Amyloid-Templated Palladium Nanoparticles for Water Purification by Electroreduction.

Electrocatalysis offers great promise for water purification but is limited by low active area and high uncontrollability of electrocatalysts. To overcome these constraints, we propose hybrid bulk electrodes by synthesizing and binding a Pd nanocatalyst (nano-Pd) to the electrodes via amyloid fibrils (AFs). The AFs template is effective for controlling the nucleation, growth, and assembly of nano-Pd on the electrode. In addition, the three-dimensional hierarchically porous nanostructure of AFs is beneficial for loading high-density nano-Pd with a large active area. The novel hybrid cathodes exhibit superior electroreduction performance for the detoxification of hexavalent chromium (Cr6+ ), 4-chlorophenol, and trichloroacetic acid in wastewater and drinking water. This study provides a proof-of-concept design of an AFs-templated nano-Pd-based hybrid electrode, which constitutes a paradigm shift in electrocatalytic water purification, and broadens the horizon of its potential engineered applications.

Fabrication of carbonyl-functional hypercrosslinked polymers as solid-phase extraction sorbent for enrichment of chlorophenols from water, honey and beverage samples.

Three carbonyl-functional novel hypercrosslinked polymers (HCP-TPS, HCP-TPA, and HCP-TPP) were successfully fabricated through an one-step Friedel-Crafts acylation reaction by copolymerizing paraphthaloyl chloride with triphenylsilane, triphenylamine, and triphenylphosphine, respectively. The resultant HCPs contained plenty of carbonyl-functional groups. Among the series of such HCPs, HCP-TPS displayed the best adsorption capability to chlorophenols (CPs), and thus it was employed as solid-phase extraction (SPE) adsorbent for enrichment of chlorophenols from water, honey, and white peach beverage prior to determination by high-performance liquid chromatography. Under the optimal conditions, the detection limits of the method (S/N = 3) were 0.15-0.3 ng mL-1 for tap water and leak water, 2.5-6.0 ng g-1 for honey sample and 0.4-0.6 ng mL-1 for white peach beverage sample. The recoveries of CPs in the spiked water, honey samples, and white peach beverage were in the range of 89.0-108.4%, 81.4-118.2%, and 85.0-113.5%, respectively. This work provides a new strategy for constructing functionalized HCPs as efficient SPE adsorbents. In this work, three novel hypercrosslinked polymers (HCPs) were synthesized by the Friedel-Crafts alkylation reaction (paraphthaloyl chloride as the alkylating agent, triphenylsilane, triphenylamine, and triphenylphosphine as the aromatic units). Then, HCP-TPS was applied to soild-phase extraction sorbent for enrichment CPs from water, honey, and white peach beverage samples.

Benzoxazine Porous Organic Polymer as an Efficient Solid-Phase Extraction Adsorbent for the Enrichment of Chlorophenols from Water and Honey Samples.

Porous organic polymers have gained great research interest in the field of adsorption. A benzoxazine porous organic polymer (BoxPOP) constructed from p-phenylenediamine, 1,3,5-trihydroxybenzene and paraformaldehyde was fabricated and explored as an adsorbent for solid-phase extraction (SPE) of four chlorophenols from water and honey samples. Under the optimized SPE conditions, the response linearity for the analysis of the SPE extract of the chlorophenols by high performance liquid chromatography-diode array detector was observed in the range of 0.2-40.0 ng mL-1 for water samples and 5.0-400.0 ng g-1 for honey samples. The method detection limits of the analytes were 0.06-0.08 ng mL-1 for water samples and 1.5-2.0 ng g-1 for honey samples. The recoveries of the analytes from fortified water and honey samples ranged from 84.8 to 119.0% with the relative standard deviations below 8.4%. The results indicate that the prepared BoxPOP is an effective adsorbent for the chlorophenols. The established method provides an alternative approach for the determination of chlorophenols in real samples.

Microcrystalline cellulose/metal-organic framework hybrid as a sorbent for dispersive micro-solid phase extraction of chlorophenols in water samples.

In this study, the microcrystalline cellulose/metal-organic framework 199 hybrid (MCC/MOF-199) was applied as sorbent for the dispersive micro-solid phase-extraction (D-µSPE) of chlorophenols. The D-µSPE method combined with high-performance liquid chromatography- ultraviolet detection (HPLC-UV) was employed to determine of four chlorophenols including 2-chlorophenol (2-CP), 4-chlorophenol (4-CP), 2,3-dichlorophenol (2,3-DCP), and 2,5-dichlorophenol (2,5-DCP) in aqueous. The main parameters of the D-µSPE process that influence the extraction (i.e. the amount of sorbent, elution condition, extraction time, and pH) were investigated and optimized. Based on the outputs, the presence of MCC on the surface of MOF-199 leads to improve the properties of MOF-199 and the MCC/MOF-199 has the highest sorption capacity, durability, and porosity in comparison with MCC and MOF-199. According to the validation study at the optimized conditions, the linearity for the analytes was achieved in the range from 0.1 to 200 ng mL-1 for 2-CP and 4-CP and 0.15 to 200 ng mL-1 for 2,3-DCP and 2,5-DCP with correlation coefficients between 0.9928 and 0.9965. The limits of detection calculated at S/N=3 were in the range of 0.03-0.05 ng mL-1. Besides, the relative standard deviations (RSDs) for three spiking levels (0.2, 10,100 ng mL-1) do not exceed 6.8% and extraction recoveries are between 81.0% and 88.3%. Finally, the D-µSPE-HPLC-UV method was successfully applied to the analysis of CPs in real water samples (mineral, river and wastewater samples) with good recoveries (95.8 to 99.5%) and satisfactory precisions (RSD < 6.8%).

Preparation of phenylboronic acid based hypercrosslinked polymers for effective adsorption of chlorophenols.

Hypercrosslinked polymers (HCPs) have demonstrated effective adsorption capabilities because of their rich porosity and high specific surface area. However, the HCPs prepared with phenylboronic acid based compounds as monomers via Friedel-Crafts alkylation reaction have not been reported yet. Herein, four new HCPs with phenylboronic acid (PBA), 1,4-benzenediboronic acid, 4-hydroxyphenylboronic acid and 4-carboxyphenylboronic acid as the respective monomers were prepared for the first time. Their Brunner-Emmet-Teller surface areas were 909.1 m2 g-1, 71.9 m2 g-1, 39.8 m2 g-1 and 29.3 m2 g-1, respectively. The prepared HCP with PBA as the monomer (named as PBA-HCP) displayed the best adsorption capability for chlorophenols. Then, it was investigated as a SPE adsorbent for the extraction of some chlorophenols from water and honey-pomelo beverage samples prior to high performance liquid-phase chromatography with diode array detection. The established method had low limits of detection for the analytes in the range from 0.06 to 0.2 ng mL-1 for water samples and from 0.3 to 1.0 ng mL-1 for honey-pomelo beverage samples. The linear response for the analytes was in the range of 0.18-100.0 ng mL-1 for water samples and 0.9-100.0 ng mL-1 for honey-pomelo beverage samples. The method also had a good repeatability with the relative standard deviations less than 7.1% and a fairly good accuracy with the method recoveries falling between 80.0% and 120.0%. The adsorption capacities of the PBA-HCP for 2-chlorophenol, 3-chlorophenol, 2,3-dichlorophenol and 2,4-dichlorophenol were 21.7 mg g-1, 31.2 mg g-1, 77.1 mg g-1 and 82.1 mg g-1, respectively. The PBA-HCP also exhibited excellent extraction capabilities for some other compounds, especially for those that have more hydrogen bonding sites.

Monolithic mixed matrix membrane based on polyethersulfone/functionalized MWCNTs nanocomposite as an SPME fiber: Application to extract chlorophenols from human urine and serum samples followed by GC-ECD.

A monolithic mixed matrix membrane of functionalized multi-walled carbon nanotubes-polyethersulfone (MWCNT/PES) was prepared in a non-covalent approach and employed as an SPME fiber for extraction of chlorophenols (CPs). The proposed extraction method was followed by GC-ECD to determine the analytes. The influencing factors on the extraction efficiency such as pH, ionic strength, extraction and desorption temperature and time were studied. Under the selected conditions, calibration curves were linear over a wide concentration range from 0.005 to 1000 µgL-1 (r2 > 0.9961) for target analytes. In addition, the limits of detection (LOD) of the method were obtained in the range of 0.3-30 ng L-1. The relative standard deviation (RSD) for single fiber repeatability (n = 5) is from 1.4 to 4.6%. Fiber-to-fiber repeatability (n = 3) was also evaluated and the RSD is in the range of 1.3-6.3%. Applications of proposed fiber for extraction of CPs from the headspace of urine and serum samples were successfully investigated. The relative recovery in the biological samples spiked with different levels of CPs were in the range of 91.6-102.5%.

Biocomposites of polypyrrole, polyaniline and sodium alginate with cellulosic biomass: Adsorption-desorption, kinetics and thermodynamic studies for the removal of 2,4-dichlorophenol.

The biocomposites of polypyrrole (PPY), polyaniline (PANI) and sodium alginate (NaAlg) with cellulosic biomass barley husk (BH) were prepared and employed for the removal of 2,4-dichlorophenol (2,4-DCP) form aqueous media. The sorption of 2,4-DCP was studied using native and biocomposites (PPY/BH, PANI/BH and NaAlg/BH) as function of various process variables. The maximum sorption (qe, 7.55-24.57 mg/g) of 2,4-DCP was achieved in the range of 7-10 pH, 0.05 g composite dose, 25 mg/L initial concentration of 2,4-DCP and 120 min contact time at 30 °C. The FTIR analysis revealed the involvement of amino, hydroxyl and carboxylic groups for the binding of 2,4-DCP on the surface of biocomposites. The Freundlich and pseudo second order kinetics models best explained the 2,4-DCP adsorption on to the biocomposites. The ∆G, ∆H and ∆S parameters were also computed, which revealed the favorable and exothermic adsorption nature of 2,4-DCP. Presence of salts affected the 2,4-DCP adsorption negatively. HCl found to be efficient desorbing agent for 2,4-DCP from composites and up to 65.12% was eluted using 0.5 N solution. In view of promising efficiency, the biocomposites have potential to remove 2,4-DCP form industrial effluents.

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[FeIII/FeII], dpa[FeV/FeIII] or dpa[FeIV/FeII] 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 FeII. The active species generated in Fedpa/H2O2 system contained the iron-oxo species (dpaFeV = O or dpaIV = 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-, SO42-, NO3- and PO43-) 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.

Electronic Tongue Coupled to an Electrochemical Flow Reactor for Emerging Organic Contaminants Real Time Monitoring.

Triclosan, which is a bacteriostatic used in household items, has raised health concerns, because it might lead to antimicrobial resistance and endocrine disorders in organisms. The detection, identification, and monitoring of triclosan and its by-products (methyl triclosan, 2,4-Dichlorophenol and 2,4,6-Trichlorophenol) are a growing need in order to update current water treatments and enable the continuous supervision of the contamination plume. This work presents a customized electronic tongue prototype coupled to an electrochemical flow reactor, which aims to access the monitoring of triclosan and its derivative by-products in a real secondary effluent. An electronic tongue device, based on impedance measurements and polyethylenimine/poly(sodium 4-styrenesulfonate) layer-by-layer and TiO2, ZnO and TiO2/ZnO sputtering thin films, was developed and tested to track analyte degradation and allow for analyte detection and semi-quantification. A degradation pathway trend was observable by means of principal component analysis, being the sample separation, according to sampling time, explained by 77% the total variance in the first two components. A semi-quantitative electronic tongue was attained for triclosan and methyl-triclosan. For 2,4-Dichlorophenol and 2,4,6-Trichlorophenol, the best results were achieved with only a single sensor. Finally, working as multi-analyte quantification devices, the electronic tongues could provide information regarding the degradation kinetic and concentrations ranges in a dynamic removal treatment.

Ferrocene-based nanoporous organic polymer as solid-phase extraction sorbent for the extraction of chlorophenols from tap water, tea drink and peach juice samples.

Ferrocene-based nanoporous organic polymer (Fc-NOP) was used as solid-phase extraction (SPE) adsorbent and showed excellent adsorption capacity for chlorophenols (CPs) compared with commercial C18 and multi-walled carbon nanotubes. Then, a SPE method with Fc-NOP packed cartridge combined with HPLC-UV detection was developed to determine CPs in tap water, black tea drinks and peach juice samples. Under optimal conditions, the detection limits of the method measured at the signal to noise ratio of 3 (S/N = 3) were 0.04-0.06 ng mL-1 for tap water and 0.10-0.20 ng mL-1 for black tea drinks and peach juice samples. Satisfactory method recoveries were achieved in the range of 87.6-119% with relative standard deviations of 3.11-7.83%. Result proved that this method was a sensitive and efficient method for determination of trace CPs in foods. The extraction result for more other compounds confirmed that the developed method had a great application potential for analysis of other trace pollutants in food samples.

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.

Poly (Octadecyl Methacrylate-Co-Trimethylolpropane Trimethacrylate) Monolithic Column for Hydrophobic in-Tube Solid-Phase Microextraction of Chlorophenoxy Acid Herbicides.

Chlorophenoxy acid herbicides (CAHs), which are widely used on cereal crops, have become an important pollution source in grains. In this work, a highly hydrophobic poly (octadecyl methacrylate-co-trimethylolpropane trimethacrylate) [poly (OMA-co-TRIM)] monolithic column has been specially prepared for hydrophobic in-tube solid-phase microextraction (SPME) of CAHs in rice grains. Due to the hydrophobicity of CAHs in acid conditions, trace CAHs could be efficiently extracted by the prepared monolith with strong hydrophobic interaction. Several factors for online hydrophobic in-tube SPME, including the length of the monolithic column, ACN and trifluoroacetic acid percentage in the sampling solution, elution volume, and elution flow rate, were investigated with respect to the extraction efficiencies of CAHs. Under the optimized conditions, the limits of detection of the four CAHs fell in the range of 0.9-2.1 µg/kg. The calibration curves provided a wide linear range of 5-600 µg/kg and showed good linearity. The recoveries of this method ranged from 87.3% to 111.6%, with relative standard deviations less than 7.3%. Using this novel, highly hydrophobic poly (OMA-co-TRIM) monolith as sorbent, a simple and sensitive online in-tube SPME-HPLC method was proposed for analysis of CAHs residue in practical samples of rice grains.

Synthesis, characterization, and application of chemically interconnected carbon nanotube monolithic sorbents by photopolymerization in polypropylene caps.

A facile and convenient approach for the preparation of interconnected multiwalled carbon nanotube (MWCNT) monolithic sorbents in recycled plastic caps has been developed. The method, which was based on the photopolymerization of the individual MWCNTs via the formation of a W/O medium internal phase emulsion (40/60 w/w%), provides control over the size of pores, rigidity, and the mechanical stability of the final solid. Pluronic L121 was used as a surfactant containing the water phase inside it and, consequently, the organic and non-polar phase, in which the MWCNTs and the cross-linker were trapped, remained on the outside of the droplets. Optical microscopy and scanning electron microscopy (SEM) were employed to characterize the morphology of both the emulsions and the final solids, respectively. In addition, nitrogen intrusion porosimetry was performed in order to study how the specific surface area of the final monolithic solid changed (from 19.6 to 372.2 m2 g-1) with the variables involved in the polymerization step. To exemplify the great sorbent potential of the synthesized material, a colorimetric assay based on the retention of methylene blue within the interconnected MWCNT monolithic structure was carried out. Finally, following the positive results, the carbon nanotube-monolithic stirred caps were applied for the determination of chlorophenols in a biological matrix such as human urine, obtaining excellent recovery values (91-98%) and good precision (5.4-9.1%) under optimized extraction conditions. Graphical abstract.

Organic-inorganic nanocomposites fabricated via functional ionic liquid as the bridging agent for Laccase immobilization and its application in 2,4-dichlorophenol removal.

In this study, organic-inorganic nanocomposite including mesoporous silica SBA-15 and chitosan was combined using carboxyl-functionalized ionic liquid as the bridging agent (SBA-CIL-CS), and which was characterized by scanning electron microscope, Fourier transform infrared spectroscopy, thermogravimetric analysis, and nitrogen adsorption-desorption isotherms. Thus prepared nanocomposite was applied to laccase immobilization via physical adsorption (SBA-CIL-CS-Lac) and utilized in 2,4-dichlorophenol (2,4-DCP) removal for the first time. SBA-CIL-CS-Lac showed relatively high immobilization efficiency, activity retention (75.3%), pH stability and storage stability. Kinetic experiment showed SBA-CIL-CS-Lac had the eminent affinity to the substrate. Circular dichroism and fluorescence analysis verified the active conformation of SBA-CIL-CS-Lac was maintained well to keep its enzymatic activity. Compared with the previous methods, SBA-CIL-CS-Lac exhibited prominent catalytic efficiency and reusability as well as pH and temperature stability for 2,4-DCP removal. The removal rate of SBA-CIL-CS-Lac for 2,4-DCP could be up to ˜90% after 35 h. Moreover, 58.8% removal rate could be retained after five operation runs. These results indicated that organic-inorganic nanocomposite SBA-CIL-CS was an ideal support for enzyme immobilization.

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.

Bio-electrodegradation of 2,4,6-Trichlorophenol by mixed microbial culture in dual chambered microbial fuel cells.

2,4,6-Trichlorophenol (TCP) was bioelectrochemically treated in anodic and cathodic compartments of two identical dual chambered microbial fuel cells MFC-A and MFC-B under anaerobic and aerobic conditions, respectively, and energy was recovered in the form of electricity. It was observed that MFC-B with bio-cathodic treatment of TCP outcompeted the MFC-A with bio-anodic treatment. The maximum power density for MFC-A with bio-anode was found to be 446.76 mW/m2 while for MFC-B with bio-cathode it was 1059.58 mW/m2. The MFC-B consistently showed higher coulombic efficiency, power density and chemical oxygen demand removal efficiency indicating the better performance of the MFC-B as compared to the MFC-A. Scanning electron micrograph also confirmed better accumulation of microbes on the anode of MFC-B and hence its better performance in terms of energy recovery. Some major genera present in the microbial community were quantified using quantitative real-time polymerase chain reaction technique. It also confirmed the dominance of electroactive species in the bio-anodic sludge of MFC-B over the bio-anodic sludge of MFC-A. Cyclic voltammogram also asserted better electrochemical activity of the bio-cathode in the treatment of chlorinated phenol toxicants in MFC-B system. The study shows that MFC can be a viable option in treatment of recalcitrant chemical compounds like TCP with the generation of energy in the form of electrical power.

Porous magnetic resin-g-chitosan beads for adsorptive removal of phenolic compounds.

In this study, porous magnetic resin grafted chitosan (R-g-Ch) beads were prepared for removal of 4-chlorophenol and phenol from aqueous solutions. The R-g-Ch beads were characterized by vibrating sample magnetometer, Fourier-transform infrared spectroscopy, scanning electron microscopy and thermogravimetry methods. The removal of the phenolic compounds was optimized by varying the experimental conditions. Results herein are well fitted to the pseudo-second order kinetic and Langmuir isotherm. The maximum adsorption capacity of phenol and 4-chlorophenol were found to be 188.6 and 99 mg/g, respectively. The thermodynamic studies suggested that the adsorption process was exothermic, irreversible and feasible within the range of 298-318 K.

Response Surface Methodology of Pre-Concentration of Chorophenols from Seawater Samples by Molecularly Imprinted Stir Bar Sorptive Extraction Combined with HPLC: Box-Behnken Design.

A novel molecularly imprinted polymer coated stir bar was prepared using 2-chlorophenol (2-CP) as template molecule and used for selective extraction of phenolic compounds including chlorophenols (CPs) directly from seawater samples. Various parameters affecting extraction have been evaluated using one variable-at-a-time and Box-Behnken design. A three-level Box-Behnken experimental design by six factors, which combined the response surface methodology, was used to optimize the selective extraction of the CPs. Six independent variables, including the absorption and desorption times (ranging from 15 to 25 min), stirring speed (ranging from 550 to 650 rpm), pH of solution (ranging from 4.0 to 6.0), amount of NaCl (ranging from 0.30 to 0.40 mol/L) and temperature of extraction process (ranging from 40 to 50°C) were coded as A, B, C, D, E and F at three various levels (-1, 0 and 1). Under the optimum conditions, the detection limits calculated were 0.17, 0.33 and 0.38 µg/L, respectively, for 2-CP, 2,4-dichlorophenol and 2,4,6-trichlorophenol. The linear ranges of method were 1.0-100.0 µg/L for all CPs studied. This method was employed for the direct extraction and determination of three CPs in seawater samples.

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.