Bioremediation of CCA-C treated wood by Aspergillus niger fermentation

This study evaluated the potential of the fungus Aspergillus niger to remove copper, chromium, and arsenic from waste wood treated with chromated copper arsenate (CCA) wood preservative. The removal of heavy metals by A. niger was carried out in two stages. In the first stage, A. niger was cultivated in carbohydrates media in order to produce large quantities of oxalic acid. Bioremediation of CCA-treated wood was performed in the second stage through both leaching of heavy metals with oxalic acid occurred during the first stage and possible biosorption of metals onto the binding sites in the cellular structure of A. niger. Oxalic acid production by A. niger was 13.4 kg/m³ at pH 6 and in an enriched nitrogen and phosphorus medium. CCA-treated chips exposed to A. niger for 10 days showed a decrease in arsenic of 97%. In addition, A. niger fermentation removed 49% copper and 55% chromium from CCA-treated chips. This study showed that fungal fermentation and passive metal removal by A. niger had a potential in arsenic release from CCA-treated waste wood.

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Aufwertung von CCA-behandeltem Holz durch Fermentation mit Aspergillus niger

Zusammenfassung Diese Studie untersuchte die Möglichkeit des Pilzes Aspergillus niger Kupfer, Chrom und Arsen von Abfallholz, das mit CCA-Holzschutzmittel behandelt worden war, zu entfernen. Die Entfernung von Schwermetallen durch A. niger wurde in zwei Stufen durchgeführt. Während der ersten Stufe wurde A. niger in Kohlenhydratmedien kultiviert, um große Mengen von Oxalsäure zu produzieren. Die Aufwertung von CCA-behandeltem Holz wurde während der zweiten Stufe durchgeführt. Sowohl das Auslaugen der Schwermetalle mit Oxalsäure als auch die mögliche Biosorption von Metallen an Rezeptoren in der Zellstruktur von A. niger fand während der ersten Stufe statt. Die Oxalsäure-Produktion durch A. niger betrug 13,4 kg/m³ bei einem pH-Wert 6 in einem mit Stickstoff und Phosphor angereichertem Medium. Die mit CCA behandelten Späne zeigten nach 10-tägiger Behandlung mit A. niger einen Arsenabfall von 97%. Zusätzlich entfernte die A. niger-Fermentation 49% Kupfer und 55% Chrom von CCA-behandelten Spänen. Diese Studie zeigte, dass Pilzfermentation und passive Metallentfernung durch A. niger eine Möglichkeit bot, Arsen von CCA-behandeltem Holz freizusetzen.

     

Extraction of heavy metals from soils using biodegradable chelating agents

Metal pollution of soils is widespread across the globe, and the clean up of these soils is a difficulttask. One possible remediation technique is ex-situ soil washing using chelating agents. Ethylenediaminetetraacetic acid (EDTA) is a very effective chelating agent for this purpose but has the disadvantage that it is quite persistent in the environment due to its low biodegradability. The aim of our work was to investigate the biodegradable chelating agents [S,S]-ethylenediaminedisuccinic acid (EDDS), iminodisuccinic acid (IDSA), methylglycine diacetic acid (MGDA), and nitrilotriacetic acid (NTA) as potential alternatives and compare them with EDTA for effectiveness. Kinetic experiments showed for all metals and soils that 24 h was the optimum extraction time. Longer times only gave minor additional benefits for heavy metal extraction but an unwanted increase in iron mobilization. For Cu at pH 7, the order of the extraction efficiency for equimolar ratios of chelating agent to metal was EDDS > NTA> IDSA > MGDA > EDTA and for Zn it was NTA > EDDS > EDTA >MGDA > IDSA. The comparatively low efficiency of EDTA resulted from competition between the heavy metals and co-extracted Ca. For Pb the order of extraction was EDTA > NTA >EDDS due to the much stronger complexation of Pb by EDTA compared to EDDS. At higher concentration of complexing agent, less difference between the agents was found and less pH dependence. There was an increase in heavy metal extraction with decreasing pH, but this was offset by an increase in Ca and Fe extraction. In sequential extractions EDDS extracted metals almost exclusively from the exchangeable, mobile, and Mn-oxide fractions. We conclude that the extraction with EDDS at pH 7 showed the best compromise between extraction efficiency for Cu, Zn, and Pb and loss of Ca and Fe from the soil.     

Environmental chemistry of aminopolycarboxylate chelating agents

Aminopolycarboxylate chelating agents are under scrutiny due to their influence on metal availability and mobility and in particular due to their persistence in the environment. In this review chelate adsorption, metal-mobilization, metal-exchange, mineral dissolution, reactive transport, photodegradation, and chemical degradation are all shown to be substantially affected by the chelated metal ion. The different reactivities of the metal-complexes have to be considered when assessing the reactions of chelating agents in the environment because they occur in natural waters predominantly in the form of metal complexes. Knowing the speciation of chelating agents in natural waters is therefore crucial for predicting their environmental fate. Despite this importance, only a few speciation measurements have been reported for natural waters, and model calculations have been frequently used instead. These calculations are, however, complicated by slow metal-exchange reactions that result in a nonequilibrium speciation and by the presence of naturally occurring ligands that compete with the chelating agents for available metals. The basis for a refined risk assessment of aminocarboxylate chelates should be the actual speciation in the natural water directly determined by analytical methods. The discussion of the influence of chelates on metal availability and fate also has to include the potential presence of other aminopolycarboxylate chelating agents besides the well-known EDTA and NTA.     

Weathering of silane treated wood

Outdoor and artificial weathering tests were performed on specimens of Scots pine sapwood treated with silanes to achieve water repellent properties. During outdoor weathering, the treatment caused a reduction in (liquid) water uptake but the sorption of moisture (air humidity) was not affected by silane treatment. The water repellent effect of vacuum-pressure treated specimens remained stable over the tested exposure period of one year, as was shown in dipping tests. Evaluation of silane treated specimens did not reveal any reduction of crack formation during exposure to weathering. The application of silanes in combination with UV light stabilizers enhanced the effectiveness of these protectants and led to higher colour stability during artificial weathering in a QUV device.     

TG-DTA studies on wood treated with flame-retardants

Cunninghamia Lanceolata wood untreated and treated with flame-retardants were analyzed using the TG-DTA simultaneous method. Results showed that upon lowering the pyrolysis temperature, wood weight loss was reduced and char yield increased in the charring phase of the pyrolysis. The TG curves were further analyzed by the thermokinetic method to obtain thermokinetic parameters of the different phases during the wood pyrolysis and to derive a thermokinetic Equation. It was found that the activation energy in the drying phase was reduced and the activation energy in the charring or calcining phase varied for the different flame-retardants used.

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Cunninghamia Lanceolata wurden vor und nach der Behandlung mit Flammschutzsalzen aufgenommen und analysiert, wobei TG- und DTA-Kurven simultan verfolgt wurden. Es zeigte sich, da? sich bei Erniedrigung der Pyrolysetemperatur auch der Gewichtsverlust des Holzes verringerte und die Menge an Kohle w?hrend der Verkohlungsphase der Pyrolyse anstieg. Aus den TG-Kurven wurden mittels thermokinetischer Methoden die kinetischen Parameter für die verschiedenen Pyrolysephasen gewonnen und entsprechende thermokinetische Gleichungen aufgestellt. Die Aktivierungsenergie in der Trocknungsphase war erniedrigt, w?hrend sie für die übrigen Phasen je nach Flammschutzmittel variierte.

     

TG-DTA studies on wood treated with flame-retardants

wood untreated and treated with flame-retardants were analyzed using the TG-DTA simultaneous method. Results showed that upon lowering the pyrolysis temperature, wood weight loss was reduced and char yield increased in the charring phase of the pyrolysis. The TG curves were further analyzed by the thermokinetic method to obtain thermokinetic parameters of the different phases during the wood pyrolysis and to derive a thermokinetic Equation. It was found that the activation energy in the drying phase was reduced and the activation energy in the charring or calcining phase varied for the different flame-retardants used.     

Effects of calcium chelating agents on the solubility of milk protein concentrate

The aim of this study was to determine the effects of calcium chelating agents on the dissolution and functionality of 10% (w/w) milk protein concentrate (MPC) powder. MPC powder dissolution rate and solubility significantly (P > 0.05) increased with addition of sodium phosphate, trisodium citrate (TSC) and sodium hexametaphosphate (SHMP), compared to MPC dispersions alone. Trisodium citrate and SHMP addition increased viscosity as a result of micelle swelling. However, dispersions containing SHMP showed a decrease in viscosity after prolonged time due to micelle dissociation. Overall, MPC powder dissolution was aided by the addition of calcium chelating agents.     

Selected properties of gas phase ammonia treated wood

Changes of physical wood properties after ammonia gas phase treatment were tested. In order to cover the wide variability of the investigated parameter, nineteen different wood species were investigated. While density is more or less not affected, equilibrium moisture content at standard climate increases significantly for almost all species. Changes of differential shrinkage and swelling in radial and tangential direction are specific to species. While some species show increased swelling or shrinkage, for other species these values decline. In most cases, ammoniation leads to increased dimension stability in radial direction but to a reduction in tangential direction. So, anisotropy of swelling and shrinkage in general increases due to ammoniation. These results show that changed physical properties of such wood have to be considered concerning conditioning and dimensioning products therefrom.     

Mechanical properties of wood treated with PF-pyrolytic oil resins

Jack pine and sugar maple wood samples were treated in a two-step process that involved first a copper chloride or a copper chloride-sodium borate mixture and then a phenol-formaldehyde resin containing a certain percentage of softwood bark pyrolytic oil. Various controls were also prepared for comparison. The modulus of rupture (MOR) of jack pine samples was generally negatively affected by the treatment, the observed values being lower than those of the controls. These values were statistically lower or equal to those of untreated samples. On the other hand, the modulus of elasticity (MOE) of treated jack pine samples was not found to be statistically different from that of the untreated wood. Mechanical properties behaved in a similar way for sugar maple wood. Unlike the other treatments, copper chloride–sodium borate and the resin containing 85% of pyrolytic oil as phenol substitute appeared to slightly improve the mechanical properties of both wood species even if not significantly so. Treatment with PF-pyrolytic oil resin resulted in similar or slightly better mechanical properties when compared to CCA-treated wood. The amount of treating water soluble salts retained in samples after the first treatment had a significant impact on MOR of both wood species and on MOE of sugar maple.     

Bonding performance of heat treated wood with structural adhesives

Bonding of untreated, intermediate (hydro-thermolysed) and heat treated wood with melamine-urea-formaldehyde (MUF), phenol-resorcinol-formaldehyde (PRF) and polyurethane (PUR) adhesives was studied. An industrial heat treatment process (Plato ^®) was used, which included two separate heat treatment stages and a drying stage in-between. Laminated beams having four lamellas were prepared from untreated and treated timber for mechanical testing of the bond lines. The results of the tests showed that heat treatment affected the shear strength and the delamination of the laminated wood depending on the adhesive system used for bonding. The PUR and MUF adhesives performed in a rather similar way, and better than the PRF adhesive. The shear strength of laminated wood bonded with the waterborne MUF and PRF adhesives decreased for the specimens made of hydro-thermolysed timber and decreased further for the specimens made of fully heat treated timber. The difference in adhesive bond shear strength between untreated, intermediate and fully treated wood was less obvious in the case of the PUR adhesive. Delamination of the PRF bond line decreased drastically for all the specimens made of heat treated timber.     

Phosphonate- and carboxylate-based chelating agents that solubilize (hydr)oxide-bound MnIII

Recent field studies suggest that dissolved MnIII should be ubiquitous at oxic/anoxic interfaces in all natural waters and may play important roles in biogeochemical redox processes. Here, we uncovered environmentally relevant synthetic phosphonate-based chelators that solubilize (hydr)oxide-bound MnIII via ligand-promoted dissolution at circum-neutral pHs and that their ability to release aqueous MnIII can be predicted based on the chemical structure. For two (hydr)oxides (manganite and birnessite) reacting with excess concentrations of pyrophosphoric acid (PP), methylenediphosphonic acid (MDP), and phosphonoacetic acid (PAA), ligand-promoted dissolution is predominant from pH 6--8, initial dissolution rates and plateau concentrations for dissolved MnIII decrease in the order PP > MDP > PAA, and at pH 5, MDP reacts equally well (with birnessite) or more efficiently (with manganite) than PP, and PAA remains the least reactive chelator. For manganite reacting with an excess concentration of aminophosphonate/carboxylate-based chelators, the aminophosphonate-containing iminodimethylenephosphonic acid and glyphosate yield appreciable amounts of dissolved MnIII, but the aminocarboxylate-based methyliminodiacetic acid yields solely dissolved MnII via MnIII reduction.     

不同螯合剂对棉织物果胶质去除效果的研究

棉纤维上的果胶质对棉织物的吸水性和染色性能影响较大．为增加果胶质去除效果，选择不同种类的螯合剂(包括聚磷酸盐类、有机膦酸盐和多羧酸类)在不同质量浓度、温度条件下对棉织物浸渍处理，并对果胶质去除率作了测定．结果表明，多羧酸类鏊合剂中的乙二胺四乙酸(EDTA)对果胶质去除效果较好，EDTA与果胶酶组合应用时，棉织物的果胶质去除率超过90％．     

Chemical changes in hydrothermal treated wood: FTIR analysis of combined hydrothermal and dry heat-treated wood

Wood specimens of Beech (Fagus silvatica L.) and Scots pine (Pinus sylvestris L.) modified by a hydrothermal treatment process were analysed by means of Fourier transform infra red spectroscopy (FTIR). The chemical transformation of the cell-wall material was studied and associated with improved wood qualities. For this purpose, FTIR spectroscopy was used as since this technique has been found appropriate to determine the intensity of specific bonds and functional groups within the polymeric structure. Cleavage of acetyl groups of the hemicellulose has been found to occur in the first treatment step under moist conditions and elevated temperature. This results in the formation of carbonic acids, mainly acetic acid. Most of the acetyl groups were found to be cleaved during the treatment of wood at high temperature, whereas only partial deacetylation was found to occur at moderate treatment temperature. The concentration of accessible hydroxyl groups was measured by acetylation and found reduced after treating at high temperature. Esterification reactions were found to occur under dry conditions at elevated temperature in the curing step, indicated by the increase of the specific ester carbonyl peak at 1740 cm^–1 in the FTIR spectrum. The esters that were formed turned out to be mainly linked to the lignin complex, considering that the newly formed carbonyl groups were found present in heat-treated wood, yet were found to be absent in the isolated holocellulose. Esterification contributes to a decrease of hygroscopicity of wood and consequently improvements of its dimensional stability and durability. However, the role of esterification in the decrease of hygroscopicity in the hydrothermal treatment process examined is believed to be minor compared to the influence of cross-linking reactions known to occur during thermal treatment of wood.

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Veränderungen der Zellwandchemie hydrothermisch behandelten Holzes

Zusammenfassung Das Holz hydrothermisch modifizierten Buchen- und Kiefernholzes wurde mit FTIR Spektroskopie untersucht. Die chemischen Veränderungen wurden mit dem Hintergrund veränderter Holzeigenschaften diskutiert. Abspaltungen von Acetylgruppen der Hemicellulosen finden vor allem bereits im ersten Prozessschritt unter feuchten Bedingungen und bei erhöhten Temperaturen statt. Dieses führt zur Bildung von Essigsäure und anderen Carbonsäuren. Bei niedrigeren Temperaturen werden weniger Carbonsäuren freigesetzt. Durch Acetylierung wurde der Gehalt an freien Hydroxylgruppen bestimmt. Durch die Hitzebehandlung reduziert sich der Gehalt freier Hydroyxlgruppen. Die Zunahme des Carbonylesterpeaks bei 1740 cm^–1 im FTIR Spektrum lässt sich durch Veresterungsreaktionen im heißen aber trocknen Curingschritt erklären. Diese Ester sind vor allem an den Ligninkomplex gebunden und weniger an die Holocellulose. Durch Veresterungen wird ein hygroskopisches, dimensionsstabiles und dauerhaftes Material geschaffen. Die Veränderung der Materialeigenschaften beruht jedoch vor allem auch auf cross-linking Reaktionen die während des Prozesses ablaufen.

     

Strengthening of archaeological wood using electroosmosis

Hundreds of waterlogged archaeological wooden pillars were discovered during the 2004 excavation of an archaeological site in Tianluo-Mountain, Zhejiang Province, China. These archaeological wooden pillars are invaluable cultural relics but are on the verge of decay and cracking due to the combination of a humid environment and bacterial surface erosion. Inspired by the stable silicified wood in the natural world, it was decided to silicify these fragile wooden pillars in situ to protect them. Wood was first treated in sodium silicate solution using electroosmosis technology, and then CaSiO₃ precipitations were formed by immersing silicified wood in calcium nitrate solution to fix silicate in the wood. The wood microstructure before and after treatment was observed using scanning electron microscopy. It could be seen that particles were widely distributed throughout the internal part after treatment, while there were no particles present before treatment. EDS results showed that the particles are comprised mainly of silicon, calcium and oxygen, so it could be confirmed that calcium silicate was formed in the wood. Mechanical property tests indicated that the silicification process improved the axial compressive strength by 143%. Thus, archaeological wood has successfully silicified and the objective of strengthening has been achieved.     

In vitro studies on chelating agents as potential iron absorption promoters

Ligands which can bind iron to keep it in solution with good stability at the neutral or alkaline pH of the small intestine can serve as useful absorption promoters of dietary iron. A number of biologically compatible compounds were screened in vitro for this ability at pH 7·5, employing three different systems.Studies carried out with iron-amino acid complexes have shown that amino acids and their derivatives were stable only in the acid pH range with stability constants of 10·9 or lower. Compounds which could solubilize insoluble ferric orthophosphate at pH 7·5 exhibited efficiencies in the order: hydroxamate of lysine > nicotinic acid > EDTA > ascorbic acid > picolinic acid > cysteine. A large number of compounds were tested for their ability to keep iron in solution at pH 7·5 at different iron: ligand ratios. Of these, ascorbic acid, inorganic polyphosphates, hydroxamates of nicotinic acid and lysine, EDTA, caffeic acid, citric acid, xanthurenic acid and phytic acid showed high chelating ability. Some of these compounds can be further exploited as iron absorption-promoting ligands.     

防腐木材胶合性能的基础研究

本试验使用两种水溶性防腐剂铜铬砷(CCA)和氨溶烷基胺铜(ACQ-3)对人工林落叶松和杨树木材进行处理,分析处理后木材表面的接触角的变化,利用差示扫描量热仪分析处理后的木材对胶粘剂固化的影响。试验结果表明:经过CCA处理后的木材表面的接触角变化相对较小;经过ACQ处理后的木材,更适合用异氢酸酯进行胶合;经过CCA处理后木材,较适合用酚醛树脂和间苯二酚胶合。