Phenolic Wastewater Research Articles

Catalytic wet peroxide oxidation of phenolic wastewater on novel Cu/Mn-UiO-66@Al2O3 ceramic tube membrane catalysts

Novel Cu and Mn supported UiO-66@Al2O3 ceramic tube (UiO-66CT) membrane catalysts were synthesized by solvothermal method combined with secondary incipient wetness impregnation method and used for efficient catalytic wet peroxide oxidation (CWPO) of phenolic wastewater. Synthesis conditions of UiO-66CT were optimized by investigating the secondary soaking times and UiO-66 content. The experimental set-up based on a novel membrane reactor was designed for the catalytic activity evaluation of the ceramic tube catalysts. Results indicated that solvothermal time of 24 h and secondary soaking time of 1 h in the UiO-66 (12.8 g/L) can effectively shorten the synthesis time with a UiO-66 loading ratio about 2.0 wt% obtained. The SEM and EDS mapping results certificated the loading of UiO-66 in the macro-pores of the ceramic tube and the successfully supporting of Cu species on the UiO-66CT. The Cu-UiO-66CT catalysts exhibited good catalytic activity (Xphenol > 99% without toxic by-products detected in the final treated wastewater). By contrast, the Mn-UiO-66CT catalysts exhibited lower catalytic activity because of the fast decomposition of H2O2 on the MnO2 catalysts. The Cu-UiO-66CT catalyst showed excellent stability with phenol conversion (initial concentration of 500 ppm) kept above 90% after reused for 5 times. The immobilization of UiO-66 into the macro-pores of Al2O3 ceramic tube and the supporting of Cu species in the UiO-66CT can not only keep the high activity of MOFs catalysts but also enhance the stability of Cu-UiO-66 in the CWPO process. This research provides a promising strategy to solve the unstability of MOFs catalysts when used for the CWPO process of wastewaters.

Efficient Treatment of Phenol Wastewater by Catalytic Ozonation over Micron-Sized Hollow MgO Rods.

Phenol is a nocuous water pollutant that threatens human health and the ecological environment. CoOx-doped micron-sized hollow MgO rods were prepared for the treatment of phenol wastewater by catalytic ozonation. Magnesium sources, precipitants, initial precursor concentration, Co/Mg molar ratio, and catalyst calcination temperature were optimized to obtain the best catalysts. Prepared catalysts were also well characterized by various methods to analyze their structure and physical and chemical properties. In this process, CoOx/MgO with the largest large surface area (151.3 m3/g) showed the best catalytic performance (100 and 79.8% of phenol and chemical oxygen demand (COD) removal ratio, respectively). The hydrolysis of CoOx/MgO plays a positive role in the degradation of phenol. The catalytic mechanism of the degradation of O3 to free radicals over catalysts has been investigated by in situ electronic paramagnetic resonance (EPR). The catalyst can be reused at least five times without any activity decline. The prepared CoOx/MgO catalyst also showed excellent catalytic performance for removal and degradation of ciprofloxacin, norfloxacin, and salicylic acid.

Co-metabolism based adaptation of anaerobes to phenolic saline wastewater in a two-phase reactor enables efficient treatment and bioenergy recovery

Anaerobic biological treatment of saline phenolic wastewater has some limitations such as slow adaptation, low biodegradability, and salinity-derived washout of biomass, though this technology has some benefits in terms of bioenergy recovery, simplicity in operation, and economic rationality. Therefore, we propose a packed-bed circular baffled reactor (PB-CBR) along with a co-metabolism strategy for phenol adaptation at salinity level of 10 g-NaCl/L. Phenol and glucose were gradually increased and decreased to 0.9 and 1.0 g/L, respectively. Stable and efficient performance was achieved with > 99.9% phenol removal, ∼98% overall biodegradability, and ∼ 0.3 L CH4/gCOD. A sudden increase in phenol to 2 g/L was then examined, where phenol removal dropped to ∼ 19% after 30 d; after another 30 d, the removal was negligible even when phenol was decreased to 1.7 g/L. The compartment-wise analysis of PB-CBR showed that phases-separation, along all compartments, maintained the overall efficiency, particularly when facing salinity or phenol shocks; otherwise, earlier compartments achieve ∼ 95% of efficiency. The microbial community analysis showed that Corynebacteriaceae, Syntrophaceae, Kosmotogaceae, and Synergistaceae were key players in phenol-degradation. Using readily biodegradable co-substrate enhanced the biodiversity. Eventually, and according to a cost-benefit analysis, the present work offers a promising opportunity to treat phenol-based saline effluents in an efficient, sustainable, and affordable way.

Efficient Catalytic Degradation of Phenol with Phthalocyanine-Immobilized Reduced Graphene-Bacterial Cellulose Nanocomposite.

In this report, phthalocyanine (Pc)/reduced graphene (rG)/bacterial cellulose (BC) ternary nanocomposite, Pc-rGBC, was developed through the immobilization of Pc onto a reduced graphene–bacterial cellulose (rGBC) nanohybrid after the reduction of biosynthesized graphene oxide-bacterial cellulose (GOBC) with N2H4. Field emission scanning electron microscopy (FESEM) and Fourier transform infrared spectroscopy (FT-IR) were employed to monitor all of the functionalization processes. The Pc-rGBC nanocomposite was applied for the treatment of phenol wastewater. Thanks to the synergistic effect of BC and rG, Pc-rGBC had good adsorption capacity to phenol molecules, and the equilibrium adsorption data fitted well with the Freundlich model. When H2O2 was presented as an oxidant, phenol could rapidly be catalytically decomposed by the Pc-rGBC nanocomposite; the phenol degradation ratio was more than 90% within 90 min of catalytic oxidation, and the recycling experiment showed that the Pc-rGBC nanocomposite had excellent recycling performance in the consecutive treatment of phenol wastewater. The HPLC result showed that several organic acids, such as oxalic acid, maleic acid, fumaric acid, glutaric acid, and adipic acid, were formed during the reaction. The chemical oxygen demand (COD) result indicated that the formed organic acids could be further mineralized to CO2 and H2O, and the mineralization ratio was more than 80% when the catalytic reaction time was prolonged to 4 h. This work is of vital importance, in terms of both academic research and industrial practice, to the design of Pc-based functional materials and their application in environmental purification.

Influences of humic-rich natural materials on efficiencies of UASB reactor: A comparative study

Two humic-rich natural materials namely peat soil and lignite were supplemented in up-flow anaerobic sludge blanket (UASB) bioreactors for the treatment of phenolic wastewater. Peat soil improved phenol degradation and resistance to shock load; ultimately, contributing to higher COD removal efficiency (83.3%), methane production (4532 mL d-1), and better reactor’s stability. Accordingly, the amount of extracellular polymeric substances (EPS) and coenzyme F420 in sludge were increased to 1.3-fold and 2.5-fold, respectively, as compared to the control treatment. The addition of lignite however displayed poor phenol degradation and no effects on the secretion of EPS and F420. The peat soil significantly influenced the microbial community structures, whereas the effect of lignite was inconspicuous. In the presence of peat soil, the abundance of syntrophic fermentation bacteria and methanogens was significantly increased. This study illustrates the potential use of peat soil in UASB for the treatment of phenolic wastewaters.

Fabrication of MIL-53(Al) based composites from biomass activated carbon (AC) for efficient p-nitrophenol adsorption from aqueous solution

BackgroundThe aim of this study was to develop a class of novel MIL-53(Al) based composite with high phenolic compound adsorption capacity to treat highly toxic phenolic wastewater. MethodMIL-53(Al)@AC-x composites with different AC loading (x) were constructed by combining MIL-53(Al) with cheap biomass AC derived from cheap rice husk. The adsorbents were characterized by various methods. Significant findingsThe results showed that the surface area and pore volume of all MIL-53(Al)@AC-x composites increased remarkably, which are much higher than those of pristine AC and MIL-53(Al). The p-nitrophenol adsorption rate of MIL-53(Al)@AC-10 was higher than pristine MIL-53(Al) by 36%. The adsorption performance decreased in the order of MIL-53(Al)@AC-10 > MIL-53(Al)@AC-15 > MIL-53(Al)@AC-5 > MIL-53(Al). The maximum adsorption capacity for p-nitrophenol of MIL-53(Al)@AC-10 reached 250 mg.g−1, which are higher than the data reported in most literature. The fabrication of AC into MIL-53(Al) is a promising method to obtain a composite with high adsorption capacity and stability. The adsorption kinetics and isotherms fitted well with pseudo-second-order model and Langmiur model. The adsorption is mainly through the π-π and hydrogen bond interactions, and hydrophobic effect.

Application of a Combined Adsorption−Ozonation Process for Phenolic Wastewater Treatment in a Continuous Fixed-Bed Reactor

This work studied the removal of phenol from industrial effluents through catalytic ozonation in the presence of granular activated carbon in a continuous fixed-bed reactor. Phenol was chosen as model pollutant because of its environmental impact and high toxicity. Based on the evolution of total organic carbon (TOC) and phenol concentration, a kinetic model was proposed to study the effect of the operational variables on the combined adsorption–oxidation (Ad/Ox) process. The proposed three-phase model expressed the oxidation phenomena in the liquid and the adsorption and oxidation on the surface of the granular activated carbon in the form of two kinetic constants, k1 and k2 respectively. The interpretation of the constants allow to study the benefits and behaviour of the use of activated carbon during the ozonisation process under different conditions affecting adsorption, oxidation, and mass transfer. Additionally, the calculated kinetic parameters helped to explain the observed changes in treatment efficiency. The results showed that phenol would be completely removed at an effective contact time of 3.71 min, operating at an alkaline pH of 11.0 and an ozone gas concentration of 19.0 mg L−1. Under these conditions, a 97.0% decrease in the initial total organic carbon was observed.

Acclimatized activated sludge for enhanced phenolic wastewater treatment using pinewood biochar

Activated sludge acclimatization was assessed for pinewood biochar to study phenol biodegradation from synthetic effluents. The biochar was produced in a continuous pyrolysis system (auger reactor) at 525 °C and was characterized by scanning electron microscopy (SEM), X-ray diffraction, Fourier Transform Infrared (FTIR), elemental analysis, and particle size evaluation. Sludge acclimatization greatly facilitated the phenol biodegradation rate, especially in the presence of biochar. Specific biodegradation rates increased from 0.0017 (g phenol/g VSS/h) for as-received activated sludge to 0.0184 (g phenol/g VSS/h) and 0.041 (g phenol/g VSS/h) for activated sludge acclimatized without (control) and with biochar, respectively at pH ~6.5, for a phenol concentration of 250 mg/L and at room temperature (T = 15–18 °C). The results furthermore demonstrated the positive effects of biochar on microbial colonization and growth. The volatile suspended solids (VSS) increased from 1 g/L for as-received sludge to 1.97 g/L and 2.96 g/L for control and activated sludge acclimatized in the presence of biochar. The sludge volume index decreased from 108 (mL/g MLSS) to 60, while for the control it increased to 298 (mL/g MLSS). The system studied showed a high degree of stability and resistance to the load shock loading when the initial phenol concentration was increased from 250 to 500 mg/L.

Core–shell magnetic Fe3O4/CNC@MOF composites with peroxidase-like activity for colorimetric detection of phenol

Rapid and accurate detection of phenolic wastewater from industries has created global concern. Herein, core–shell magnetic cellulose nanocrystal supported MOF (Fe3O4/CNC@ZIF-8) with robust peroxidase-like activity was synthesized with tannic acid as modifier and bridge. The peroxidase-mimic catalytic activity of as-prepared Fe3O4/CNC@ZIF-8 was further investigated using o-phenylenediamine (OPD) as peroxidase substrates in the presence of H2O2. Moreover, the experimental conditions were optimized and the kinetic analysis results showed that Fe3O4/CNC@ZIF-8 had higher affinity towards both the substrate OPD and H2O2 than horseradish peroxidase (HRP). Finally, a phenol colorimetric assay with a linear range of 2–200 µM and a detection limit of 0.316 µM was constructed. The catalytic mechanism of Fe3O4/CNC@ZIF-8 with phenol was further investigated by fluorescence test and the generated ·OH was proved to act a crucial role to produce quinoid radicals. Additionally, the synthesized magnetic material had excellent stability and recyclability and ease to separation. These results suggest that the Fe3O4/CNC@ZIF-8 may be one of the promising candidates as peroxidase mimic for colorimetric detection of phenol.

Preparation of a three-dimensional porous PbO2-CNTs composite electrode and study of the degradation behavior of p-nitrophenol

In this study, a new type of porous PbO2-CNTs electrode was prepared by the oxygen bubble template method to remove the organic pollutant p-nitrophenol in water. The electrode microscopic morphology, phase composition and element composition were characterized by physical methods such as scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). According to linear scanning voltammetry (LSV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS), the 3D-PbO2-CNTs composite electrode shows a higher exchange current density, larger electrochemically active surface area and smaller charge transfer resistance than the 3D-PbO2 and flat-PbO2-CNT electrodes. The 3D-PbO2-CNTs composite electrode was applied to the degradation of p-nitrophenol, and the results indicate that it has the strongest ability to generate hydroxyl radicals and the best electrocatalytic degradation efficiency. The degradation process follows pseudo-first-order reaction kinetics, and the intermediate products were characterized using GC–MS and a degradation mechanism for p-nitrophenol was proposed. From measurements of the cell voltage for degrading simulated phenolic wastewater, it was found that the battery voltage for the 3D-PbO2-CNTs composite electrode is 3.52 V, which is lower than that obtained for the 3D-PbO2 (3.59 V) and flat-PbO2-CNTs (3.85 V) electrodes, indicating that the anode material is effective in reducing energy consumption. In general, the new 3D-PbO2-CNTs electrode has good application prospects in the field of degrading organic polluted wastewater.

Engineered defect-rich TiO2/g-C3N4 heterojunction: A visible light-driven photocatalyst for efficient degradation of phenolic wastewater

Photocatalytic technology has been considered as an effective way for pollutants removal. Considering that the nature of the photodegradation of pollutants is the free radical reaction on the surface of the catalyst, promoting the generation of free radicals is a direct and effective way to facilitate the mineralization of pollutants. Unfortunately, the shortcomings strongly limit its photocatalytic activity such as insufficient sunlight utilization, small catalytic surface and rapid recombination of charge. Here, a heterostructure of defect-rich TiO2 nanoparticles anchored in g-C3N4 was fabricated by a synchronous compound process. This heterostructure (4TiO2/g-C3N4) exhibits an enhanced visible light absorption due to its narrow band gap energy of 2.27 eV. Therefore, it possesses an outstanding photocatalytic activity for the degradation of phenol (1.63 × 102 μmol g−1 h−1), p-nitrophenol (1.15 × 102 μmol g−1 h−1), o-cresol (1.43 × 102 μmol g−1 h−1) and p-cresol (1.45 × 102 μmol g−1 h−1). The calculated quantum yields of 4TiO2/CN for pollutants degradation are 1.29 × 10−6 for phenol, 9.10 × 10−7 for p-nitrophenol, 1.14 × 10−6 for o-cresol and 1.15 × 10−6 for p-cresol, respectively. By utilizing the periodic topology of MOFs, this work provides an improved approach for constructing TiO2/g-C3N4 heterojunctions with enhanced degradation of robust organic pollutants.

Enhanced Photocatalytic Degradation of Phenol Using Urchin-Like ZnO Microrod-Reduced Graphene Oxide Composite under Visible-Light Irradiation

In this study, visible-light-driven ZnO microrod-rGO heterojunction composites were successfully synthesized via a facile and scalable hydrothermal process. The prepared photocatalyst heterojunction was examined using different techniques including XRD, SEM, FTIR, UV-Vis spectroscopy, and TGA to reveal their crystal phase, morphology, and other optical properties. The photocatalytic performance of the obtained ZnO-rGO composites was measured by the photodegradation of phenol under visible light illumination. The addition of graphene over the catalyst exhibited an enhanced photocatalytic activity for phenol degradation due to its high surface area and decreasing rate of electron-hole separation. Kinetic studies proved that the degradation of phenol process happened by following the pseudo-first-order kinetic model. The effective conditions for degradation of phenol using ZnO-rGO composite were 0.2 g L-1catalyst dose, pH -4, and initial concentration 20 ppm of phenol solution. Comparing with ZnO microrods, the heterojunction composite degraded the organic pollutants of phenol solution up to 84.2% of efficiency displaying the highest photocatalytic activity, whereas urchin-like ZnO catalyst exhibited much less photocatalytic activity for phenol degradation under visible light irradiation. This result envisages immense properties, showing a great potential industrial application for the removal of phenolic wastewater.

Improved separation performance of carbon nanotube hollow fiber membrane by peroxydisulfate activation

Membrane separation has been widely used to address the global water crisis, but is limited by the permselectivity trade-off. Herein, an effective strategy was adopted to overcome this drawback by integrating membrane separation with peroxydisulfate (PDS) activation on a carbon nanotube (CNT) hollow fiber membrane. During the phenolic wastewater treatment, the CNT hollow fiber membrane not only performed as the separation barrier, but also as the catalyst to activate PDS to degrade the micro-size phenol timely. Compared to the sole filtration (33%), the advanced oxidation functions (AOFs)-based membrane has a higher phenol removal rate (97%) under the optimal conditions: neutral condition (pH = 6), 0.5 mM PDS, and hydraulic retention time (HRT) of 39.6 s. The separation mechanism was confirmed to be the non-radical reaction pathways (electro-transfer, and 1O2) through radical quenching, electron paramagnetic resonance (EPR), linear sweep voltammetry (LSV), and open circuit potential model. Such results suggested this work exhibited a high promising prospect for the remediation of organic pollution by a CNT hollow fiber membrane with AOFs.

Process Optimization and Modeling of Phenol Adsorption onto Sludge-Based Activated Carbon Intercalated MgAlFe Ternary Layered Double Hydroxide Composite.

A sewage sludge-based activated carbon (SBAC) intercalated MgAlFe ternary layered double hydroxide (SBAC-MgAlFe-LDH) composite was synthesized via the coprecipitation method. The adsorptive performance of the composite for phenol uptake from the aqueous phase was evaluated via the response surface methodology (RSM) modeling technique. The SBAC-MgAlFe-LDH phenol uptake capacity data were well-fitted to reduced RSM cubic model (R2 = 0.995, R2-adjusted = 0.993, R2-predicted = 0.959 and p-values < 0.05). The optimum phenol adsorption onto the SBAC-MgAlFe-LDH was achieved at 35 °C, 125 mg/L phenol, and pH 6. Under the optimal phenol uptake conditions, pseudo-first-order and Avrami fractional-order models provided a better representation of the phenol uptake kinetic data, while the equilibrium data models’ fitting follows the order; Liu > Langmuir > Redlich–Peterson > Freundlich > Temkin. The phenol uptake mechanism was endothermic in nature and predominantly via a physisorption process (ΔG° = −5.33 to −5.77 kJ/mol) with the involvement of π–π interactions between the phenol molecules and the functionalities on the SBAC-LDH surface. The maximum uptake capacity (216.76 mg/g) of SBAC-MgAlFe-LDH was much higher than many other SBAC-based adsorbents. The improved uptake capacity of SBAC-LDH was attributed to the effective synergetic influence of SBAC-MgAlFe-LDH, which yielded abundant functionalized surface groups that favored higher aqueous phase uptake of phenol molecules. This study showcases the potential of SBAC-MgAlFe-LDH as an effective adsorbent material for remediation of phenolic wastewater

Zeolitic imidazolate frameworks in mixed matrix membranes for boosting phenol/water separation: Crystal evolution and preferential orientation

The treatment of phenolic wastewater has become a critical but challenging issue for growing concerns over human health and the environment. In this study, the highly permeable mixed matrix membranes (MMMs) were fabricated by embedding structure- and morphology-tailored zeolitic imidazolate frameworks (ZIFs) in poly(ether-block-amide) (PEBA) bulk for pervaporation (PV) separation of phenol/water mixture. The crystal evolution from rhombic dodecahedral ZIF-8 particles to anisotropic ZIF-L nanosheets (ZLNs) was achieved by varying precursor concentration in aqueous system, and the morphology of ZIFs was precisely adjusted. Using a spin-coating method, the horizontally-oriented ZLNs constructed a typical brick-and-mortar architecture in the polymer matrix, suggesting their excellent interfacial compatibility. The high aspect-ratio ZLNs created preferential pathways for phenol but limited water transport in the membrane. Notably, the ZLNs/PEBA MMMs exhibited ultra-high phenol permeance of 4.96 × 105 GPU and phenol/water selectivity of 32.5 in separation of 1000 ppm phenol aqueous solution at 60 °C, which surpassed the overall performance of other phenol-selective membranes. Besides, the presence of ZLNs endowed the MMMs with good thermal and mechanical properties, guaranteeing long-term stability in realistic conditions. These findings of regulating morphology and preferential orientation of two-dimensional metal-organic framework fillers might have significant implications in designing high-performance membranes for various applications.

Carbon- and metal-based mediators modulate anaerobic methanogenesis and phenol removal: Focusing on stimulatory and inhibitory mechanism

In this study, anaerobic batch experiments were conducted to investigate the effect of carbon-based (biochar) and metal-based (nanoscale zero-valent iron, NZVI and zero valent iron, ZVI) mediators on the AD process treating phenolic wastewater. Fresh apricot shell- and wood-derived biochar (BiocharA, BiocharB) could remove the phenol efficiently (77.1% and 86.2%), suggesting that biodegradation cooperated with adsorption had advantage in phenol removal. BiocharB, NZVI and ZVI enhanced the methane production by 17.6%, 23.7% and 23.2%, respectively. Apart from serving as carrier for microbial growth, BiocharB might promote the direct interspecies electron transfer (DIET) since the Anaerolineaceae/Clostridium sensu stricto, which have potential for DIET, were enriched. NZVI and ZVI added systems mainly enhanced the abundance of Clostridium sensu stricto (24.5%, 37.6%) and Methanosaeta. Interestingly, BiocharA inhibited the methanogenesis completely. An inhibitory mechanism was proposed: the exposure of absorbed microbes on the BiocharA to the highly concentrated phenol in biochar’ pores resulted in the inhibition of methanogens, especially for Methanosarcina. In conclusion, this study showed that suitable biochar (BiocharB) could serve as an alternative redox mediator for realizing simultaneously the efficient phenol removal and methane production.

Effect of the ratio ZnO: ZrO2 on the photocatalytic ability of phenol degradation in ZnO-ZrO2 nanocompsite materials

The ZnO-ZrO2 nanocompsite materials in the molar ratio (1:0; 1:1; 1:2; 2:1; 3:4; 4:3; 0:1) were prepared by a two-stage precipitation method with ultrasonic vibrations. The obtained ZnO-ZrO2 materials were characterized by XRD, SEM, UV-vis. XRD data identified phase of the ZnO and phase of ZrO2 in all obtained samples. The average crystallite size of the samples was between 18 to 30 nm. As UV-Vis spectra, the band gap of ZnO-ZrO2 composite (ZZ34R) is 3,06eV. The photocatalytic reactions confirmed that the nanocomposite sample showed higher photocatalytic activity than the pure oxides samples for the degradation phenol under 100W incandescent lamp. Among the prepared samples, the best sample for photocatalytic degration of phenol is the ZZ34R which the molar ratio ZnO:ZrO2 = 3:4 with 23% remaining phenol content after 300 minutes. The photodegradation phenol of sample with ultrasonic vibrations is higher than the sample without ultrasonic vibrations. This indicates that the materials are capable of treating phenol in wastewater.

Dual-functional biocatalytic membrane containing laccase-embedded metal-organic frameworks for detection and degradation of phenolic pollutant

In this work, a metal–organic framework material, zeolitic imidazolate framework-90 (ZIF-90), was firstly used to encapsulate laccase (LAC) and to prepare ZIF-90/LAC biocomposites. Afterward, the composites were combined with bacterial cellulose (BC) and carboxylated multi-walled carbon nanotubes (c-MWCNTs) by a facile method to achieve a novel cellulose membrane with biocatalytic function, displaying excellent detection and degradation properties towards phenolic pollutant. Notably, the membrane was directly employed as a biosensor electrode, and it exhibited a linear response to catechol from 20 to 400 μM with a detection limit of 1.86 µM (S/N = 3), as well as satisfactory selectivity, reproducibility, and stability. In addition, the biocatalytic membrane showed higher degradation efficiency towards catechol than pure LAC, and the catechol degradation efficiency of the membrane generally ranged from 93.4% to 82.1% for five cycles. Moreover, the membrane was successfully applied in enzyme membrane reactor (EMR), achieving satisfactory results. The novel membrane harbors a broad application prospect in the fields of real-time monitor and treatment of phenolic wastewater.

Quantitative detection of phenol in wastewater using square wave voltammetry with pre-concentration

Phenol is a common pollutant found in wastewater, and its allowable discharge limit is 0.5 parts-per-million (ppm). Therefore, it is critical to monitor phenol in the sub-ppm range with high sensitivity and a low limit of detection. Herein, we report a quantitative method for detecting phenol in industrial wastewater through square wave voltammetry (SWV), in which phenol is oxidized to phenoxyl radicals and then became catechol and hydroquinone for detection. By using this method, phenol in the sub-ppm range can be detected reliably over a wide pH range. The sensitivity can be further improved by using a pre-concentration step for phenol before scanning. The method has a limit of detection of 0.1 ppb for phenol. Finally, three graphite electrodes were applied as working, counter and reference electrodes, respectively, in a millifluidic device for continuous detection of phenol in industrial wastewater flowing at 300 μL/min. Because of its simplicity, the sensor can be mass-produced and deployed on a large scale to monitor phenol in industrial wastewater.

Comparative Study on Phenolic Wastewater Treatment by Advanced Electrochemical Oxidation Processes

Considering the direct and the indirect oxidation of AEOP's, the kinetic and therefore the reaction rate constant were significantly analyzed throughout the oxidation time. The phenol degradation efficiency has been investigated during the oxidation time with varied independent parameters like initial phenol concentration (100, 250,500) mg/L, applied current density (30, 50, 70) mAcm-2 and electrolyte circulation (6, 9, 12) L/hr. It was estimated that, for 180 min oxidation time, 70 mAcm-2 current density, 12 L/hr flowrate, and 100 mg/L initial phenol concentration, the direct anodic oxidation achieved phenol degradation efficiency of 74.4% with graphite and 83.7% with β-PbO2 anodes. Otherwise, the indirect oxidation at the same condition achieved phenol degradation efficiency of 88.9% with Fe anode and carbon felt cathode.