Abdurrahman Tanyolaç

CONTINUOUS ELECTROCHEMICAL TREATMENT OF PHENOLIC WASTEWATER IN A TUBULAR REACTOR

The electrochemical treatment of phenolic wastewater in a continuous tubular reactor, constructed from a stainless steel tube with a cylindrical carbon anode at the centre, was investigated in this study, being first in literature. The effects of residence time on phenol removal was studied at 25 degrees C, 120 g l(-1) electrolyte concentration for 450 and 3100 mg l(-1) phenol feed concentrations with 61.4 and 54.7 mA cm(-2) current densities, respectively. The change in phenol concentration and pH of the reaction medium was monitored in every run and GC/MS analyses were performed to determine the fate of intermediate products formed during the electrochemical reaction in a specified batch run. During the electrolysis mono, di- and tri-substituted chlorinated phenol products were initially formed and consumed along with phenol thereafter mainly by polymerization mechanism. For 10 and 20 min of residence time phenol removal was 56% and 78%, respectively, with 450 mg l(-1) phenol feed concentration and above 40 min of residence time all phenol was consumed within the column. For 1, 1.5, 2 and 3h of residence time, phenol removal achieved was 42%, 71%, 81% and 98%, respectively, at 3100 mg l(-1) phenol feed concentration. It is noteworthy that more than 95% of the initial phenol was converted into a non-passivating polymer without hazardous end products in a comparatively fast and energy-efficient process, being a safe treatment.

Electrochemical treatment of deproteinated whey wastewater and optimization of treatment conditions with response surface methodology.

Electrochemical treatment of deproteinated whey wastewater produced during cheese manufacture was studied as an alternative treatment method for the first time in literature. Through the preliminary batch runs, appropriate electrode material was determined as iron due to high removal efficiency of chemical oxygen demand (COD), and turbidity. The electrochemical treatment conditions were optimized through response surface methodology (RSM), where applied voltage was kept in the range, electrolyte concentration was minimized, waste concentration and COD removal percent were maximized at 25 degrees C. Optimum conditions at 25 degrees C were estimated through RSM as 11.29 V applied voltage, 100% waste concentration (containing 40 g/L lactose) and 19.87 g/L electrolyte concentration to achieve 29.27% COD removal. However, highest COD removal through the set of runs was found as 53.32% within 8h. These results reveal the applicability of electrochemical treatment to the deproteinated whey wastewater as an alternative advanced wastewater treatment method.

Multi-substrate growth kinetics of Pseudomonas putida for phenol removal

Abstract The biodegradation of phenol by a pure culture of Pseudomonas putida was investigated in a continuously fed stirred-tank reactor, under aerobic conditions. The dilution rate was varied between 0.0174 h−1 and 0.278 h−1, covering a wide range of dissolved oxygen and the inhibition region of phenol. Through non-linear analysis of the data, a dual-substrate growth kinetics, Haldane kinetics for phenol and Monod kinetics for oxygen, was derived with high correlation coefficients. Respective biokinetic parameters were evaluated as μm = 0.569 h−1, Kp = 18.539 mg/l, Ki = 99.374 mg/l, Ko = 0.048 mg/l, Yx/p = 0.521 g microorganism/g phenol and Yx/o = 0.338 g microorganism/g oxygen, being in good agreement with other studies in the literature. Maintenance factors for both phenol and oxygen were calculated for the first time for P. putida while the saturation coefficient for oxygen, Ko, was genuinely evaluated from the constructed model, not imported or adapted from other studies as reported in the literature. All pertinent biokinetic parameters for P. putida have been calculated from continuous system data, which are most appropriate for use in continuous bioprocess applications.

Reaction conditions for laccase catalyzed polymerization of catechol

Poly(catechol) was synthesized in batch runs with laccase from Trametes versicolor (ATCC 200801). The polymerization reaction was conducted in a closed, temperature controlled system containing acetone and sodium acetate buffer for pH control. The effects of the solvent mixture, monomer (catechol), enzyme, medium pH and temperature on the polymerization rate were investigated with respect to initial reaction conditions and depletion rate of dissolved oxygen in the medium. Maximum initial reaction rate was attained with 10% (v/v) acetone-sodium acetate buffer at pH 5.0, 25 degrees C, 0.02 U/ml enzyme and 250 mg/l initial catechol and 10 mg/l dissolved oxygen. A general saturation enzyme kinetics response was observed for catechol substrate. Temperature rise supported the rate increase up to 45 degrees C, after which the rate tended to be stable due to a drop in dissolved oxygen concentration as well as enzyme instability.

Reaction kinetics for laccase-catalyzed polymerization of 1-naphthol.

Laccase-catalyzed oxidative polymerization of 1-naphthol was carried out in a closed system containing acetone and sodium acetate buffer. The effects of initial 1-naphthol and dissolved oxygen concentrations on the initial reaction rate were investigated. A multiplicative mathematical model, using a function of 1-naphthol and dissolved oxygen concentrations, was developed for enzymatic polymerization and the corresponding biokinetic parameters have been evaluated for the first time. The activation energy and reaction rate constant of the laccase-catalyzed 1-naphthol polymerization were calculated as 57 kJ/mol and 311 l/s, respectively. The activation energy calculated was in the typical range of 30-60 kJ/mol and rate constant was of the order of magnitude of previously reported values for laccase-catalyzed reactions with different monomers.

Continuous electrochemical treatment of simulated industrial textile wastewater from industrial components in a tubular reactor.

The continuous electrochemical treatment of industrial textile wastewater in a tubular reactor was investigated. The synthetic wastewater was based on the real process information of pretreatment and dyeing stages of the industrial mercerized and non-mercerized cotton and viscon production. The effects of residence time on chemical oxygen demand (COD), color and turbidity removals and pH change were studied under response surface optimized conditions of 30 degrees C, 25 g/L electrolyte concentration and 3505 mg/L COD feed concentration with 123.97 mA/cm(2) current density. Increasing residence time resulted in steady profiles of COD and color removals with higher treatment performances. The best column performance was realized at 3h of residence time as 53.5% and 99.3% for COD and color removals, respectively, at the expense of 193.1 kWh/kg COD with a mass transfer coefficient of 9.47 x 10(-6) m/s.

Biosynthesis and Characterization of Laccase Catalyzed Poly(Catechol)

Enzymatic polymerization of catechol was conducted batch-wise using laccase enzyme produced by the culture Trametes versicolor (ATCC 200801). The polymerization reaction was carried out in 1:1 (v/v) aqueous-acetone solution, buffered at pH 5.0 with sodium acetate (50 mM) in a sealed, temperature-controlled reactor at 25°C. The molecular weight of the produced polymer was determined with GPC. FT-IR, DSC, and TGA were employed to investigate the structure and thermal behavior of synthesized poly(catechol). It was found that catechol units were linked together with ether bonds and thermal stability of the catechol increased in the poly(catechol) polymeric structure effectively. The number average molecular weight of poly(catechol) was found as 813 ± 3 Da with a very narrow polydispersity value of 1.17 showing selective polymerization of catechol by the enzyme.

Optimization of urease immobilization onto non-porous HEMA incorporated poly(EGDMA) microbeads and estimation of kinetic parameters

Jack bean urease (urea aminohydrolase, EC 3.5.1.5) was immobilized onto modified non-porous poly(ethylene glycol dimethacrylate/2-hydroxy ethylene methacrylate), (poly(EGDMA/HEMA)), microbeads prepared by suspension copolymerization for the potential use in hemoperfusion columns, not previously reported. The conditions of immobilization; enzyme concentration, medium pH, substrate and ethylene diamine tetra acetic acid (EDTA) presence in the immobilization medium in different concentrations, enzyme loading ratio, processing time and immobilization temperature were investigated for highest apparent activity. Immobilized enzyme retained 73% of its original activity for 75 days of repeated use with a deactivation constant kd = 3.72 x 10(-3) day(-1). A canned non-linear regression program was used to estimate the intrinsic kinetic parameters of immobilized enzyme with a low value of observable Thiele modulus (phi < 0.3) and these parameters were compared with those of free urease. The best-fit kinetic parameters of a Michaelis-Menten model were estimated as Vm = 3.318 x 10(-4) micromol/s mg bound enzyme protein, Km = 15.94 mM for immobilized, and Vm = 1.074 micromol NH3/s mg enzyme protein, Km = 14.49 mM for free urease. The drastic decrease in Vm value was attributed to steric effects, conformational changes in enzyme structure or denaturation of the enzyme during immobilization. Nevertheless, the change in Km value was insignificant for the unchanged affinity of the substrate with immobilization. For higher immobilized urease activity, smaller particle size and concentrated urease with higher specific activity could be used in the immobilization process.

Effects of reaction conditions on laccase-catalyzed α-naphthol polymerization

Enzymatic oxidative polymerization of α-naphthol was carried out batch-wise with the laccase enzyme, produced by Trametes versicolor (ATCC 200801). The polymerization reaction was conducted in a closed, temperature controlled system containing acetone (solvent) and sodium acetate buffer for pH control. The effects of the organic solvent (acetone) composition, monomer (α-naphthol) and enzyme concentrations, buffer pH and temperature on the polymerization rate were investigated with respect to initial reaction conditions and depletion rate of dissolved oxygen. The optimum acetone composition, pH, monomer, dissolved oxygen and enzyme concentrations were determined as 50% (v/v), 5, 3409 gm−3, 20.3 gm−3 and 0.173 U cm−3, respectively; these values provided the most desirable conditions for initial reaction rate. Temperature rise supported the rate increase up to 37 °C, after which the rate tended to be stable due to a drop in dissolved oxygen concentration. The product polymer, poly(α-naphthol), with an average molecular weight of 4920 Da was soluble in common organic solvents. © 2000 Society of Chemical Industry

The effects of biofilm characteristics on the external mass transfer coefficient in a differential fluidized bed biofilm reactor

Abstract A differential fluidized bed biofilm reactor (DFBBR) was used for the first time to evaluate the external mass transfer coefficient of phenol for a spherical bioparticle of Pseudomonas putida . The reaction kinetics in the biofilm was maintained at first order and respective culture kinetic parameters were assessed from a set of continuous fermenter experiments. The fluidized bed was operated under nearly fixed hydrodynamic conditions such as bed porosity and fluidization rate to study only the effects of biofilm thickness and density on mass transfer. The mass transfer coefficient was calculated with the analytical solution of effectiveness factor for the bioparticle using density-dependent effective diffusion coefficient. The results of the study revealed that the mass transfer coefficient increased with biofilm thickness at decreasing biofilm density values, which could not have been predicted by correlations in the literature. This increase may be attributed to increasing porosity and roughness of the biofilm surface.