查看更多>>摘要：Removal of manganese (Mn~(2+)) and ammonium (NH3-N) is an important issue in drinking water treatment. In this study, iron-manganese co-oxide (FMO) with high catalytic oxidation activity for Mn~(2+) and NH3-N was integrated with gravity-driven membrane (GDM) to treat surface water containing high concentration of Mn~(2+) (0.93-1.07 mg/L) and NH3-N (0.95-1.73 mg/L). The effect of FMO on flux stabilization, permeate quality and bio-cake layer was investigated in comparison with a single GDM system during 105 days of operation. The results indicated that flux decline rate during the initial 30 days was mitigated by FMO, and FMO/GDM system obtained similar stable permeate flux with GDM. Scanning electron microscope images suggested that FMO particles significantly increased thickness of the bio-cake layer, but resistance of the bio-cake layer in FMO/GDM was comparable with that of GDM due to porous structure. As for contaminants removal, FMO/GDM system achieved steady and efficient removal of Mn~(2+) (~97.7%) and NH3-N (~77.4%) throughout the whole operation period, mainly attributed to the strong catalytic oxidation activity of FMO. In contrast, Mn~(2+) was hardly removed by GDM during the 105 days of operation, while only 10.4% ± 8.1% of NH3-N was removed by GDM during the initial 30 days. Moreover, removal of dissolved organic matter was slightly improved by FMO, probably due to the increase of microbial community diversity and biodegradation in the bio-cake layer with FMO. In general, FMO enables GDM to effectively remove Mn~(2+) and NH3-N from surface water without compromising permeate flux, and therefore the integrated FMO/GDM system is promising for decentralized purification of surface water contaminated by Mn~(2+) and NH3-N.
查看更多>>摘要：Biofouling is a major challenge for desalination, water treatment, and water reuse applications using polymer-based membranes. Two classes of novel silver-based metal azolate frameworks (MAF) are proposed to decorate polyamide (PA) forward osmosis membranes and to improve numerous aspects of fouling and transport. Membranes functionalized with two concentrations of each MAF are compared with a pristine control material, with results that clearly highlight their tunability and bio-inhibitory effects. We report for the first time PA membranes yielding near complete suppression of a robust biofilm-forming bacterium (Pseudomonas aeruginosa) and inactivation of planktonic bacteria, while maintaining high selectivity. These features improve the long-term water flux performance of the membranes, tested during 24 h of accelerated biofouling and organic fouling conditions, and showing lower than 10% and 20% decline in water flux. These enhancements were achieved with only 0.03-0.06% mass of additives and little generation of hazardous waste products, indicating that low-cost and environmentally benign functionalization can prevent biofouling growth while maintaining selectivity and transport for high-performance desalination, water treatment and reuse.
查看更多>>摘要：In the framework of modern bioprocessing continuous ultrafQtration/diafiltration (UF/DF) is getting increasingly popular. However, while continuous UF can be easily implemented using a so-called single pass tangential flow filtration (SPTFF) module, continuous DF requires a more complicated setup including several SPTFF modules and intermittent dilution steps. Recently, we introduced a novel module design for continuous DF allowing simultaneous delivery of fresh buffer while withdrawing the permeate, thus achieving high degrees of buffer exchange within a single unit. In addition, the system allows to cyclically switch the flow direction of DF buffer through the membranes. Those uncommon features, however, also make it more difficult to determine an operation optimum experimentally by means of trial and error. Therefore, here a detailed finite element model of the physical processes within the module is presented, predicting key figures such as the obtained diafiltration efficiency and the resulting pressures. Because within the module all flow channels are filled by a 3D-printed porous grid supporting the membranes from both sides, the modified Brinkman equation was used to simulate the hydrodynamics, while common mass balance differential equations including accumulation, convection, and an anisotropic dispersion term were used for the simulation of concentration profiles of dissolved species. The predicted key figures are in good agreement with experimental results, obtained for feed solutions including up to 50 g/L of protein and being operated with and without switching the flow direction of the diafiltration buffer. A thorough parameter study reveals that the module shows the best performance for unidirectional flow of the diafiltration buffer, reaching diafiltration efficiencies independence to the applied diavolumes which are comparable to the ones of a conventional multi-stage setup using three SPTFF modules. Therefore, the simulation-based evaluation of optimum operation conditions reveals that the new module design has the potential to realize truly continuous diafiltration setups with high efficiency, requiring only one unit and no extra external piping for returning diafiltration in counterflow. Such simplified setups should be especially useful in small, flexible processing plants as they are increasingly demanded in the biopharmaceutical industry.
查看更多>>摘要：The self-floating Ti3C2 MXene-coated polyurethane sponge (MXene@PU module) was prepared via the simple coating operation for thermal activation of peroxydisulfate (PDS) and production of clean water. Coating MXene on the surface of PU significantly improved the degradation of model pollutant carbamazepine (CBZ) compared with PU alone under simulated solar radiation. Because of the excellent photothermal conversion performance of Ti3C2 MXene and the unique double-deck structure of MXene@PU module, the interfacial temperature of MXene@PU module reached about 140 °C, far higher than that of PU (about 82 °C). Radical identification experiments demonstrated that both hydroxy! radical and sulfate radical contributed to the degradation of organic pollutant. Addition of Cl", HPO42", HCO3" and natural organic matter in solution generated inhibitory effect on CBZ degradation. The prepared MXene@PU module exhibited excellent stability after long-time experiment. Importantly, the interfacial evaporation process produced abundant recycled water and no pollutant was detected in recycled water. This study provides a feasible way to utilize the renewable solar energy for removal of organic pollutants and production of clean water.
查看更多>>摘要：Goji berries represent a valuable source of phenolic compounds with a strong antioxidant and free radical scavenging activity combined to huge quantities of small sugars. This study was aimed at evaluating the potential of three tight ultrafiltration (UF) membranes with molecular weight cut-off (MWCO) from 1.0 to 3.5 kDa in the fractionation of phenolic compounds from sugars in the aqueous extract of dried goji berries. The aqueous extract produced in optimized conditions of water-to-solid ratio and temperature (6.66 mL/g and 65 °C, respectively) was preliminarily clarified by UF in order to remove suspended solids and colloidal particles. A membrane diafiltration (DF) process was developed in order to fractionate phenolic compounds from sugars with selected UF membranes from the clarified extract. The membrane performance was evaluated in terms of productivity and selectivity towards target compounds. All selected membranes allowed high recovery (more than 80%) of phenolic compounds into the retentate. On the other hand, the yield of carbohydrates increased in the permeate by increasing the diafiltration volume. Among the selected membranes, the 2.5 kDa membrane allowed to reduce the concentration of total carbohydrates from 26.5 up to 2.2 g glucose/L (a reduction of 91.7%) in a diafiltration/batch concentration process producing a concentrated extract enriched in phenolic compounds of interest for pharmaceutical or nutraceutical applications.
查看更多>>摘要：Electrochemical processes such as electrocoagulation (EC) and electrooxidation (EO) have proved their effectiveness for the treatment of industrial refractory wastewater. This study aimed to strategically combine EC and EO processes for the treatment of highly contaminated wastewater (COD of 10,360 ± 665 mg/L and phosphorus concentration of 22.9 + 0.9 mg/L) coming from industrial container wash water (IWW). In this regard, the EO and EC processes were investigated individually and then in combination. For the EO process, different operating parameters were investigated such as the type of anode, current density, type of electrolyte, amount of electrolyte, treatment time, and contamination concentration, while for the EC the current density and pH were studied. Although EO process decreased up to 91 ± 4.9% of COD, this process did not allow to reach the guideline (800 mg/L of COD) required for effluent discharge in the sewage urban networks. This was mainly attributed to the presence of phosphate ions which are known as hydroxyl radical scavengers. EC process was then firstly used as pre-treatment to remove phosphate ions from IWW, followed by EO process. The EC-EO combination allowed 97% and 95% of phosphorus and COD removal to meet the sewer discharge standard, respectively. A cost analysis showed that the EC-EO coupling reduced the operating costs to 7.3 CAD $/m3 compared to 24 CAD$/m3 recorded while EO process was used alone for the treatment of IWW.
查看更多>>摘要：In this work, a series of symmetrical "H-shaped" tetramine monomers bearing different amounts of side groups and linking units were designed and synthesized via a simple one-step electrophilic substitution reaction of aromatic dialdehyde and aniline. Then, these new designed tetramine monomers using as the crosslinking center were reacted with 6FDA to prepare the network polyimide (PI) membranes. Due to the robust 3D crosslinked structures, all the network PI membranes possessed high rigidity (Tg = 322 ~ 337 °C), excellent thermal stability (Tdt5% =425-471 °C), and superior mechanical performance with the tensile strengths ranging from 107.2 to 123.0 MPa and elongations of 4.2-5.4%, while the stone-like solubility in common solvents. Interestingly, during the period of tridimensional polycondensation reaction of these designed network Pis, a broad operating flexibility without the risk of gelation was observed, which is beneficial to their actual productions. Furthermore, gas transport results proved that changing the amounts of-CH3 side groups at the o?tho-positions of the aniline ring and extending their framework's linking units in the crosslinking center provide viable ways to fine-tune the fractional free volume (FFV) within the polymers, which in turn tailor their gas transport properties efficiently. Specifically, the optimum membrane termed as 6FDA-OHTA showed a huge increment about ~ 340% for CO2 permeability accompanying with only ~ 5.6% reduction for CO2/N2 ideal selectivity in comparison with those of the original 6FDA-PTA membrane. We hope this study can open a new avenue to the rational design of network PI membranes to meet various separation needs, especially from the view of crosslinking center structure variation.
查看更多>>摘要：A hybrid catalyst system consisted of MWCNT and Co-TiO2 through simple physical mixing was applied for peroxymonosulfate activation for antipyrine degradation. With 2 mM peroxymonosulfate, the removal rate of antipyrine is significantly increased from 53.24% and 86.23% to 100% in the presence of same weight of 0.2 g/L MWCNTs, Co-TiO2, and MWCNTs/Co-TiO2 (half/half) mixture, respectively in 12 min. The influence of various parameters, including the ratio of Co-TiO2/MWCNT, catalyst dose, peroxymonosulfate dose, antipyrine concentration, and initial pH, were further investigated in detail. The underlying catalytic mechanism of the synergistic effect was unraveled by quenching tests and EPR analysis. It was attributed to the electrons tranferration between Co-TiO2 and MWCNT, and the acceleration of Co~(3+)/Co~(2+) by generated superoxide. This work not only provides a novel and efficient method of pharmaceutical wastewater treatment, but also reveals a new perspective to use the catalyst more efficiently.
查看更多>>摘要：Arsenic pollution in the groundwater is a serious worldwide problem, where arsenite and arsenate are the most prevalent forms in groundwater. Most of the conventional methods are able to remove arsenate effectively as compared with arsenite. Hence, for complete elimination of arsenic, prior oxidation of arsenite to arsenate is needed. The present work assessed the possibility of electrochemically activated persulfate (PS) based advanced oxidation process (EAOP) for arsenite removal from the aqueous medium. EAOP using Pt/Ti as both anode and cathode, can completely oxidize arsenite with an initial concentration of 1 mg L~(-1) within 60 min of electrolysis at pH 3;; ferrous ion concentration 250 mg L~(-1), persulfate concentration 500. mg L~(-1) but failed to remove the arsenate (generated by the oxidation of asenite) from the aqueous medium. However, iron anode mediated persulfate advanced oxidation process was found to be more effective for both oxidation of arsenite and complete elimination of arsenic within 60 min of electrolysis at pH 3, applied voltage 2 V, and 500 mg L~(-1) PS. The average operating cost estimated is 0.33 $ m~(-3) At pH 3, the oxidation of arsenite is taking place by both hydroxyl and sulfate radicals;; whereas, at neutral and alkaline conditions, hydroxyl radicals and ferryl ions play a major role in the oxidation of arsenite. Overall, persulfate mediated advanced oxidation is effective for arsenite removal from aqueous medium.
查看更多>>摘要：How to achieve the efficient generation of Fe(II) from Fe(III) in Fenton reaction is a significant issue. In this work, a novel composite of oxidized multiwalled carbon nanotubes-Schwertmannite (CNTs-SCH) were successfully synthesized through a coprecipitation and hydrothermal strategy. The results indicated that the prepared 15%CNTs-SCH would exhibit an excellent catalytic performance in activation of hydrogen peroxide for degradation of tetracycline. The Fe(III)/Fe(II) redox couple circulation would be greatly enhanced from dynamic and thermodynamic aspects. The sulfate radicals generating from SO42" on the surface of Schwertmannite would contribute to TC degradation, which was in line with the enhanced generation rate of Fe(II) and hydroxyl radical in the 15%CNTs-SCH system. In addition, C = C and C = O (in CNTs) were acting as key active sites in prompting formation of Fe(II) and hydroxyl radical. What's more, the effects of pH, CNTs-SCH, hydrogen peroxide dosages, and common anions on TC removal were assessed. This investigation showed that the prepared 15%CNTs-SCH was an effective catalyst for hydrogen peroxide activation in the heterogeneous system with a wide pH range and good recyclability, confirming its stronger potential practical application.
NSTL