Ethanol washing of PAH-contaminated soil and Fenton oxidation of washing solution

As a means to remediate soil contaminated by polycyclic aromatic hydrocarbons, we investigated a combined process involving ethanol washing followed by a Fenton oxidation reaction. Artificial loamy soil was contaminated with various representative polycyclic aromatic hydrocarbons (i.e., fluorene, anthracene, pyrene, benzo(b)fluoranthene, or benzo(a)pyrene) at concentrations ten times higher than regulatory soil standards of The Netherlands or Canada, and then washed four times in ethanol, which reduced the concentration of polycyclic aromatic hydrocarbon contamination to below the regulatory standard. Fenton oxidation of ethanol solutions containing anthracene, benzo(a)pyrene, pyrene, acenaphthylene, acenaphthene, benz(a)anthracene, benzo(j)fluoranthene, or indeno(1,2,3-cd)pyrene showed a removal efficiency of 73.3%–99.0%; by contrast, solutions containing naphthalene, fluorene, fluoranthene, phenanthrene, or benzo(b)fluoranthene showed a removal efficiency of 9.6%–27.6%. Since each of the nonremediated polycyclic aromatic hydrocarbons, excluding benzo(b)fluoranthene, are easily biodegradable, these results indicate that the proposed treatment can be successfully applied to polycyclic aromatic hydrocarbon-contaminated soil that does not contain high concentrations of benzo(b)fluoranthene. The main reaction products resulting from Fenton oxidation of ethanol solutions containing anthracene or benz(a)anthracene were anthraquinon or benz(a)anthracene-7,12-dione, respectively; while 1,8-naphthalic anhydride was produced by solutions of acenaphthylene and acenaphthene, and 9-fluorenone by a fluorene solution. Received: June 9, 1998 / Accepted: March 24, 1999     

有机溶剂浸取石油污染土壤中的多环芳烃

采用索氏提取法和气相色谱分析了某炼油厂周边土壤中的多环芳烃的种类及含量,考察了6种有机溶剂对土壤中多环芳烃的浸取效果,探讨了溶剂与溶质溶解度参数差异对浸取效果的影响。结果表明：土壤试样中含有蒽、荧蒽、芘、 、苯并[a]蒽、苯并[b]荧蒽、苯并[k]荧蒽和苯并[a]芘8种多环芳烃,其含量分别为4.20,22.05,10.62,4.26,5.54,0.80,0.94,4.18 mg/kg;筛选出二氯甲烷作为土壤中多环芳烃的浸取溶剂;最佳浸取条件为浸取时间10 min、浸取温度30 ℃、溶剂与土壤的液固比5:1（mL/g）、土壤含水量8%,在此条件下,总多环芳烃浸出率为83.0%,各种多环芳烃的浸出率分别为蒽97.8%、荧蒽78.2%、芘99.9%、 98.5%、苯并[a]蒽81.1%、苯并[b]荧蒽47.6%、苯并[k]荧蒽14.8%、苯并[a]芘58.7%。     

大气粉尘中常见多环芳烃类化合物的提取及含量测定

采用便携式PM2.5采样器和玻璃纤维滤膜对大气粉尘进行采样,以加压液体萃取、超声波辅助提取和微波辅助提取3种方法对多环芳烃类化合物进行提取,以超高效液相色谱和质谱联用方法进行测定。共检测出16种多环芳烃类化合物,分别为:萘、苊、苊烯、芴、菲、蒽、荧蒽、芘、苯并[a]蒽、■、苯并[b]荧蒽、苯并[k]荧蒽、苯并[a]芘、二苯并[a,h]蒽、茚并[1,2,3-c,d]芘和苯并[g,h,i]苝。3种提取方法均可有效提取大气粉尘中的多环芳烃类化合物,加压液体萃取法的提取效率最高、超声波辅助提取法次之、微波辅助提取法最低。超高效液相色谱和质谱连用方法可有效地分析大气粉尘中的多环芳烃类化合物,线性方程的相关系数不低于0.998 3,测定值的相对标准偏差不超过0.80%,检出限不高于0.27 ng/g。     

Toxicity and source assignment of polycyclic aromatic hydrocarbons in road dust from urban residential and industrial areas in a typical industrial city in Korea

This study analyzed the toxicity and sources of polycyclic aromatic hydrocarbons (PAHs) in road dust from six representative areas (three urban residential areas and three industrial areas) from a typical industrial city in Korea. The concentrations and the toxicity equivalent concentrations (TEQs) in road dust varied by area, depending on the type of traffic and industrial activities and the PAHs identified. High correlations between the total concentration and the TEQ of PAHs in road dust were found in road dust from both the urban and industrial areas. To identify the sources of PAHs, this study utilized a factor loading method in a principal component analysis, the ratio of PAHs from combustion sources to total PAHs (ΣCOMB to ΣPAH), and bivariate plots of phenanthrene/anthracene (PA/Ant) versus fluoranthene/pyrene (FL/Pyr), and ΣCOMB/ΣPAH versus FL/Pyr in road dust. The identified origin of the PAHs was fuel combustion, including gasoline, diesel, oil, and coal, used in urban and industrial areas.     

The Effect of Interaction Between White-rot Fungi and Indigenous Microorganisms on Degradation of Polycyclic Aromatic Hydrocarbons in Soil

White-rot fungi applied for soil bioremediation have to compete with indigenous soil microorganisms. The effect of competition on both indigenous soil microflora and white-rot fungi was evaluated with regard to degradation of polycyclic aromatic hydrocarbons (PAH) with different persistence in soil. Sterile and non-sterile soil was artificially contaminated with ¹⁴C-labeled PAH consisting of three (anthracene), four (pyrene, benz[a]anthracene) and five fused aromatic rings (benzo[a]pyrene, dibenz[a,h]anthracene). The two fungi tested,Dichomitus squalens and Pleurotus ostreatus, produced similar amounts of ligninolytic enzymes in soil, but PAH mineralization by P. ostreatus was significantly higher. Compared to the indigenous soil microflora, P.ostreatus mineralized 5-ring PAH to a larger extent, while the indigenous microflora was superior in mineralizing 3-ring and 4-ring PAH. In coculture the special capabilities of both soil microflora and P. ostreatus were partly restricted due to antagonistic interactions, but essentially preserved. Thus, soil inoculation with P. ostreatus significantly increased the mineralization of high-molecular-weight PAH, and at the same time reduced the mineralization of anthracene and pyrene. Regarding the mineralization of low-molecular-weight PAH, the stimulation of indigenous soil microorganisms by straw amendment was more efficient than application of white-rot fungi.     

Use of fungal technology in soil remediation: A Case Study

Two white rot fungi Irpex lacteus and Pleurotus ostreatus and a PAH-degrading bacterial strain of Pseudomonas putida were used as inoculum for bioremediation of petroleum hydrocarbon-contaminated soil from a manufactured-gas-plant-area. Also two cocultures comprising a fungus with Pseudomonas putida were applied. After 10-week treatment out of 12 different PAHs, concentration of phenanthrene, anthracene, fluoranthene and pyrene decreased up to 66%. The ecotoxicity of the soil after bioremediation did not reveal any effect on the survival of Daphnia magna, a crustacian. However, the toxic effect on seed germination of plant Brassica alba and oxidoreductase activity of bacterium Bacillus cereus decreased after 5 and 10 weeks of treatment.     

Characterisation of polycyclic aromatic hydrocarbons in flue gas and residues of a full scale fluidized bed combustor combusting non-hazardous industrial waste

This paper studies the fate of PAHs in full scale incinerators by analysing the concentration of the 16 EPA-PAHs in both the input waste and all the outputs of a full scale Fluidized Bed Combustor (FBC). Of the analysed waste inputs i.e. Waste Water Treatment (WWT) sludge, Refuse Derived Fuel (RDF) and Automotive Shredder Residue (ASR), RDF and ASR were the main PAH sources, with phenanthrene, fluoranthene and pyrene being the most important PAHs. In the flue gas sampled at the stack, naphthalene was the only predominant PAH, indicating that the PAHs in FBC’s combustion gas were newly formed and did not remain from the input waste. Of the other outputs, the boiler and fly ash contained no detectable levels of PAHs, whereas the flue gas cleaning residue contained only low concentrations of naphthalene, probably adsorbed from the flue gas. The PAH fingerprint of the bottom ash corresponded rather well to the PAH fingerprint of the RDF and ASR, indicating that the PAHs in this output, in contrast to the other outputs, were mainly remainders from the PAHs in the waste inputs. A PAH mass balance showed that the total PAH input/output ratio of the FBC ranged from about 100 to about 2600 depending on the waste input composition and the obtained combustion conditions. In all cases, the FBC was clearly a net PAH sink.     

Occurence and Distribution of Polycyclic Aromatic Hydrocarbons in Ankara Precipitation

Urban atmospheric environment contains many trace organic pollutants that are related to the incomplete fuel combustion in domestic heating, industrial plants and automobile traffic. Removal of these pollutants from the atmosphere takes place through wet and dry deposition as well as chemical transformations. In this study, concentrations of polycyclic aromatic hydrocarbons (PAHs) in wet deposition samples were determined at an urban site of Turkey. Wet and dry deposition samples were collected using Andersen Rain Sampler. The sampler was modified accordingly for the collection of organic pollutants. Collected samples were preconcentrated by using solid phase extraction (SPE) disks and consecutively analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). Among the 13 compounds quantified in this study, anthracene, fluoranthene, and pyrene were found more frequently and at elevated concentrations (202, 271 and 260 ng L^-1 mean concentrations, respectively).Concentrations of PAHs were found to be high in winter period.     

Slurry phase bioremediation of PAHs in industrial landfill samples at laboratory scale

The effect of Tween 80 and selected bacteria additions on the bioremediation of PAH contaminated landfill soil (70.38mgkg(-1)) was evaluated in a slurry phase bioreactor. A phenanthrene-degrading consortium was selected by enrichment cultures and used as autochthonous inoculum. The Tween 80 addition increased the aqueous concentration of both high and low molecular weight PAHs. In the experiment with Tween 80 and inoculum addition, added microorganisms improved (>90%) the biodegradation of two- and three-ring PAHs as well as of the four-ring PAHs pyrene and fluoranthene. Biodegradation of the higher molecular weight PAHs was about 30% in experiments with Tween 80 addition, with and without inoculum addition.     

Assessment of Heavy Metal and PAH Contamination of Urban Streambed Sediments on Macroinvertebrates

The results from measuring PAH and metal contamination together with macroinvertebrate communities at 62 headwater stream sites gives a significant insight into the range and scale of contamination. Monitoring streambed sediments at 62 sites from rural to inner city and in industrial locations presented a unique opportunity to distinguish the conditions that enhance pollution runoff at sites that are less obviously `at risk' and to compare these results with sites of expected high contamination, for example in industrial areas and at motorway junctions. We used pCCA (partial Canonical Correspondence Analysis) to tease out the relationships between individual macroinvertebrate families and specific metal and PAH contaminants, and showed that it is not always the metals and PAHs with the greatest total concentrations that are doing the damage to the ecology. Ni and Zn are the critical metals, while benzo(b)fluoranthene, anthracene and fluoranthene are the most contaminating PAHs. The results identify previously unrecognized `high risk' pollution sources, lay byes used for commercial parking, on-street residential parking areas, and the junctions at the bottom of hills with traffic lights, where surface runoff feeds rapidly to the streams. While this study looks at sites across Yorkshire, UK, it clearly has a broader significance for understanding contamination risks from diffuse runoff as a prerequisite for effective sustainable urban drainage system (SUDS) agendas and the protection of urban stream ecology.     

A Study of the Use of Alfalfa (Medicago sativa L.) for the Phytoremediation of Organic Contaminants in Soil

This article presents the results of a study that was conducted to determine the effectiveness of using alfalfa (Medicago sativa L.) to enhance the phytoremediation of three different types of chemical contaminants. The chemicals studied were trinitrotoluene (TNT), the polycyclic aromatic hydrocarbon (PAH) pyrene, and the polychlorinated biphenyl (PCB) Aroclor 1248. Experiments were conducted using soils that contained high and low organic matter content. The results indicated that recoveries of pyrene and TNT from soil were highly dependent on the soil organic matter content, while the recovery of PCB was not. Significantly low levels of pyrene and TNT were recovered from all treatments in the soil with 6.3 percent organic matter content compared to recovery levels found in soil with 2.6 percent organic matter. The presence of alfalfa plants had a significant effect on the transformation of TNT and PCB in the low organic matter content soil only and had no effect on the fate of pyrene. In the low organic matter soil, only 15 percent and 17 percent of the initial TNT and PCB levels, respectively, were transformed in the unplanted control soils compared to 66 percent and 77 percent in the alfalfa planted pots. In both soil types, pyrene dissipation could not be attributed to the presence of alfalfa plants. Overall, it was concluded that under high soil organic matter conditions, adsorption and covalent binding to the soil organic matter appeared to be the dominant force of pyrene and TNT removal. The effectiveness of using alfalfa to enhance PCB and TNT transformations was more significant in the lower organic matter soil; thus phytoremediation had a greater effect in soils with lower organic matter content. © 2001 John Wiley & Sons, Inc.     

萘降解菌的筛选及其对多环芳烃的降解

从柴油污染土壤中筛选分离出一株萘降解菌N-3,进行了菌种鉴定及萘双加氧酶基因(nah)验证,并考察了该菌对不同种类多环芳烃(PAHs)的降解能力及降解过程中脱氢酶活性的变化。实验结果表明:该菌为铜绿假单胞菌(Pseudomonas aeruginosa),含有nah基因;当分别对液体培养基中质量浓度为50 mg/L的萘、菲、蒽、芘、芴降解84 h时,菌株N-3对萘、菲、蒽、芘、芴的降解率分别为28.81%,34.83%,36.65%,27.50%,23.47%。菌株N-3的脱氢酶活性与其对不同PAHs的降解率呈一定的正相关性。该菌不仅能有效降解萘,且对其他种类PAHs也有一定降解作用。     

Sedimentary Record of Polycyclic Aromatic Hydrocarbons in the Gulf of Trieste (Northern Adriatic Sea)

To reconstruct a history of polycyclic aromatic hydrocarbon (PAH) pollution in the Gulf of Trieste, one of the largest urbanized areas in the Adriatic Sea, we analyzed three long sediment cores collected between 1996 and 1997. Concentrations of total PAHs, the sum of 16 PAH compounds and six of their methylated analogues, in all three cores show a decrease from 600–800 ng g⁻¹, at the surface, to levels below 250 ng g⁻¹ in deepest layers (down to 3 m). The same trend was shown with separate representative pyrogenic PAHs (pyrene, benzofluoranthene and phenanthrene). Using Hg as a recent geochronological tracer, we observe an increasing input of PAHs since the beginning of the 20th Century and, especially, after the Second World War coinciding with increasing industrialization and urbanization of the region. This correlation is supported by PAH ratios that are indication of combustion processes and represent a marker for anthropogenic inputs. No correlation exists between PAHs and black carbon within the core profiles, indicating two different fractions of the ‘black carbon continuum’.     

Root Exudates Impact on Phenanthrene Availability

In order to improve and optimize phytoremediation of PAH we propose to focus on the rhizospheric processes controlling PAH degradation. In this paper the effect of root exudates on PAH availability is studied. Model organic compounds (malic acid, malonic acid and EDTA) representing root exudates have been tested for their effect on phenanthrene sorption on a reference non polluted agricultural soil material. Phenanthrene adsorption isotherms were first obtained with batch experiments. Results showed linear isotherms and phenanthrene sorption was enhanced as the concentration of organic compounds in the solution increased. Column leaching experiments were then used to simulate the effect of root exudation following the soil pollution. Inlet solutions containing the different organic acids used were flowed through the column containing the artificially polluted soil material. Elution curves showed that the phenanthrene was less easily eluted when the solution injected contained the organic acids. However, magnitude of the phenomena did not fit with adsorption constants obtained in batch experiments. Phenanthrene desorption appeared limited by sequestration but organic acids seemed able to partially disturb the soil material structure to limit the sequestration effect.     

Use of biosurfactants from urban wastes compost in textile dyeing and soil remediation

A compost isolated humic acid-like (cHAL) material was pointed out in previous work for its potential as auxiliary in chemical technology. Its potential is based on its relatively low 0.4gL(-1) critical micellar concentration (cmc) in water, which enables cHAL to enhance the water solubility of hydrophobic substances, like phenanthrene, when used at higher concentrations than 0.4gL(-1). This material could be obtained from a 1:1 v/v mixture of municipal solid and lignocellulosic wastes composted for 15 days. The compost, containing 69.3% volatile solids, 39.6% total organic C and 21C/N ratio, was extracted for 24h at 65 degrees C under N2 with aqueous 0.1molL(-1) NaOH and 0.1molL(-1) Na4P2O7, and the solution was acidified to separate the precipitated cHAL in 12% yield from soluble carbohydrates and other humic and non-humic substances. In this work two typical applications of surfactants, i.e., textile dyeing (TD) and soil remediation by washing (SW), were chosen as grounds for testing the performance of the cHAL biosurfactant against the one of sodium dodecylsulfate (SDS), which is a well established commercial synthetic surfactant. The TD trials were carried out with nylon 6 microfiber and a water insoluble dye, while the SW tests were performed with two soils contaminated by polycyclic aromatic hydrocarbons (PAH) for several decades. Performances were rated in the TD experiments based on the fabric colour intensity (DeltaE) and uniformity (sigmaDeltaE), and in the SW experiments based on the total hydrocarbons concentration (CWPAH) and on the residual surfactant (Cre) concentrations in the washing solution equilibrated with the contaminated soils. The results show that both cHAL and SDS exhibit enhanced performance when applied above their cmc values. However, while in the TD case a significant performance effect was observed at the surfactants cmc value, in the SW case the required surfactants concentration values were equivalent to 25-125xcmc for cHAL and to 4-22xcmc for SDS. The vis-a-vis comparison of the two surfactants gave the following results: in the TD case the cHAL biosurfactant at 0.4gL(-1) yields good colour intensity and equal colour uniformity as SDS at 5gL(-1), in the SW case cHAL was found to enhance CWPAH by a factor of 2-4 relative to SDS with one soil, whereas with the other soil the two surfactants behaved similarly. The Cre data, however, showed that both soils absorbed by far more SDS (68-95%) than cHAL (12-54%). The results point out intriguing technological and environmental perspectives deriving from the use of compost isolated biosurfactants in the place of synthetic surfactants.     

Remediation of Soil and Ground Water Contaminated with PAH using Heat and Fe(II)-EDTA Catalyzed Persulfate Oxidation

The feasibility of degrading 16 USEPA priority polycyclic aromatic (PAH) hydrocarbons (PAHs) with heat and Fe(II)-EDTA catalyzed persulfate oxidation was investigated in the laboratory. The experiments were conducted to determine the effects of temperature (i.e. 20 ^∘C, 30 ^∘C and 40 ^∘ C) and iron-chelate levels (i.e., 250 mg/L-, 375 mg/L- and 500 mg/L-Fe(II)) on the degradation of dissolved PAHs in aqueous systems, using a series of amber glass jars as the reactors that were placed on a shaker inside an incubator for temperature control. Each experiment was run in duplicate and had two controls (i.e., no persulfate in systems). Samples were collected after a reaction period of 144 hrs and measured for PAHs, pH and sodium persulfate levels. The extent of degradation of PAHs was determined by comparing the data for samples with the controls. The experimental results showed that persulfate oxidation under each of the tested conditions effectively degraded the 16 target PAHs. All of the targeted PAHs were degraded to below the instrument detection limits (∼4 μ/L) from a range of initial concentration (i.e., 5 μ/L for benzo(a)pyrene to 57 μ/L for Phenanthrene) within 144 hrs with 5 g/L of sodium persulfate at 20 ^∘ C, 30 ^∘C and 40 ^∘C. The data indicated that the persulfate oxidation was effective in degrading the PAHs and that external heat and iron catalysts might not be needed for the degradation of PAHs. The Fe(II)-EDTA catalyzed persulfate also effectively degraded PAHs in the study. In addition, the data on the variation of persulfate concentrations during the experiments indicated that Fe(II)-EDTA accelerated the consumption of persulfate ions. The obtained degradation data cannot be used to evaluate the influence of temperature and Fe(II) levels on the PAH degradation because the PAHs under each of the tested conditions were degraded to below the instrument detection limit within the first sampling point. However, these experiments have demonstrated the feasibility of degrading PAHs in aqueous systems with persulfate oxidation. Additional tests are being conducted to evaluate the effectiveness of treating PAHs in soils and obtaining the rate of degradation of PAHs with persulfate oxidation. Two sets of laboratory experiments were conducted to evaluate the ability of sodium persulfate in oxidizing real world PAH-contaminated soils collected from a Superfund site in Connecticut. The first set of soil sample were treated only with persulfate and to the second batch, mixture of persulfate and Fe(II)-EDTA solutions were added. The results of the second test showed that within 24 hours, 75% to 100% of the initial concentrations of seven PAH compounds detected in the soil samples were degraded by sodium persulfate mixed with FE(II)-EDTA.     

Treatment of urban stormwater for dissolved pollutants: A comparative study of natural organic filter media

Sorption capacities were evaluated for the dissolved stormwater (SW) pollutants onto two tree mulches and jute fiber. SW spiked with predetermined concentrations of copper (Cu), cadmium (Cd), hexavalent chromium (Cr ⁺⁶), lead (Pb), zinc (Zn), and benzo[a]pyrene (B[a]P), naphthalene (NP), fluoranthene (FA), 1,3‐dichlorobenzene (DCB), and butylbenzylphthalate (BBP) were used in this study. Each medium removed close to 100 percent of all the pollutants at the concentrations studied. Sorption capacities (μg/g) of the three organic media were in the order of jute > hardwood mulch > softwood mulch, and on a mole basis, both the heavy metals and the toxic organics were sorbed by the three media in an identical sequence: Cr ⁺⁶ > Cu, Zn > Cd > Pb; and NP > DCB > FA > B[a]P > BBP. Sorption capacities of the hardwood wood mulch and jute fiber for the pollutants were correlated with distinctive physical properties of the pollutants. © 2005 Wiley Periodicals, Inc.     

活性炭固定床吸附分离溶液中表面活性剂和多环芳烃

利用活性炭固定床吸附分离表面活性剂和多环芳烃(PAH)的混合溶液,选取了具代表性的表面活性剂(TX100)和PAH(菲(PHE)等)。实验结果表明,流量越低、活性炭填充量越多、表面活性剂浓度越高、PAH浓度越低,越有利于表面活性剂的回收和PAH的去除。定义了有效回收时间,该时间是指PAH穿透10%的时间与表面活性剂穿透90%的时间之差,该时间越长,越有利于表面活性剂的回收。采用BDST和Thomas模型对TX100和PHE进行了吸附模拟,效果均较好;BDST模型拟合结果表明,当活性炭对TX100的吸附接近饱和时仍对PHE有较强的吸附能力。活性炭固定床吸附分离法可节约运行成本0.06元/L。     

Occurrence of organic pollutants in recovered soil fines from construction and demolition waste

The objective of this study was to characterize recovered soil fines from construction and demolition (C&D) waste recycling facilities for trace organic pollutants. Over a period of 18 months, five sampling trips were made to 14 C&D waste recycling facilities in Florida. Screened soil fines were collected from older stockpiles and newly generated piles at the sites. The samples were analyzed for the total concentration (mg/kg) of a series of volatile organic compound (VOCs) and semi-volatile organic compounds (semi-VOCs). The synthetic precipitation leaching procedure (SPLP) test was also performed to evaluate the leachability of the trace organic chemicals. During the total analysis only a few volatile organic compounds were commonly found in the samples (trichlorofluoromethane, toluene, 4-isopropyltoluene, trimethylbenzene, xylenes, and methylene chloride). A total of nine VOCs were detected in the leaching test. Toluene showed the highest leachability among the compounds (61.3-92.0%), while trichlorofluoromethane, the most commonly detected compound from both the total and leaching tests, resulted in the lowest leachability (1.4-39.9%). For the semi-VOC analysis, three base-neutral semi-VOC compounds (bis(2-ethylhexyl)phthalate, butyl benzyl phthalate, and di-n-butyl phthalate) and several PAHs (acenaphthene, pyrene, fluoranthene, and phenanthrene) were commonly detected in C&D fines samples. These compounds also leached during the SPLP leaching test (0.1-25%). No acid extractable compounds, pesticides, or PCBs were detected. The results of this study were further investigated to assess risk from land applied recovered soil fines by comparing total and leaching concentrations of recovered soil fines samples to risk-based standards. The results of this indicate that the organic chemicals in recovered soil fines from C&D debris recycling facilities were not of a major concern in terms of human risk and leaching risk to groundwater under reuse and contact scenarios.     

Preparation of Liquid Epoxidized Natural Rubber by Oxidative Degradations Using Periodic Acid,Potassium Permanganate and UV-Irradiation

Epoxidized natural rubber (ENR) needs to be degraded into shorter chain lengths, to form liquid epoxidized natural rubber (LENR), for applications such as coating and adhesives. Since ENR contains both C=C and epoxide groups as reactive sites for degradation reactions, thus, LENR could be prepared by different methods through cleavages of C=C or epoxide groups, or a combination of both sites. Different mechanisms would produce different terminals on the LENR. This paper reports the oxidative degradation by (a) periodic acid, (b) potassium permanganate and (c) ultra violet (UV) irradiation. The degraded rubbers were characterized by gel permeation chromatography (GPC), nuclear magnetic resonance (NMR) and Fourier transform infra-red spectroscopy (FTIR). Ester and ketone terminals were formed in all the three methods, but lactone and hydrofuranic structures were observed only in degradation by UV irradiation. NMR spectrum reveals that cyclization of ENR has occurred during degradation by periodic acid. At lower periodic acid concentration, degradation takes place only via C=C cleavage, but at higher concentration, the attack to the epoxide groups becomes more prominent. Potassium permanganate has attacked both the double bonds and epoxide groups. On the other hands, epoxide group was not affected during degradation by UV irradiation, which cleaved only the C=C bonds.