Phenol Removal Rate Research Articles

Removal of chemical and microbial water pollutants by cold plasma combined with Ag/TiO2-rGO nanoparticles

This study aimed to investigate the synergistic effect of the cold atmospheric plasma (CAP) and heterogeneous photocatalytic processes in an aqueous solution to enhance water purification efficacy and reduce the energy cost required by CAP. 0.1% Ag/TiO2-reduced graphene oxide (rGO) nanoparticles (NPs) photo-composite were prepared and fully characterized. Data showed that Ag nanoparticles and the rGO play an important role in increasing the efficiency of the whole treatment process and the photo-composite (0.1% Ag/TiO2-1% rGO at 400 °C) revealed the highest phenol removal rate with excellent reusability. Also, complete inactivation (~ 5log10 reduction) of both E. coli and S. aureus by NPs was observed without CAP exposure, whereas a minimal effect (0.1–0.5 log10) on viruses (Adenovirus (AdV), rotavirus, and ɸX174) was observed after 10 min incubation. Interestingly, the photocatalytic virus inactivation test was promising, as it resulted in > 4.7log10 reduction of AdV at 2 min treatment, whereas < 1log10 could be reduced using only CAP at the same treatment time. Accordingly, we believe that this work could provide new insights into how the synergy between CAP and 0.1% Ag/TiO2-1% rGO photo-composite in aqueous media imposes a great potential for environmental applications, such as water purification and microbial inactivation.

Efficient treatment of phenol wastewater by co-culture of Chlorella vulgaris and Candida tropicalis

The increased water contamination with phenolic compounds has emerged as an important environmental concern due to their considerable ecotoxicities and associated health issues. Here, a co-cultured microalgae/microorganism system, Chlorella vulgaris and Candida tropicalis, has been developed for efficient treatment of phenol and microalgal biomass accumulation. Our results show that the C. vulgaris and C. tropicalis co-culture system can achieve the highest phenol removal rate as 233.3 mg/L/d and the total chlorophyll accumulation as 23.0 mg/L with the initial volume ratio of C. vulgaris and C. tropicalis at 1:3, which are 5.2 and 7.2 times higher than that of C. vulgaris monoculture respectively. The maximum phenol removal ability of the constructed co-culture system was tested as 1500 mg/L within 6 days. Transcriptome analysis suggested that the co-cultured C. vulgaris/C. tropicalis can utilize phenol as carbon source for its growth and metabolism, and the removal mechanism of phenol was mainly due to the biodegradation process other than bio-absorption. Simulated wastewater experiment shows that the co-culture system can not only efficiently remove the phenol compounds, also can significantly decrease the ammonia nitrogen (NH3−N), total phosphorus (TP) and chemical oxygen demand (COD) of wastewater with removal efficiencies as high as 93%, 92%, 80% and 100%, respectively. Our work provided a promising way for the treatment of phenol compounds and then promoting the growth of C. vulgaris using phenol containing wastewater.

Heteroatoms-doped biochar derived from deciduous resource as persulfate catalysts for efficient degradation of phenol

Phenol, as the representative recalcitrant aromatic organic compounds (AOCs) in wastewater, has been listed as the priority pollutant due to its toxicity to organisms and ecosystem. Therefore, the exploration of efficient and practical technology for phenol elimination from wastewater has become an important research topic. Peroxymonosulfate-based advanced oxidation processes (PMS-based AOPs) have been developed to be an efficient phenol-degrading strategy. Thereinto, the development of high-performance and cost-effective catalyst is the crux of degrading pollutants in PMS-based AOPs. In this study, the ubiquitous ginkgo deciduous resource is expected to convert into low-cost heteroatoms self-doped biochar to activate PMS for the removal of phenol. The removal rate of phenol (10 mg/L) achieved 90% within 60 min in pH of 6 by using 1.0 mmol/L of PMS and 0.5 g/L of catalyst. The phenol degradation in the catalytic process was accomplished via •OH, SO4• −, 1O2, and electron-transfer. On the basis of the correlation analysis, oxygen functional groups and sulfur functional groups were considered as the active sites that may be the most relevant to removal efficiency. This study proposed a facile method for converting deciduous waste resource into catalyst for triggering efficient catalytic oxidation process to degrade organic pollutants.

Polyhydroxyalkanoate Pellets as Novel Immobilization Medium for Phenol Biodegradation by Activated Sludge

Biofilm enhances the performances of biological wastewater treatment systems. This study aimed to investigate the feasibility of using biodegradable polyhydroxyalkanoate (PHA) pellets as novel biofilm carrier for phenol biodegradation. Two identical laboratory-scale reactors were operated with fill, react, settle, draw and idle periods in the ratio of 2:12:2:1:7 for a 24-h cycle. One reactor was supplemented with 2% (v/v) of PHA pellet and operated as sequencing batch biofilm reactor (SBBR), whereas the other reactor was operated as sequencing batch reactor (SBR) and used as the control reactor. The performances of SBBR and SBR in degrading phenol were studied at three phases with the introduction of 300, 500 and 1000 mg L-1 phenol, respectively. The removal of phenol was found best described using zero-order kinetics, with R2 &gt; 0.97. At all phases, the phenol removal rate during react period for SBBR (7.30 ± 0.55 to 9.33 ± 1.06 mg L-1 min-1) was found higher compared to those for SBR (4.28 ± 0.66 to 8.35 ± 0.68 mg L-1 min-1), with significance difference observed at low phenol concentration. Whereas for chemical oxygen demand biodegradation kinetics, SBRR exhibited significantly higher rate compared to SBR at all phases. From the scanning electron microscopy image, the attachment of activated sludge onto PHA pellet was observed. The results indicated the potential of PHA serving as alternative biofilm carrier in biofilm process.

Application of pier waste sludge for catalytic activation of proxy-monosulfate and phenol elimination from a petrochemical wastewater.

This investigation aimed to remove phenol from real wastewater (taken from a petrochemical company) by activating peroxy-monosulfate (PMS) using catalysts extracted from pier waste sludge. The physical and chemical properties of the catalyst were evaluated by FE-SEM/EDS, XRD, FTIR, and TGA/DTG tests. The functional groups of O-H, C-H, CO32-, C-H, C-O, N-H, and C-N were identified on the catalyst surface. Also, the crystallinity of the catalyst before and after reaction with petrochemical wastewater was 103.4 nm and 55.8 nm, respectively. Operational parameters of pH (3-9), catalyst dose (0-100 mg/L), phenol concentration (50-250 mg/L), and PMS concentration (0-250 mg/L) were tested to remove phenol. The highest phenol removal rate (94%) was obtained at pH=3, catalyst dose of 80 mg/L, phenol concentration of 50 mg/L, PMS concentration of 150 mg/L, and contact time of 150 min. Phenol decomposition in petrochemical wastewater followed the first-order kinetics (k> 0.008 min-1, R2> 0.94). Changes in pH factor were very effective on phenol removal efficiency, and maximum efficiency (≈83%) was achieved in pH 3. The catalyst stability test was performed for up to five cycles, and phenol removal in the fifth cycle was reduced to 42%. Also, the energy consumption in this study was 77.69 kW h/m3. According to the results, the pier waste sludge catalyst/PMS system is a critical process for eliminating phenol from petrochemical wastewater.

Efficient biodegradation of phenol at high concentrations by Acinetobacter biofilm at extremely short hydraulic retention times

Efficient biofilm-forming bacteria are crucial for biofilm wastewater treatment reactors. Nevertheless, finding a suitable bacterial culture with high biodegradation capabilities and ability to grow a stable and effective biofilm that can survive the reactor environment poses a challenge. Here, we present a newly isolated bacterium Acinetobacter EMY that exhibits excellent growth rate, biofilm formation capability, and ability to biodegrade phenol at high concentrations. The phenol degradation rate of Acinetobacter EMY immobilized on polyethylene biocarriers in batch and continuous moving bed bioreactors (MBBRs) treated with phenol as the sole carbon source was significantly higher than that of a bacterial suspension. The continuous MBBR demonstrated impressive phenol removal rates (8.11 and 10.95 kg/m3/d at extremely short hydraulic retention times of 0.5 and 0.25 h, respectively). The phenol removal efficacy was 100% for hydraulic retention times of ≥0.5 h and 67.25% at 0.25 h. The Acinetobacter EMY biofilm batch bioreactor loaded with 165, 330, 665, 1150, and 2100 mg/L phenol achieved the maximum biodegradation rates of 7.65, 7.03, 9.15, 4.48, and 4.16 kg/m3/d, respectively. The new Acinetobacter EMY isolate showed enhanced phenol biodegradation capabilities compared with other isolates in similar studies. Chemical oxygen demand measurements proved that Acinetobacter EMY also consumed the intermediates of phenol degradation. In summary, Acinetobacter EMY is a promising bacterium for use in MBBR systems that treat water containing phenols.

Biodegradation Kinetics of Phenol and 4-Chlorophenol in the Presence of Sodium Salicylate in Batch and Chemostat Systems

The biodegradation of phenol, sodium salicylate (SA), and 4-chlorophenol (4-CP) by Pseudomonas putida (P. putida) was evaluated by batch and chemostat experiments in single and binary substrate systems. The Haldane kinetics model for cell growth was chosen to describe the batch kinetic behavior to determine kinetic parameters in the single or binary substrates system. In the single phenol and SA system, the kinetic constants of μm,P = 0.423 h−1, μm,A = 0.247 h−1, KS,P = 48.1 mg/L, KS,A = 71.7 mg/L, KI,P = 272.5 mg/L, and KI,A = 3178.2 mg/L were evaluated. Experimental results indicate that SA was degraded more rapidly by P. putida cells compared to phenol because SA has a much larger KI value than phenol, which makes the cells less sensitive to substrate inhibition even though the μm,P value is larger compared to μm,A. The ratio of inhibition of phenol degradation due to the presence of SA (IA1) to the inhibition of SA degradation due to the presence of phenol (IA2) is 2.3, indicating that SA has a higher uncompetitive inhibition on phenol biodegradation compared to that of phenol on SA biodegradation in the binary substrate system. In the ternary substrate system, the time required for the complete degradation of SA and phenol was 14 and 11.5 d and an approximately 90% removal efficiency for 4-CP was achieved within 14 d. In the chemostat system, the removal rates of phenol and SA were 96.6 and 97.0%, while those of SA and 4-CP were 91.4% and 95.2%, respectively. The model prediction agreed satisfactorily with the experimental results of the chemostat system.

Controllable high-efficiency transformation of H2O2 to reactive oxygen species via electroactivation of Ti-peroxo complexes

In this paper, TiO2/ACF anode was prepared via “ship-in-a-bottle” method. TiO2 modification could dramatically improve the H2O2 adsorption capacity of anode. Four activation potentials (1.83, 2.04, 2.07 and 2.10 V) of Ti-peroxo complexes on TiO2/ACF surface were found through cyclic voltammetry method, which might correlate to the decompositions of complexes with different configurations. The generation and quenching of reactive oxygen species (ROS) on TiO2/ACF anode at different working voltages were studied, indicating that •O2– was the main species when voltage was below 2 V while •OH was the main species when voltage was above 2 V. Adding H2O2 in batches showed great advantages in ROS generation and hence phenol degradation, compared with one-time addition strategy. The equilibrium adsorption amount of H2O2 on TiO2/ACF was the optimal addition amount for each batch. The TiO2/ACF anode exhibited the best performance at 6 V with the phenol removal rate of 99.2 %. The experimental results could offer a novel method to treat refractory wastewater efficiently and economically.

Self-cleaning ceramic membranes coated with low crystalline Fe2O3@CMWCNTs for highly efficient photo-Fenton removal of aromatic compounds

Nanomaterials coated ceramic membranes have become one of the most promising methods to degrade organic pollution. In this study, low crystalline metal nanomaterials were coated on ceramic membranes for the first time. This research fabricated a ceramic membrane with low crystalline Fe2O3@carboxylic multi-walled carbon nanotubes (CMWCNTs) and evaluated its aromatic compounds-degrading ability and self-cleaning ability. The coated membrane demonstrated an excellent removal rate (＞90%) of phenol and atrazine in 120 min’s continuous flow filtration via surface photo-Fenton reaction. Quenching experiments reveal the active substances of the reaction system were singlet oxygen (1O2) and a small amount of hydroxyl radical (·OH). With humic acid (HA) and bovine serum albumin (BSA) as model pollutants, the polluted membranes recovered 84.4% and 77.0% flux through the photo-Fenton reaction respectively, which proved the self-cleaning performance of the coated membrane. After 6 cycles, an average degradation efficiency of 92% for phenol was maintained in continuous flow filtration. These results indicated the efficacy of the photo-Fenton coupling coated membrane for treating organically polluted water and its relevance for the design and application of future photo-Fenton membrane filtration system.

Engineering of Band Structure of Bismuth Selenide Ultrathin Nanosheets as Multifunctional Material for Photocatalytic Application

AbstractN‐substituted bismuth selenide (BSN) material is synthesized by a one‐step solvothermal route and used for the photocatalytic application. As‐prepared BSN consists of ultrathin nanosheets and has a quasi hexagonal morphology. The results show the superior performance of BSN‐2 for degradation of multi‐pollutants and the ciprofloxacin and phenol removal rates reach 88.8 and 83.6%, respectively, under irradiation of simulated solar for 2 h, which is much higher than those over pristine bismuth selenide. The significant improvement of photocatalytic performance is attributed to ultrathin nanosheets structure and N introduction that contribute to the inhibition of photoelectron‐hole pair recombination and the enhancement of light absorption. The possible mechanism is proposed based on characterization and theoretical calculation of the energy band structure. The results indicate that BSN‐2 is a high‐efficient photocatalyst for the removal of multi‐organic pollutants in wastewater and this research provides a simple strategy for reasonable design and synthesis of Bi‐based materials for environmental remediation.

Oxygen vacancies-enriched and porous hierarchical structures of ZnO microspheres with improved photocatalytic performance

Controlling the morphology and surface defects is an effective strategy for enhancing photocatalytic performance. In this paper, we have successfully prepared zinc oxide (ZnO) microspheres with oxygen vacancies-enriched and porous hierarchical structures by hydrothermal annealing. The porous hierarchical structure of the ZnO microspheres was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and other analytical techniques, and their photocatalytic properties were studied by the decomposition of methylene blue, tetracycline and phenol in condition simulated sunlight. The porous hierarchical structure of ZnO–SO42- microspheres showed higher photocatalytic activity compared to ZnO–Cl- and ZnO–NO3- (ZnO from different sources of zinc as ZnO-X, where X is SO42−, Cl− and NO3−, respectively.). Under sunlight, the photocatalytic removal rates of methylene blue, tetracycline and phenol by ZnO–SO42- were 98%, 100% and 83%, respectively. Meanwhile, the photoelectrochemical tests showed that the porous hierarchical structures of ZnO–SO42- microspheres had the best photocurrent response and the lowest charge transfer resistance. After five cycles of photocatalytic degradation of phenol, the synthesized ZnO microspheres also showed good durability and stability. In addition, superoxide radicals (•O2−) and hydroxyl radicals (•OH) were identified as the active species by the trapping experiments. This study showed that the improvement of photocatalytic performance of ZnO microspheres could be owing to abundant oxygen vacancies and the porous hierarchical structures.

Simulation and dynamic control of removal phenols from coal gasification wastewater by synergistic extraction

Coal chemical wastewater has a high organic content and poor biochemical performance. The phenolic substances in wastewater cannot meet the discharge standard, which damages the environment and endangers human health. In this study, to remove phenolic substances from coal chemical wastewater, a process of dephenol treatment was studied, which integrated the selection of extractant, process simulation, and dynamic control. In view of the low removal rate of polyphenols, a new extraction solvent was designed to reduce the polyphenol content. The four synergistic extraction solvents of Mesityl oxide + n-pentanol, MPK + n-pentanol, MIPK + n-pentanol, and MIBK + n-pentanol were optimized and calculated by molecular simulation, and electrostatic potential analysis, NBO analysis, interaction energy analysis, and non-covalent interaction analysis were used to elucidate the nature of the synergy between molecules. The results show that the interaction energy of mesityl oxide + n-pentanol + phenol and mesityl oxide + n-pentanol + catechol is higher than other solvents, which are − 46.13 kJ mol−1 and − 40.36 kJ mol−1, respectively. The difference of the interaction energy of mesityl oxide + n-pentanol + phenol and mesityl oxide + n-pentanol + water is − 14.30 kJ mol−1 and that of mesityl oxide + n-pentanol + catechol and mesityl oxide + n-pentanol + water is −8.53 kJ mol−1, which shows the superiority of mesityl oxide + n-pentanol for the extraction and recovery of phenols. The results showed that the extraction performance of the synergistic extractants is stronger than that of the single extractants. Aspen Plus software was used to simulate the extraction and recovery of phenols with mesityl oxide + n-pentanol as the extractant, and the operation parameters were optimized with the smallest total annual cost as the target. The amount of fresh extractant added is only 0.95 kg/h, and the removal rate of phenol and catechol reached 99.95% and 97.97%, respectively, and the total phenol concentration dropped from 6499 mg/L to 56 mg/L. In addition, the little difference between experimental data and simulation results also indicates that mesityl oxide + n-pentanol is an effective extraction solvent. Finally, Aspen dynamic simulation investigated the dynamic response results under disturbances in the feed flow rate and feed component, and the results showed that the process operation under disturbances can quickly restore a stable value. The control scheme is effective.

Activation of peroxydisulfate by ball-milled α-FeOOH/biochar composite for phenol removal: Component contribution and internal mechanisms

Persulfate-based advanced oxidation process is considered as a promising technology for the degradation of phenol, where efficient, cost effective, and green methods with high peroxydisulfate (PS) activation capacity is of increasing demand. In this work, an in-situ liquid phase precipitation combined with ball milling method was applied for the synthesized of α-FeOOH/biochar, as be the PS activator for phenol degradation. Results showed that the ball-milled α-FeOOH and red pine wood biochar prepared at 700 °C (BM-α-FeOOH/PBC700) exhibited the highest catalytic property with PS for phenol oxidation (a phenol removal rate of 100%), compared with the BM-α-FeOOH (16.0%) and BMPBC700 (66.3%). The presence of intermediate products such as hydroquinone and catechol, and total organic carbon (TOC) removal rate (88.9%) proved the oxidation of phenol in the BM-α-FeOOH/PBC700+PS system. The characterization results showed that the functional groups (e.g., CO, C–O, Fe–O, and Si–O), the dissolved organic matter (DOM) in biochar, the loading of Fe element, and higher degree of graphitization and defect structures, contributed to the activation of PS to form free radicals (i.e., SO4·−, ·OH, ·O2−, and hVB+) for phenol oxidation, of which, SO4·− and ·OH account for 72.1% of the phenol removal rate. The specific contribution to the PS activation for phenol oxidation by each part of the materials was calculated based on the “whole to part” experiment. The contribution of DOM, acid-soluble substance, and carbon matrix and basal part in BM-α-FeOOH/PBC700 were 6.0%, 40.9%, and 53.1%, respectively. The reusability experiments of BM-α-FeOOH/PBC700 demonstrated that the composite was relatively stable after four cycles of reuse. Among three co-existing anions (NO3−, Cl−, and HCO3−), HCO3− played the most significant inhibition effects on phenol removal through reducing the phenol removal rate from 89.6% to 77.9%. This work provides guidance for the design of high active and stable carbon materials that activate PS to remove phenol.

Degradation Effect of UV Synergistic Biomass Activated Carbon Materials on Phenol Pollutants in Water

The purpose of the study is to purify the water containing phenol pollutants. The degradation effect of phenol pollutants in water is studied through the combined action of UV and biomass-activated carbon. First, the phenol solution is prepared in the laboratory to simulate the polluted water. Second, the phenol adsorption effects of UV synergistic biomass activated carbon, biomass activated carbon and ordinary industrial activated carbon under different influencing factors are compared by experiments. Finally, the results are analyzed and the conclusions are drawn. The results show that the UV synergistic biomass activated carbon has the strongest degradation ability for phenol, and the highest removal rate is 66.5% when the shaking time is 65 minutes. The adsorption ability of the industrial activated carbon for phenol is the worst. When the initial concentration of phenol is 25mg/L, the maximum phenol removal rate is 96.8%. The maximum phenol removal rate of biomass activa ted carbon appears in the initial concentration of phenol and the phenol removal rate is 60 mg/L. The reaction temperature has little effect on the phenol removal rate of UV synergistic biomass activated carbon and biomass activated carbon. The phenol removal ability of UV synergistic biomass activated carbon and biomass activated carbon reaches the highest when the dosage of activated carbon is 2.0 g, and the rates are 96.4% and 91.1%, respectively. When the pH of the solution is 7, the removal rate of UV synergistic biomass activated carbon reaches a maximum of 97%. When the pH of the solution is 6, the removal rate of biomass-activated carbon reaches the maximum. When the pH of the ordinary industrial activated carbon is 7, the removal rate is the maximum. Due to different influencing factors, UV synergistic biomass activated carbon has the strongest phenol degradation ability. This study provides a reference for the purification of polluted water.

Enhancing the stability and electrocatalytic activity of Ti-based PbO2 anodes by introduction of an arc-sprayed TiN interlayer

Ti/TiN/PbO2 electrodes were prepared using an arc-sprayed TiN interlayer on Ti substrates, followed by the anodic electrodeposition of a PbO2 catalytic surface layer on it. In order to investigate the positive effect of the TiN interlayer on the stability and electrocatalytic activity of the anodes, microstructural, surface roughness, adhesion evaluation, accelerated life and electrochemical performance tests and electrooxidation experiments of phenol simulated wastewater were conducted and compared with Ti/PbO2 anodes without the interlayer. The experimental results demonstrated that the arc-sprayed TiN interlayer with a thickness of 140–180 μm had a higher surface roughness and hardness than that of its titanium substrate. The coatings forming the electrode were firmly bonded to the substrate. The conductivity of the Ti-based PbO2 anode containing the TiN interlayer was significantly improved. The PbO2 surface coating achieved a faster deposition rate and finer grains, which produce a number of anode active sites and the electrocatalytic performance was boosted with a removal rate of phenol of up to 85.2%, which was higher than that of Ti/PbO2 by 30.6%. Simultaneously, the anode stability was also significantly enhanced, i.e., the Ti/TiN/PbO2 anode constructed by introducing the TiN interlayer exhibited excellent stability and electrocatalytic performance. The high-performance anode obtained relied not only on the presence of the arc-sprayed TiN interlayer, which significantly improved the overall physicochemical properties of the electrode, but also on the kinetic rate of the electrocrystallization growth of the refined PbO2 coating that was accelerated.

One-pot synthesis of β-cyclodextrin magnetic carbon nanotube (β-CD@MMWCNT) for effective removal of phenol from oily wastewater

In this work, a novel composite material based on β-cyclodextrin magnetic carbon nanotube (β-CD@MMWCNT) was developed by a one-pot method (in situ co-precipitation) and applied as an adsorbent to remove phenol from oily wastewater. The basic structure, surface morphology, as well as physical and chemical properties of the composite material were analyzed. β-CD@MMWCNT was successfully prepared, confirmed by the attachment of Fe3O4 and β-cyclodextrin particles on the surface. The adsorption behavior of phenol on β-CD@MMWCNT conformed to the Langmuir isotherm model and the pseudo-first-order kinetic model. The adsorption was a spontaneous endothermic process, and the adsorption capacity calculated by Langmuir model was 67.67 mg/g at 20 °C. Moreover, the adsorbent still maintained 85% of the adsorption capacity after 7 cycles. Specially, the adsorbent was used to adsorb phenol from simulated oily wastewater, and the removal rate of phenol reached 92.6%. And the possible adsorption mechanisms were also proposed by infrared and Raman spectroscopy. In summary, β-CD@MMWCNT can be used as a potential adsorbent to remove phenol from oily wastewater.

Electrochemical study of a novel high-efficiency PbO2 anode based on a cerium-graphene oxide co-doping strategy: Electrodeposition mechanism, parameter optimization, and degradation pathways

A novel and efficient Ti/SnO2-Sb/PbO2-GO-Ce electrode was successfully fabricated based on the co-deposition of Ce ions and graphene oxide (GO) into β-PbO2 crystals and used as an anode for electrocatalytic oxidation of phenol. The electrodeposition mechanism, parameter optimization, mechanism analysis, and potential degradation pathways were discussed in depth. The co-doping of GO and Ce resulted in the high directional specificity of β(301), orderly and dense grain arrangement of PbO2 crystals. At the same time, the oxygen evolution potential, •OH generation capacity and lifetime were also improved. The effects of experimental parameters on phenol removal efficiency were evaluated, including the applied current density, electrode gap, supporting electrolyte, initial NaCl concentration, initial pH, and initial phenol concentration. Under the optimal conditions, the removal efficiency of phenol can reach 375.6 g m-2 h-1 for 20 min electrolysis, which is about 1.2 times that of the pure PbO2 electrode. The active oxygen species (•OH, ClO- and HClO) were important attributes to the degradation of phenol. Additionally, a potential degradation pathway for phenol was proposed. After 10 successive recycles, there was no significant difference of the electro-generated •OH, cell voltage and phenol removal rate, which confirms the stability and admirable reusability of Ti/SnO2-Sb/PbO2-GO-Ce electrode.

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.

Electrocatalytic composite membrane with deep-permeation nano structure fabricated by flowing synthesis for enhanced catalysis

An electrocatalytic composite membrane with deep-permeation nano structure (DPNS) has been fabricated by flowing synthesis. The nano electrocatalyst MnO2 is in situ successfully assembled in membrane pores and uniformly immobilized in membrane pores along the direction of membrane thickness. The size of MnO2 nanoparticles immobilized in membrane pores is in the range of 33–35 nm, which is one-tenth of that immobilized on the membrane surface. The increased current density and the lower charge transfer resistance of the electrocatalytic composite membrane implied that a fast electron transfer can be achieved. As a concept-of-proof, the removal of phenol was applied to test the catalytic performance of the electrocatalytic composite membrane under the flow-through reaction mode, and the removal rate of phenol of being over 97% can be achieved under the condition of membrane flux of being 13.5 L m−2 h−1. The apparent reaction rate constant could be increased by 2–3 orders of magnitude, owing to the enhanced contact by uniform distribution of membrane pores, as well as the confined space effect of membrane pores and the flow-through synergism enhancing mass transfer. The species of free radical can be determined as ·OH via ESR measurements for phenol oxidation. This electrocatalytic composite membrane (ECCM) with DPNS has good reusability and can provide a promising prospect for industrial application.

Upgrading sequencing batch reactor using attached biofilm

A conventional sequencing batch reactor (SBR) was upgraded using fixed biofilm carriers with a specific surface area around 18m2 m-3 . The upgraded SBR was investigated to remove phenol from high strength wastewater operated under various operational conditions. The operational conditions used were variable volume exchange ratio (VER) up to 75%, hydraulic retention time (HRT) from (10.7-21.3hr), aeration time (from 2 to 8hr), and initial phenol concentration up to 600mgL-1 . It was found that the upgraded SBR increased the removal efficiencies of biological oxygen demand (BOD5 ), chemical oxygen demand (COD), and total suspended solids (TSS) by about 10% using high strength wastewater without phenol compared to SBR. Furthermore, the removal rate of phenol for the upgraded SBR was higher than conventional SBR by about 18% at 600mgL- of initial phenol concentration under the same operational conditions. Compared to the conventional SBR, the upgraded version reduced the aeration step by 25% and achieved higher removal efficiency of phenol. Moreover, it reduced the excess sludge by about 23% and enhanced its properties by lowering the sludge volume index (SVI) by about 33%. PRACTITIONER POINTS: Upgrading conventional SBR by adding biofilm carriers is necessary for wastewater treatment with high strength wastewater. The upgraded SBR has a higher resistance toward phenol compound due to the presence of the attached biofilm. The upgraded SBR enhances sludge settling properties, decreases the amount of excess sludge, and also reduces the start-up period. The number of cycles per day by upgraded SBR was more than the conventional SBR by 15%. The upgraded SBR is an effective system and has good operational stability.