Size-controlled synthesis of spherical ZrO2 nanoparticles by reverse micelles-mediated sol-gel process

Spherical ZrO₂ nanoparticles have been successfully synthesized by a reverse micelles (RMs)-mediated sol-gel process. Hydrolysis of zirconium n-propanol solution was confined in the microreactors made of water/cetyltrimethyl ammonium bromide (CTAB)/cyclohexane/n-butanol RMs, as well as investigating the template effects of RMs in particle size and shape control. It was found that there was significant particle size and shape replication between RMs and ZrO₂ nanoparticles after polycondensation, indicating that the RMs microreactors stabilized by surfactants could control the nucleation, growth and agglomeration process during the hydrolysis and thus the size and shape of ZrO₂ nanoparticles. Furthermore, spherical ZrO₂ nanoparticles could be customized in the range of 10–30 nm, and their roundness value was greater than 0.90.     

Preparation of yttria-stabilized ZrO2 nanofiltration membrane by reverse micelles-mediated sol-gel process and its application in pesticide wastewater treatment

8 mol% yttria-stabilized ZrO₂ (8YSZ) nanofiltration (NF) membranes were prepared from size-controlled spherical ZrO₂ nanoparticles with an average diameter of ˜10 nm and a particle roundness value greater than 0.90, and the nanoparticles were efficiently fabricated by a reverse micelles (RMs)-mediated sol-gel process. It was found that yttria doping not only suppressed the tetragonal to monoclinic (t-m) phase transition, ensuring the membranes integrity, but also decreased the tetragonal grain size, increased the specific surface area, narrowed the pore size distribution and thus optimized the NF performance. The as-prepared 8YSZ NF membranes with a thickness of ˜260 nm exhibited high NF performances, while the pure water permeability and molecular weight cut-off (MWCO) were 3.9-4.2 L m⁻² h^-1 bar^-1 and 800 ± 50 Da respectively. In the treatment of pesticide wastewater, the removal rate of carbofuran by 8YSZ NF membranes was more than 82%, while the maximum removal rate could reach 89%. Furthermore, the contaminated membranes could be restored as ever after alkali wash and low-temperature calcination, implementing multiple reuses.     

Charged modified tight ceramic ultrafiltration membranes for treatment of cationic dye wastewater

Tight ceramic uitrafiltration membranes have been proven to exhibit good rejection performance for reactive dye wastewater at high temperatures because of their high thermal and chemical resistance.However,the application of ceramic membranes for the treatment of cationic dye wastewater is chal-lenging because of their surface charge.In this study,a ceramic membrane is modified by grafting aminosilane (KH-551) to enhance the positive charge of the membrane surface.The rejection perfor-mance of the charged modified ceramic membrane toward the methylene blue solution is significantly improved.The modification substance is bonded to the ceramic membrane surface via covalent bonding,which imparts good thermal stability.The modified ceramic membrane exhibits stable separation perfor-mance toward the methylene blue solution.Overall,this study provides valuable guidance for the adjust-ment of the ceramic membrane surface charge for treating industrial cationic dye wastewater.     

Investigation of two ultrafiltration membranes for treatment of olive oil mill wastewater

In this study, a promising treatment method is given for the olive oil mill wastewater (OMWW). Although the same steps of this method have been used in different studies before, flow scheme is novel. The membrane filtration of pretreated OMWW was investigated by using two ultrafiltration membranes in this study. Pretreatment steps were pH adjustment (pH = 2) and cartridge filter filtration, and pH adjustment (pH = 6) and cartridge filter filtration. Each step of cartridge filter filtration was batch process and effluent from the filter was recycled back to OMWW tank. Pretreated OMWW was sent to feed vessel of experimental set-up. Recovery of olive oil in the OMWW was realized collecting it from the top of pretreated OMWW. Ultrafiltration membranes used were JW and MW membranes supplied by Osmonics. The effects of main operating parameters (transmembrane pressure, feed flow rate, pH and membrane type) on the permeate flux and membrane fouling were examined. The effectiveness of the different membranes and operating conditions was evaluated using retention coefficients calculated from COD and TOC of experimental studies. The highest permeate flux (25.9 l/m² h) was obtained using MW membrane under operational conditions of Qf = 200 l/h flow rate and TMP = 4 bar, while the highest removals were obtained at Qf = 100 l/h flow rate and TMP = 1 bar. COD, TOC, SS, oil and grease concentrations of MW membrane effluent were 6400 mg/l, 2592 mg/l, 320 mg/l, and 270 mg/l, respectively.     

Modification of polysulfone ultrafiltration membranes by CO2 plasma treatment

Carbon dioxide plasmas were used to modify hydrophobic polysulfone ultrafiltration membranes to create hydrophilic surfaces throughout the membrane structure. The water contact angle of the upstream side of the membrane (facing the plasma) decreased to zero after treatment and did not change even after several months of aging. The water contact angle of the downstream side decreased with increasing CO₂ plasma treatment time and became zero for treatment times ≥ 1 min (P = 10 W). Functional groups introduced by CO₂ plasma treatment were examined using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). For the treated membranes, the atomic concentration of oxygen increased dramatically and small amounts of nitrogen incorporation were also observed. Membrane performance was tested with water flux measurements as well as protein fouling studies. For treated membranes, the water flux recovery measured after protein fouling was significantly higher than that for control membranes, with nearly 100% recovery after gentle cleaning in water. Moreover, the amount of protein adsorption decreased by over 75% for the treated membranes compared to control membranes. This suggests the protein fouling layer is essentially completely reversible on the CO₂ plasma treated membranes.     

A compact process for the treatment of olive mill wastewater by combining OF and UV/H2O2 techniques

Olive oil production results in important quantities of wastewater containing large amounts of total solids and organic carbon as well as low oil concentrations. This paper describes the treatment of olive mill wastewater (OMW) by combining an ultrafiltration (UF) technique and an advanced oxidation process (AOP) using UV/H₂O₂. It further demonstrates the technical feasibility of this compact and stable process to remove a large part of total solids and organic carbon. Indeed, OF reduces the pollutants contained in the OMW with an apparent rejection coefficient R_COD in the range of 94%. The UV/H₂O₂ oxidation process may be easily used, in combination with UF, to finish the treatment of the permeate. The results obtained in batch and continuous mode showed that this technique offered a treated solution which complies with legal requirements. A final concentration of 17 mg_TOC dm⁻³ was obtained, which corresponds to a final COD of 52 mg dm⁻³, while the legal requirement is 125. Furthermore, the final effluent is fully decolorized.     

Effect of additives concentration on the surface properties and performance of PVDF ultrafiltration membranes for refinery produced wastewater treatment

The aim of this study was to investigate the effect of pore-forming hydrophilic additives on the porous asymmetric polyvinylideneflouride (PVDF) ultrafiltration (UF) membrane morphology and transport properties for refinery produced wastewater treatment. PVDF ultrafiltration membranes were prepared via a phase inversion method by dispersing lithium chloride monohydrate (LiCl·H₂O) and titanium dioxide (TiO₂) nanoparticles in the spinning dope. The morphological and performance tests were conducted on PVDF ultrafiltration membranes prepared from a different additive content. The top surface and cross-sectional area of the membranes were observed using a field emission scanning electron microscope (FESEM) and energy dispersive X-ray (EDX) analysis. The surface wettability of porous membranes was determined by the measurement of a contact angle. The mean pore size and surface porosity were calculated based on the permeate flux. The results indicated that the PVDF/LiCl/TiO₂ membranes with lower TiO₂ nanoparticles loading possessed smaller mean pore size, more apertures inside the membrane with enhanced membrane hydrophilicity. LiCl·H₂O has been employed particularly to reduce the thermodynamic miscibility of dope which resulted in increasing the rate of liquid–liquid demixing process. The maximum flux and rejection of refinery wastewater using PVDF ultrafiltration membrane achieved were 82.50 L/m² h and 98.83% respectively at 1.95 wt.% TiO₂ concentration.     

Corrosion resistant ZrO2/SiC ultrafiltration membranes for wastewater treatment and operation in harsh environments

This work focused on the fabrication of a ZrO₂/SiC ultrafiltration membrane by dip coating a high porous SiC support with a ZrO₂ slurry prepared by ceramic processing. The membranes were sintered in different temperatures (1000−1300 °C). With the optimal temperature, it was obtained a mechanically strong, homogenous, and defect free separation layer with 45 μm of thickness and average pore size of 60 nm. A pure water permeability of 360 L.m⁻² h⁻¹ bar^-1 and high retentions of humic acid, indigo dye, and hemoglobin were observed. In a pilot test with an olive oil/water emulsion, 99.91 % of oil was removed without fouling. Long-term corrosion tests at basic and acid baths did not cause change in pore size and morphology. In conclusion, the ZrO₂/SiC membrane has potential to operate in harsh conditions (e.g. heavily contaminated industrial effluents or urban wastewaters) and when severe membrane cleaning and disinfection are required, such as food and pharmaceutical industries.     

The use of RO to remove emerging micropollutants following CAS/UF or MBR treatment of municipal wastewater

The removal of various organic micropollutants (OMPs), including six antibiotics (ERY, ROX, CLA, SMX, SMZ, and TMP), three pharmaceuticals (ibuprofen, salicylic acid, and diclofenac), one industrial product (BPA), and one hormone (cholesterol), was investigated in two pilot plants treating the same raw sewage of the Tel-Aviv WWTP. The effluent production by CAS-UF was 45 m³/h while that of MBR was 40 L/h. Each system's effluent constituted the feed for its RO, which comprised three RO steps after the CAS/UF and a semi-batch RO system after the MBR. Despite significant molecular differences between the selected OMPs, high removal rates were achieved after the RO stage (> 99% for macrolides, pharmaceuticals, cholesterol, and BPA, 95% for diclofenac, and > 93% removal of sulfonamides). However, low antibiotics concentrations and 28–223 ng/L residuals of ibuprofen, diclofenac, salicylic acid, cholesterol, and BPA in the MBR/RO and CAS-UF/RO permeates showed that although RO is an efficient removal solution, it cannot serve as an absolute barrier to OMPs. Therefore, additional treatment techniques should be considered to be incorporated aside the RO to ensure complete removal of such substances.     

Chemical cleaning of reverse osmosis membranes used for treating wastewater from a rolling mill process

An analysis of fouling material and the effects of chemical cleaning were examined for a reverse osmosis (RO) membrane, which was used for the treatment of wastewater from a rolling mill process in the steel industry. The bulk foulant accumulated in the membrane module consisted mainly of CaSO₄·2H₂O, and the organic contaminants were contained at a very low level. The test pieces obtained from the exhausted RO membrane module (spiral-wound type) were used to examine chemical cleaning with the following solutions: acid and alkaline solutions with EDTA added, 50% methanol, and 10% ethyleneglycol monobutyrate (EGMB). Although a major component of the fouling material was calcium salt, the acid or alkaline solution containing EDTA did not promote the effective recovery of the water flux. On the other hand, cleaning with 50% methanol or 10% EGME solution increased the water flux significantly. The atomic force microscopy images of the membrane surface indicated that relatively large particles accumulated at the surface of the fouled membranes, and the large particles remained even after acid or alkaline cleaning. In the case of EGMB cleaning after alkaline cleaning, large particles did not remain, and uniform and fine particles were observed. The results that calcium salt, a major fouling material, was not removed effectively with the acid and alkaline solution may be due to trace organic materials in the fouling layer that act as a binder for inorganic fouling materials.     

One-step cleaning method for flux recovery of an ultrafiltration membrane fouled by banknote printing works wastewater

A method was developed to clean ultrafiltration (UF) membranes fouled by banknote printing works wastewater.The cleaning agent was comprised of 0.7 wt.% NaOH, 0.8 wt.% Na₂EDTA, 0.3 wt.% Turkey red oil and 98.2 wt.% de-ionized water. Membrane flux recovered adequately when the cleaning agent was circulated for 20–30 min at 1.5 m/s and 50–60°C. The membrane surfaces before and after cleaning were characterized by SEM/EDX. The spent cleaning agent was analyzed by TOC and ICP. The results showed foulants were removed from the fouled membrane by the cleaning. Pilot-scale experiments were also conducted to validate the efficiency of the cleaning method. This one-step cleaning method replaced an existing four-step cleaning method and was employed to clean OF units in banknote printing works wastewater plants.     

Integration of immersed membrane ultrafiltration with coagulation and activated carbon adsorption for advanced treatment of municipal wastewater

A pilot-scale hollow-fiber ultrafiltration unit was installed in the wastewater treatment plant of Rethymno, Crete, Greece. The system was fed with treated unchlorinated effluent. Three sets of experiments were conducted. At first, the UF pilot unit was operated as a direct filtration unit. During the second phase, ultrafiltration was combined with the addition of a coagulant (alum). The last phase of the experiments involved the addition of activated carbon (either powdered or granular) into the system. During direct filtration, the average COD removal was 19%, while the average DOC was removed to a similar extent (25%). Effluent turbidity was practically independent of the influent turbidity with an overall average removal of 90%. Faecal and total coliform were also removed efficiently reaching average removals of 99.94% and 99.96%, respectively. Removal of heavy metals in particulate form also took place. When ultrafiltration was combined with in-line coagulation, the results were similar to those exhibited without coagulation. Combining ultrafiltration with powdered activated carbon resulted in DOC removal as high as 60%. However, after the addition of the PAC, the transmembrane pressure increased rapidly due to the formation of PAC cake on the membrane surface. Application of granular activated carbon resulted in 36% reduction of DOC without causing an increase to the trans-membrane pressure. Heavy metals present in the secondary effluent were also removed very efficiently by the GAC in the UF tank.     

水解酸化-A2/O-MBR-BAC组合工艺处理焦化废水试验研究

为解决焦化行业废水处理不达标的问题,试验研究了水解酸化-A2/O-膜生物反应器（MBR）-活性炭过滤（BAC）的组合工艺处理焦化废水的可行性。结果表明,进水NH3-N的质量浓度为88 mg/L左右时,出水NH3-N的质量浓度稳定在3 mg/L左右,组合工艺对NH3-N的去除率能达到96%。同时,进水CODCr的质量浓度在970mg/L左右,出水CODCr去除率能达到90%,出水满足GB 8978—1996《污水综合排放标准》一级标准,该工艺对焦化废水有很好的处理效果。     

ZVI/Fe2+/H2O2类Fenton法深度处理烟草薄片废水

采用零价铁(ZVI)/Fe2+/H2O2类Fenton法深度处理造纸法烟草薄片废水(二级生化出水),探讨了反应时间、初始pH、Fe2+浓度、H2O2浓度和ZVI质量浓度对COD和色度去除效果的影响。结果表明,当反应时间为60 min、初始pH为5.0、Fe2+浓度为1.0 mmol/L、ZVI质量浓度为2.0 g/L、H2O2浓度10 mmol/L时,处理后色度为84 C.U.、脱色率为95.5%;COD为73 mg/L,COD去除率为80.4%。与传统Fenton法对比发现,ZVI/Fe2+/H2O2类Fenton法具有可在弱酸性条件下(pH=5.0)使用、总铁需求量少(减少26%)和产泥量少(减少2/3左右)的优点。     

水解酸化-A2/O -MBR-BAC组合工艺处理焦化废水试验研究

为解决焦化行业废水处理不达标的问题,试验研究了水解酸化-A2/O -膜生物反应器(MBR)-活性炭过滤(BAC)的组合工艺处理焦化废水的可行性.结果表明,进水NH3-N的质量浓度为88 mg/L左右时,出水NH3-N的质量浓度稳定在3 mg/L左右,组合工艺对NH3-N的去除率能达到96％.同时,进水CODCr的质量浓...     

O3/H2O2组合工艺处理丁苯橡胶生产废水的研究

针对合成橡胶生产废水,特别是丁苯橡胶(SBR)生产废水的悬浮物浓度高,成分复杂,可生化性差,难以达到国家排放标准等问题,以O3/H2O2组合工艺对SBR生产废水进行非均相催化氧化处理实验,探讨了影响COD去除率的各种因素,确定了最佳的混凝和催化氧化条件.研究结果表明:采用混凝-催化氧化工艺可使原水的COD从860 mg/L降至145 mg/L,去除率83.1%,出水达到国家二级排放标准.     

UV-H2O2工艺对焦化废水中氰化物深度处理研究

在新颁布的《炼焦化学工业污染物排放标准》(GB 16171—2012)中,总氰化物的排放限值降至0.2 mg/L,这使得传统除氰工艺已无法满足处理要求。以某焦化厂经生化、混凝处理后的出水为研究对象,探究了UV-H2O2工艺用于深度除氰的可行性。实验结果表明:在p H=10、n(H2O2)∶n(CN)=250∶1的条件下,UV-H2O2工艺处理30 min后总氰去除率可达80%,出水总氰(<0.18 mg/L)满足新标准要求。     

二级气浮+A/O法处理炼油废水

采用隔油-浮选-生化曝气的二级处理工艺处理某炼油废水.实践表明,两级浮选和A/O生化工艺可有效地去除有机物、NH3-N和TN,是目前国内较成熟的炼油废水处理工艺,处理后的污水水质达到<污水综合排放标准>一级标准及<石油炼制工业污水污染物排放标准>中一级一类标准,而且出水水质较稳定.     

炼油污水A/O处理工艺模拟与优化

针对我国某炼油厂含油系列污水处理生化段缺氧/好氧(A/O)工艺,利用BioWin 5.0模拟软件,进行了模拟和优化。结果表明,校正后的模型能够较好地反映目前A/O工艺的运行状况。然后调节工艺参数对校正后的模型进行优化,结果表明:在优化后的运行条件下,出水COD几乎没有变化,TN去除率提高2.9%,曝气能耗下降了17.8%,节约了运行费用。     

IC-A/O工艺处理谷物蛋白废水

针对苏州某生物科技有限公司生产的谷物蛋白废水有机物浓度较高、可生化性能好的特点,选择内循环厌氧反应器(IC)-A/O工艺对其进行处理,经调试运行,出水COD、氨氮、SS达到《污水综合排放标准》(GB 8978—1996)一级标准。该组合工艺运行稳定,自动化程度高,处理效果好,运行费用低。