Treatment Of Simulated Wastewater Research Articles

Degradation of tetracycline by FeNi-LDH/Ti3C2 photo-Fenton system in water: From performance to mechanism

Recently, photo-Fenton technology has been widely used to degrade tetracycline (TC) because of its great efficiency and wide application range. Herein, Fe–Ni layered double hydroxides (FeNi-LDH)/Ti3C2 photo-Fenton system was constructed in this study. The results showed the introduction of Ti3C2 solved some problems of FeNi-LDH such as poor conductivity, easy aggregation, and high recombination rate of photoelectron. Benefiting from these advantages, FeNi-LDH/Ti3C2 exhibited excellent TC removal rate of 94.7% while pure FeNi-LDH was only 54%. Besides, FeNi-LDH/Ti3C2 possessed strong pH tolerance (2–11) and the removal efficiency was still up to 82% after the four-cycle experiment. Furthermore, the quenching experiments revealed the reaction mechanism, where ∙OH and ·O2− were the primary active radicals for degrading TC. Last, the results of the simulated wastewater treatment and the inorganic ion interference tests showed that FeNi-LDH/Ti3C2 possessed practical application potential. In brief, this study shows that FeNi-LDH/Ti3C2 can offer a certain theoretical basis for the actual development of hydrotalcite in heterogeneous photo-Fenton systems.

The anode is more beneficial to the advanced treatment of wastewater containing antibiotics by three-dimensional electro-biofilm reactor: Degradation, mechanism and optimization

The three-dimensional electrode biological aerated filter (3DE-BAF) has the potential to overcome inherent limitations of conventional electrochemical and biofilm methods. Electrochemical means could enhance the performance and sustainability of biofilm technologies and stimulate the spread of new applications in (waste) water treatment. This paper describes the construction and performance of 3DE-BAF in the treatment of simulated wastewater represented by tetracycline (TC). This is followed by a discussion of electrode performance, the electron transport mechanism and the electrode’s effect on the biological community of 3D-EBAF. Given the gap between experimental studies and practical applications, the enlarged anode 3DE-BAF named 3DEAE-BAF reactor was applied with good results to duck farm wastewater. This study could provide guidance as to developing new methods to construct a highly stable 3DE-BAF. The paper concludes that improved 3DE-BAF technology is promising for advanced treatment of livestock wastewater containing antibiotics.

Chiral inversion of 2-arylpropionoic acid (2-APA) enantiomers during simulated biological wastewater treatment

This study examined the removal and enantio‑specific fate of a suite of eleven chiral 2-arylpropionic acids (2-APAs) during biological wastewater treatment simulated in a laboratory-scale membrane bioreactor (MBR). Using pure (R)- and (S)- enantiomers in the MBR influent, chiral inversion was determined through the increase in the concentration of the non-dominant enantiomer and changes in the enantiomeric fraction (EF) between the two enantiomers during the treatment process. Effective (>90%) and similar removal rates between (R)- and (S)- enantiomers were confirmed for eight 2-APAs. In this study, 2-APAs exhibited diverse and distinctive chiral inversion behaviours: two 2-APAs showed (R→S) unidirectional inversion, three 2-APAs showed (S→R) unidirectional inversion, and six 2-APAs showed bidirectional inversion. This is the first study to report chiral inversion behaviours of a comprehensive suite of 2-APAs with a variety of functional groups substituted onto the aryl ring. A decrease in effluent EF over time was observed for two 2-APAs. This study shows that chiral inversion of 2-APAs varies significantly from compound to compound, despite the high similarity in their chemical structures.

Enhancement of chromium removal and energy production simultaneously using iron scrap as anodic filling material with pyrite-based constructed wetland-microbial fuel cell

Iron scraps was used as the anodic filling material coupled with pyrite as a substrate in a constructed wetland-microbial fuel cell (IsAno-PS) to investigate the power production and treatment of simulated wastewater that contained chromium. During 76 days of operation, the IsAno-PS facilitated the removal of total chromium, ammonia nitrogen, total phosphorus and energy production because of the synergetic effect between pyrite and iron scraps (p < 0.05). By XRD analysis and microbial composition analysis, chemical reduction (adsorption, complexation and reduction) and biological reduction were determined during the chromium removal reaction. According to alpha and beta diversity of microbial community composition in the system, the microbial community was significantly (p < 0.05) influenced by iron scraps. Electrically active bacteria like Firmicutes, were highly enriched, while the Fe (III)-reducing bacteria Geobacter and chromium-reducing bacteria Bacilli increased in the IsAno-PS. In network analysis, adding iron scraps was accompanied by distinct microbial communities, which could conductive to the bioremediation of chromium and participate in nitrogen cycle. Furthermore, Chloroflexi, which related to iron and sulfur cycling was identified as a module hub, implying taxa with low abundances can have important roles in ecosystem function. Iron scraps could affect the chromium removal by regulating the production of EPS. Chromate reductase (ChrR) gene decreased due to Fe2+ released by iron scraps. Overall, iron scraps used as the anodic filling material coupled with pyrite as a substrate in CW-MFCs could be an efficient configuration CW-MFC.

Microfluidic aqueous two-phase system-based nitrifying bacteria encapsulated colloidosomes for green and sustainable ammonium-nitrogen wastewater treatment

A novel strategy was proposed for preparing micro-scale monodisperses nitrifying bacteria (NB) encapsulated Ca-Alg@CaCO3 colloidosomes by exploiting capillary microfluidic device, as an attempt to treat ammonium-nitrogen wastewater in an environment-friendly, efficient and repeatable manner based on the aqueous two-phase (ATPS) system. By complying with the spatial confined urease mediate biomineralization reactions, ATPS droplets (Dextran in Polyethylene glycol) containing urease, NB regent and alginate were used as templates to prepare 500 μm Ca-Alg@CaCO3 colloidosomes with 16.48 Mpa mechanical strength. The activity of NB encapsulated in the colloidosomes was high. The simulated wastewater treated with the colloidosomes achieved a high removal rate even at harsh temperature and pH value. In both simulated and real wastewater treatment, prolonged reuse times (216 h) with high removal rate (＞90%, after being applied 72 h) were obtained by using Ca-Alg@CaCO3 colloidosomes, as compared with that (96 h) by using general alginate microbeads.

Feammox process driven anaerobic ammonium removal of wastewater treatment under supplementing Fe(III) compounds

Ammonium removal in wastewater treatment plants demands large quantities energy input, such as aeration for wastewater and the addition of organics for nitrate reduction. Anaerobic ammonium oxidation coupled to Fe(III) reduction, called Feammox process play a crucial role in natural nitrogen cycle, which has been rarely investigated in the field of wastewater treatment. Besides, Iron-reducing bacteria (FeRB) as function bacteria of Feammox could transfer electrons to iron oxide by oxidizing organics. The possibility of anaerobic ammonium removal coupled with organics should be investigated to assess the potential of Feammox process for conventional wastewater treatment. In this study, five Fe(III) compounds, Fe2O3, Fe3O4, Fe(OH)3, Citrate-Fe and pyrite were supplemented to investigate the effect of iron oxides on ammonium removal in serum bottles with working volume of 100 mL. It was found that ammonium removal efficiency of the Fe2O3 group was the highest. To simulate wastewater treatment process in sewage treatment plant, three Up-flow anaerobic sludge blanket reactors with volume of 250 mL adding Fe2O3 were applied with influent of ammonium and carbon sources. It was found that the organics significantly inhibited the ammonium removal by Feammox process. This was attributed to that carbon sources and ammonium could be used as electron donors for Fe(III) reduction. In addition, this nitrogen removal was also likely related with the iron cycle, i.e., Fe(III) reduction with ammonium oxidation and Fe(II) oxidation with nitrate/nitrite reduction. This study provides a promising alternative technology for anaerobic ammonium removal in wastewater treatment. Optimizing nitrogen removal and carbon sources applied in conventional wastewater plants are required in future.

One-step synthesis of carbon quantum dot-carbon nanotube composites on waste eggshell-derived catalysts for enhanced adsorption of methylene blue

Pristine CNTs always suffer from a slow adsorption rate or low adsorption capacity. Development of CNT-based adsorbents is highly desirable to improve their adsorption performance. In this study, novel carbon quantum dot-carbon nanotube composite (CQD-CNT) adsorbents and defective CNTs were synthesized for the first time by one-step chemical vapor deposition using catalysts derived from waste eggshells. The coverage of CQDs on CNTs endowed CQD-CNT with a larger surface area (324.4 m3/g), more abundant pore structures and surface functional groups compared to defective CNTs. The adsorption of methylene blue (MB) on CQD-CNT was systematically studied, and CQD-CNT demonstrated good adsorption capacity and extremely fast adsorption rate for MB at a wide pH range (2–12) and different temperatures (293–313 K). A high removal efficiency of 99.5% was achieved in 5 min, and the maximum adsorption capacity was 299.4 mg/g, which was 1.3 and 4.6 times higher than that of defective CNTs and pristine CNTs, respectively. The adsorption results were closely fitted by Langmuir isotherm model and pseudo-first-order kinetic model. The adsorption of MB on CQD-CNT involved multiple adsorption mechanisms, including electrostatic interactions, hydrogen bonding, π-π stacking interaction and pore filling. In addition, CQD-CNT showed good reusability and stability, retaining a removal efficiency of 95.1% after 5 cycles. Finally, high decolorization rates (98.6–100%) were obtained using CQD-CNT in the treatment of simulated textile wastewater. These results demonstrate that CQD-CNT benefitted from one-step green synthesis and the effective utilization of waste eggshells has potential applications in wastewater treatment.

Preparation of fluorinated covalent organic polymers at room temperature for removal and detection of perfluorinated compounds

Covalent organic polymers (COPs) are promising adsorbents for the removal and detection of various types of pollutants. However, the preparation of COPs that exhibit uniform dispersion and good appearance at room temperature is challenging. Herein, fluorinated covalent organic polymers (F-COPs) with different morphologies were synthesized through the Schiff base reaction of 4,4-diamino-p-terphenyl (DT) and 2,3,5,6-tetrafluoroterephthalaldehyde (TFA). The as-prepared F-COPs could selectively adsorb perfluorinated compounds (PFCs) owing to their fluoro-affinity, hydrophobicity, hydrogen bonding, and electrostatic attraction. The adsorption kinetics and isotherm simulation results showed that the adsorption process conformed to the second-order kinetics and the Langmuir model. The saturated adsorption capacity calculated by the Langmuir model was found to be 323–667 mg/g. The F-COPs were applied to the treatment of simulated fluorine industrial wastewater, and the PFC removal efficiencies of 92.3–100.0% were achieved. Moreover, ultra-high-performance liquid chromatography–mass spectrometry (UPLC–MS) was conducted for the detection of trace-level PFCs using F-COPs as dispersive solid-phase extraction (DSPE) adsorbents. The limits of detection were 0.05–0.13 ng/L and the limits of quantification were 0.17–0.43 ng/L. This study facilitates the synthesis of COPs at room temperature and extends the application of COPs as pretreated materials for environmental remediation and detection.

Construction of high-performance CeO2 ultrafiltration membrane for high-temperature dye/salt separation

CeO2 is an alternative membrane material for precise separation under harsh conditions because of its single fluorite structure and outstanding high-temperature stability. In this study, uniform and stable CeO2 colloidal sols were successfully prepared using an ultrasound-assisted precipitation method with an average particle size of approximately 5 nm. To prepare crack-free CeO2 membranes with a controllable thickness, concentration of polyvinyl alcohol in the colloidal sol and the coating time were investigated. An integrated membrane layer was fabricated by adjusting the sol to PVA solution mass ratio to 1:1 with a coating time of 30 s. After calcination at 500 °C, a thin CeO2 membrane (approximately 200 nm thick) was obtained. In addition, the CeO2 material derived from the as-prepared sol showed a fluorite structure and lattice fringes corresponding to different crystal planes, indicating the formation of a pure CeO2 thin membrane. The CeO2 membrane exhibited a high performance, with a molecular weight cut-off of 3.9 kDa and a high water permeance of 100 L m−2 h−1·bar−1. It showed excellent thermal stability, promising good potential applicability at high temperatures. Additionally, it exhibited the dye rejection rates of >99% for Direct Red 80 and 95.5% for Congo Red, and salt rejection rates of <1% at 60 °C in the simulated dye wastewater treatment. Overall, this study presents a new tight ultrafiltration membrane material that has good potential for high-temperature dye wastewater treatment.

Reversal of wettability of carbon cloth by microwave-assisted modification technology for efficient oil-water separation application

A modified layer of ZnO coating with the thickness of about 0.57 μm has been uniformly deposited on carbon cloth by microwave-assisted modification technology for reversing the wettability of carbon cloth, resulting in the fabrication of ZnO/CC Mem. The inherent properties of carbon fibers absorbing microwave radiation and converting it into volumetric heating contribute to the uniform deposition of ZnO modified coating on carbon cloth. After modification, the WCA of as-prepared ZnO/CC Mem is 0° while the corresponding UWOCA is up to 158.4 ± 1.1°, exhibiting the excellent superhydrophilicity/underwater superoleophobicity. In the process of gravity driven oil-water separation, a high filtrate flux about 18,625 ± 100 L/(m 2 h), is found in the separation of oil-water mixture, and the corresponding separation efficiency is 99.9%; While for the treatment of simulated kitchen oily wastewater, a bilayer ZnO/CC Mem is used. The corresponding filtrate flux and separation efficiency are 15,880 ± 100 L/(m 2 h) and 99.8%, respectively. In addition, the fouled ZnO/CC Mem could restore the virgin performance by a simple cleaning process. • A modified layer of ZnO coating had been uniformly deposited on carbon cloth by microwave-assisted modification technology for efficient oil-water separation. • The underwater oil contact angle of ZnO/CC Mem was up to 158.4 ± 1.1°, exhibiting the excellent superhydrophily/underwater superoleophobicity. • A high filtrate flux and excellent separation efficiency were found in the separation of simulated kitchen oily wastewater by ZnO/CC Mem.

Construction of Deino-flr-2 radiation-tolerant genetically engineered strain containing flr-2 fluoride-tolerant gene and its enrichment behavior for U(VI)

In order to solve the problem of lack of resistance of active microorganisms to the complex ion environment in the treatment of uranium-containing wastewater, the Deino-flr-2 radiation-resistant genetically engineered bacteria containing flr-2 fluorine-resistant gene was constructed and characterized. Utilizing the reductase activity of Deinococcus radiodurans (DR) itself and the enrichment of U(VI) by the surface active functional groups of the bacteria, the treatment of simulated low-concentration uranium-containing wastewater will be realized. In the most favorable conditions, accounting for approximately 90% of U(VI) was removed. The calculated data disclosed that the enrichment process of U(VI) by Deino-flr-2 well fit with the pseudo-second-order kinetic and Freundlich isotherm model.

Synthesis of magnetic nanoparticles-containing nanocomposite hydrogel and its potential application for simulated radioactive wastewater treatment

Nanocomposite hydrogels, bearing different functional groups, are potential materials for removing contaminants from water with high capacity and selectivity. A novel polyfunctional nanocomposite hydrogel (NCHG) was developed for the treatment of radioactive waste. It is based on magnetic composite nanoparticles (MCNPs) formed by encapsulating magnetite in polystyrene-co-polymethacrylic acid (PS-co-PMAA) miniemulsion. The MCNPs were then used as a physical crosslinker for the graft polymerization of sodium styrene sulfonate SSS and acrylic acid AA in the presence of polyacrylamide PAM to form an interconnected NCHG bearing different functional groups. The NCHG was characterized by FTIR, DLS, and TEM. The results indicated that a successful encapsulation of magnetite NPs took place and the MCNPs were ~100 nm in size. The presence of the MCNPs in the graft polymerization system greatly enhanced the conversion %. The optimum ultrasound homogenization of the polymerization reaction was found to be 11 min and the optimum gamma radiation dose for the initiation of polymerization reaction was 25 kGy. The NCHG was used for the removal of Cs+, Co2+, and Sr2+ ions from simulated radioactive waste. The initial concentration was studied from 50 to 600 mg/L, and the equilibrium adsorption capacities of Cs+, Co2+, and Sr2+ were found to increase from 8.49 to 53.37, 11.17–80.69, and 10.75–65.35 mg/g, respectively. The calculated thermodynamic parameters namely, Gibbs free energy (ΔG°), Enthalpy (ΔH°) and entropy (ΔS°) indicated an endothermic chemisorption process.

Preparation of Functionalized Mesoporous Silica as a Novel Carrier and Immobilization of Laccase.

Amino-modified mesoporous silica (SBA-15-NH2) was prepared by hydrothermal method, which is a kind of excellent carrier for enzyme immobilization. The structure of SBA-15 was characterized by SEM and FTIR, which proved that amino group was successfully attached to the surface of SBA-15. The carrier had good mesoporous structure proved by nitrogen adsorption and desorption test. Using SBA-15-NH2 as the carrier, the optimal conditions of laccase immobilization by two different cross-linking methods were explored. At the same time, the properties of the immobilized enzyme and free enzyme were compared. The results showed that the activity of immobilized laccase by two-step method (2977.5 U/g) was much higher than that by one-step method (239.5 U/g). The optimal conditions were as follows: free laccase (35°C, pH=4.5), two-step immobilized laccase (40°C, pH=4.0), one-step immobilized laccase (35°C, pH=4.0). The two-step method was more adaptable to temperature. The pH adaptation range of the immobilized enzyme is wider, and the thermal stability is greatly enhanced. After five cycles of repeated reaction, the residual enzyme activity of two-step and one-step methods was 56% and 43% of the original. The treatment of simulated wastewater containing 2,4-dichlorophenol (2,4-DCP) by immobilized laccase was also studied. Under optimum conditions (40°C, pH=5.0, 20 mg/L), the removal of 2,4-DCP reached 89.06%. The immobilized laccase is really effective for treatment of 2,4-DCP-containing wastewater.

Removal of uranium(VI) from simulated wastewater by a novel porous membrane based on crosslinked chitosan, UiO-66-NH2 and polyvinyl alcohol

The development of highly efficient adsorbent presents an enticing prospect for U(VI)-containing radioactive wastewater treatment. In this work, a novel porous cCS/PVA/UiO-66-NH2 membrane absorbent comprising of crosslinked chitosan (cCS), polyvinyl alcohol (PVA) and UiO-66-NH2 is designed and prepared. The adsorption capacity of porous cCS/PVA/UiO-66-NH2 membrane achieves 316.50 mg g−1 under an optimal condition. Furthermore, the porous cCS/PVA/UiO-66-NH2 membrane exhibits a high selectivity for U(VI) adsorption in simulated radioactive wastewater treatment. The possible mechanism of U(VI) adsorption onto porous cCS/PVA/UiO-66-NH2 membrane mainly includes surface complexation and cation exchange processes. In addition, the porous cCS/PVA/UiO-66-NH2 membrane also exhibits excellent cycling adsorption-‍desorption performance. All these results demonstrate that the porous cCS/PVA/UiO-‍66-NH2 membrane is a promising candidate for application in U(VI) removal from radioactive wastewater.

Electro-enhanced chlorine-mediated ammonium nitrogen removal triggered by an optimized catalytic anode for sustainable saline wastewater treatment.

Electrochemical technology has unique superiorities in chlorine-mediated pollutant oxidation, but has limited application in saline wastewater treatment due to inadequate efficiency and high energy consumption. To promote electrochemical oxidation capacity, a novel but low-cost electrode containing TiO2/Co-WO3/SiC was prepared and optimized, achieving highly efficient chlorine-mediated ammonium nitrogen oxidation (98.3±2.2% in 120min, with initial NH4+-N of 10.2±0.5mgL-1) in a simple electrochemical system with supplied current density only at 1.00mAcm-2. Comparing with unmodified carbon fiber cloth, the catalytic anode achieved 96.0% nitrogen selectivity, enhanced the system current efficiency by 20.6% and reduced the energy consumption by 54.4%, making the treatment of simulated mariculture wastewater both energy-saving (36.5±2.8kWhkg-1 NH4+-N) and cost-effective (1.45US$m-3), comparing with previously reported electrochemical processes (54-622kWhkg-1 NH4+-N). The nitrogen content (<1mgL-1) in the treated wastewater, containing only 0.18mgL-1 NH4+-N, meets the discharge standard of mariculture wastewater. The promoted electrochemical oxidation should be attributed to the chloride derived species (HOCl and ClO-) and related active species (Cl, ClO, OH, etc.). This easily prepared and reusable catalytic electrode is a promising alternative to conventional anode materials in sustainable electrochemical treatment of saline wastewater.

A critical evaluation of the use of accumulated energy as a parameter for the scale‐up of solar photoreactors during the treatment of simulated industrial wastewater by solar photo‐Fenton

AbstractBACKGROUNDThis work presents a critical evaluation of the use of accumulated energy (QUV) as a parameter for the scale‐up of solar photoreactors. The combined effect of initial pollutant load, iron concentration and UV radiation on industrial wastewater treatment by solar photo‐Fenton was investigated to identify photolimitation and photosaturation conditions.RESULTSThe assays were carried out using a flat‐plate collector (photoreactor with 12 and 20 mg L−1 of iron under average solar UVA irradiances in the range from 16 to 27 W m−2. In effluents with low initial organic load (45–90 mg L−1), the effect of the initial Fenton reaction was predominant against the contribution of solar radiation. Conversely, the contribution of solar radiation to the process performance was greater in effluents with the highest initial organic load (180–270 mg L−1). Within the range of solar radiation investigated, the process was photolimited when carried out with 20 mg L−1 of iron; however, with 12 mg L−1 of iron the process became photosaturated at irradiances above 15 W m−2.CONCLUSIONSUnder photosaturation, the extra energy available that cannot be absorbed by the catalyst resulted in ca 60% overestimation of QUV, which can finally lead to 20–30% cost overrun due to photoreactor oversize. © 2021 Society of Chemical Industry

A novel two-step adaptive multioutput semisupervised soft sensor with applications in wastewater treatment.

To make full use of unlabeled data for soft-sensor modelling and to address the coexistence of a large number of hard-to-measure variable issues, this study proposed a novel two-step adaptive heterogeneous co-training multioutput model. First, unlabeled data with the highest confidence were selected to optimize the model. Then, the proposed model co-trained Gaussian process regression (GPR) and least squares support vector machine (LSSVM) algorithms with two sets of independent labeled data. Second, at each step of the model update, the Kalman filter (KF) worked together with a moving window (MW) to strengthen the model to address process dynamics. Finally, the proposed model was demonstrated by a simulated wastewater treatment platform, BSM1, and a real sewage treatment plant. The root-mean-square error (RMSE) and root-mean sum of squares of the diagonal (RMSSD) were obviously reduced, and the correlation coefficient (R) and correlation coefficient (RR) reached 0.8 in both case studies. The results suggest that the proposed model can significantly improve prediction performance.

The enhanced properties in photocatalytic wastewater treatment: Sulfanilamide (SAM) photodegradation and Cr6+ photoreduction on magnetic Ag/ZnFe2O4 nanoarchitectures

Ag/ZnFe2O4 nanoarchitectures composed of ZnFe2O4 nanoparticles loading onto Ag nanowires were fabricated by hydrothermal method. The Ag/ZnFe2O4 nanocomposites possessed excellent performance in simulated photocatalytic wastewater treatment like sulfanilamide (SAM) photodegradation and Cr6+ photoreduction. The improvement of photoactivity could be ascribed to the successful formation of Schottky interface between ZnFe2O4 nanoparticles and Ag nanowires and the enhanced light absorption ability in visible light region with modified energy band structures, which make further efforts to the ameliorate separation and improved mobility of photo-induced charge carriers with enhanced performance in photocatalysis. The Ag/ZnFe2O4 nanocomposites exhibited outstanding photoactivity than single component and more importantly, the unique magnetic properties enabled the Ag/ZnFe2O4 photocatalysts to be recycled easily with the aid of external magnetic field, which make it possible for practical applications.

In-situ synthesis of PA/PVDF composite hollow fiber membranes with an outer selective structure for efficient fractionation of low-molecular-weight dyes-salts

A polyamide/poly(vinylidene fluoride) composite hollow fiber membrane (HFM) was designed by in situ interfacial polymerization (IP) during the fiber spinning process. Using a piperazine aqueous solution as the bore fluid and a dual-bath coagulation, the PA outer layer was formed via IP of the PIP in the bore fluid and TMC in the second reactive bath during phase inversion process. Chemical structure, membrane morphology and surface property were characterized by using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscope (XPS), scanning electron microscope (SEM), and zeta potential. The effects of several parameters involved in the membrane fabrication (e.g., piperazine concentration, bore fluid flow rate, residence time and heat treatment temperature) on the morphology and performance of resultant composite HFMs were investigated. The composite HFM showed a performance that is comparable favorably with conventional nanofiltration membranes in terms of showed water permeability (10.2 L/m2·h·bar), high rejection to dyes (i.e., 100% for CR and EBT, 99.99% for RhB and MB, 98.3% for MO) and low salt rejections (NaCl 6.2%). Moreover, the newly developed composite HFM showed good stability and flux recovery with simple water rinsing for treatment of simulated textile wastewater. This work is expected to provide a new approach to designing composite HFMs for the treatment and reuse of textile wastewater.

Flocculation behaviors of a novel papermaking sludge-based flocculant in practical printing and dyeing wastewater treatment

In our previous studies, several papermaking sludge-based flocculants (PSBFs) were synthesized from wood pulp papermaking sludge. The structure-activity relationships of the PSBFs have been investigated in simulated dye wastewater treatment, but their efficiencies in practical printing and dyeing wastewater (PPDW) treatment are unknown. Herein, an PSBF was prepared, and its performance is discussed in comparison to polyaluminium chloride (PAC) and polyacrylamide (PAM) in PPDW treatment. The PSBF was used in three ways: as an independent flocculant, as a PAC aid, or used to treat the effluent of the PAC system. The results indicated that adding PSBF alone produced similar color and chemical oxygen demand (CODCr) removals as the PAC system alone, but PSBF performed better than PAC when the pH of PPDW was higher than 7.0. Adding PSBF as a PAC aid improved the color, CODCr and turbidity removals, but the elimination efficiencies were slightly lower than those of the PAC + PAM system. However, when PSBF was used as a flocculant to treat the effluent of the PAC system (PAC → PSBF), the effluent qualities were enhanced. Compared with the PAC system, the color and CODCr removals of PAC → PSBF system increased by 16.21% and 13.26%, respectively. The excitation and emission matrix fluorescence results indicated that PSBF removed tryptophan-like pollutants more efficiently than PAC. Considering the pH requirements of the subsequent bioreactor treatment in practice, the PAC → PSBF system were also investigated at the PPDW pH level of 7.0. Its maximum removal efficiencies of color, CODCr and turbidity were 90.17%, 32.60% and 82.50%, respectively.