Removal of aqueous phenolic compounds from a model system by oxidative polymerization with turnip (Brassica napus L var purple top white globe) peroxidase

Turnip roots, which are readily available in Mexico, are a good source of peroxidase, and because of their kinetic and biochemical properties have a high potential as an economic alternative to horseradish peroxidase (HRP). The efficiency of using turnip peroxidase (TP) to remove several different phenolic compounds as water‐insoluble polymers from synthetic wastewater was investigated. The phenol derivatives studied included phenol, 2‐chlorophenol, 3‐chlorophenol, o‐cresol, m‐cresol, 2,4‐dichlorophenol and bisphenol‐A. The effect of pH, substrate concentration, amount of enzyme activity, reaction time and added polyethylene glycol (PEG) was investigated in order to optimize reaction conditions. A removal efficiency ≥85% was achieved for 0.5 mmol dm^?3 phenol derivatives at pH values between 4 and 8, after a contact time of 3 h at 25 °C with 1.28 U dm^?3 of TP and 0.8 mmol dm^?3 H₂O₂. Addition of PEG (100–200 mg dm^?3) significantly reduced the reaction time required (to 10 min) to obtain >95% removal efficiency and up to 230% increase in remaining TP activity. A relatively low enzyme activity (0.228 U dm^?3) was required to remove >95% of three phenolic solutions in the presence of 100–200 mg dm^?3 PEG. TP showed efficient and fast removal of aromatic compounds from synthetic wastewaters in the presence of hydrogen peroxide and PEG. These results demonstrate that TP has good potential for the treatment of phenolic‐contaminated solutions. © 2002 Society of Chemical Industry     

Removal of aqueous phenol and 2‐chlorophenol with purified soybean peroxidase and raw soybean hulls

In this study, the removal of phenol and 2‐chlorophenol using soybean seed‐hulls in the presence of hydrogen peroxide is demonstrated. The performance of a stirred membrane reactor containing soluble purified SBP was compared with a batch stirred reactor containing raw soybean seed‐hulls. The purified enzyme reactor proved to be ineffective while excellent results were obtained with the crude seed‐hulls for the removal of phenol and 2‐chlorophenol. Four sequential batch reactors containing raw seed‐hulls achieved greater than 96% removal of phenol with a retention time of 20 min in each reactor. A single batch reactor containing raw seed‐hulls was effective in removing greater than 98.5% of 2‐chlorophenol (initially at 1000 ppm) in less than 15 min. The performance of these reactors is comparable to existing HRP‐based technology. The stability of the soybean peroxidase (SBP) enzyme was also examined in the presence of detergents (SDS, Tween 20 and Triton X‐100). Low concentrations of the detergents significantly increased the enzyme activity and higher concentrations of detergents (up to 20% w/v) did not inactivate the SBP enzyme. These results demonstrate that SBP has good potential for the treatment of phenol contaminated solutions. © 1999 Society of Chemical Industry     

Simultaneous purification and immobilization of bitter gourd (Momordica charantia) peroxidases on bioaffinity support

This paper demonstrates the construction of an inexpensive bioaffinity adsorbent by simply incubating Sephadex G 50 matrix with jack bean meal extract at room temperature. Sephadex G 50 adsorbed 17 mg Con A (concanavalin A) per g of the matrix. Con A‐adsorbed Sephadex was employed for the immobilization of glycoenzymes directly from ammonium sulfate‐fractionated proteins of bitter gourd. The obtained bioaffinity support was very efficient for high yield immobilization of peroxidases from bitter gourd and it bound nearly 425 enzyme units per g of the matrix. Bitter gourd peroxidase immobilized on lectin–Sephadex support showed a very high effectiveness factor, ‘η,’ of 1.25. Immobilized BGP preparation was quite stable against the denaturation induced by pH, heat, urea, Triton X 100, Tween 20, SDS, Surf Excel and water‐miscible organic solvents: dimethyl sulfoxide and dimethyl formamide. Low concentration of detergents like SDS, Tween 20, and Triton X 100 enhanced the activity of soluble and immobilized bitter gourd peroxidase. Peroxidase bound to the bioaffinity support exhibited very high resistance to proteolysis caused by the trypsin treatment. Con A–Sephadex‐bound bitter gourd peroxidase retained 85% of its initial activity after treatment with 2.5 mg trypsin per cm³ of incubation mixture for 1 h at 37 °C while the soluble enzyme lost nearly 40% of the initial activity under similar incubation conditions. Immobilized bitter gourd peroxidase preparation appeared to be more rigid to proteolysis mediated by trypsin compared with soluble bitter gourd peroxidase. Copyright © 2004 Society of Chemical Industry     

Effect of lipids and surfactants on extracellular lipase production by Yarrowia lipolytica

The production of extracellular lipase in submerged cultures of Yarrowia lipolytica CECT 1240 has been investigated. Several compounds have been added to the culture medium, in order to assess their efficiency as inducers of lipase production. First, the effect of triglycerides (olive oil, sunflower oil, tributyrin) and fatty acids (oleic acid) has been studied. The highest activity level was obtained with sunflower oil (58 U cm^?3), followed by olive oil (49 U cm^?3). The cultures with tributyrin and oleic acid attained similar activities (33 U cm^?3). Then, several surfactants (Tween 80, Triton X‐100, gum arabic, polyethylene glycol 200) were added to the cultures with sunflower oil, in an attempt to increase the levels of extracellular lipase activity. The obtained activities were slightly lower than those achieved without surfactants. The assay of a wide range of surfactant concentrations in the case of PEG‐200 (with which the highest activity levels had been attained) did not improve the results. This strain secreted lipase concentrations two‐fold higher and showed significantly different behaviour towards the presence of surfactants in the culture medium, compared with other wild‐type Yarrowia lipolytica strains. Copyright © 2003 Society of Chemical Industry     

Removal of aqueous phenol catalysed by a low purity soybean peroxidase

The application of a low purity soybean peroxidase (LP‐SBP), obtained from wasted seed hulls, as catalyst for phenol polymerisation in aqueous solution in the presence of hydrogen peroxide is described. The polymers formed precipitate out from solution and may be readily separated by physico‐chemical techniques. LP‐SBP offers the advantage of reduced cost compared with horseradish peroxidase (HRP). The SBP activity in fresh hulls was greater than in aged hulls and was preserved at ?10 °C. There was a linear correlation between initial phenol concentration (1, 2, 5 and 10 mmol dm^?3) and the minimum dosage of LP‐SBP required to precipitate 95% of the phenolic polymers. Polyethylene glycol (molecular weight, 6000) at 1000 mg dm^?3 did not extend LP‐SBP lifetime. At all phenol concentrations tested, a retention time of about 100 min was sufficient to achieve yields of 95%. © 2002 Society of Chemical Industry     

Lecithin‐enhanced biotransformation of cholesterol to androsta‐1,4‐diene‐3,17‐dione and androsta‐4‐ene‐3,17‐dione

A biotransformation process using Mycobacterium sp was studied for androsta‐1, 4‐diene‐3,17‐dione (ADD) and androsta‐4‐ene‐3,17‐dione (AD) production from cholesterol. Cholesterol has a poor solubility in water (～1.8 mg dm^?3 at 25 °C), which makes it difficult to use as the substrate for biotransformation. Lecithin is a mixture of phospholipids of phosphatidylcholine (PC) and phosphatidylethanolamine (PE), which behave like surfactants and can form planar bi‐layer structures in an aqueous medium. Therefore, a small amount of lecithin (<1 g dm^?3) can be used to form stable colloids with cholesterol at a relatively high concentration (20 g dm^?3) in water. In this work, an energy density of 1000 J cm^?3 from sonication was provided to overcome the self‐association of cholesterol and to generate a stable lecithin–cholesterol suspension that could be used for enhanced biotransformation. The lecithin–cholesterol suspension was stable and could withstand typical autoclaving conditions (121 °C, 15 psig, 20 min). In contrast to conventional surfactants, such as Tween 80, that are commonly used to help solubilize cholesterol, lecithin did not change the surface tension of the aqueous solution nor cause any significant foaming problem. Lecithin was also biocompatible and showed no adverse effect on cell growth. Compared with the medium with Tween 80 as the cholesterol‐solubilizing agent, lecithin greatly improved the biotransformation process in regard to its final product yield (～59% w/w), productivity (0.127–0.346 g dm^?3 day^?1), ADD/AD ratio (6.7–8), as well as the long‐term process stability. Cells can be reused in repeated batch fermentations for up to seven consecutive batches, but then lose their bioactivity due to aging problems, possibly caused by product inhibition and nutrient depletion. © 2002 Society of Chemical Industry     

Impact of the presence of solids on peroxidase‐catalyzed treatment of aqueous phenol

The impact of the presence of solids on the treatment of aqueous solutions of phenol using horseradish peroxidase (HRP) and hydrogen peroxide was investigated. The solids studied were silica gel, kaolin, bentonite, cellulose and peat moss. Kaolin, bentonite, cellulose and peat moss enhanced phenol transformation at pH 5.0 and 7.0 starting at concentrations of 100, 1000 or 10 000 mg dm^?3. At pH 9.0, bentonite and kaolin had negative impacts when present at 10 000 mg dm^?3 and peat moss when present at 1000 mg dm^?3 and 10 000 mg dm^?3. In the case of bentonite and peat moss, the enhancing effects at pH 7.0 were associated with the dissolved or colloidal constituents, while in the case of kaolin, the enhancing effects were due to the solid material. Freshly made bentonite suspensions inactivated the peroxidase enzyme; however aged bentonite suspensions and their supernatants did not affect enzyme stability. H₂O₂ was unstable in solutions containing peat moss constituents. Phenolic solutions treated in the presence of bentonite, kaolin and peat moss were significantly less toxic than the controls, indicating that these materials were able to interact with and partially neutralize precursors of toxic reaction products. Copyright © 2003 Society of Chemical Industry     

Effects of surfactants on hydrodynamics and mass transfer in a split‐cylinder airlift reactor

Effects of various concentrations (0–5 ppm) of anionic (sodium dodecyl sulfate, SDS) and non‐ionic (Tween‐80 and Triton X‐405) surfactants on gas hold‐up and gas–liquid mass transfer in a split‐cylinder airlift reactor are reported for air–water. Surfactants were found to strongly enhance gas hold‐up. Non‐ionic surfactants were more effective in enhancing gas hold‐up compared to the anionic surfactant SDS. An enhanced gas hold‐up and a visually reduced bubble size in the presence of surfactants implied an enhanced gas–liquid interfacial area for mass transfer. Nevertheless, the overall gas–liquid volumetric mass transfer coefficient was reduced in the presence of surfactants, suggesting that surfactants greatly reduced the true liquid film mass transfer coefficient and this reduction outweighed the interfacial area enhancing effect. Presence of surfactants did not substantially affect the induced liquid circulation rate in the airlift vessel.     

Anaerobic biodegradation of phenol in sulfide‐rich media

In the refinery industry, the washing processes of middle‐distillates using caustic solutions generate phenol‐ and sulfide‐containing waste streams. The spent caustic liquors generated contain phenols at concentrations higher than 60 g dm^?3(638.3 mmol dm^?3). For sulfur compounds, the average sulfide concentration was 48 g dm^?3(1500 mmol dm^?3) in these streams. The goal of this study was to evaluate the specific impact of phenol and sulfide concentrations towards the phenol‐biodegradation activity of a phenol‐acclimated anaerobic granular sludge. An inhibition model was used to calculate the phenol and sulfide inhibitory concentrations that completely stopped the phenol‐biodegradation activity (IC100). A maximum phenol‐biodegradation activity of 83 µmol g^?1 VSS h^?1 was assessed and the IC100 values were 21.8 mmol dm^?3 and 13.4 mmol dm^?3 for phenol and sulfide respectively. The limitation of the phenol biodegradation flow by phenol inhibition seemed to be related to the more important sensitivity of phenol‐degrading bacteria. The up‐flow anaerobic sludge bed reactor operating in a non‐phenol‐dependent inhibition condition did not present any sensitivity to sulfide concentrations below 9.6 mmol dm^?3. At this residual concentration, the pH and bisulfide ions' concentration might be responsible for the general collapsing of the reactor activity. Copyright © 2004 Society of Chemical Industry     

Catalytic removal of phenol from aqueous solutions in a trickle‐bed reactor

The degradation of high concentrations of phenol (1g/dm^?3) in aqueous media at high temperatures (100–190 °C) and pressures (2.0 MPa) has been studied by catalytic wet air oxidation in a trickle‐bed reactor. The effect of reaction temperature, weight hourly space velocity (WHSV) and hydrogen peroxide concentration on phenol concentration, total organic carbon (TOC) and chemical oxygen demand (COD) conversion by using a commercial copper catalyst has been investigated. At 150 °C, TOC removal increased by 28% with the WHSV of 62.5 h^?1. The addition of hydrogen peroxide as a free radical promoter significantly enhanced the depletion rate of phenol. A kinetic study has been carried out leading to the determination of the kinetic constants for the removal of TOC. Copyright © 2005 Society of Chemical Industry     

己内酰胺在硫酸铵晶体表面吸附特性

引言 己内酰胺(caprolactam,CPL)受热时发生聚合反应,可作为尼龙-6纤维、工程塑料、聚酰胺等单体的原料,是一种重要的石油化工产品[1-2].硫酸铵是己内酰胺工艺的重要副产物,如意大利SNIA甲苯法工艺每生产1t己内酰胺副产硫酸铵约4.2 t[3].     

Determination of the efficiency and removal mechanism of cobalt by crab shell particles

The effects of contact time, solution pH and ionic strength on interactions between cobalt (⁵⁹Co) ions in synthetic liquid waste and particles of raw crab shell, Portunus trituberculatus, in batch reactions were studied. Approximately 19.5 mg dm^?3 Co was removed within 6 h after contact with 1.0 g dm^?3 crab shell at an initial concentration of 20 mg dm^?3 Co. Due to the dissolution of calcium carbonate in the crab shell, the solution pH changed spontaneously to 10, leading to precipitation of cobalt ions. The efficiency of cobalt removal depended on solution pH, but was less pH sensitive than for controls without crab shell. The maximum uptake of Co at an initial pH value of 5.0 was 510 mg g^?1 crab shell. The removal efficiency was affected slightly by ionic strength up to 2.0 mol dm^?3 of NaCl. Scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS) indicated that the removal mechanism of Co by crab shell resulted primarily from the dissolution of calcium carbonate followed by precipitation of cobalt on the surface of the shell. Compared with commonly used ion‐exchange resins such as natural zeolite, Durasil 70, and Durasil 230, the efficiency of Co removal by a column of mixture of crab shell and activated carbon was at least three‐fold greater, indicating that crab shell is a suitable biosorbent for the removal of cobalt from liquid waste. Copyright © 2004 Society of Chemical Industry     

Bacterial biodegradation of phenol and 2,4‐dichlorophenol

Nine bacterial strains capable of utilising phenol and 2,4‐dichlorophenol (DCP) have been isolated from a mixed culture grown on substrates containing these compounds. One of these strains, a Micrococcus sp, was further investigated under aerobic conditions using phenol and DCP as sole carbon and energy sources at various pH values. Phenol degradation was enhanced under alkaline conditions, and up to 500 mg dm^?3 phenol was mineralised within 50 h at pH 10. DCP was more recalcitrant; however up to 883 mg g^?1 and 230 mg g^?1 were degraded within 10 days, when using initial DCP concentrations of 100 and 200 mg dm^?3, respectively. Biomass measurements showed cell growth, proving that both phenol and DCP are used as growth substrates for this isolate. Copyright © 2003 Society of Chemical Industry     

Stimulation of Phenol Removal Efficiency of Aspergillus versicolor by Surfactants,a Promising Way to Treat Phenol-Containing Waste Waters

The effect of the cationic surfactant, dodecyl trimethyl ammonium bromide (DTAB), on phenol bioremoval efficiency of an Aspergillus versicolor strain was examined. The strain was grown in mineral salt (MS) medium and the effect of DTAB was investigated as a function of different pH values, phenol and surfactant concentrations. The effect of pH was tested within the range of 4–7 and the maximum bioremoval was found at pH 4. Initial phenol concentrations investigated ranged from 100 to 600 mg/L, and the effects of surfactant concentrations on the removal were tested with 0, 0.25, 0.5 and 1 mM DTAB, which showed that 0.5 mM surfactant was the most effective concentration. The maximum bioremoval rates found after 72 h incubation were 99.48 and 99.15 % in 100 and 200 mg/L initial phenol-containing samples, respectively, where the phenol removal capacity of the fungus was only 142.373 mg/g in the DTAB blank samples. The maximum phenol uptake capacity of 267.162 mg/g was measured in the presence of 0.5 mM DTAB at 200 mg/L initial phenol concentration. These results showed that DTAB considerably increased the bioremoval efficiency of the strain tested at relatively lower phenol concentrations. The feasibility of this bioremoval method for industrial wastewater treatment is discussed.     

Zeolite synthesis from coal fly ash for the removal of lead ions from aqueous solution

Fly ash samples from the Bayswater and Eraring power plants, located in New South Wales, Australia, were used in a preliminary study on zeolite synthesis by hydrothermal treatment with sodium hydroxide under various conditions. The treated fly ash was tested for the ability to remove lead ions from aqueous solution. Both fly ashes were partially converted to zeolite. The zeolites formed under the experimental conditions were zeolite Na‐P1 and sodalite octahydrate for the Bayswater ash and phillipsite, zeolite X, zeolite Na‐P1 and sodalite octahydrate for the Eraring ash. The type of zeolite formed was dependent on the treatment time and sodium hydroxide concentration. In the case of the Bayswater ash, zeolite Na‐P1 was formed by treatment with 4 mol dm^?3 NaOH for 48 h while treatment with 5 mol dm^?3 NaOH for 96 h produced sodalite octahydrate at the expense of zeolite Na‐P1. In the case of the Eraring ash, phillipsite was formed following treatment with 3 mol dm^?3 NaOH, zeolite X and zeolite Na‐P1 were formed following treatment with 4 mol dm^?3 NaOH and sodalite octahydrate was formed following treatment with 5 mol dm^?3 NaOH. A maximum cation exchange capacity of ～400 meq/100 g was achieved by both treated ash samples. Treatment of a solution with a lead ion concentration of 120 ppm using 0.5 g of both treated ash samples (S/L ratio = 0.25 g/100 cm³) achieved complete removal in 5 min, whereas treatment with 0.1 g of each material (S/L ratio = 0.05 g/100 cm³) achieved complete lead ion removal after 24 h. © 2001 Society of Chemical Industry     

Electrochemical conversion of phenolic wastewater on carbon electrodes in the presence of NaCl

The electrochemical conversion of highly concentrated synthetic phenolic wastewater was studied on carbon electrodes in a batch electrochemical reactor. The effects of reaction temperature, electrolyte concentration, current density and initial phenol concentration on phenol conversion were elucidated. The wastewater was synthetically prepared and used in reactions carried out generally at 25 °C with an initial phenol concentration of 3500 mg dm^?3. Although current density increased, phenol conversion% and initial phenol conversion rate did not increase correspondingly above 35 °C and an electrolyte concentration of 90 g dm^?3. As the voltage values applied were increased, the increasing current density resulted in fast phenol conversion. Kinetic investigations denoted that overall phenol destruction kinetics was of zero order with an activation energy of 10.9 kJ mol^?1. Under appropriate conditions, phenol was completely converted within 15 min for an initial phenol concentration of 98 mg dm^?3 while 8 h was required to gain 95% conversion using 4698 mg dm^?3. Solid polymeric materials were produced at initial phenol concentrations above 500 mg dm^?3 using the appropriate current density. In the reaction medium, only mono‐, di‐ and tri‐substituted chlorophenols were formed and 100% of all species were either oxidised or contributed to the formation of a polymeric structure. Almost all of the phenol loaded to the reactor was converted into non‐passivating polymeric products, denoting a safe and easy method for the separation of phenol. © 2001 Society of Chemical Industry     

Effect of surfactants on the soil desorption of hexachlorocyclohexane (HCH) isomers and their anaerobic biodegradation

The extensive utilization of hydrophobic organic compounds (HOCs) such as pesticides generates high environmental pollution levels. Due to their hydrophobicity, this type of compound tends to accumulate in soil organic matter and, thus, soil desorption limits their availability for microbial degradation. The use of surfactants may increase the pollutant's desorption from the soil. One of the pesticides with strong sorption characteristics is hexachlorocyclohexane (HCH), a mixture of isomers: α‐, β‐, γ‐ and δ‐HCH. In this work, we evaluated the use of three surfactants, Triton X100, Tween 80 and sodium dodecyl sulfate (SDS), on the HCH desorption from a sandy loam soil. The effects of the addition of these surfactants on anaerobic biodegradation were studied. To attain this purpose, different assays were performed to evaluate both effects. Triton X100 exerted the best desorption of HCH isomers, followed by Tween 80, whereas SDS caused no significant desorption of the isomers. Triton had a strong inhibitory effect on the HCH biodegradation, while Tween 80 did not decrease the degradation rates of the different isomers. Moreover, the degradation rates of β‐ and δ‐HCH were significantly enhanced (around 10%). On the other hand, detrimental effects on the biodegradation rates and yields were due to the ageing of the soil, depending on the period of exposure of the soil to the pollutant. Copyright © 2005 Society of Chemical Industry     

BTEX removal from contaminated groundwater by a co‐culture of Pseudomonas putida and Pseudomonas fluorescens immobilized in a continuous fibrous‐bed bioreactor

A fibrous‐bed bioreactor with immobilized cells of Pseudomonas putida and Pseudomonas fluorescens was used to treat groundwater contaminated with benzene, toluene, ethylbenzene, and xylenes (collectively know as BTEX). The kinetics of BTEX biodegradation in the fibrous‐bed bioreactor operated under continuous well‐mixed conditions was studied at room temperature. Aeration was not used in the process fed with groundwater samples with an average total BTEX concentration of 2.75 mg dm^?3. All BTEX compounds present in the groundwater feed were concurrently and completely biodegraded even under oxygen‐limited or hypoxic conditions. Nearly 100% removal efficiency was obtained when the retention time was greater than 1 h. BTEX removal efficiency decreased with decreasing the retention time, with p‐ and o‐xylenes showed up first in the treated groundwater, followed by benzene and then other BTEX compounds. Biodegradation rates of BTEX generally increased with increasing BTEX concentration and loading rate. The maximum BTEX biodegradation rate was 5.76 mg h^?1 dm^?3 at the loading rate of 6.54 mg dm^?3 h^?1. The bioreactor had a stable performance, maintaining its ability for efficient BTEX degradation without requiring additional nutrients for more than 1 month. The good performance of the fibrous‐bed bioreactor was attributed to the high cell density (～15 g dm^?3 reactor volume) in the fibrous matrix. © 2002 Society of Chemical Industry     

Continuous bioremediation of phenol‐polluted air in an external loop airlift bioreactor with a packed bed

An external loop airlift bioreactor with a small amount (99% porosity) of stainless steel mesh packing inserted in the riser section was used for bioremediation of a phenol‐polluted air stream. The packing enhanced volatile organic chemical and oxygen mass transfer rates and provided a large surface area for cell immobilization. Using a pure strain of Pseudomonas putida, fed‐batch and continuous runs at three different dilution rates were completed with phenol in the polluted air as the only source of growth substrate. 100% phenol removal was achieved at phenol loading rates up to 33 120 mg h^?1 m^?3 using only one‐third of the column, superior to any previously reported biodegradation rates of phenol‐polluted air with 100% efficiency. A mathematical model has been developed and is shown to accurately predict the transient and steady‐state data. Copyright © 2006 Society of Chemical Industry     

表面活性剂对木薯秆酶水解的影响

采用纤维素酶促水解的方法,以木薯秆为底物,研究了5种表面活性剂(SDS、Tween 20、Tween 80、Triton x-100、Triton x-114)及其用量对木薯秆酶水解得率的影响。结果表明,除SDS外,其他4种表面活性剂对木薯秆酶水解有不同程度的促进作用,Tween 20的效果最为显著。添加2.5 g/L的Tween 20水解72 h和5.0 g/L的Triton x-114水解60 h,酶水解得率分别达到了49.23%、49.48%,比空白样提高了33.45%和34.13%。