular reactor (3–6 g) and in rotary kiln (10–30 g). At 400–600°C the fractions obtained from both reactors are: solid 16–25 (wt.%); liquids 25–40; water 15–20 and gases 15–50. GC-MS analyses of pyrolysis liquids reveal the occurrence of phenolic derivatives and ethanol from lignin, furanic and linear oxygenated compounds from cellulose and hemicellulose. Finally the chars produced by the pyrolysis of M×G pellets in rotary kiln present good calorific values close to 29,000 J/g. Additionally, activated carbons with a BET surface area as high as 800–900 m²/g are produced from pellets. These results indicate that chars have a good potential either for energy production, e.g. briquetting, or as adsorbents precursors.     

Individual and combined toxicity of some petroleum aromatics to the marine amphipod Elasmopus pectenicrus

Toxicity of 4 components of petroleum oils to the marine amphipod Elasmopus pectenicrus (Bate) has been assessed. Two ephemeral aromatic hydrocarbons, naphthalene (A) and 1, 2, 4-trimethylbenzene (B) were more toxic than two persistent aromatics, o-cresol (C) and o-toluidine (D). The acute toxicity concentrations obtained for individual aromatic compounds were always greater than the actual concentrations found in the water-soluble fractions (WSF) of fuel oils. Results from mixtures of 2 or more components indicated that the LC₅₀ levels were primarily determined by the more toxic substances, A and B. Naphthalene and 1, 2, 4-trimethylbenzene became more toxic to the E. pectenicrus when present in a mixture of more than 2 components, and the toxicity increased with increasing numbers of components present. Synergistic effects, therefore, possibly occur in the whole WSF. No antagonistic effects were observed among the 4 petroleum aromatics.University of Texas, Marine Science Institute Contribution No. 290     

Effects of temperature on pyrolysis products of oil sludge

Temperature is the determining factor of pyrolysis, which is one of the alternative technologies for oil sludge treatment. The effects of final operating temperature ranging from 350 to 550°C on pyrolysis products of oil sludge were studied in an externally-heating fixed bed reactor. With an increase of temperature, the mass fraction of solid residues, liquids, and gases in the final product is 67.00%–56.00%, 25.60%–32.35%, and 7.40%–11.65%, and their corresponding heat values are 34.4–13.8 MJ/kg, 44.41–46.6 MJ/kg, and 23.94–48.23 MJ/Nm³, respectively. The mass and energy tend to shift from solid to liquid and gas phase (especially to liquid phase) during the process, and the optimum temperature for oil sludge pyrolysis is 500°C. The liquid phase is mainly composed of alkane and alkene (C₅–C₂₉), and the gas phase is dominantly HC_S and H₂.     

Pyrolysis of WEEE plastics using catalysts produced from fly ash of coal gasification

Catalytic pyrolysis of thermoplastics extracted from waste electrical and electronic equipment (WEEE) was investigated using various fly ash-derived catalysts. The catalysts were prepared from fly ash by a simple method that basically includes a mechanical treatment followed by an acid or a basic activation. The synthesized catalysts were characterized using various analytical techniques. The results showed that not treated fly ash (FA) is characterized by good crystallinity, which in turn is lowered by mechanical and chemical treatment (fly ash after mechanical and acid activation, FAMA) and suppressed almost entirely down to let fly ash become completely amorphous (fly ash after mechanical and basic activation FAMB). Simultaneously, the surface area resulted increased. Subsequently, FA, FAMB and FAMA were used in the pyrolysis of a WEEE plastic sample at 400°C and their performance were compared with thermal pyrolysis at the same temperature. The catalysts principally improve the light oil yield: from 59 wt.% with thermal pyrolysis to 83 wt.% using FAMB. The formation of styrene in the oil is also increased: from 243 mg/g with thermal pyrolysis to 453 mg/g using FAMB. As a result, FAMB proved to be the best catalyst, thus producing also the lowest and the highest amount of char and gas, respectively.

Open image in new window

     

Removal of cyanide in aqueous solution by oxidation with hydrogen peroxide in presence of activated alumina

This work is dedicated to the removal of free cyanide from aqueous solution by oxidation with hydrogen peroxide H₂O₂ catalyzed by neutral activated alumina. Effects of initial molar ratio [H₂O₂]₀/[CN^?]₀, catalyst amount, pH, and temperature on cyanide removal have been examined. The presence of activated alumina has increased the reaction rate showing thus, a catalytic activity. The rate of removal of cyanides increases with rising initial molar ratio [H₂O₂]₀/[CN^?]₀ but decreases at pH 10 to 12. Increasing the alumina amount from 1.0 to 30 g/L has a beneficial effect, and increasing the temperature from 20 °C to 35 °C improves cyanide removal. The kinetics of cyanide removal has been found to be of pseudo-first-order with respect to cyanide and the rate constants have been determined.     

Sorption of phenanthrene to biochar modified by base

Biochar (BC) is a potential material for removal of polycyclic aromatic hydrocarbons from soil and water, and base modification is a promising method for improving its sorption ability. In this study, we synthesized a series of base-modified biochars, and evaluated their sorption of phenanthrene. Original biochars were produced by pyrolysis of three feedstocks (rice straw, wood and bamboo) at five temperatures (300°C, 350°C, 400°C, 500°C and 700°C). Base-modified biochars were further obtained by washing of biochars with base solution. The base soluble carbon (SC) was extracted from the supernatant, which were only obtained from biochars pyrolyzed at low temperatures (<500°C) and the content was decreased with the increase of pyrolysis temperature. The SC content between different feedstocks followed the trend of rice straw>wood>bamboo when same pyrolysis conditions were applied. It was found that base modification improved the sorption of phenanthrene on biochars that SC could be extracted from (extractable-BCs). However, base treatment but had limited effects for biochars that no SC could be extracted from. It suggested that base modification improved the sorption of phenanthrene to extractable-BCs by removing the SC and thus increasing the surface area and hydrophobicity. Therefore, base modification was suggested to be used in modifying extractable-BCs.

Open image in new window

     

Thermogravimetric coupled with Fourier transform infrared analysis study on thermal treatment of monopotassium phosphate residue

In China, safe disposal of hazardous waste is more and more a necessity, urged by rapid economic development. The pyrolysis and combustion characteristics of a residue from producing monopotassium phosphate (monopotassium phosphate residue), considered as a hazardous waste, were studied using a thermogravimetric, coupled with Fourier transform infrared analyzer (TG-FTIR). Both pyrolysis and combustion runs can be subdivided into three stages: drying, thermal decomposition, and final devolatilization. The average weight loss rate during fast thermal decomposition stage in pyrolysis is higher than combustion. Acetic acid, methane, pentane, (acetyl) cyclopropane, 2,4,6-trichlorophenol, CO, and CO₂ were distinguished in the pyrolysis process, while CO₂ was the dominant combustion product.     

Vorschlag zur Auswertung von PAK-Kontaminationen

The behaviour of this group of substances may be considered as an example for the ubiquitous occurence of xenobiotics in the environment. Regrettably, the measurements presented in numerous publications often cannot be directly compared with each other. A first step towards harmonization can be achieved by referring the measuring programmes or the presentation of results to the six aromatics of the German Drinking Water Ordinance (TWV) (Σ6) or the sixteen compounds of the EPA list. The tendency of the PAH group to fractionation in air, water, and soil as well as in some cases during analysis must be taken into acount. In this respect, the first six aromatics of the EPA list are only partially suitable for comparisons of results. The six TWV aromatics in soils, sediments, aquatic suspended solids, and sewage sludges, and to a certain extent also in airborne dust, make up a mass portion of C_Σ6=40–50% of the Σ16 according to EPA. For Fluoranthene (Fluo) and Benzo(a)pyrene (Bap) as quide parameters, concentration quotients [single aromatic versus (Σ6)] may be given as estimates, which are on average C_Fluo=33%, and C_Bap=13%. By means of these quotients it is possible to calculate the values for the whole list by means of the data of the single aromatic C_Fluo×3=C_Σ6, or C_Bap×7,7=C_Σ6, and as a check C_Fluo/C_Bap=2,5. For estimating purposes, the relation between the two lists may be assumed als C_Σ6×2=C_Σ16. These estimating values apply to mixes of PAH, which originate from many single sources (emitters), are transported through the atmosphere with dust and settle, and/or enter water bodies after being washed from road surfaces. The estimates serve as plausibility check and for extrapolation, but they cannot replace the analysis for individual substances in the identification of the pollution source or in the study of their environmental behaviour.     

Characterization and performance of V2O5/CeO2 for NH3-SCR of NO at low temperatures

A series of CeO₂ supported V₂O₅ catalysts with various loadings were prepared with different calcination temperatures by the incipient impregnation. The catalysts were evaluated for low temperature selective catalytic reduction (SCR) of NO with ammonia (NH₃). The effects of O₂ and SO₂ on catalytic activity were also studied. The catalysts were characterized by specific surface areas (S_BET) and X-ray diffraction (XRD) methods. The experimental results showed that NO conversion changed significantly with the different V₂O₅ loading and calcination temperature. With the V₂O₅ loading increasing from 0 to 10 wt%, NO conversion increased significantly, but decreased at higher loading. The optimum calcination temperature was 400°C. The best catalyst yielded above 80% NO conversion in the reaction temperature range of 160°C–300°C. The formation of CeVO₄ on the surface of catalysts caused the decrease of redox ability.     

Thermochemical conversion of municipal solid waste into energy and hydrogen: a review

The rising global population is inducing a fast increase in the amount of municipal waste and, in turn, issues of rising cost and environmental pollution. Therefore, alternative treatments such as waste-to-energy should be developed in the context of the circular economy. Here, we review the conversion of municipal solid waste into energy using thermochemical methods such as gasification, combustion, pyrolysis and torrefaction. Energy yield depends on operating conditions and feedstock composition. For instance, torrefaction of municipal waste at 200 °C generates a heating value of 33.01 MJ/kg, while the co-pyrolysis of cereals and peanut waste yields a heating value of 31.44 MJ/kg at 540 °C. Gasification at 800 °C shows higher carbon conversion for plastics, of 94.48%, than for waste wood and grass pellets, of 70–75%. Integrating two or more thermochemical treatments is actually gaining high momentum due to higher energy yield. We also review reforming catalysts to enhance dihydrogen production, such as nickel on support materials such as CaTiO₃, SrTiO₃, BaTiO₃, Al₂O₃, TiO₃, MgO, ZrO₂. Techno-economic analysis, sensitivity analysis and life cycle assessment are discussed.

     

Thermochemical pretreatment of meat and bone meal and its effect on methane production

Since the solubilization of meat and bone meal (MBM) is a prerequisite in many MBM disposal approaches, enhancement of the solubilization by means of thermochemical pretreatment was investigated in this study at two temperatures (55°C and 131°C) and six sodium hydroxide (NaOH) concentrations (0, 1.25, 2.5, 5, 10 and 20 g/L). The MBM volatile solid (VS) reduction ratio was up to 66% and 70% at 55°C and 131°C, respectively. At the same temperature, the VS reduction ratio increased with the increase in the dosage of NaOH. The study on the methane (CH₄) production potential of pretreated MBM shows that the addition of NaOH at 55°C did not cause the inhibition of the succeeding CH₄ production process. However, CH₄ production was inhibited by the addition of NaOH at 131°C. The CH₄ production potential was in the range of 389 to 503 mL CH₄/g VS MBM and 464 to 555 mL CH₄/g VS MBM at 55°C and 131°C, respectively.     

As(III) adsorption onto Fe-impregnated food waste biochar: experimental investigation,modeling, and optimization using response surface methodology

Biochar derived from food waste was modified with Fe to enhance its adsorption capacity for As(III), which is the most toxic form of As. The synthesis of Fe-impregnated food waste biochar (Fe-FWB) was optimized using response surface methodology (RSM), and the pyrolysis time (1.0, 2.5, and 4.0 h), temperature (300, 450, and 600 °C), and Fe concentration (0.1, 0.3, and 0.5 M) were set as independent variables. The pyrolysis temperature and Fe concentration significantly influenced the As(III) removal, but the effect of pyrolysis time was insignificant. The optimum conditions for the synthesis of Fe-FWB were 1 h and 300 °C with a 0.42-M Fe concentration. Both physical and chemical properties of the optimized Fe-FWB were studied. They were also used for kinetic, equilibrium, thermodynamic, pH, and competing anion studies. Kinetic adsorption experiments demonstrated that the pseudo-second-order model had a superior fit for As(III) adsorption than the pseudo-first-order model. The maximum adsorption capacity derived from the Langmuir model was 119.5 mg/g, which surpassed that of other adsorbents published in the literature. Maximum As(III) adsorption occurred at an elevated pH in the range from 3 to 11 owing to the presence of As(III) as H₂AsO₃^? above a pH of 9.2. A slight reduction in As(III) adsorption was observed in the existence of bicarbonate, hydrogen phosphate, nitrate, and sulfate even at a high concentration of 10 mM. This study demonstrates that aqueous solutions can be treated using Fe-FWB, which is an affordable and readily available resource for As(III) removal.

     

Bioenergetics and survival of the marine snail Thais lima during long-term oil exposure

The carnivorous snail Thais lima was fed Mytilus edulis during a 28-d exposure to the water soluble fraction (WSF) of Cook Inlet crude oil. The LC-50 of T. lima declined from >3000 ppb aromatic hydrocarbons on Day 7 to 818±118 ppb on Day 28. The LC-50 of M. edulis declined from >3 000 ppb aromatic hydrocarbons on Day 7 to 1 686±42 ppb on Day 28. Predation rate declined linearly with increasing aromatic hydrocarbon concentration up to 302 ppb; little predation occurred at 538 ppb and none at 1 160 or 1 761 ppb. Snail absorption efficiency averaged 93.5% and did not vary as a function of WSF dose. Total energy expenditure (R+U) increased at 44 ppb aromatics and declined at lethal WSF exposures. At sublethal WSF exposures, percentages of total energy expenditure were: respiration (87%), ammonia excretion (9%) and primary amine loss (4%). These percentages did not vary as a function of WSF dose or time. Oxygen:nitrogen ratios were not affected by WSF concentration or time and indicated that T. lima derived most of its energy from protein catabolism. The uptake of aromatic hydrocarbons into the soft tissues of snails and mussels was directly related to the WSF concentration. Naphthalenes accounted for 67 to 78% of the aromatic hydrocarbons in T. lima and 56 to 71% in M. edulis. The scope for growth was negative above 150 ppb WSF aromatic hydrocarbons and above 1 204 ppb soft-body aromatic hydrocarbons. These snails were physiologically stressed at an aromatic hydrocarbon concentration which was 19% of the 28-d WSF LC-50 (818±118 ppb) and/or 48% of the 28-d LC-50 of soft tissue aromatics (2 502 ppb).     

The toxic and environmental evaluation of pyrolytic liquids by Allium cepa test

In this study, liquid products obtained from the pyrolysis of hazelnut shell (HS), with and without ultra-high molecular weight polyethylene (UHMWPE), were subjected to the Allium cepa test system. Pyrolysis in conjunction with the A. cepa test is a promising technology not only from the perspective of energy savings and a source of precious material, but in terms of the removal of hazardous material from the environment in safe manner. Dosages of pyrolytic liquids dissolved in water were determined according to lethal dose (LD₅₀), with three different solution concentrations. The preparates were dyed with acetocarmine. The mitotic index decreased and chromosomal aberration, especially stickiness and c-mitosis, increased with dosage and time. The addition of UHMWPE to HS in the pyrolysis process resulted in less harmful chemical agents, as observed by the relatively higher mitotic index and lower levels of chromosomal aberration.     

Changes in soil organic matter composition after afforestation of arable farmland in northeast China

Since the 1970s, a substantial area of arable farmland in a semi-humid area of northeast China has been planted as deciduous forests (Populus tomentosa Carr.). This study investigates the effects of afforestation on soil organic carbon (SOC) content and the chemical composition of the soil. Soil samples (Calcic chernozem) were collected from the upper 10?cm of paired arable land and secondary forests established 5 and 25 years previously. Carbon isotope analysis and pyrolysis–gas chromatography/mass spectrometry were used to determine SOC composition. The results show that (i) compared to the arable land, five years of afforestation caused a decrease in SOC and N concentration, while 25 years of afforestation resulted in an increase in SOC content; (ii) stable isotope δ¹³C analyses of the forest soils show gradual loss of crop-derived C and an accumulation of forest-derived C; and (iii) afforestation increased lignin abundance and decreased decompositional activity in the 25-year-old forest topsoil. Higher amounts of short-/mid-chain aliphatic compounds were observed in the 5-year-old forest (5–10?cm); and (iv) the arable soil contained substantially higher amounts of decomposed plant material and microbially derived substances. The results obtained suggest that long-term afforestation increases the SOC concentration, and alters the chemical composition of SOC.     

Size-dependent photosynthetic performance in the giant clam <Emphasis Type="Italic">Tridacna maxima</Emphasis>, a mixotrophic marine bivalve

Giant clams form a symbiosis with photosynthetic algae of the genus Symbiodinium that reside in clam mantle tissue. The allometry of symbiont photosynthetic performance was investigated as a mechanism for the increasing percentage of giant clam carbon respiratory requirements provided by symbionts as clam size increases. Chlorophyll fluorescence measurements of symbionts of the giant clam Tridacna maxima were measured during experiments conducted in September of 2009 using specimens 0.5–200 g tissue wet weight (3–25 cm long), collected from waters around southern Taiwan (N 21°36′, E 120°47′) from July to August of 2009. Light-dependent decreases in effective quantum yield (∆F/F _m′) calculated as the noontime maximum excitation pressure over PSII (Q _m), relative electron transport rates (rETR), and dark-adapted maximum quantum yield (F _v/F _m) all varied as a quadratic function of clam size. Both Q _m and rETR increased as clam size increased up to ~10–50 g then decreased as clam size increased. F _v/F _m decreased as clam size increased up to ~5–50 g then increased as clam size increased. Chlorophyll fluorescence measurements of rETR were positively correlated with gross primary production measured during chamber incubations. Overall, symbionts of mid-sized clams ~5–50 g exhibited the highest light-dependent decreases in effective photosynthetic efficiencies, the highest relative electron transport rates, and the lowest maximum photosynthetic efficiencies, and symbiont photosynthetic performance is allometric with respect to host clam size.     

Emission factors of gaseous carbonaceous species from residential combustion of coal and crop residue briquettes

Experiments were performed to measure the emission factors (EFs) of gaseous carbonaceous species, such as CO₂, CO, CH₄, and non-methane volatile organic compounds (NMVOCs), from the combustion of five types of coal of varying organic maturity and two types of biomass briquettes under residential burning conditions. Samples were collected in stainless steel canisters and 2,4-dinitrophenylhydrazine (DNPH) cartridges and were analyzed by GC-FID/MS and HPLC, respectively. The EFs from crop residue briquette burning were generally higher than those from coals, with the exception of CO₂. The dominant NMVOC species identified in coal smoke were carbonyls (41.7%), followed by C2 unsaturated hydrocarbons (29.1%) and aromatics (12.1%), while C2 unsaturated hydrocarbons were the dominant species (68.9%) emitted from the combustion of crop residue briquettes, followed by aromatics (14.4%). A comparison of burning normal crop residues in stoves and the open field indicated that briquettes emitted a larger proportion of ethene and acetylene. Both combustion efficiency and coal organic maturity had a significant impact on NMVOC EFs from burning coal: NMVOC emissions increased with increasing coal organic maturity but decreased as the combustion efficiency improved. Emissions from the combustion of crop residue briquettes from stoves occurred mainly during the smoldering process, with low combustion efficiency. Therefore, an improved stove design to allow higher combustion efficiency would be beneficial for reducing emissions of carbonaceous air pollutants.     

Monolignol biosynthesis and genetic engineering of lignin in trees, a review

This paper summarizes our previous and current research on genetic engineering of lignin biosynthesis for the purposes of improving wood pulping and bleaching efficiency. For these purposes, our targets were to produce transgenic trees with low content of lignin that is also chemically reactive (high lignin S/G ratio). Using aspen as a model species, we have characterized the biochemical functions of various genes and the kinetic properties of these gene products involved in monolignol biosynthetic pathway. The results of these characterizations proved strong evidence for a principle phenolic flux leading to the formation of monolignols. Biochemical evidence further demonstrated that, in this principle flux, 4CL could be the enzyme limiting total lignin accumulation, whereas CAld5H might control the lignin S/G ratio. These propositions were fully supported by the in vivo functions of these enzymes. Transgenic trees with inhibited 4CL enzyme activity exhibited 5–45% reduction in lignin contents. The chemical structure of the resulting lignin remained essentially unchanged. More importantly, the lignin reduction was compensated for by a concomitant increase in cellulose content. When antisense 4CL and sense coniferaldehyde 5-hydroxylase (CAld5H) genes were simultaneously transferred into aspen via Agrobacterium, transgenic trees expressing each one and both of the transgenes were produced. Lignin reductions up to 55% were achieved in antisense 4CL plants and up to 3-fold S/G increases were observed in sense CAld5H plants. These effects were independent but additive, with plants expressing both transgenes having less lignin and higher S/G ratio. Consistent with our previous results, lignin reduction has always resulted in an increase in cellulose content. These transgenics could be potentially valuable for pulp production. But more importantly, these benchmark transgenics are rich sources of information for functional genomics and metabolic engineering, allowing the generation of the ultimate raw materials for wood pulp production.