Fabrication of iron-dipicolinamide catalyst with Fe-N bonds for enhancing non-radical reactive species under alkaline Fenton process

Iron dipicolinamide (Fedpa), as an efficient Fenton-like catalyst, was fabricated to excite hydrogen peroxide (H₂O₂) for the removal of 2,4-dichlorophenol (2,4-DCP). The unique structures and the electronic properties of Fedpa were contributed to its excellent catalytic performance in alkaline Fenton process. Fe was chelated with dpa by four Fe-N bonds leaved two labile sites, which reduced the oxidation potential of dpa[Fe^III/Fe^II], dpa[Fe^V/Fe^III] or dpa[Fe^IV/Fe^II] to 0.316 V and 1.189 V respectively, and made it easily be bound with H₂O₂ to initiate the reaction. The results showed that 99.5% removal rate of 2,4-DCP (0.58 mM) was achieved by using 0.027 g/L Fedpa and 5.8 mM H₂O₂ in 60 min at pH 9.9. The coordination between Fe and dpa enhanced the catalytic efficiency of Fe^II. The active species generated in Fedpa/H₂O₂ system contained the iron-oxo species (dpaFe^V = O or dpa^IV = O), O₂^- and HO. The iron-oxo species was the main non-radical reactive species for the degradation of 2,4-DCP and some degradation intermediates were detected by GC-QTOF. Furthermore, the influence of factors, such as Fedpa loading, solution pH, temperature and anions (F^-, Cl^-, SO₄^2-, NO₃^- and PO₄^3-) on the catalytic performance of Fedpa were also discussed. This process of complexation between Fe and dpa combined with a green oxidant H₂O₂ presents a new insight for the use of Fenton-like system in the degradation of refractory organics.

Laccase immobilization on amino-functionalized magnetic metal organic framework for phenolic compound removal

An amino-functionalized magnetic metal organic framework (MOF), Fe₃O₄-NH₂@MIL-101(Cr), was employed for laccase immobilization for the first time. The immobilized laccase was synthesized by the adsorption and covalent binding method, thus exhibited high activity recovery, large immobilization capacity and good tolerance to low pH and high temperature conditions. The excellent stability enabled the immobilized laccase to retain 89% of its initial activity after storage for 28 days. When the ambient temperature reached 85 °C, the immobilized laccase showed 49.1% residual activity even after 6 h preservation. The stability of laccase in organic solvents such as methanol was also greatly improved. Application of the immobilized laccase for 2,4-dichlorophenol removal was also investigated. The adsorption by Fe₃O₄-NH₂@MIL-101(Cr) contributed to a quick removal in the first hour, and the removal efficiency reached 87% eventually. When the reaction was completed, the immobilized laccase could be separated from the solution by a magnet. The results introduced a novel support for laccase immobilization, and the immobilized laccase had great potential in wastewater treatment.

Laccase removal of 2-chlorophenol and sulfamethoxazole in municipal wastewater

Laccases were studied for their ability to remove two compounds, 2-chlorophenol and sulfamethoxazole, in batch studies, both in buffered solutions and in wastewater samples from different points in a municipal water resource recovery facility. Two enzymes with and without a mediator (acetosyringone) were investigated: a commercial product derived from Myceliphthora thermophile and a laboratory-generated enzyme mix derived from Tramates versicolor. The chlorophenol was removed rapidly by the commercial enzyme in the presence of acetosyringone, but the primary products were coupling complexes of the reactants. Excellent removal was achieved without acetosyringone by the natural enzyme mix. Sulfamethoxazole was poorly removed in all laboratory-generated chemically buffered solutions, but was very well removed, without the addition of mediators, in secondary effluent suspensions from a municipal water resource recovery facility. Mechanistic studies are still required, but the results suggest that treatment via direct addition of enzymes is feasible to remove recalcitrant compounds in municipal wastewater.

Preparation of magnetic polyimide@ Mg-Fe layered double hydroxides core-shell composite for effective removal of various organic contaminants from aqueous solution

In this work, a novel core-shell structured magnetic polyimide@layered double oxides (LDO) composites coating a porous polyimide (PI)-coated Fe3O4 magnetic core and layered double hydroxide (LDH) has been successfully synthesized by solve-thermal synthesis and co-precipitation process. The magnetic PI@LDO composites were characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), thermogravimetry analysis (TGA) and magnetic properties analysis. The composite materials displayed core-shell structure with flower-like morphology. The magnetic PI@LDO composites were applied to remove tetracycline (TC), 2,4-dichlorophenol (2,4-DCP) and glyphosate (GP) from aqueous solution. The action pH value was ranged from 5 to 9 for TC and GP and 3 to 7 for 2,4-DCP, respectively. Cl- showed a weak competitive adsorption effect to TC, 2, 4-DCP and GP. In addition, the presence of humic acid (HA) could slightly reduce the adsorption capacity of magnetic PI@LDO composites. The adsorption process could be well described by pseudo-second-order model for TC and GP, while pseudo-first-order model for 2,4-DCP. The experimental data of TC and 2,4-DCP could be fitted better with Freundlich model, while that of GP were fitted better with Langmuir model. The adsorptions of TC, 2,4-DCP and GP were both spontaneous and endothermic. The adsorption capacity decreased slightly after adsorption-desorption cycles repeated five times. This study demonstrated that magnetic PI@LDO exhibited great potential to be a mild and cost-effective adsorbent for the removal of various organic contaminants from wastewater.

Removal of dichlorophenol by Chlorella pyrenoidosa through self-regulating mechanism in air-tight test environment

Microalgae are surprisingly efficient to remove pollutants in a hermetically closed environment, though its growth is inhibited in the absence of pollutants. The final pH, algal density, Chl-a content, and the removal efficiency of 2,4-dichlorophenol (2,4-DCP) by Chlorellar pyrenoidosa in a closed system were observed under different initial pH, lighting regimes, and various carbon sources. The optimal condition for 2,4-DCP removal was obtained, and adopted to observe the evolution of above items by domesticated and origin strains. The results showed that both respiration and photosynthesis participated in the degradation of 2,4-DCP, and caused the changes of pH. The photosynthesis seemed to increase the solution pH, while the respiration and the biodegradation of 2,4-DCP to decrease the solution pH. The domesticated strain achieved nearly 100% removal when initial concentrations of 2,4-DCP lower than 200 μg L^-1, due to providing a appropriate but narrow pH evolution range, mostly falling between 6.5 and 7.9. The research helps to understand the mechanism of biodegradation of chlorophenol compounds by green algae.

Enzyme-Nanowire Mesocrystal Hybrid Materials with an Extremely High Biocatalytic Activity

The laccase-Cu₂O-nanowire mesocrystal hybrid materials were developed with a superior catalytic activity inspired by natural biocatalysis processes in living cells that highly resemble the metal ions activation and the well-organized spatial structure of the natural rough endoplasmic reticulum. The enzyme and nanobiocatalyst activities of the obtained hybrid material exhibited an approximate 10-fold and 2.2-fold increase than the free enzyme, surpassing the currently available nanobiocatalysts. The comprehensive catalytic performance of the hybrid materials has been further demonstrated using a prototype continuous-flow reactor for the bioremediation of 2,4-dichlorophenol-contaminated water, which showed a high degradation efficiency and remarkable reusability. These new highly efficient nanobiocatalysts are expected to be used for diverse applications in biotechnology, biosensing, and environmental remediation.

Degradation of 2, 4-dichlorophenol in aqueous solution by dielectric barrier discharge: Effects of plasma-working gases, degradation pathways and toxicity assessment

Chlorinated phenols are a class of contaminants found in water and have been regarded as a great potential risk to environment and human health. It is thus urgent to develop effective techniques to remove chlorinated phenols in wastewater. For this purpose, we employed dielectric barrier discharge (DBD) in this work and studied the efficiency of DBD for the degradation of 2,4-dichlorophenol (2,4-DCP), one of the most typical chlorophenols in the environment. The effects of pH value, applied voltage and plasma-working gases on the dichlorophenol-removal efficiency were investigated. The results demonstrate that DBD plasma could successfully degrade 2,4-DCP, achieving efficiency of 98.16% (k = 1.09 min^-1) in the Ar-DBD system, and 77.60% (k = 0.48 min^-1) in the N₂-DBD system, with the process following the first-order kinetics. The removal efficiency was reduced in the presence of radical scavengers, confirming that hydroxyl radicals played a key role in the degradation process, while other active substances were also found such as nitrogen radicals in the N₂-DBD system, which was found to have also contribution to the degradation of 2,4-DCP. The intermediates and final products generated in the degradation process were analyzed using gas chromatography-mass spectrometry (GC-MS). Based on the identification of intermediates, the degradation pathways and mechanism were proposed and discussed. Besides, the toxicity of the DBD treated 2,4-DCP solution was also assessed using GFP-expressing recombinant Escherichia coli (E. coli) as the testing organism, showing that plasma treatment could substantially reduce the toxic effect of 2,4-DCP.

Adsorptive removal of phenolic compounds from aqueous solutions using pine cone biomass: kinetics and equilibrium studies

In this study, a novel inexpensive biosorbent of pine cone powder was used for the treatment of wastewater contaminated with phenol and chlorophenols (CPhs). The biosorbent was thoroughly characterized by using CHN and BET measurements, as well as FTIR, SEM, and XRD analyses. Kinetic and equilibrium biosorption experiments showed that the uptake was more than 80% within the first 30 min of contact time at pH 5.0. The biosorption of 4-CPh onto pine cone powder was higher than those of phenol and 2-CPh. The kinetic data were consistent with the pseudo-first-order kinetic model, and the Langmuir isotherm model best represented the equilibrium data. The maximum biosorption capacities of phenol, 2-CPh, and 4-CPh were 164.51, 189.44, and 220.12 mg/g, respectively, at 30 ± 1 °C. Therefore, the pine cone powder is an effective low-cost adsorbent for the removal of phenol and CPhs from the contaminated water.

Typha latifolia as potential phytoremediator of 2,4-dichlorophenol: Analysis of tolerance, uptake and possible transformation processes

2,4-Dichlorophenol (2,4-DCP) is considered a priority pollutant due to its high toxicity. Therefore, it is urgent to develop technologies for the disposal of this pollutant. Various remediation processes have been proposed for the elimination of 2,4-DCP in contaminated water, however, most of them involve high costs of operation and maintenance. This study aimed to determine the capacity of remediation of 2,4-DCP in water by Typha latifolia L. wild plants. For that, the tolerance, removal, accumulation and biotransformation of 2,4-DCP by T. latifolia were investigated. The plants were exposed to 2,4-DCP solutions with a concentration range from 1.5 to 300 mgL^-1 for 10 days. They exhibited a reduction in chlorophyll levels and growth rate when 2,4-DCP solutions were ≥30 mgL^-1 and ≥50 mgL^-1, respectively. The removal of contaminant was dose-depended, being 99.7% at 1.5-3 mgL^-1, 59-70% at 10-70 mgL^-1 and 35-42% at 100-300 mgL^-1 of 2,4-DCP in the solution. Studies indicated that 2,4-DCP was mainly accumulated in root tissue rather than in shoot tissue. Acid hydrolysis of biomass extracts suggests 2,4-DCP bioconjugates formation in root tissue as a response mechanism. Additionally, an increment in glutathione S-transferase (GST) activity could indicate a 2,4-DCP conjugation with glutathione as a detoxification mechanism of T. latifolia.

Reductive removal of 2,4-dinitrotoluene and 2,4-dichlorophenol with zero-valent iron-included biochar

In order to remediate organic contaminants in natural waters and soils, a novel zero-valent iron [Fe(0)]-included biochar was synthesized via slow pyrolysis. 2,4-Dinitrotoluene (DNT) and 2,4-dichlorophenol (DCP) were removed in water via sorption to the Fe(0)-included biochar. Compared to sorption control without Fe(0), the sorbed DNT and DCP were further transformed to reduction products by Fe(0)-included biochar. Compared to the reduction control with Fe(0), the presence of biochar promoted the reductive transformation of DNT and DCP. Increasing the pyrolysis temperature resulted in enhancing the removal of DNT and DCP, suggesting that the aromaticity of biochar may be responsible for the removal. The yields of the reduction products also indicated that unlike the direct reduction by Fe(0), different reduction pathways existed in the reduction of DNT and DCP with Fe(0)-included biochar. The results suggest that Fe(0)-included biochar is a viable option to immobilize and transform redox-sensitive organic contaminants in natural environments.

Adsorption and regenerative oxidation of trichlorophenol with synthetic zeolite: Ozone dosage and its influence on adsorption performance

Regeneration of loaded adsorbents is a key step for the sustainability of an adsorption process. In this study, ozone was applied to regenerate a synthetic zeolite for the adsorption of trichlorophenol (TCP) as an organic model pollutant. Three initial concentrations of TCP in water phase were used in adsorption tests. After the equilibrium, zeolite loaded different amounts of TCP was dried and then regenerated with ozone gas. It was found that the adsorption capacity of zeolite was increased through three regeneration cycles. However, the adsorption kinetics was compromised after the regeneration with slightly declined 2nd order reaction constants. The ozone demand for the regeneration was highly dependent on the TCP mass loaded onto the zeolite. It was estimated that the mass ratio of ozone to TCP was 1.2 ± 0.3 g O3/g TCP.

Impact of continuous and intermittent supply of electric assistance on high-strength 2,4-dichlorophenol (2,4-DCP) degradation in electro-microbial system

The high-strength 2,4-DCP, which exists in two states: dissolved and colloidal, was studied by a continuously electro-microbial system (CEMS) and an intermittently electro-microbial system (IEMS). The hydrolysis rate of colloidal 2,4-DCP in the IEMS without electric assistance was much higher than that in the CEMS. However, the degradation rate of the dissolved 2,4-DCP and the dissolved intermediates (2-chlorophenol and 4-chlorophenol) in the IEMS without electric assistance were much lower than that in the CEMS. By adjusting the intermittent operation mode, the degradation time of 2,4-DCP was shortened greatly. Microbial characteristics in the CEMS and the IEMS were different. The correlation analysis for the main factors affecting the hydrolysis was performed by SPSS, and it was found that the correlation coefficient (rp) was -0.912 for extracellular polymeric substances (EPS) content, 0.823 for zeta potential and 0.632 for relative hydrophobicity, respectively.

A new combined green method for 2-Chlorophenol removal using cross-linked Brassica rapa peroxidase in silicone oil

This study proposes a new technique to treat waste air containing 2-Chlorophenol (2-CP), namely an integrated process coupling absorption of the compound in an organic liquid phase and its enzymatic degradation. Silicone oil (47V20) was used as an organic absorbent to allow the volatile organic compound (VOC) transfer from the gas phase to the liquid phase followed by its degradation by means of Cross-linked Brassica rapa peroxidase (BRP) contained in the organic phase. An evaluation of silicone oil (47V20) absorption capacity towards 2-CP was first accomplished by determining its partition coefficient (H) in this solvent. The air-oil partition coefficient of 2-CP was found equal to 0.136 Pa m(3) mol(-1), which is five times lower than the air-water value (0.619 Pam(3) mol(-1)). The absorbed 2-CP was then subject to enzymatic degradation by cross-linked BRP aggregates (BRP-CLEAs). The degradation step was affected by four parameters (contact time; 2-CP, hydrogen peroxide and enzyme concentrations), which were optimized in order to obtain the highest conversion yield. A maximal conversion yield of 69% and a rate of 1.58 mg L(-1) min(-1)were obtained for 100 min duration time when 2-CP and hydrogen peroxide concentrations were respectively 80 mg L(-1) and 6 mM in the presence of 2.66 UI mL(-1) BRP-CLEAs. The reusability of BRP-CLEAs in silicone oil was assessed, showing promising results since 59% of their initial efficiency remained after three batches.

Permeable reactive barrier of coarse sand-supported zero valent iron for the removal of 2,4-dichlorophenol in groundwater

In this study, coarse sand-supported zero valent iron (ZVI) composite was synthesized by adding sodium alginate to immobilize. Composite was detected by scanning electron microscope (SEM), X-ray diffraction (XRD), and X-ray fluorescence (XRF). SEM results showed that composite had core-shell structure and a wide porous distribution pattern. The synthesized composite was used for degradation of 2,4-dichlorophenol (2,4-DCP) contamination in groundwater. Experimental results demonstrated that degradation mechanism of 2,4-DCP using coarse sand-supported ZVI included adsorption, desorption, and dechlorination. 2,4-DCP adsorption was described as pseudo-second-order kinetic model. It was concluded that dechlorination was the key reaction pathway, ZVI and hydrogen are prime reductants in dechlorination of 2,4-DCP using ZVI.

The potential of using low cost naturally available biogenic substrates for biological removal of chlorophenol

This study details the application of naturally available biogenic substrates (NABS) in microbial degradation of 2-chlorophenol (CP). Jatropha deoiled cakes (JDC) and Karanja deoiled cakes (KDC) are used as NABS. The potential of NABS is compared with standard biogenic substrate, glucose. The study was carried out with both acclimatized mixed culture and pure culture, Pseudomonas putida. Microbial activity of the culture was monitored by measuring reduction in chlorophenol concentration, COD, toxicity and Cl(-) ions evolution. The study was carried out for a total of 42days. It was observed that culture having NABS has shown similar chlorophenol reduction but higher COD and toxicity reduction. Amongst NABS, Jatropha deoiled cake (JDC) has shown superior results of 71% COD reduction compared to glucose and KDC. This study is one of the first kind illustrating the potential of these substrates in removing toxic chemicals from wastewaters.

Characterization and evaluation of the efficiency of SiO2/tetra-α-(2,4-di-tert-butylphenoxy)-phthalocyaninato zinc nanocomposite as photosensitizers for oxidation of 2,4,6-trichlorophenol

A photosensitizer tetra-α-(2,4-di-tert-butylphenoxy)-phthalocyaninato zinc [ZnPc(OAr)4] was successfully encapsulated in SiO2 nanoparticle by the microemulsion method. The photosensitized composite nanoparticle was able to degrade 2,4,6-trichlorophenol (TCP) in aqueous solution. Under visible light irradiation, the nanoparticles efficiently generated reactive oxygen species; 95.4% of TCP was degraded after 270 min of reaction. Some aromatic compounds and aliphatic carboxylic acids were detected by mass spectrometry as the reaction intermediates. The results were different from those of previously reported photocatalytic reactions, in which valence band holes or hydroxyl radicals functioned as the main oxidants. The photosensitizing composite nanoparticle is potentially applicable to the oxidation of phenol.

Dynamics of a microbial community exposed to several concentrations of 2-chlorophenol in an anaerobic sequencing batch reactor

The aim of this study was to contribute to the knowledge on the dynamic of the microbial community involved in anaerobic degradation of different concentrations of 2-chlorophenol (2CP, from 28 to 196 mg 2CP-C/L) and a mixture of 2CP and phenol (from 28 to 196 mg phenol-C/L) and its relationship with the respiratory process in two anaerobic sequencing batch reactors (ASBR). The dynamic of the microbial community was evaluated by denaturant gradient gel electrophoresis (DGGE) and ecological indices (S and J indices). The respiratory process was evaluated by means of substrate consumption efficiency, biogas yield, and specific consumption rates as response variables. The high consumption efficiency (90%) and the constant biogas yields obtained at concentrations up to 140 mg C/L may be related with the evenness of microbial populations (J index=0.97±0.2) present in both reactors. Pseudomonas genus was present in all concentrations tested, suggesting a possible relationship with the dehalogenation observed in both reactors. The decrease in specific consumption rate and biogas yield as well as the accumulation of phenol and volatile fatty acids observed in both reactors at 196 mg 2CP-C/L might be associated with the disappearance of the bands related to Caulobacter and Bacillus. At these conditions, the disappearance of fermentative or acetogenic bacteria resulted in reduction of substrates required to carry out methanogenesis, which eventually might cause the declination in methanogenic populations present in the reactors.

Preparation and use of maize tassels' activated carbon for the adsorption of phenolic compounds in environmental waste water samples

The determination and remediation of three phenolic compounds bisphenol A (BPA), ortho-nitrophenol (o-NTP), parachlorophenol (PCP) in wastewater is reported. The analysis of these molecules in wastewater was done using gas chromatography (GC) × GC time-of-flight mass spectrometry while activated carbon derived from maize tassel was used as an adsorbent. During the experimental procedures, the effect of various parameters such as initial concentration, pH of sample solution, eluent volume, and sample volume on the removal efficiency with respect to the three phenolic compounds was studied. The results showed that maize tassel produced activated carbon (MTAC) cartridge packed solid-phase extraction (SPE) system was able to remove the phenolic compounds effectively (90.84-98.49%, 80.75-97.11%, and 78.27-97.08% for BPA, o-NTP, and PCP, respectively). The MTAC cartridge packed SPE sorbent performance was compared to commercially produced C18 SPE cartridges and found to be comparable. All the parameters investigated were found to have a notable influence on the adsorption efficiency of the phenolic compounds from wastewaters at different magnitudes.

Cell wall bound anionic peroxidases from asparagus byproducts

Asparagus byproducts are a good source of cationic soluble peroxidases (CAP) useful for the bioremediation of phenol-contaminated wastewaters. In this study, cell wall bound peroxidases (POD) from the same byproducts have been purified and characterized. The covalent forms of POD represent >90% of the total cell wall bound POD. Isoelectric focusing showed that whereas the covalent fraction is constituted primarily by anionic isoenzymes, the ionic fraction is a mixture of anionic, neutral, and cationic isoenzymes. Covalently bound peroxidases were purified by means of ion exchange chromatography and affinity chromatography. In vitro detoxification studies showed that although CAP are more effective for the removal of 4-CP and 2,4-DCP, anionic asparagus peroxidase (AAP) is a better option for the removal of hydroxytyrosol (HT), the main phenol present in olive mill wastewaters.

An efficient dye-sensitized BiOCl photocatalyst for air and water purification under visible light irradiation

A photosensitized BiOCl catalyst was found to be effective for photocatalytic water purification and air remediation under visible light irradiation (λ > 420 nm). Prepared by a solvothermal method, the BiOCl crystals possessed a 3D hierarchical spherical structure with the highly active facets exposed. When sensitized by Rhodamine B (RhB), the photocatalyst system was more active than N-doped TiO2 for breaking down 4-chlorophenol (4-CP, 200 ppm) and nitric monoxide (NO, 500 ppb). The high activity could be attributed to the hierarchical structure (supplying feasible reaction tunnels for adsorption and transition of reactants or products) and the efficient exposure of the {001} facets. The former provides an enriched oxygen atom density that promotes adsorption of cationic dye RhB, and creates an oxygen vacancy state. The HO˙ and ˙O2(-) radicals produced from the injected electrons from the excited dye molecule (RhB*) into the conduction band of BiOCl were responsible for the excellent photocatalytic performance of the RhB-BiOCl system.

Molecular imprinted polymer of methacrylic acid functionalised β-cyclodextrin for selective removal of 2,4-dichlorophenol

This work describes methacrylic acid functionalized β-cyclodextrin (MAA-βCD) as a novel functional monomer in the preparation of molecular imprinted polymer (MIP MAA-βCD) for the selective removal of 2,4-dichlorophenol (2,4-DCP). The polymer was characterized using Fourier Transform Infrared (FTIR) spectroscopy, Brunauer-Emmett-Teller (BET) and Field Emission Scanning Electron Microscopy (FESEM) techniques. The influence of parameters such as solution pH, contact time, temperature and initial concentrations towards removal of 2,4-DCP using MIP MAA-βCD have been evaluated. The imprinted material shows fast kinetics and the optimum pH for removal of 2,4-DCP is pH 7. Compared with the corresponding non-imprinted polymer (NIP MAA-βCD), the MIP MAA-βCD exhibited higher adsorption capacity and outstanding selectivity towards 2,4-DCP. Freundlich isotherm best fitted the adsorption equilibrium data of MIP MAA-βCD and the kinetics followed a pseudo-second-order model. The calculated thermodynamic parameters showed that adsorption of 2,4-DCP was spontaneous and exothermic under the examined conditions.

Coupled photocatalytic-biodegradation of 2,4,5-trichlorophenol: effects of photolytic and photocatalytic effluent composition on bioreactor process performance, community diversity, and resistance and resilience to perturbation

Sequentially coupled advanced oxidation-biodegradation systems have proven effective for treating a variety of wastewaters, but in several cases the pretreatment did not improve, or even hindered, subsequent biodegradation. Therefore, investigating the relationship between advanced oxidation pretreated effluent and subsequent bioreactor performance can help to optimize these systems. Here, a photocatalytic reactor was used to produce four unique effluents from 2,4,5-trichlorophenol (TCP) by varying light wavelength, catalyst presence, and reaction time, demonstrating that the conditions of photocatalytic pretreatment can be tuned to achieve a variety of treatment objectives. The photocatalytic effluents were characterized for chemical oxygen demand (COD), chloride release, aromaticity, and residual TCP concentration. The four effluents were normalized to 40 mg COD/L, combined with biological medium components, and fed to continuous bioreactors. Bioreactors were assayed for COD removal, TCP removal, optical density (OD), and microbial diversity via denaturing gradient gel electrophoresis. In general COD removal in the bioreactors increased as aromatic character of the photoeffluent decreased, but the least aromatic effluent performed poorly indicating the nuanced relationship between photoreactor effluent composition and bioreactor performance. While neither indicator of community diversity, richness nor evenness, correlated with COD removal or biomass accumulation, each effluent produced a unique community as indicated through similarity indices. All conditions demonstrated strong overall TCP removal. After two weeks at steady state, the reactors were perturbed with a 120-μM spike of TCP. Overall the most aromatic photoeffluent produced the most resistant community to the perturbation, while the optimum effluents at steady state produced communities with poor resistance in terms of biomass accumulation and COD removal. These results highlight the tradeoffs between steady state performance and resistance to perturbation that are necessary to optimize a combined advanced oxidation-biodegradation treatment strategy.

Effect of copper oxide concentration on the formation and persistency of environmentally persistent free radicals (EPFRs) in particulates

Environmentally persistent free radicals (EPFRs) are formed by the chemisorption of substituted aromatics on metal oxide surfaces in both combustion sources and superfund sites. The current study reports the dependency of EPFR yields and their persistency on metal loading in particles (0.25, 0.5, 0.75, 1, 2, and 5% CuO/silica). The EPFRs were generated through exposure of particles to three adsorbate vapors at 230 °C: phenol, 2-monochlorophenol (2-MCP), and dichlorobenzene (DCBz). Adsorption resulted in the formation of surface-bound phenoxyl- and semiquinoine-type radicals with characteristic EPR spectra displaying a g value ranging from ∼ 2.0037 to 2.006. The highest EPFR yield was observed for CuO concentrations between 1 and 3% in relation to MCP and phenol adsorption. However, radical density, which is expressed as the number of radicals per copper atom, was highest at 0.75-1% CuO loading. For 1,2-dichlorobenzene adsorption, radical concentration increased linearly with decreasing copper content. At the same time, a qualitative change in the radicals formed was observed--from semiquinone to chlorophenoxyl radicals. The two longest lifetimes, 25 and 23 h, were observed for phenoxyl-type radicals on 0.5% CuO and chlorophenoxyl-type radicals on 0.75% CuO, respectively.

Optimization of a greener method for removal phenol species by cloud point extraction and spectrophotometry

A greener method based on cloud point extraction was developed for removing phenol species including 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP) and 4-nitrophenol (4-NP) in water samples by using the UV-Vis spectrophotometric method. The non-ionic surfactant DC193C was chosen as an extraction solvent due to its low water content in a surfactant rich phase and it is well-known as an environmentally-friendly solvent. The parameters affecting the extraction efficiency such as pH, temperature and incubation time, concentration of surfactant and salt, amount of surfactant and water content were evaluated and optimized. The proposed method was successfully applied for removing phenol species in real water samples.

The use of used automobile tyres in a partitioning bioreactor for the biodegradation of xenobiotic mixtures

Waste tyres were utilized as the sorption phase in a two-phase partitioning bioreactor (TPPB) for the biodegradation of a binary mixture of 2,4-dichlorophenol (DCP) and 4-nitrophenol (4NP). These compounds are extensively used in the chemical industry and are found in many industrial effluents. Although both compounds are toxic and are on the EPA list of priority pollutants, a higher inhibitory effect on microorganisms is exerted by DCP, and our experimental tests were focused on strategies to reduce its negative impact on microbial activity. Sorption/desorption tests for the DCP-4NP mixture were first performed to verify the related uptake/release rates by the tyres, which showed that the tyres had a higher capacity for DCP uptake and practically no affinity for 4NP. An acclimatized mixed culture was then utilized in a sequencing batch reactor (SBR) operated in conventional and two-phase mode. For the binary DCP-4NP mixture a significant reduction in DCP toxicity, and a concomitant enhancement in substrate removal efficiency (up to 83%for DCP and approximate 100% for 4NP) were clearly seen for the TPPB operated with 10% and 15% v/v tyres, for influent concentrations up to 180 mg/L, with practically negligible biodegradation in the conventional single phase reactor. The long-term utilization of tyres was confirmed at an influent loading of 180 mg/L with a test performed over 20 work cycles showing an improvement of the removal performance for both compounds.

Application of response surface methodology (RSM) for optimisation of COD, NH3-N and 2,4-DCP removal from recycled paper wastewater in a pilot-scale granular activated carbon sequencing batch biofilm reactor (GAC-SBBR)

In this study, the potential of a pilot-scale granular activated carbon sequencing batch biofilm reactor (GAC-SBBR) for removing chemical oxygen demand (COD), ammoniacal nitrogen (NH3-N) and 2,4-dichlorophenol (2,4-DCP) from recycled paper wastewater was assessed. For this purpose, the response surface methodology (RSM) was employed, using a central composite face-centred design (CCFD), to optimise three of the most important operating variables, i.e., hydraulic retention time (HRT), aeration rate (AR) and influent feed concentration (IFC), in the pilot-scale GAC-SBBR process for recycled paper wastewater treatment. Quadratic models were developed for the response variables, i.e., COD, NH3-N and 2,4-DCP removal, based on the high value (>0.9) of the coefficient of determination (R(2)) obtained from the analysis of variance (ANOVA). The optimal conditions were established at 750 mg COD/L IFC, 3.2 m(3)/min AR and 1 day HRT, corresponding to predicted COD, NH3-N and 2,4-DCP removal percentages of 94.8, 100 and 80.9%, respectively.

[Mechanism of reductive dechlorination of trichlorophenol with different electron donors]

A test was conducted to examine the degradation effect and reductive dechlorination pathway of 2, 4, 6-trichlorophenol (2,4,6-TCP) in the presence of different electron donors, such as glucose, sodium lactate, sodium pyruvate and sodium acetate. The results showed that, compared with the effect of glucose, sodium lactate, sodium pyruvate and sodium acetate enhanced the dechlorination of 2, 4, 6-TCP effectively, among which sodium lactate could serve as a kind of hydrogen release compound, and the electrons required for reductive dechlorination were released in a sustained way. Substrate metabolism dehydrogenase activity was improved by the external electron donor; after reaction for 240 h, the activity of dehydrogenase was increased in the four electron donor systems, by 21.49%, 25.78%, 136.85% and 139.3%, respectively. The main reductive dechlorination products of 2,4,6-TCP included 2,4-dichlorophenol (2,4-DCP), 4-chlorophenol (4-CP) and phenol; when sodium acetate was used as the electron donor, 4-CP was the main degradation product, and the transformation ratio from 2,4,6-TCP to 4-CP was more than 22%.

Reductive dechlorination of 2,4-dichlorophenol by Pd/Fe nanoparticles prepared in the presence of ultrasonic irradiation

Palladium/Iron (Pd/Fe) nanoparticles were prepared by using ultrasound strengthened liquid phase reductive method to enhance dispersion and avoid agglomeration. The dechlorination of 2,4-dichlorophenol (2,4-DCP) by Pd/Fe nanoparticles was investigated to understand its feasibility for an in situ remediation of contaminated groundwater. Results showed that 2,4-DCP was first adsorbed by Pd/Fe nanoparticles, then quickly reduced to o-chlorophenol (o-CP), p-chlorophenol (p-CP), and finally to phenol (P). The induction of ultrasound during the preparation of Pd/Fe nanoparticles further enhanced the removal efficiency of 2,4-DCP, as a result, the phenol production rates increased from 65% (in the absence of ultrasonic irradiation) to 91% (in the presence of ultrasonic irradiation) within 2h. Our data suggested that the dechlorination rate was dependent on various factors including Pd loading percentage over Fe(0), Pd/Fe nanoparticles availability, temperature, mechanical stirring speed, and initial pH values. Up to 99.2% of 2,4-DCP was removed after 300min reaction with these conditions: Pd loading percentage over Fe(0) 0.3wt.%, initial 2,4-DCP concentration 20mgL(-1), Pd/Fe dosage 3gL(-1), initial pH value 3.0, and reaction temperature 25°C. The degradation of 2,4-DCP followed pseudo-first-order kinetics reaction and the apparent pseudo-first-order kinetics constant was 0.0468min(-1).

[Reductive degradation of chlorophenols in aqueous solution by gamma irradiation]

Because chlorine is an electron withdrawing group, the highly chlorinated phenols may react quickly with hydrated electrons rather than with hydroxyl radicals. The process of reactions of four chlorophenols (4-CP, 2-CP, 2,4-DCP, 2,4,6-TCP) with e(aq)(-) was investigated in aqueous solutions by detecting the concentration of CPs, Cl- and intermediates. In the e(aq)(-) reductive system, the experimental results showed that the order of four kinds of chlorophenol degradation and dechlorination was 2,4,6-TCP > 2,4-DCP > 2-CP > 4-CP. The greater the chlorine content was the higher reactivity of hydrated electrons towards chlorophenols was. Furthermore, hydrated electrons may preferentially attack the ortho-position of chlorine atom rather than the para-position of chlorine atom. Phenol and Cl- were detected as the final product of the reductive reaction. Additionally, processes of degradation and dechlorination of CPs were observed as the pseudo-first-order kinetics. The reaction constant of degradation of 4-CP, 2-CP, 2,4-DCP and 2,4,6-TCP were 0.154, 0.253, 0.750 and 1.188 kGy(-1), respectively. Meanwhile, the dechlorination of 4-CP, 2-CP, 2,4-DCP and 2,4,6-TCP were 0.137, 0.219, 0.251 and 0.306 kGy(-1), respectively.

Simultaneous 4-chlorophenol and nitrogen removal in moving bed sequencing batch reactors packed with polyurethane foam cubes of various sizes

Moving bed sequencing batch reactors (MBSBRs) packed with 8% (v/v) of 8-, 27- and 64-mL polyurethane (PU) foam cubes, respectively, were investigated for simultaneous 4-chlorophenol (4-CP) and nitrogen removal at increasing 4-CP concentration. When the 4-CP concentration exceeded 300 mg L(-1), the MBSBR with 27-mL foam cubes was observed to outperform the other MBSBRs in removing 4-CP and nitrogen. The reasons were: (1) there were more biomass in inner layer of the 27-mL cubes, compared to that of the 8-mL cubes, which was more shielded from the inhibitory effect of 4-CP and (2) the 27-mL cubes were more mobile than the 64-mL cubes. Although increasing 4-CP concentration to 600 mg L(-1) resulted in incomplete removal of 4-CP in the MBSBRs, results of the batch reactor with 27-mL foam cubes showed that complete 4-CP removal within the REACT period could be achieved by increasing the packing volume to 20%.

Removal of chlorophenolics from pulp and paper mill wastewater through constructed wetland

This study evaluates the treatment efficiency of horizontal subsurface flow (HSSF) constructed wetland for the removal of AOX (adsorbable organic halides) and chlorophenolics from pulp and paper mill wastewater. The dimensions of HSSF constructed wetland were 3.5 m in length, 1.5 m in width, and 0.28 m in depth, with surface area of 5.25 m2. The HSSF constructed wetland unit was planted with an ornamental plant species, Canna indica. Under hydraulic retention time (HRT) of 5.9 days, the average AOX removal was 89.1%, and 67% to 100% removal of chlorophenolics from pulp and paper mill wastewater was achieved. The complete removal of 2,3-dichlorophenol, 3,4-dichlorophenol, 2,3,5-trichlorophenol, 2,4,6-trichlorophenol, 3,5-dichlorocatechol, 3,6-dichlorocatechol, and 4,5,6-trichloroguaiacol was observed. Some of the chlorophenolics were found to accumulate in the plant biomass and soil. The evapotranspiration rate varied from 6.7 to 12.7 mm day(-1) during the experimental period. The mass balance of chlorophenolics was also studied in constructed wetland system.

[Adsorption of phenol chemicals by surfactant-modified zeolites]

Two kinds of zeolites were prepared from fly ash and modified by surfactant subsequently. Surfactant-modified zeolites were studied for adsorption of phenol chemicals (phenol, p-chlorphenol, bisphenol A). It showed that the adsorption affinity of zeolite to phenol chemicals was significantly improved after surfactant modification. The adsorption isotherms of phenol chemicals were well fitted by the Langmuir isotherm. For the two surfactant-surfactant modified zeolites, the maximum adsorption amounts of phenol, p-chlorphenol, and bisphenol A calculated from the Langmuir equation were 37.7, 52.36, 90.9 mg x g(-1) and 10.7, 22.83, 56.8 mg x g(-1), respectively. When pH values of solutions were higher than the pK(a) values of phenol chemicals, the removal efficiencies were getting higher with the increase of pH values. The octanol/water partition coefficient (K(ow)) was also found to be an important factor affecting adsorption of phenol chemicals by the modified zeolites. Higher K(ow) value, which means the greater hydrophobicity of the chemicals, resulted in a higher removal.

[Degradation of 2, 4-dichlorophenol in aqueous solution by ZVI/EDDS/air system]

A new oxidation system of Fenton-like system (ZVI/EDDS/Air) has been developed to degrade 2,4-chlorophenols (2,4-DCP) in aqueous solution. The influences of initial conditions, i. e., EDDS concentration, iron dosage, aeration rate, 2,4-DCP concentration and pH as well as reaction temperature on the degradation of 2,4-DCP were studied. The results demonstrated that this ZVI/EDDS/Air system was able to effectively degrade 2,4-DCP in aqueous solution, and the degradation of 2,4-DCP conforms to the pseudo-first-order reaction kinetics equation. Removal of above 99% 2,4-DCP was achieved in ZVI/EDDS/Air system at room temperature and pressure after 1 h reaction when the initial conditions were 2,4-DCP 100 mg x L(-1), EDDS 0.80 mmo x L(-1), ZVI 20 g x L(-1), aeration rate 2 L x (min x L)(-1). Compared with ZVI/EDTA/Air system, ZVI/EDDS/Air system showed higher efficiency in the degradation of 2,4-DCP at ambient circumstance and was more environmentally benign.

Magnetic nanoscaled Fe3O4/CeO2 composite as an efficient Fenton-like heterogeneous catalyst for degradation of 4-chlorophenol

Magnetic nanoscaled Fe(3)O(4)/CeO(2) composite was prepared by the impregnation method and characterized as a heterogeneous Fenton-like catalyst for 4-chlorophenol (4-CP) degradation. The catalytic activity was evaluated in view of the effects of various processes, pH value, catalyst addition, hydrogen peroxide (H(2)O(2)) concentration, and temperature, and the pseudo-first-order kinetic constant of 0.11 min(-1) was obtained for 4-CP degradation at 30 °C and pH 3.0 with 30 mM H(2)O(2), 2.0 g L(-1) Fe(3)O(4)/CeO(2), and 0.78 mM 4-CP. The high utilization efficiency of H(2)O(2), calculated as 79.2%, showed a promising application of the catalyst in the oxidative degradation of organic pollutants. The reusability of Fe(3)O(4)/CeO(2) composite was also investigated after six successive runs. On the basis of the results of metal leaching, the effects of radical scavengers, intermediates determination, and X-ray photoelectron spectroscopic (XPS) analysis, the dissolution of Fe(3)O(4) facilitated by CeO(2) played a significant role, and 4-CP was decomposed mainly by the attack of hydroxyl radicals (•OH), including surface-bound •OH(ads) generated by the reaction of Fe(2+) and Ce(3+) species with H(2)O(2) on the catalyst surface, and •OH(free) in the bulk solution mainly attributed to the leaching of Fe.

Sorption of chlorophenols from aqueous solution by granular activated carbon, filter coal, pine and hardwood

Wood and coal, as low-cost sorbents, have been evaluated as an alternative to commercial granular activated carbon (GAC) for chlorophenol removal. Kinetic experiments indicated that filter coal had a significantly lower rate of uptake (approximately 10% of final uptake was achieved after three hours) than the other sorbents, owing to intra-particle diffusion limitations. The data fitted a pseudo-second-order model. Sorption capacity data showed that GAC had a high sorption capacity (294-467 mg g(-1)) compared with other sorbents (3.2-7.5 mg(g-1)). However, wood and coal had a greater sorption capacity per unit surface area than GAC. Sorption equilibrium data was best predicted using a Freundlich adsorption model. The sorption capacity for all sorbents was 2-chlorophenol < 4-chlorophenol < 2, 4-dichlorophenol, which correlates well with solute hydrophobicity, although the relative differences were much less for coal than the other sorbents. The results showed that pine, hardwood and filter coal can be used as sorbent materials for the removal of chlorophenol from water; however, kinetic considerations may limit the application of filter coal.

[Characteristics and mechanism of 2,4,6-TCP degradation by the "Fe0/enriched-bacteria" system]

The synergistic mechanism of 2, 4, 6-trichlorophenol (TCP) degradation using a combination of Fe0 and anaerobic dechlorinating bacteria with batch processing was investigated. Experimental results showed that under the conditions of pH 7.0, Fe0 5 g x L(-1) and 2,4,6-TCP 30 mg x L(-1), the growth and interface enrichment of enriched-bacteria could be promoted by Fe0, the cell mass (expressed by D600) of Fe0/enriched-bacteria was about 1.7 times as high as that of the individual predominant groups of dechlorinating bacteria. After 96 h reaction, large amount of bacteria attached to the iron surface, with short rod or coccus-like morphology. The pH value of the system was maintained at 7.8, which could be beneficial to the reductive dechlorination reaction and the growth of the enriched-bacteria. The major pathway of 2,4,6-TCP degradation in the Fe0/enriched-bacteria system was 2,4,6-TCP to 2,4-DCP and then to 4-CP.

Nano-scale Au supported on Fe3O4: characterization and application in the catalytic treatment of 2,4-dichlorophenol

Catalytic hydrodechlorination (HDC) is an effective means of detoxifying chlorinated waste. Gold nanoparticles supported on Fe(3)O(4) have been tested in the gas phase (1 atm, 423 K) HDC of 2,4-dichlorophenol. Two 1% w/w supported gold catalysts have been prepared by: (i) stepwise deposition of Au on α-Fe(2)O(3) with subsequent temperature-programmed reduction at 673 K (Au/Fe(3)O(4)-step); (ii) direct deposition of Au on Fe(3)O(4) (Au/Fe(3)O(4)-dir). TEM analysis has established the presence of Au at the nano-scale with a greater mean diameter (7.6 nm) on Au/Fe(3)O(4)-dir relative to Au/Fe(3)O(4)-step (4.5 nm). We account for this difference in terms of stronger (electrostatic) precursor/support interactions in the latter that can be associated with the lower pH point of zero charge (with respect to the final deposition pH) for Fe(2)O(3). Both catalysts promoted the preferential removal of the ortho-Cl substituent in 2,4-dichlorophenol, generating 4-chlorophenol and phenol as products of partial and total HDC, respectively, where Au/Fe(3)O(4)-step delivered a two-fold higher rate (2 × 10(-4) mol(Cl) h(-1) m(Au)(-2)) when compared with Au/Fe(3)O(4)-dir. This unprecedented selectivity response is attributed to activation of the ortho-C-Cl bond via interaction with electron-deficient Au nanoparticles. The results demonstrate the feasibility of a controlled recovery/recycling of chlorophenol waste using nano-structured Au catalysts.

Immobilization of laccase on magnetic bimodal mesoporous carbon and the application in the removal of phenolic compounds

A novel magnetically separable laccase immobilized system was constructed by adsorbing laccase into bimodal carbon-based mesoporous magnetic composites (CMMC). A large adsorption capacity (491.7 mg g(-1)), excellent activity recovery (91.0%) and broader pH and temperature profiles than free laccase have been exhibited by the immobilized laccase. Thermal stability was enhanced to a great extent and operational stability was increased to a certain extent. The shift of kinetic parameters indicated affinity change between enzyme and substrate. Application of the immobilized system in phenol and p-chlorophenol removal was investigated in a batch system. Adsorption effects of the support were responsible for the quick removal rate in the first hour, and up to 78% and 84% of phenol and p-chlorophenol were removed in the end of the reaction, respectively, indicating that the magnetic bimodal mesoporous carbon is a promising carrier for both immobilization of laccase and further application in phenol removal.

[Condition optimization for degradation of chlorophenols using laccase from Amillariella mellea]

Crude laccase extracted from the Amillariella mellea fermentation broth was directly used to catalyze the degradation of 2,4-chlorophenol (2,4-DCP) and 2-chlorophenol (2-CP). The effects of reaction time, pH, temperature, chlorophenol concentration, and laccase dosage on the removal efficiency of chlorophenols were investigated. Optimal catalytic conditions for the degradation of chlorophenols were obtained and the degradation kinetics were analyzed. The results indicated that the crude laccase from Amillariella mellea was able to effectively degrade 2,4-DCP and 2-CP, with higher catalytic ability towards 2,4-DCP degradation. For 2,4-DCP degradation, the optimal temperature was 40 degrees C, the optimal substrate concentration was 75 mg x L(-1), the optimal enzyme dosage was 0. 1 U x mL(-1), and the optimal pH was 6.5. Under these conditions, the maximum degradation rate of 2,4-DCP reached > 97% after 10 h. For 2-DCP degradation, the optimal temperature was 50 degrees C, the optimal substrate concentration was 100 mg x L(-1), the optimal enzyme dosage was 0.1 U x mL(-1), and the optimal pH was 6. Under these conditions, the maximum degradation rate of 2-CP was over 93% after 10 h. The reaction process of laccase-catalyzed 2,4-DCP and 2-CP degradation obeyed the first-order kinetics equation. The laccase from Amillariella mellea was able to effectively degrade chlorophenols, indicating its potential application value in phenolic pollutant control and environmental protection.

Kinetic modeling of bioregeneration of chlorophenol-loaded granular activated carbon in simultaneous adsorption and biodegradation processes

A kinetic model incorporating adsorption, desorption and biodegradation processes was developed to describe the bioregeneration of granular activated carbon (GAC) loaded with 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP), respectively, in simultaneous adsorption and biodegradation processes. The model was numerically solved and the results showed that the kinetic model was well-fitted (R(2)>0.83) to the experimental data at different GAC dosages and at various initial 4-CP and 2,4-DCP concentrations. The rate of bioregeneration in simultaneous adsorption and biodegradation processes was influenced by the ratio of initial chlorophenol concentration to GAC dosage. Enhancement in the rate of bioregeneration was achieved by using the lowest ratio under either one of the following experimental conditions: (1) increasing initial chlorophenol concentration at constant GAC dosage and (2) increasing GAC dosage at constant initial chlorophenol concentration. It was found that the rate enhancement was more pronounced under the second experimental condition.

Development of a highly sensitive assay for enzyme-mediated reductive degradation of polychlorinated dibenzo-p-dioxin

The degradation of 2-chloro-4,5-O-(4'-methyl-7', 8'-diphenyl)ether (CMDPE), an analog of 2,7-dichlorodibenzo-p-dioxin (2,7-DCDD), mediated by Geobacillus sp. UZO 3 cell-free extract was monitored. Ethyl acetate extracts of a complete reaction mixture incubated at 65°C for 18 h were analyzed either by thin layer chromatography (TLC) fractionation coupled with spectrometric detection or by gas chromatography-mass spectrometry (GC-MS). The reaction product 4-methylumbelliferone (4MU) was successfully isolated by TLC and visualized by a transilluminator at 450 nm. The 4MU, 4-chlorophenol, and reaction intermediate 6-chlorophenoxy-4-methylumbelliferone were all successfully detected by GC-MS. The presence of these compounds suggest that Geobacillus sp. UZO 3 cell-free extract also catalyzes the reductive cleavage of the diaryl ether bonds of CMDPE in a similar mechanism previously reported in 2,7-DCDD. In the present study, the authors describe a simple and highly sensitive fluorescent assay for a new dioxin degrading enzyme(s).

Self-bioremediation of cork-processing wastewaters by (chloro)phenol-degrading bacteria immobilised onto residual cork particles

Cork manufacturing is a traditional industry in Southern Europe, being the main application of this natural product in wine stoppers and insulation. Cork processing begins at boiling the raw material. As a consequence, great volumes of dark wastewaters, with elevated concentrations of chlorophenols, are generated, which must be depurated through costly physicochemical procedures before discarding them into public water courses. This work explores the potential of bacteria, isolated from cork-boiling waters storage ponds, in bioremediation of the same effluent. The bacterial population present in cork-processing wastewaters was analysed by DGGE; low bacterial biodiversity was found. Aerobic bacteria were isolated and investigated for their tolerance against phenol and two chlorophenols. The most tolerant strains were identified by sequencing 16S rDNA. The phenol-degrading capacity was investigated by determining enzyme activities of the phenol-degrading pathway. Moreover, the capacity to form biofilms was analysed in a microtitre plate assay. Finally, the capacity to form biofilms onto the surface of residual small cork particles was evaluated by acridine staining followed by epifluorescence microscopy and by SEM. A low-cost bioremediation system, using phenol-degrading bacteria immobilised onto residual cork particles (a by-product of the industry) is proposed for the remediation of this industrial effluent (self-bioremediation).

Phytoremediation of trichlorophenol by Phase II metabolism in transgenic Arabidopsis overexpressing a Populus glucosyltransferase

Trichlorophenol (TCP) and its derivatives are introduced into the environment through numerous sources, including wood preservatives and biocides. Environmental contamination by TCPs is associated with human health risks, necessitating the development of cost-effective remediation techniques. Efficient phytoremediation of TCP is potentially feasible because it contains a hydroxyl group and is suitable for direct phase II metabolism. In this study, we present a system for TCP phytoremediation based on sugar conjugation by overexpressing a Populus putative UDP-glc-dependent glycosyltransferase (UGT). The enzyme PtUGT72B1 displayed the highest TCP-conjugating activity among all reported UGTs. Transgenic Arabidopsis demonstrated significantly enhanced tolerances to 2,4,5-TCP and 2,4,6-TCP. Transgenic plants also exhibited a strikingly higher capacity to remove TCP from their media. This work indicates that Populus UGT overexpression in Arabidopsis may be an efficient method for phytoremoval and degradation of TCP. Our findings have the potential to provide a suitable remediation strategy for sites contaminated by TCP.

[Degradation of organic pollutants by photo-Fenton-like system with hematite]

Hematite was used as the catalyst to degrade the rhodamine B and 2,4-dichlorophenol under visible light irradiation. The effect of pH, catalyst dosage and dissolved iron on the degradation efficiency were studied. UV-Vis spectrophotometer, infrared spectrometer, fluorescence spectrophotometry and the chemical oxygen demand (COD) were employed to evaluate the mechanism during the degradation process. The result indicated that RhB could be degraded effectively by the Cata/RhB/H2O2/vis system. The optimum conditions were 0.6 g x L(-1) catalyst; pH 3.0 and 1.5 x 10(-3) mol x L(-1) H2O2. RhB was decomposed after 180 min and 56% of 2,4-DCP was degraded after 24 h by this syetem. Dissolved Fe ion was a relatively weak factor for the catalyst system. The catalyst had excellent stability with little loss of activity after 6 recycling experiments. The degradation process was dominated by the hydroxyl radical (*OH) generated in the heterogeneous Fenton-like system.

Removal efficiency and toxicity reduction of 4-chlorophenol with physical, chemical and biochemical methods

Chlorophenols are well-known priority pollutants and many different treatments have been assessed to facilitate their removal from industrial wastewater. However, an absolute and optimum solution still has to be practically implemented in an industrial setting. In this work, a series ofphysical, chemical and biochemical treatments have been systematically tested for the removal of 4-chlorophenol, and their results have been compared in order to determine the most effective treatment based on removal efficiency and residual by-product formation. Chemical treatments based on advanced oxidation processes (AOP) produced the best results on rate and extent of pollutant removal. The non-chemical technologies showed advantages in terms of complete (in the case of adsorption) or easy (enzymatic treatments) removal of toxic treatment by-products. The AOP methods led to the production of different photoproducts depending on the chosen treatment. Toxic products remained in most cases following treatment, though the toxicity level is significantly reduced with combination treatments. Among the treatments, a photochemical method combining UV, produced with a KrCl excilamp, and hydrogen peroxide achieved total removal of chlorophenol and all by-products and is considered the best treatment for chlorophenol removal.

Removal of chlorophenolic derivatives by soil isolated ascomycete of Paraconiothyrium variabile and studying the role of its extracellular laccase

The ability of Paraconiothyrium variabile, a laccase producing ascomycete recently isolated from soil, was studied to eliminate chlorophenol derivatives in submerged culture medium. Among the tested compounds, ρ-chlorophenol (ρ-CP) and pentachlorophenol (PCP) were found to have minimum and maximum toxic effects, respectively, on the growth of the microorganism and at the same time high and low bioelimination percentages. The fungal strain was able to remove 86% of ρ-CP (with initial concentration of 40 mg l(-1)) and 56% of 2,4-dichlorophenol (2,4-DCP; with same concentration as ρ-CP) after 9 days of incubation while no elimination was observed in the presence of 2,4,6-trichlorophenol (2,4,6-TCP) and PCP. Monitoring of laccase production level in the fermentation broth together with pollutant removal confirmed the key role of this copper-containing oxidase in chlorophenol derivatives elimination. The type of laccase inducer (guaiacol) and its final concentration (250 μM) and also initial pH of the fermentation broth (pH=5.5) in the elimination of ρ-CP increased the final removal yield from 86% to 94.3%.

Enhanced mitigation of para-chlorophenol using stratified activated carbon adsorption columns

The adsorptive removal of toxic para-chlorophenol using activated carbon adsorption columns is a proven effective engineering process. This paper examined the possibility to stratify an adsorbent bed into layers, in order to enhance the adsorption process performance in terms of increased column service time and adsorbent bed saturation. Four different types of fixed-bed adsorption columns are used and compared under the same operating conditions, but with the variation of column geometry and activated carbon particle size stratification. The Type 3 column - a cylindrical column with particle stratification packing, is found to be the most efficient choice, as the extent of column service time and adsorbent bed saturation are the largest. This could eventually decrease the frequency of adsorbent replacement/regeneration and hence reduce the operating cost of the fixed-bed adsorption process. The Homogeneous Surface Diffusion Model (HSDM) was applied successfully to describe the dynamic adsorption of para-chlorophenol onto Filtrasorb 400 (F400) activated carbon in different types of columns. The Redlich-Peterson isotherm model equation, an experimentally derived external mass transfer correlation and a constant surface diffusivity are used in the HSDM. The optimised surface diffusivity of para-chlorophenol is found to be 1.20E-8 cm(2)/s, which is in good agreement with other phenolics/F400 carbon diffusing systems in literature.

Sorption of chlorophenols onto fruit cuticles and potato periderm

To better understand the interaction mechanisms of plant surfaces with polar organic compounds, sorption of 4-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol by fruit cuticles (i.e., tomato, apple, and pepper), and potato tuber periderm were investigated. The roles of cuticular components (waxes, cutin, cutan and sugar) on sorption of chlorophenols are quantitatively compared. Cutin and waxes govern the sorption capacity of bulk apple cuticle by hydrophobic interactions. Potato periderm with highest sugar content exhibits the lowest sorption capability for the chlorophenols. With the increase of hydrophobicity (i.e., Kow ) of sorbate, the relative contribution of lipophilic components (wax, cutin and cutan) on total sorption increases, however, the ratios of Koc to Kow decreases due to increasing ionization degree of sorbates.

[Effects of pH value on the adsorption and degradation of 2, 4-DCP by nanoscale zero-valent iron]

To evaluate the effect of pH on the degradation of 2,4-DCP by zero-valent iron nanoparticles (with the particle size of 30-40 nm in diameter) samples were taken for TEM, SEM-EDX, and ICP-OES analysis and investigated on the particle morphology changes and 2,4-DCP removal under different pH conditions. It is shown that iron nanoparticles agglomerate from individual particles and tiny clusters into massive aggregate assemblies with their surfaces oxidized and coated by the needle-like rotten iron oxide products (FeOOH) in the degradation process, which will block up a further reaction of 2,4-DCP dechlorination, while the low pH value condition in acidic system can effectively suppress particles aggregation and the surface oxidation, although iron loss in the solid phase is somehow inevitable. Large quantity of Fe2+ ions soaked out from iron nanoparticles significantly promote 2,4-DCP removal by reduction, and the solution pH tends to go up in the reaction process. Acidic conditions facilitate 2,4-DCP dechlorination, and the removal efficiency became higher with the pH reduced, in which 90% of 2,4-DCP removal is reached in 24 h under the pH value of 3.

[Catalytic hydrodechlorination of 2,4-dichlorophenol over Pd/TiO2]

Pd/TiO2 catalysts were prepared by the deposition-precipitation and impregnation methods, and were further characterized by TEM, XRD and ICP-AES. The liquid catalytic hydrodechlorination of 2,4-dichlorophenol over the catalysts was investigated. It is demonstrated that despite catalyst prepared by deposition-precipitation method exhibits higher activity than that synthesized from impregnation method, both catalysts show good performance in hydrodechlorination process. When initial concentration of the reactant was 3.11 mmol x L(-1), pH was 12 and amount of catalyst used was 50 mg, hydrodechlorination of 2,4-dichlorophenol was completed within 45 min. Acidic condition facilitates hydrodechlorination process. The initial activity was not significantly influenced when the amount of catalyst used varied between 15-80 mg, which proves that mass transport limitation exerts little impact on hydrodechlorination reaction. Finally, the initial activity sharply enhanced with the increase of initial concentration of 2,4-dichlorophenol when the concentration was in the range of 0.62-3.11 mmo x L(-1) while it almost remained constant with further increasing the initial concentration. Therefore, the catalytic hydrodechlorination of 2,4-dichlorophenol over Pd/TiO2-DP follows the Langumuir-Hinshelwood model, indicating that the catalytic hydrodechlorination is controlled by 2,4-dichlorophenol adsorption.