Application of sludge-based carbonaceous materials in a hybrid water treatment process based on adsorption and catalytic wet air oxidation

This paper describes a preliminary evaluation of the performance of carbonaceous materials prepared from sewage sludges (SBCMs) in a hybrid water treatment process based on adsorption and catalytic wet air oxidation; phenol was used as the model pollutant. Three different sewage sludges were treated by either carbonisation or steam activation, and the physico-chemical properties of the resultant carbonaceous materials (e.g. hardness, BET surface area, ash and elemental content, surface chemistry) were evaluated and compared with a commercial reference activated carbon (PICA F22). The adsorption capacity for phenol of the SBCMs was greater than suggested by their BET surface area, but less than F22; a steam activated, dewatered raw sludge (SA_DRAW) had the greatest adsorption capacity of the SBCMs in the investigated range of concentrations (<0.05 mol L(-1)). In batch oxidation tests, the SBCMs demonstrated catalytic behaviour arising from their substrate adsorptivity and metal content. Recycling of SA_DRAW in successive oxidations led to significant structural attrition and a hardened SA_DRAW was evaluated, but found to be unsatisfactory during the oxidation step. In a combined adsorption-oxidation sequence, both the PICA carbon and a selected SBCM showed deterioration in phenol adsorption after oxidative regeneration, but a steady state performance was reached after 2 or 3 cycles.

[Efficiency of micro-pressurized fluidized hybrid biological reactor for treating phenolic wastwater]

A dynamic experiment was conducted continuously to study the efficiency of the new micro-pressurized fluidized hybrid biological reactor (MP-FHBR) for treating artificial phenolic wastewater. The experimental results showed that the COD volumetric loading and phenolic volumetric loading of MP-FHBR could reach 4.86 kg/(m3 x d) and 1.96 kg/(m3 x d) respectively; effluent COD was lower than 200 mg/L; phenol concentrations of effluent were lower than 1 mg/L; removal rates of COD and phenol reached 90% and 99% above respectively. When volumetric loading of phenol in MP-FHBR reached 2.04 kg/(m3 x d), phenol will accumulate gradually in the reactor along with the reactor running, and specific TTC-dehydrogenase activity of microbe in the reactor declines. When phenol concentration of influent was 800 mg/L, the optimum HRT was 9-10 h. Because of the influence of hydraulic loading on the settling performance of sedimentation tank of the reactor, MP-FHBR was superior to treating higher-concentration phenolic wastewater.

Pyridine and phenol removal using natural and synthetic apatites as low cost sorbents: influence of porosity and surface interactions

A natural phosphate rock and two synthetic mesoporous hydroxyapatites were evaluated for the removal of pyridine and phenol from aqueous solutions. Experiments performed by the batch method showed that the sorption process occurs by a first order reaction for both pyridine and phenol. In contrast, the Freundlich model was able to describe sorption isotherms for phenol but not for pyridine. In parallel, the three apatites exhibit similar pyridine sorption capacities whereas phenol loading was in agreement with their respective specific surface area. This was attributed to the strong interaction arising between pyridine and apatite surface that hinders further inter-particular diffusion. This study suggests that, despite its low specific surface area, natural phosphate rock may be used as an efficient sorbent material for specific organic pollutants, with comparable efficiency and lower processing costs than some activated carbons.

Efficiency of phenol biodegradation by planktonic Pseudomonas pseudoalcaligenes (a constructed wetland isolate) vs. root and gravel biofilm

In the last two decades, constructed wetland systems gained increasing interest in wastewater treatment and as such have been intensively studied around the world. While most of the studies showed excellent removal of various pollutants, the exact contribution, in kinetic terms, of its particular components (such as: root, gravel and water) combined with bacteria is almost nonexistent. In the present study, a phenol degrader bacterium identified as Pseudomonas pseudoalcaligenes was isolated from a constructed wetland, and used in an experimental set-up containing: plants and gravel. Phenol removal rate by planktonic and biofilm bacteria (on sterile Zea mays roots and gravel surfaces) was studied. Specific phenol removal rates revealed significant advantage of planktonic cells (1.04 × 10(-9) mg phenol/CFU/h) compared to root and gravel biofilms: 4.59 × 10(-11)-2.04 × 10(-10) and 8.04 × 10(-11)-4.39 × 10(-10) (mg phenol/CFU/h), respectively. In batch cultures, phenol biodegradation kinetic parameters were determined by biomass growth rates and phenol removal as a function of time. Based on Haldane equation, kinetic constants such as μ(max) = 1.15/h, K(s) = 35.4 mg/L and K(i) = 198.6 mg/L fit well phenol removal by P. pseudoalcaligenes. Although P. pseudoalcaligenes planktonic cells showed the highest phenol removal rate, in constructed wetland systems and especially in those with sub-surface flow, it is expected that surface associated microorganisms (biofilms) will provide a much higher contribution in phenol and other organics removal, due to greater bacterial biomass. Factors affecting the performance of planktonic vs. biofilm bacteria in sub-surface flow constructed wetlands are further discussed.

DC water plasma at atmospheric pressure for the treatment of aqueous phenol

This study investigated the decomposition of aqueous phenol by direct current (DC) water plasma. The operation of DC water plasma was carried out in the absence of inert gases or air injected and cooling-controlled and pressure-controlled devices. The results indicated that 1 mol.% (52.8 g L(-1)) phenol was drastically decomposed by DC water plasma touch with energy efficiencies of 1.9 x 10(-8)-2.2 x 10(-8) mol J(-1). Also, the value of chemical oxygen demand (COD) was reduced from 100 000 mg L(-1) down to 320 mg L(-1) over a short retention time. The maximum decomposition rate of the COD was 258 mg COD min(-1) for the arc power of 0.91 kW. In the effluent analysis, H(2) (63-68%), CO (3.6-6.3%), CO(2) (25.3-28.1%) were major products in the exhaust gas and CH(4), C(2)H(2), HCOOH and C(6)H(6) in trace level. Further, HCOOH and HCHO were observed in the liquid effluents. Within the current paper, the results indicated that the DC water plasma torch is capable of an alternative green technology for phenol wastewater containing high COD.

Degradation of phenol using a combination of ultrasonic and UV irradiations at pilot scale operation

In the present work, combination of ultraviolet (UV) irradiations (using 8 W UV tube) with ultrasonic (US) irradiations (rated power 1 kW and frequency of 25 kHz) has been investigated for the degradation of phenol at pilot scale of operation. Different modes of operation viz. UV alone, US alone, UV/US, UV/TiO(2) (photocatalysis), UV/H(2)O(2), UV/NaCl, UV/US/TiO(2) (sonophotocatalysis) and H(2)O(2) assisted sonophotocatalysis have been investigated with an objective of maximizing the extent of phenol degradation. Effect of presence of hydrogen peroxide and sodium chloride at a concentration of 10 g/l and TiO(2) over a range of 0.5-2.5 g/l has been investigated. It has been observed that 2.0 g/l of TiO(2) is the optimum concentration, beyond which a decrease in the extent of degradation is observed. Maximum extent of degradation of phenol was 37.75% for H(2)O(2) assisted photosonocatalysis at pH of 2. The present work is first of its kind to report the use of combined ultrasonic and UV irradiations at pilot scale operation and obtained results should induce some degree of certainty in proposed industrial applications of sonochemical reactors for wastewater treatment.

[Degradation mechanism of phenol with electrogenerated hydrogen peroxide on a Pd/C gas-diffusion electrode]

Using a self-made Pd/C gas-diffusion electrode as the cathode and Ti/IrO2/RuO2 as the anode, the degradation of phenol was investigated in an undivided electrolysis device by the electrochemical oxidation process. Hydroxyl radical (*OH) was determined in the reaction mixture by the electron spin resonance spectrum (ESR). The result indicated that the Pd/C catalyst in Pd/C gas-diffusion electrode system accelerated the two-electron reduction of O2 to H2O2 when feeding air, which is in favor of producing *OH. After 120 min electrolysis in Pd/C gas-diffusion electrode system, the steady concentration of H2O2 was 7.5 mg/L. The removal efficiency of phenol and COD reached about 97.2% and 50% after 120 min electrolysis, respectively, which suggested that most of phenol were oxidized to intermediates using the Pd/C gas-diffusion electrode. Furthermore, the ratio of BOD5/COD of the solutions was 9.1 times larger than the initial ones. Hence the electrochemical oxidation can enhance the biodegradation character of the phenol solution. The degradation of phenol was supposed to be cooperative oxidation by direct and/or indirect electrochemical oxidation at the anode and H2O2, *OH produced by oxygen reduction at the cathode. UV-Vis and GC-MS identified catechol, hydroquinone, and benzoquinone as the main aromatic intermediates, and adipic, maleic, fumaric, succinic, malonic, and oxalic acids as the main aliphatic carboxylic intermediates. A reaction scheme involving all these intermediates was proposed.

Preparation and characterization of polar polymeric adsorbents with high surface area for the removal of phenol from water

Preparation of methyl methacrylate (MMA)/divinylbenzene (DVB) and ethylene glycol dimethacrylate (EGDMA)/DVB copolymers via suspension polymerization yielded precursors which possess residual vinyl groups. Post-crosslinking of appropriate dichloroethane swollen precursors without external crosslinking agent in the presence of anhydrous ferric chloride (FeCl(3)) yielded post-crosslinked resins with high surface area and suitable polarity. FT-IR spectrum indicated that increasing the proportion of MMA or EGDMA in monomer mixtures notably reduces the amount of the pendant vinyl groups onto the matrix of the precursors. Furthermore, the pendant vinyl groups of precursors were almost absent when the content of MMA and EGDMA increased to 40 mol% and 20 mol% in the monomers, respectively. The specific surface areas and pore volumes of copolymers showed a remarkable increase after post-crosslinking. Experimental results showed that isotherms of phenol adsorption onto these polymeric adsorbents could be represented by Freundlich model and Langmuir model reasonably. PDE-5 pc exhibited higher adsorption capacity of phenol than other adsorbents, which resulted from synergistic effect of larger specific surface area and polar groups onto the network. Column adsorption/desorption dynamic curves suggested that PDE-5 pc is a potential candidate for treatment of chemical effluent containing phenol and phenolic pollutants.

Determination of alkylphenols in eluates from pyrolysis solid residues using dispersive liquid-liquid microextraction

Dispersive liquid-liquid microextraction (DLLME) coupled with gas chromatography-mass spectrometry (GC-MS) was applied for the determination of 11 alkylphenols in eluates of chars produced in the co-pyrolysis of different wastes. The optimized DLLME procedure, 4 mL of sample solution, 15 microL of trichloroethylene as extraction solvent, 1 mL of acetone as dispersion solvent and addition of 15% (w/v) of NaCl, was validated. Under the optimum conditions, the enrichment factors were in the range of 82-180. Calibration curves were constructed for each analyte in pure water in the concentration range of 0.5-8 microg/L with correlation coefficients higher than 0.999. The limits of detection were between 0.07 and 0.17 microg/L. The repeatability of the method was evaluated using water samples fortified with the analyte mixture at two concentration levels: the relative standard deviation (RSD) values were between 3.7% and 8.0% for a concentration of 0.5 microg/L, and between 4.2% and 6.4% for a concentration of 3 microg/L. The recoveries of the analytes evaluated by fortification of real eluate samples were in the range of 67.9-97.9% for eluate 1 (obtained from a decontaminated char) and in the range of 61.9-101.4% for eluate 2 (obtained from the untreated char). o-Methylphenol presented low recoveries for both eluates showing a possible matrix effect. The results obtained show that this method is adequate for the determination of alkylphenols in environmental aqueous samples and presents itself as a fast and inexpensive technique, using minor amounts of organic solvents.

Phenol biodegradation in a batch jet loop bioreactor (JLB): kinetics study and pH variation

Phenol biodegradation in a batch jet loop bioreactor (JLB) using activated sludge was investigated. The biodegradation experiments were conducted at different phenol concentrations (S(0)) from 50 to 1000 mg/l. The results of the biodegradation of phenol by JLB show that a good phenol removal of 100%. The biodegradation capacity of the JLB was higher than that of the stirred tank reactor reported in literatures. The Haldane equation was adopted in order to describe the relation between the specific growth rates (micro) and S(0). Kinetic constants of Haldane equation were micro(m) = 0.119 1/h, K(s) = 11.13 mg/l and K(i) = 250.88 mg/l. Model equations were simulated using the MATHCAD 7.0 software's ordinary differential equation solver. Simulations were performed at each experiment with different initial phenol concentrations.

[Effects of surfactants on the biodegradation of phenol by Candida tropicalis]

The method of liquid fermentation culture was used to study the influence of two synthetic surfactants, cetyl trimethylammonium bromide (CTAB) and Triton X-100, and a biosurfactant, dirhamnlipid (diRL), on phenol degradation by Candida tropicalis CICC 1463. The results showed that at the beginning of degradation the yeast population decayed, phenol metabolization and bacterial growth did not occur simultaneously, which indicated the toxicity of phenol and formation of intermediate product. CTAB was toxic to C. tropicalis, and it restrained phenol removal. The phenol degradation was accelerated by Triton X-100 of low concentrations of 0.1 and 0.3 CMC, and the complete degradation was achieved at 24 h and 36 h, respectively, compared to 48 h of control. When Triton X-100 concentration was increased to 1.0 CMC or higher concentration, decay of yeast in the initial phase was weakened, but phenol removal and bacterial growth were lagged. The biosurfactant diRL enhanced phenol degradation and growth of the C. tropicalis markedly, and the effect increased with increasing of diRL concentration. Complete degradation was achieved at 24 h in the presence of 1.0 and 3.0 CMC diRL. The diRL concentration also decreased gradually during the fermentation. These results indicated that diRL could reduce phenol toxicity to a great extent and favor the bacterial growth as co-substrate.

Kinetics determination of electrogenerated hydrogen peroxide (H2O2) using carbon fiber microelectrode in electroenzymatic degradation of phenolic compounds

The kinetics of electrogenerated hydrogen peroxide (H(2)O(2)), which can activate peroxidases in an electroenzymatic process, was examined by an amperometric technique using a carbon fiber microelectrode that was modified by polyaniline (PAn) film and platinum particles. The electrogeneration of H(2)O(2) was found to be dependent on the pH and applied potential, and resulting in a variable current response of the carbon fiber microelectrode. The highest amount of H(2)O(2) was electrogenerated when 2.3 V was applied between the Pt/Ti anode and a reticulated vitreous carbon (RVC) cathode at pH 6.0, with a current response of 0.0190 microA min(-1). Phenol was completely degraded by the electroenzymatic reaction of the immobilized horseradish peroxidase (HRP), and the time required for the electrogeneration of H(2)O(2) increased according to the initial concentration of phenol. The degradation stoichiometric ratio between the electrogenerated H(2)O(2) and the aqueous phenol under HRP immobilized on RVC was found to be 1:1.

Multifunctional biomagnetic capsules for easy removal of phenol and bisphenol A

This paper reports fabrication, optimization and characterization of multifunctional biocapsules with immobilized enzyme using a layer-by-layer configuration and their application for removal of phenol and bisphenol A (BPA). The method is based on the combined use of enzymatic oxidation of the BPA and subsequent binding of the reaction product onto a chitosan core biopolymer. This platform has multiple functions including: (1) enzymatic degradation of BPA, (2) adsorption of the degraded compound within the core material, (3) colorimetric quantification and (4) magnetic capabilities. We examined various configurations of core/shell structures of alginate and chitosan and determined the stability and the optimum conditions in which these structures provide the most effective removal capacity. The amount of BPA that can be removed per capsule is 5.6 ppm while phenol can be removed up to 10 ppm per capsule within 15 h.

Phenolic compounds and their anti-oxidative properties and protein kinase inhibition from the Chinese mangrove plant Laguncularia racemosa

Phenolic compounds, named integracin D (1), (7'R, 8'S, 8S)-8-hydroxyisoguaiacin (3), (2R, 3R) pinobanksin-3-caffeoylate (5) and threo-8S-7-methoxysyringylglycerol (6), respectively, were isolated from the Chinese mangrove plant Laguncularia racemosa (L) Gaertn. f. (Combretaceae), together with 23 known phenolic metabolites. Their structures were elucidated on the basis of extensive spectroscopic analyses including that of IR, UV, MS, CD, 1D and 2D NMR spectra as well as by comparison with literature data. Compound 5 showed significant anti-oxidative activity in the DPPH and TEAC free-radical-scavenging assays, while several of the phenolic compounds were tested for protein kinase inhibitory activity in an assay involving 24 different human tumor related protein kinases. Compounds 5, 7, and 23 showed potential inhibition with IC(50) values between 2.2 and 3.6microg/mL toward individual kinases. The ellagic acid derivatives were tested for insecticidal activity.

[Non-dissociated species and dissociated species photodegradation and the rate constants prediction of phenolic compounds]

Xe lamp was employed to simulate the sunlight as light source to study the direct photolysis of three kinds of phenolic pollutants under different pH values. The effects of the dissociation on their photolysis were investigated, and a calculation method and a forecasting model for the photolysis rate constants under the situation of dissociation and non-dissociation of phenolic pollutants were established. The experiment results showed that the photolysis rate constant of pentachlorophenol (PCP) increased from 25.30 x 10(-4) min(-1) to 82.90 x 10(-4) min(-1) when pH value varied from 4.0 to 9.0, and that of nitrophenol (PNP) decreased from 11.90 x 10(-4) min(-1) to 3.18 x 10(-4) min(-1) Similar to the PNP, the photolysis rate constant of phenol decreased from 32.50 x 10(-4) min(-1) to 13.40 x 10(-4) min(-1) with the pH value increased from 4.0 to 11.0. From analysis of the results, a power function relationships between the total photolysis rate constants (K) and dissociation degrees (alpha) of these three phenolic compounds could be established. If alpha had been determined, the dissociation and non-dissociation species photolysis rate constants could be calculated by the tangent equation of the power function. The effect of dissociation on the photolysis should be mainly attributed to the formation of the negative oxygen ions, which led to the changes of the activities of benzene ring and substituent groups. These results will provide theoretical references to further understand environmental behaviors of phenolic compounds in natural waters.

[Sorption of phenol and nitrobenzene in water by CTMAB/CPAM organobentonites]

A series of cetyltrimethyl amonium bromide bentonite (C-Bt), cationic polyacrylamide bentonite (P-Bt) and composite organobentonite (C/P-Bt) were synthesized by modifying bentonite with cetyltrimethyl ammonium bromide (CTMAB) and/or cationic polyacrylamide (CPAM). The basal spacings of the obtained organobentonites were analyzed with XRD. The sorption capacities of phenol and nitrobenzene to these organobentonites from water were examined. The results showed that the basal spacing values of C/P-Bt were larger than those of C-Bt and P-Bt, which indicated a simultaneous intercalation of bentonite interlayers by CTMAB and CPAM. The sorption capacity of C/P-Bt was better than that of C-Bt. Under the same equilibrium concentration (7 045 mg/L for phenol and 409 mg/L for nitrobenzene) , the sorbed amounts of phenol and nitrobenzene on 60C/4% P-Bt were 150 and 69 mg/g, which enhanced 26% and 28% respectively comparing with those on 60C-Bt. Furthermore, the sorption capacity of 60C/4% P-Bt was better than the sum of 60C-Bt and 4% P-Bt, and the sorbed amounts of phenol and nitrobenzene enhanced 22% and 26% respectively, showing an obvious synergistic sorption effect. An explanation for these results was that the arrangement model of CTMAB within the C/P-Bt interlayers was affected by CPAM, which led to the formation of organic phase with better affinity to the organic compounds. This novel organobentonites may have wide applications in organic pollution control.

Production of activated carbon by K2CO3 activation treatment of cornstalk lignin and its performance in removing phenol and subsequent bioregeneration

Activated carbon was produced by fast precarbonization of cornstalk lignin in a fluidized bed followed by K2CO3 activation. The results showed that the product is essentially microporous carbon whose Brunauer-Emmett-Teller surface area and pore volume when the carbon was activated at 800 degrees C were 1410 m2/g and 0.77 mL/g, respectively. The potential usefulness of the resultant carbons for removal of phenol from water and their subsequent bioregeneration capabilities were also investigated. The kinetics study showed that all the carbons exhibited a fast adsorption rate and the carbon activated at 800 degrees C had the largest amount of phenol adsorbed due to its greater specific surface area and pore volume. The adsorption isotherms by applying the Langmuir method showed that the monolayer adsorption capacity of carbon activated at 800 degrees C could reach 110.9 mg/g.

Fenton-like oxidation and mineralization of phenol using synthetic Fe(II)-Fe(III) green rusts

BACKGROUND, AIM, AND SCOPE

In literature, the environmental applications of green rust (GR) have mainly been pointed out through the reduction of inorganic contaminants and the reductive dechlorination of chlorinated organics. However, reactions involving GR for the oxidation and mineralization of organic pollutants remain very scantly described. In this study, the ability of three synthetic Fe(II)-Fe(III) green rusts, GR(CO (3)(2-)), GR(SO(4)(2-)), and GR(Cl(-)), to promote Fenton-like reaction was examined by employing phenol as a model pollutant. Unlike the traditional Fenton's reagent (dissolved Fe(II) + H(2)O(2)), where the pH values have to be lowered to less than 4, the proposed reaction can effectively oxidize the organic molecules at neutral pH and could avoid the initial acidification which may be costly and destructive for the in situ remediation of contaminated groundwater and soils. The green rust reactivity towards the oxidative transformation of phenol was thoroughly evaluated by performing a large kinetic study, chemical analyses, and spectroscopic investigations.

MATERIALS AND METHODS

The kinetics of phenol removal was studied at three initial phenol concentrations for three green rusts under similar conditions (pH = 7.1; 1 g L(-1) of GR; 30 mM H(2)O(2)) and reaction rates were calculated based on mass and surface area. The oxidation rate constants are compared with that of magnetite, a well-known mixed iron (II, III) oxide. The mineralization of phenol was investigated at various H(2)O(2) doses and GR concentrations. In order to describe the phenol transformation in GR/H(2)O(2) system, several investigations were performed including HPLC and ion exclusion chromatography analysis, TOC, dissolved iron, and H(2)O(2) concentration measurements. Finally, X-ray powder diffraction and Raman spectroscopy were used to identify the oxidation products of GRs.

RESULTS AND DISCUSSION

In GR/H(2)O(2) system, the kinetics of phenol removal at neutral pH was very fast and independent of the initial phenol concentration. No aromatic intermediates were detected and final by-products are mainly of short chain organic acids (oxalic acid and formic acid). Green rusts exhibit different reactivity toward Fenton-like oxidation of phenol. Both on mass and surface area basis, the reactivity of Fe(II)-Fe(III) species toward the oxidation of phenol was highest for GR(Cl(-)), little less for GR(SO(4)(2-)) or GR(CO(3)(2-)), and even less for magnetite (Fe(3)O(4)). Phenol degradation pseudo-first order rate constants (k(surf)) values were found to be: 13 x 10(-4), 3.3 x 10(-4), 3.5 x 10(-4), and 0.4 x 10(-4) L m(-2) s(-1) for GR(Cl(-)), GR(SO(4)(2-)), GR(CO(3)(2-)), and Fe(3)O(4), respectively. The mineralization yield of phenol as well as the decomposition rate of H(2)O(2) was higher for GR(Cl(-)) than for GR(SO(4)(2-)) or GR(CO(3)(2-)), mainly due to the higher Fe(II) content of GR(Cl(-)). Both X-ray diffraction analysis and Raman spectroscopy showed that the oxidation of GR with H(2)O(2) may lead to feroxyhyte (delta-FeOOH), with possible formation of poorly crystallized goethite (alpha-FeOOH), depending on GR type.

CONCLUSIONS

This original work shows that the heterogeneous Fenton-like reaction using GR/H(2)O(2) is very effective toward degradation and mineralization of pollutants. In summary, this study has demonstrated that the green rust-promoted oxidation reaction could contribute to the transformation of water contaminants in the presence of H(2)O(2.)

RECOMMENDATIONS AND PERSPECTIVES

These results could serve as the basis for the understanding of the transformation of organic pollutants in iron-rich soils in the presence of chemical oxidant (H(2)O(2)) or for the development of wastewater treatment process. However, some experimental parameters should be optimized for a high-scale application. Further work needs to be done for the reactive transport and transformation of organic compounds in a green rust-packed column. The reusability of GR in mineral-catalyzed reaction should be also investigated.

Enhanced anaerobic biodegradability of real coal gasification wastewater with methanol addition

Coal gasification effluent is a typical refractory industrial wastewater with a very poor anaerobic biodegradability due to its toxicity. Methanol was introduced to improve anaerobic biodegradability of real coal gasification wastewater, and the effect of methanol addition on the performance was investigated in a mesophilic upflow anaerobic sludge bed reactor with a hydraulic retention time of 24 hr. Experimental results indicated that anaerobic treatment of coal gasification wastewater was feasible with the addition of methanol. The corresponding maximum COD and phenol removal rates were 71% and 75%, respectively, with methanol concentration of 500 mg COD/L for a total organic loading rate of 3.5 kg COD/(m3 x day) and a phenol loading rate of 0.6 kg/(m3 x day). The phenol removal rate was not improved with a higher methanol concentration of 1000 mg COD/L. Substrate utilization rate (SUR) tests indicated that the SURs of phenol were 106, 132, and 83 mg phenol/(g VSS x day) at methanol concentrations of 250, 500, and 1000 mg COD/L, respectively, and only 45 mg phenol/(g VSS x day) in the control reactor. The presence of methanol could reduce the toxicity of coal gasification wastewater and increase the biodegradation of phenolic compounds.

Removal of phenol in a constructed wetland system and the relative contribution of plant roots, microbial activity and porous bed

Analysis of a low organic load constructed wetland (CW) system was performed in order to understand the relative role of its various components contribution in phenol removal (100 mg/L) under controlled plant biomass/gravel/water experimental ratios (50 g/450 g/100 mL). The results [expressed as phenol50/time (hours) required to remove 50% of the initial phenol concentration] showed that the highest phenol removal occurred by combined biofilms from roots and gravel attached (phenol50=19), followed by gravel biofilm (phenol50=105) and planktonic (suspended in water) bacteria (phenol50=>200). An in depth analysis revealed that plants contribution alone (antibiotics sterilized) was minor (phenol50=>89) while roots supported biofilm resulted in a significant phenol removal (phenol50=15). Therefore in this type of CW, the main phenol removal active fraction could be attributed to plant roots' biofilm bacteria.

Oxidation of phenol in a bioremediation medium using Fenton's reagent

The oxidation of phenol by Fenton's reagent was investigated in a medium suitable for bioremediation. An experimental design approach, based on a central composite rotatable design, was used to quantify the effects of H2O2 concentration (2000 to 5000 mg 1(-1)) and FeSO4.7H2O concentration (500 to 2000 mg 1(-1)). Performance of the chemical oxidation by Fenton's reagent was evaluated by determining the percentage of phenol oxidized at equilibrium. The analysis of variance test indicated that both H2O2 and FeSO4.7H2O concentrations had a positive effect on phenol oxidation. Hydrogen peroxide concentration was the dominating parameter for the removal of phenol by Fenton's reagent. The optimal concentrations of H2O2 and FeSO4.7H2O for complete oxidation of 2000 mg 1(-1) phenol in the medium were found to be 4340 mg 1(-1) and 1616 mg 1(-1), respectively, at 25 degrees C and pH 3. Oxidation of phenol in the culture medium was found to be significantly different than in pure water.

Removal of phenol from aqueous solutions by adsorption onto organomodified Tirebolu bentonite: equilibrium, kinetic and thermodynamic study

A natural bentonite modified with a cationic surfactant, cetyl trimethylammonium bromide (CTAB), was used as an adsorbent for removal of phenol from aqueous solutions. The natural and modified bentonites (organobentonite) were characterized with some instrumental techniques (FTIR, XRD and SEM). Adsorption studies were performed in a batch system, and the effects of various experimental parameters such as solution pH, contact time, initial phenol concentration, organobentonite concentration, and temperature, etc. were evaluated upon the phenol adsorption onto organobentonite. Maximum phenol removal was observed at pH 9.0. Equilibrium was attained after contact of 1h only. The adsorption isotherms were described by Langmuir and Freundlich isotherm models, and both model fitted well. The monolayer adsorption capacity of organobentonite was found to be 333 mg g(-1). Desorption of phenol from the loaded adsorbent was achieved by using 20% acetone solution. The kinetic studies indicated that the adsorption process was best described by the pseudo-second-order kinetics (R(2) > 0.99). Thermodynamic parameters including the Gibbs free energy (DeltaG degrees), enthalpy (DeltaH degrees), and entropy (DeltaS degrees) were also calculated. These parameters indicated that adsorption of phenol onto organobentonite was feasible, spontaneous and exothermic in the temperature range of 0-40 degrees C.

The investigation of catalytic ozonation and integrated catalytic ozonation/biological processes for the removal of phenol from saline wastewaters

The effectiveness of the catalytic ozonation process (COP) with a GAC catalyst was assessed based on the degradation and COD removal of phenol from the saline wastewater, as compared with the single ozonation process (SOP). The COP attained a much higher level of phenol degradation compared to the SOP. The influence of several variables was investigated, including pH of solution, NaCl concentration, and dosage of GAC, for their effects on COP phenol degradation in a synthetic saline wastewater. The maximum degradation of phenol was achieved at pH 8 and 20 g/L GAC. NaCl had no adverse effect on phenol removal at ranges between 0.5 and 50 g/L. The activated carbon acted mostly as a catalyst for ozone decomposition, and the subsequent generation of hydroxyl radicals. Furthermore, the GAC preserved its catalytic properties after 5 times reuse. The capability of a biological process to treat COP effluent was also investigated. Results showed that a 10 min reaction time in COP under optimum conditions reduces the concentrations of phenol and COD to an acceptable level for efficient post-treating in a suspended growth bioreactor at a short aeration time of 4h. Thus, the integration of COP with a biological process is proven to be a technically and economically effective method for treating saline wastewaters containing recalcitrant compounds.

Continuous flow photocatalytic treatment integrated with separation of titanium dioxide on the removal of phenol in tap water

We studied the continuous flow photocatalytic treatment integrated with separation/reuse of titanium dioxide on the removal of phenol (20 mg l(-1)) in electrolytes containing tap water. A circulative flow tubular photoreactor and a separation tank were used, where inflow of phenol continuously flowed into a mixing tank (for titanium dioxide suspension) and treated water overflowed from the separation tank. Black light and sunlight were used by turns as the light source on the photocatalytic treatment. Photocatalytic removal of phenol was maximum at the circulative flow rate of 600 ml min(-1) and the transmittance of 0.3%. Integration of circulative photocatalytic treatment and titanium dioxide separation and continuous use of titanium dioxide could be performed effectively at low inflow of 10 ml min(-1). The titanium dioxide slurry sedimented spontaneously by standing was continuously used for at least 72 h without decreasing the efficiency of the photocatalytic treatment. The used titanium dioxide can be replaced with a fresh one by draw and fill method without interrupting the treatment.

Zeolite-templated microporous carbon as a superior adsorbent for removal of monoaromatic compounds from aqueous solution

A microporous carbon with very high specific surface area and narrow pore size distribution was synthesized using Y zeolite as a template. The structural, porosity, and surface characteristics of the material were investigated by elemental analysis, N2 adsorption, powder X-ray diffraction, and Raman spectroscopy. The batch adsorption technique was performed to assess adsorption of three monoaromatic compounds, phenol, 1,3-dichlorobenzene, and 1,3-dinitrobenzene, on the synthesized carbon. Nonporous graphite, single-walled carbon nanotubes, and two commercial microporous activated carbons were also included as comparative adsorbents. The synthesized microporous carbon showed extraordinarily high adsorption affinity (comparable or higher than activated carbons and carbon nanotubes) for the three adsorbates, and very fast adsorption/ desorption kinetics (equilibrium reached less than 3 h) and complete adsorption reversibility for phenol. These adsorption properties were attributed to the large hydrophobic surface area and the regular-shaped, open and interconnected three-dimensional pore structure of the synthesized microporous carbon. Additionally, with normalization of adsorbent surface area adsorption of a bulky solute, 1,2,4,5-tetrachlorobenzene, was prominently higher on the synthesized carbon than on the activated carbons, due to alleviated size exclusion effect. Findings of the present work highlight the potential of using zeolite-templated carbons as effective adsorbents for removal of hydrophobic organic contaminants in water treatment.