Aerobic biodegradation and inhibition kinetics of poly‐aromatic hydrocarbons (PAHs) in a petrochemical industry wastewater in the presence of biosurfactants

BACKROUND: In Izmir, Turkey, wastewaters from the petrochemical industry are treated using conventional activated sludge systems. A significant proportion of poly‐aromatic hydrocarbons (PAHs) with high‐molecular weights remains in this treatment system and inhibits the biological activity. Biosurfactants increase PAHs degradation by enhancing the solubility of the petroleum components. The aerobic inhibition kinetics of PAHs has not previously been investigated in the presence of biosurfactants for a real petrochemical industry wastewater. RESULTS: Among the kinetic models used (Monod‐type, zero, first‐order and second‐order) it was found that the Monod kinetic was effective for describing the biodegradation of PAHs in petrochemcal industry wastewater in the presence of three biosurfactants, namely Rhamnolipid (RD), Surfactine (SR) and Emulsan (EM) in an aerobic activated sludge reactor (AASR). The maximum PAH removal rate (R_max) and specific growth rate of PAH degrading bacteria (µ_max) increased, while the half saturation concentration of PAH (K_s) decreased at 15 mg L^?1 RD concentration compared with the control without biosurfactant at a sludge retention time (SRT) of 25 days. CONCLUSION: PAH oxidation is typified by competitive inhibition at RD concentrations > 15 mg L^?1 resulting in increases in K_s values with PAH accumulation. Low inhibition constant (K_ID) values reflect difficulties in the metabolizability of PAHs. Metabolite production decreased at RD = 25 mg L^?1 in the PAHs indeno (1,2,3‐cd) pyrene (IcdP), flourene (FLN), phenanthrene (PHE) and benzo(a)pyrene (BaP). Copyright © 2011 Society of Chemical Industry     

Simulation of a membrane bioreactor for regeneration of degreasing systems

The dynamic behaviour of membrane bioreactors (MBRs) with negligible biomass growth due to the presence of toxic substances was modelled to simulate a pilot plant test in an industrial degreasing unit. Modelling was done by introducing a substrate biodegradation rate into a material balance equation of an MBR. This was followed by a discrimination procedure between the simulated and measured values, from which best‐fit specific substrate uptake rates (q_sp) were determined at different air supply rates. The results showed clear improvement of q_sp with increased air supply, indicating a possible increase in the active cell population in the reactor due to reduced toxicity. The highest specific substrate uptake rate (q_sp = 0.08 g_substrate g_biomass^?1 d^?1) determined was assumed equal to the maintenance coefficient (q_m) for the biodegradation of the substrate under the test conditions. The understanding of the dynamics provided a reference in subsequent regeneration system improvement. Copyright © 2006 Society of Chemical Industry     

‘Living’ Radical Polymerization of Styrene Using Tetraphenylethane-based Polyurethane Iniferter

A novel polyurethane iniferter synthesized from 1,1,2,2-tetraphenyl-1,2-ethane diol and toluene diisocyanate has been used to polymerize styrene through a ‘living’ radical mechanism. A rate equation (R_p∝[styrene]^1·1 [polyurethane iniferter]^0·93) and overall activation energy (E_a=99kJmol^-1) have been deduced from the kinetic results. The molecular weight of the polystyrene increased with increasing polymerization time and conversion. When the polystyrene was post-polymerized in the presence of styrene and methyl methacrylate, a high molecular weight polystyrene and polystyrene–poly(methyl methacrylate) block copolymer were obtained, respectively. © 1997 SCI.     

Removal of oxytetracycline (OTC) in a synthetic pharmaceutical wastewater by sequential anaerobic multichamber bed reactor (AMCBR)/completely stirred tank reactor (CSTR) system: biodegradation and inhibition kinetics

BACKGROUND: The antibiotics in industrial and munipical wastewaters could not be removed effectively in conventional anaerobic and aerobic biological treatment plants. Few studies have been performed to investigate the biodegradation and inhibition kinetics of oxytetracycline (OTC) on methanogens and total volatile fatty acids (TVFA). RESULTS: A high rate anaerobic multichamber bed reactor (AMCBR) was effective in removing the molasses‐chemical oxygen demand (COD), and the OTC antibiotic with yields as high as 96% at an influent OTC loading rate of 133.33 gOTC m^?3 day^?1 at a hydraulic retention time (HRT) of 2.25 days. Increasing the OTC loading rates from 22.22 gOTC m^?3 day^?1 to 133.33 gOTC m^?3 day^?1 improved both hydrolysis and specific utilization of molasses‐COD. The inhibition constants of TVFA (K_I?TVFA?meth) and OTC (K_I?OTC?meth) on methanogens decreased at OTC loadings > 133.33 gOTC m^?3 day^?1. The direct effect of OTC loadings > 133.3 gOTC m^?3 day^?1 on acidogens and methanogens was evaluated using the Haldane inhibition kinetic. CONCLUSION: OTC antibiotic was effectively removed in a sequential AMCBR/completely stirred tank reactor (CSTR). The Haldane inhibition constant (K_ID) decreased significantly at high OTC loads indicating the increase in toxicity. Copyright © 2012 Society of Chemical Industry     

Analysis of the Activated Sludge Process in an MBR under Starvation Conditions

An aerobic membrane bioreactor (MBR) at complete biomass retention was studied over a period of time under starvation conditions. Kinetic parameters were determined in a no‐feed batch test. The decay rate of activated sludge, k_d = 0.05 d^–1, was determined by tracking the decrease of MLSS. The ratio of MLVSS/MLSS was in the range 0.76–0.85. The pH values were between 7.02 and 8.23. As a function of different initial concentrations of MLSS, specific nitrification rates q_N, decreased from 4.23 to 0.02 mg‐N/(g MLVSS d) and specific biodegradation rates q_b increased from 0.23 to 1.90 mg‐COD/(g MLVSS d). From experimental data the kinetic constants for respiration, which followed Monod kinetics, were determined as q_O2max = 9.8 mg‐O₂/(g MLVSS h), K_x = 2.9 g/dm³. Additionally, a linear correlation between MLSS and mean floc size was found to exist during the biodegradation process.     

Biodegradation kinetics of trans‐4‐methyl‐1‐cyclohexane carboxylic acid in continuously stirred tank and immobilized cell bioreactors

BACKGROUND: Naphthenic acids are carboxylic acid compounds of oil sands wastewaters that contribute to aquatic toxicity. Biodegradation kinetics of an individual naphthenic acid compound in two types of continuous‐flow bioreactors were investigated as a means of improving remediation strategies for these compounds. RESULTS: This study evaluates the kinetics of biodegradation of trans‐4‐methy‐1‐cyclohexane carboxylic acid (trans‐4MCHCA) using two bioreactor systems and a microbial culture developed in previous work. Using a feed concentration of 500 mg L^?1 the biodegradation rate of trans‐4MCHCA in the immobilized cell bioreactor was almost two orders of magnitude higher than that in a continuously stirred tank bioreactor. The maximum reaction rates of 230 mg (L d)^?1 at a residence time of 1.6 d (40 h) and 22 000 mg (L d)^?1 at a residence time of 2.6 h were observed in the continuously stirred tank and immobilized cell bioreactors, respectively. In a second immobilized cell system operating with a feed concentration of 250 mg L^?1, a comparable maximum reaction rate (21 800 mg (L d)^?1) was achieved at a residence time of 1.0 h. CONCLUSION: The use of immobilized cell bioreactors can enhance the biodegradation rate of naphthenic acid compounds by two orders of magnitude. Further, biodegradation greatly reduces the toxicity of the effluent wastewater. Copyright © 2009 Society of Chemical Industry     

Effect of acrylic acid neutralization on ‘livingness’ of poly[styrene‐ran‐(acrylic acid)] macro‐initiators for nitroxide‐mediated polymerization of styrene

BACKGROUND: The effect of acrylic acid neutralization on the degradation of alkoxyamine initiators for nitroxide‐mediated polymerization (NMP) was studied using styrene/acrylic acid and styrene/sodium acrylate random copolymers (20 mol% initial acrylate feed concentration) as macro‐initiators. The random copolymers were re‐initiated with fresh styrene in 1,4‐dioxane at 110 °C at SG1 mediator/BlocBuilder^® unimolecular initiator ratios of 5 and 10 mol%. RESULTS: The value of k_pK (k_p = propagation rate constant, K = equilibrium constant) was not significantly different for styrene/acrylic acid and styrene/sodium acrylate compositions at 110 °C (k_pK = 2.4 × 10^?6–4.6 × 10^?6 s^?1) and agreed closely with that for styrene homopolymerization at the same conditions (k_pK = 2.7 × 10^?6–3.0 × 10^?6 s^?1). All random copolymers had monomodal, narrow molecular weight distributions (polydispersity index M?_w/M?_n = 1.10–1.22) with similar number‐average molecular weights M?_n = 19.3–22.1 kg mol^?1. Re‐initiation of styrene/acrylic acid random copolymers with styrene resulted in block copolymers with broader molecular weight distributions (M?_w/M?_n = 1.37–2.04) compared to chains re‐initiated by styrene/sodium acrylate random copolymers (M?_w/M?_n = 1.33). CONCLUSIONS: Acrylic acid degradation of the alkoxyamines was prevented by neutralization of acrylic acid and allowed more SG1‐terminated chains to re‐initiate the polymerization of a second styrenic block by NMP. Copyright © 2008 Society of Chemical Industry     

Effect of annealing time and molecular weight on melt memory of random ethylene 1‐butene copolymers

The effects of annealing time and molecular weight on the strong melt memory effect observed in random ethylene 1‐alkene copolymers are analyzed in a series of model ethylene 1‐butene copolymers with 2.2 mol% branches. Melt memory is associated with molten clusters of ethylene sequences from the initial crystals that remain in close proximity and are unable to diffuse quickly to the randomized melt state, thus increasing the recrystallization rate. Melt memory persists even for greater than 1000 min annealing indicating a long‐lived nature of the clusters that only fully dissolve at melt temperatures above a critical value (>160 °C). Below the critical melt temperature, molecular weight and annealing temperature have a strong influence on the slow kinetics of melt memory. For the copolymers analyzed, slow dissolution of clusters is experimentally observed only for M_w < 50 000 g mol^?1. More stable clusters that survive higher annealing temperatures display slower dissolution rates than clusters remaining at lower temperatures. The threshold crystallinity level to enable melt memory (X_c,threshold) decreases with increasing molecular weight and decreasing annealing temperature similarly to the variation of the chain diffusivity in the melt. The process leading to melt memory is thermally activated as the variation of X_c,threshold with temperature follows Arrhenius behavior with high activation energy (ca 108 kJ mol^?1) that is independent of molecular weight. © 2018 Society of Chemical Industry     

Synthesis and characterization of copolymer of styrene with methacrylic acid initiated by triphenylbismuthonium 1,2,3,4‐ tetraphenylcyclopentadienylide

The radical copolymerization of styrene with methacrylic acid (MAA) initiated by triphenylbismuthonium 1,2,3,4‐tetraphenylcyclopentadienylide in dioxan at 80 ± 0.1 °C for 3 h results in the formation of alternating copolymer as evidenced from the values of reactivity ratios as r₁ (styrene) = 0.03 and r₂ (MAA) = 0.025. The kinetic expression is R_p α [I]^0.5 [Sty] [MAA] and overall energy of activation is computed to be 23 kJ/mol. The FTIR spectrum of the copolymer shows the presence of bands at 3054 cm^?1 assigned to the phenyl group of styrene and at 1724 cm^?1 assigned to the ? COOH group of MAA. The ¹H‐NMR spectrum of the copolymer shows peaks between 7.20 and 7.27 δ assigned to the phenyl protons of styrene and at 12.5 δ assigned to the COOH proton of MAA. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 1838–1843, 2005     

Radiation-induced graft copolymerization of styrene to cellulose

The radiation-induced graft copolymerization of styrene to cellulose has been studied in vacuo at 30°C and at dose rates from (0.37 to 8.73) × 10^?2 W/kg. Dioxan was used as solvent for monomer and polystyrene homopolymer, and water (2% total volume) was incorporated as swelling agent for cellulose. The concentration of styrene in the bulk medium was varied from 0.432 to 3.46 moles/l., and the rates of both grafting and homopolymerization were shown to be proportional to [monomer] · [intensity]^1/2. The value of 3.3 × 10^?4 l. mole^?1 sec^?1 derived for k_p²/k_t in homopolymerization is similar to that for normal free-radical polymerization of styrene. However, reduced termination during grafting yielded a much higher value (58 l. moles^?1 sec^?1). Degradation of cellulose in the absence of monomer was followed viscometrically, and values of 13.5 and 24.6 were derived for G (scission) in vacuo and in air, respectively.     

Microfunnel magnetic stirring-assisted dispersive liquid–liquid microextraction-derivatization technique,for the determination of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (Mutagen X) in aqueous samples by GC-ECD

A simple, highly sensitive and reliable microfunnel magnetic stirring-assisted dispersive liquid–liquid microextraction method (MF-MSA-DLLME) was developed based on the derivatization of mutagen X in aqueous samples and determined using gas chromatography with electron capture (GC-ECD). The effects of different variables on the extraction efficiency were investigated and optimized. The calibration curve showed good linearity in the concentration range of 0.05–400 μgL^?1 (r² = 0.998) and precision (RSD = 5.0%). Under optimum conditions, the limit of detection (LOD) and the limit of quantification in drinking water were 0.015 and 0.05 µg L^?1, respectively. The developed method was successfully applied for the determination of six Mutagen X (MX) in real samples.     

Kinetics and Mechanism of Copolymerization of Styrene with Acrylonitrile Using Triphenylbismuthonium 1,2,3,4-Tetraphenylcyclopentadienylide as the Radical Initiator

The radical copolymerization of styrene with acrylonitrile in dioxan at 60±0.1°C for 1 h. in the presence of triphenyl-bismuthonium 1,2,3,4-tetraphenylcyclopentadienylide follows ideal kinetics, with bimolecular termination and results in the formation of alternating copolymer as evidenced from the values of the reactivity ratios as r₁ (Sty) = 0.266 and r₂ (AN) = 0.054. The overall energy of activation is computed to be 21 kJ mol^?1. The FTIR spectrum of the copolymer shows the presence of bands at 3054 cm^?1 assigned to the phenyl group of styrene and at 2238 cm^?1 assigned to the cyanide group of AN. The ¹H-NMR spectrum of the copolymer shows peaks between 7.25 and 7.71δ assigned to the phenyl protons of styrene. The nitrogen percent for AN was evaluated by elemental analysis.     

An evaluation of the impact of SG1 disproportionation and the addition of styrene in NMP of methyl methacrylate

A kinetic modeling study is presented for batch nitroxide mediated polymerization (NMP) of methyl methacrylate (MMA; nitroxide: N‐tert‐butyl‐N‐[1‐diethylphosphono‐(2,2‐dimethylpropyl)] (SG1)). Arrhenius parameters for SG1 disproportionation (A = 1.4 10⁷ L mol^?1 s^?1; E_a = 23 kJ mol^?1) are reported, based on homopolymerization data accounting for unavoidable temperature variations with increasing time, that is, nonisothermicity. For low targeted chain lengths (TCLs ≤ 300), this nonisothermicity is also relevant for NMP of MMA with a small amount of styrene. Parameter tuning to copolymerization data confirms a penultimate monomer unit effect for activation (s_a2 = k_a12/k_a22=6.7; 363 K; 1: MMA; 2: styrene). To obtain, for a broad TCL range (up to 800), a dispersity well below 1.3 an initial styrene mass fraction of ca. 10% is required. An interpretation of the comonomer incorporation is performed by calculating the fractions of activation‐growth‐deactivation cycles with a given amount of monomer units and the copolymer composition distribution. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2545–2559, 2018     

Polymerization of N-vinylcarbazole over cobalt (II) exchanged 13X molecular sieves

Polymerization of N-vinylcarbazole over Co(II)-13X molecular sieves in toluene solution has been studied. The rate of polymerization has been observed to be second order both in monomer concentration and in the exchange level of Co(II), and linearly dependent on catalyst loading. An apparent activation energy of 8.71 kcal mol^?1 (36.41 kJ mol^?1) has been found for the polymerization. The effect of different parameters on molecular weight has also been studied. The general kinetic features of the reaction are somewhat different from those reported for monomers like isobutyl vinyl ether, styrene etc. on simple and rare earth exchanged 13X molecular sieves.     

Kinetics of phase separation of poly(styrene‐co‐methyl methacrylate) and poly(styrene‐co‐acrylonitrile) blends

The phase behavior and kinetics of phase separation for blends of the random copolymer poly(styrene‐co‐methyl methacrylate) (SMMA) and poly(styrene‐co‐acrylonitrile) (SAN) were studied by using small‐angle laser light scattering. The partially miscible SMMA/SAN blends undergo spinodal decomposition (SD) and subsequent domain coarsening when quenched inside the unstable region. For blends of SMMA and SAN, the early stages of the phase separation process could be observed, unlike a number of other blends where the earliest stages are not visible by light scattering. The process was described in terms of the Cahn–Hilliard linear theory. Subsequently, a coarsening process was detected and the time evolution of q_m at the beginning of the late stages of phase separation followed the relationship q_m∝t^?1/3, corresponding to an evaporation–condensation mechanism. Self‐similar growth of the phase‐separated structures at different timescales was observed for the late stage. Copyright © 2004 Society of Chemical Industry     

Application of response surface methodology for optimization and determination of palladium by in-tube ultrasonic and air-assisted liquid–liquid microextraction coupled with flame atomic absorption spectrometry

A highly sensitive, simple and rapid in-tube ultrasonic and air-assisted liquid–liquid microextraction (IT-UAA-LLME) coupled with flame atomic absorption spectrometry was developed for preconcentration and determination of palladium (Pd) in soil and water samples. The effective parameters were optimized by the Plackett–Burman (P–B) and Box–Behnken design (BBD) methods. Under the optimum conditions, the calibration graph was linear over the range of 5–800 μgL^?1 (R² = 0.998). Detection limit, relative standard deviation (RSD) and the enrichment factor were 0.94 μgL^?1, 2.64% (n = 7, C = 40 μgL^?1) and 156, respectively. The proposed method was successfully applied for the determination of trace amounts of Pd in the soil and water samples.     

Biosorption potential of Neurospora crassa cells for decolorization of Acid Red 57 (AR57) dye

Biosorption of Acid Red 57 (AR57) on to Neurospora crassa was studied with variation of pH, contact time, biosorbent and dye concentrations and temperature to determine equilibrium and kinetic models. The AR57 biosorption was fast and equilibrium was attained within 40 min. Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models were applied to experimental equilibrium data for AR57 biosorption at various temperatures. The equilibrium data fitted very well to all the equilibrium models in the studied concentration range of AR57. Maximum biosorption capacity (q_max) of AR57 on to N. crassa was 2.16 × 10^?4 mol g^?1 at 20 °C. The kinetics of biosorption of AR57 were analyzed and rate constants were derived. The overall biosorption process was best described by a pseudo‐second‐order kinetic model. The changes in Gibbs free energy, enthalpy and entropy of biosorption were also evaluated for the biosorption of AR57 on to N. crassa. The results indicate that the biosorption was spontaneous and exothermic in nature. Copyright © 2006 Society of Chemical Industry     

Anion Exchange Resins of Tri-n-butyl Ammonium Functional Groups for Dye Baths and Textile Wastewater Treatment

Effectiveness of two strongly basic anion exchange resins of the gel (Dowex PSR-2) and macroporous structure (Dowex PSR-3) was compared in order to remove three hazardous dyes such as C.I. Acid Orange 7 (AO7), C.I. Reactive Black 5 (RB5), and C.I. Direct Blue 71 (DB71) contained in water and textile wastewaters. Batch adsorption experiments were carried out to analyze the effect of phase contact time, initial dye concentration, and the presence of auxiliary materials (anionic and cationic surfactants, Na₂CO₃, and Na₂SO₄). The Langmuir model better described the adsorption process of the dyes onto both resins than the Freundlich model. The monolayer adsorption capacities (q_e) of Dowex PSR-3 were calculated as 336.4 mg/g for AO7, 317.9 mg/g for RB5, and 150.4 mg/g for DB71 at 25^°C. Dowex PSR-2 of the gel structure is characterized by considerably lower values of q_e (50.1 mg/g for AO7, 17.2 mg/g for RB5, and 9.7 mg/g for DB71). Of special importance are high values of the working ion exchange capacities of Dowex PSR-3 determined from the breakthrough curves towards AO7 and RB5 equal to 127 and 85 mg/cm³, respectively. The pseudo second-order kinetic model described the experimental sorption data better than the pseudo first-order model. Methanol addition to the 1 M HCl and 1 M NaOH solutions improved the effectiveness of dye desorption.     

Benzoyl peroxide–p‐acetylbenzylidenetriphenyl arsoniumylide initiated copolymerization of citronellol and styrene

Alternating copolymers, containing styrene and citronellol sequences, have been synthesized by radical polymerization using benzoylperoxide (BPO)–p‐acetylbenzylidenetriphenyl arsoniumylide (pABTAY) as initiator, in xylene at 80 ± 1 °C for 3 h under inert atmosphere. The kinetic expression is R_p ∝ [BPO]^0.88 [citronellol]^0.68 [styrene]^0.56 with BPO and R_p ∝ [pABTAY]^0.27 [citronellol]^0.76 [styrene]^0.63 with pABTAY, ie the system follows non‐ideal kinetics in both cases, because of primary radical termination and degradative chain transfer reactions. The activation energy with BPO and pABTAY is 94 kJ mol^?1 and 134 kJ mol^?1, respectively. Different spectral techniques, such as IR, FTIR, ¹H NMR and ¹³C NMR, have been used to characterize the copolymer, demonstrating the presence of alcoholic and phenyl groups of citronellol and styrene. The alternating nature of the copolymer is shown by the product of reactivity ratios r₁ (Sty) = 0.81 and r₂ (Citro) = 0.015 using BPO and r₁ (Sty) = 0.37 and r₂ (Citro) = 0.01 using (pABTAY), which are calculated by the Finemann–Ross method. A mechanism of copolymerization is proposed. © 2001 Society of Chemical Industry