改性PVDF中空纤维膜处理压裂返排液研究

针对中空纤维膜应用于水力压裂返排液处理时存在的膜污染严重、通量衰减快、影响处理效率等问题,研究了PVDF固含量、凝固浴温度等因素对PVDF膜性能的影响,通过非溶剂致相分离法制备了PVDF中空纤维膜,并采用表面接枝技术,对PVDF中空纤维膜进行了表面亲水化改性。压裂返排液吸附实验结果表明,表面接枝降低了PVDF的接触角,提高了膜的亲水性。与未接枝改性的PVDF膜相比,亲水改性后的PVDF膜表面吸附的压裂返排液更少。将亲水性中空纤维膜用于页岩气水力压裂返排液的过滤处理,应用结果表明其对压裂返排液中的总铁、SS、浊度、细菌去除率达到90%以上,长时间运行后的通量保持率高,有较好的抗膜污染性。     

改性聚偏氟乙烯中空纤维膜处理压裂返排液研究

针对中空纤维膜应用于水力压裂返排液处理时存在膜污染严重、通量衰减快、影响处理效率等问 题,研究了PVDF（聚偏氟乙烯）固含量、凝固浴温度等因素对PVDF膜性能的影响,通过非溶剂致相分离法制 备PVDF中空纤维膜,并采用表面接枝技术,对PVDF中空纤维膜进行了表面亲水化改性。压裂返排液吸附实 验结果表明,表面接枝降低了PVDF的接触角,提高了膜的亲水性。将亲水性中空纤维膜用于页岩气水力压裂 返排液的过滤处理,应用结果表明其对压裂返排液中的总铁、SS、浊度、细菌去除率达到90％以上,长时间运行 后的通量保持率高,有较好的抗膜污染性。     

纳米TiO_2改性膜生物反应器处理污水的研究

采用啧涂纳米TiO2的方法对聚偏氟乙烯（PVDF）微滤膜进行改性,用改性膜生物反应器（MBR）和非改性MBR处理污水,对比了两者的出水水质、膜通量和膜过滤阻力。结果表明,两套MBR的出水水质均可达到《生活杂用水水质标准》（CJ25．1—89）的要求;纳米TiO2改善了膜表面的亲水性和粗糙度,从而使改性MBR的清水膜过滤阻力和不同抽吸压力下的膜过滤阻力均低于非改性MBR的,而其在不同抽吸压力下的稳定膜通量则高于非改性MBR的。     

改性微滤膜深度处理城市污水的研究

采用改性SiO2纳米粒子对微滤膜进行改性,考察了改性微滤膜的分离特性及对城市污水的深度处理效果.结果表明,改性后的微滤膜表面的亲水性明显提高,膜的传质系数增大,膜阻力系数减小,膜的耐污性能大大增强;采用改性微滤膜处理城市污水厂的二级出水,膜出水水质可满足<城市污水再生利用城市杂用水水质>(GB/T 18920--2002)的要求,且连续运行10 h后,膜通量仍可稳定在150 L/(m2·h)以上;适量增大过膜压力可提高膜通量和水回收率,错流过滤方式比死端过滤方式的膜通量高,内压进水方式比外压进水方式的膜通量高.     

氧化石墨烯与纳米TiO_2改性PVDF膜的性能研究

自制氧化石墨烯(GO)与纳米TiO_2复合改性PVDF中空纤维超滤膜(简称GOTiO_2改性PVDF膜),测定其表面功能特性,考察其对微污染物腐殖酸(HA)的截留特性与抗污染性能。结果表明:GO-TiO_2改性PVDF膜的静态水接触角下降为38. 6°±1. 2°(原膜为80. 6°±1. 8°),表面亲水性能得到很大改善。改性后膜表面富含大量的—COOH、—OH等亲水性基团,亲水性表面为GO-聚酰胺-TiO_2复合结构。GO-TiO_2改性PVDF膜的通量衰减率得到显著改善,其通量总衰减率下降到35. 6%(改性前总衰减率为51. 2%);改性膜不可逆衰减率大幅下降,约为原膜的1/4。改性膜抗污染性能明显改善,其对HA的静态吸附量由改性前的295. 0 mg/m2下降到158. 6 mg/m2。水力反冲洗能使GO-TiO_2改性PVDF膜的通量恢复率达到94%,而原膜只有69%。GO-TiO_2改性PVDF膜的截留性能得到显著提升,其对HA的截留率从81. 0%上升到90. 1%,过滤周期延长了约2. 5倍。     

表面改性纳米氧化铝亲水共混膜制备及其水处理效能

经低温等离子体处理后,在纳米氧化铝(Al_2O_3)表面接枝甲基丙烯酸-2-羟乙酯(HEMA)或其聚合物,制备了Al_2O_3-g-HEMA纳米复合颗粒。采用纳米Al_2O_3及Al_2O_3-g-HEMA纳米复合颗粒分别与聚偏氟乙烯(PVDF)共混,制备了PVDF/Al_2O_3膜和PVDF/Al_2O_3-g-HEMA膜,并与未改性PVDF膜进行比较。考察了改性纳米Al_2O_3表面的接枝情况和平均粒径,以及上述3种超滤膜处理聚驱采油废水的通量、出水水质及膜污染情况。结果表明,经表面改性的纳米Al_2O_3,其颗粒团聚得到良好控制,平均粒径大幅下降。PVDF/Al_2O_3膜和PVDF/Al_2O_3-g-HEMA膜的亲水性、纯水通量、处理聚驱采油废水的运行通量及清洗后通量恢复率均大幅提高。3种膜对聚丙烯酰胺、油类和TOC均有良好的去除效果,且共混改性不影响膜对大分子物质的去除。以PVDF/Al_2O_3-g-HEMA纳米复合颗粒作为添加剂制备的共混膜,其通量、去除效果和抗污染能力等综合性能最佳,是深度处理聚驱采油废水的理想膜材料。     

表面处理碳纳米管对水泥砂浆性能影响的研究

采用酸化处理技术使碳纳米管表面基团化(接枝—COOH、—OH),以其作为纳米增强剂改性水泥砂浆。结果表明:表面处理能有效降低碳纳米管的有序度,减弱颗粒间吸附力。接枝基团还能与水泥水化产物产生一定的化学结合,提高砂浆的物理力学性能。电阻测试结果显示:表面处理的碳纳米管/水泥砂浆具有更高的力/电感知灵敏度,且在15 kN循环荷载作用下电阻变化率衰减较小,力/电响应较为稳定。基团含量较高的羟基碳纳米管(CNT-OH)改性砂浆具有较强的机敏性能,比普通碳纳米管掺入时在单调和15 kN循环荷载下电阻变化率分别提高了22.0%和11.1%。     

防污自洁聚偏氟乙烯膜的制备与表征

基于荷叶效应原理,利用聚偏氟乙烯(PVDF)溶液涂膜构筑微米结构,采用氧等离子体诱导化学沉积的方法在PVDF膜表面构筑纳米结构.利用扫描电镜、原子力显微镜、X射线光电子能谱仪及接触角测量仪等研究了PVDF膜表面的微结构及化学组成与疏水性能的关系.结果表明:PVDF溶液涂膜后可形成直径约为8μm的乳突,膜表面与水的接触角为88°;化学浴沉积法可在PVDF膜上生成刺状线性网络纳米结构,该表面与水的接触角为157°,滚动角为4°;化学气相沉积法可在PVDF膜生成鸟爪状的纳米结构,与水的接触角为155°,滚动角为4°.集灰试验证明,用两种沉积方法制备的PVDF膜表面均具有良好的防污自洁性能.     

聚羧酸减水剂合成方法最新研究进展

聚羧酸减水剂（PCEs）具有强大的分子设计能力,可通过引入特殊官能团、改变分子链结构、调节分子量及分子量多分散指数等化学手段或通过阴离子交换插层反应、共挤出技术等物理手段对PCEs进行修饰改性,从而制备不同功能型的PCEs。本文从合成方法角度讨论普通自由基聚合、可逆加成-断裂链转移（RAFT）聚合、化学改性、物理改性及化学改性和物理改性相结合制备PCEs的结构特点,分析纳米PCEs在水泥中的工作机理。此外,对PCEs的发展进行了展望,即从分子设计和合成工艺改善角度优化高性能聚羧酸减水剂。     

微滤膜用于污水回用处理的试验研究

采用中空纤维微滤膜对中水站出水进行了深度处理试验研究.试验结果表明,经过微滤膜过滤后,出水浊度小于1 NTU,对CODCr的去除率为30%左右,出水中未检出大肠杆菌,但对NH3-N的去除效果不佳.对膜污染过程研究发现,微滤膜在进行水力反冲洗后,跨膜压差增加会很快,这时需对膜进行化学反冲洗,并且根据处理原水情况选择化学反冲洗药剂.     

New PVDF membranes: The effect of plasma surface modification on retention in nanofiltration of aqueous solution containing organic compounds

New nanofiltration membranes were prepared by non-solvent-induced phase inversion from a PVDF/DMF/water system. The effect of exposure time before coagulation on the membrane characteristics (morphology, thickness, overall porosity, tensile strength) was investigated. PVDF membrane prepared at a fixed exposure time of 45s (PF45) was further plasma surface modified (RF 13.56 MHz) (PF45psm), introducing amino groups on the membrane. The performances of PF45, PF45psm and of a commercial nanofiltration membrane (N30F) were tested in the removal of two dyes from aqueous solution, characterized by different charge and molecular weight (congo red and methylene blue). The observed rejections depended more on the charge of the compound than on their molecular weights and results were optimized for the plasma modified membrane (PF45psm) with respect to unmodified (PF45) and commercial N30F membranes. In particular, methylene blue was retained for 100% by PF45psm with a relative flux of 65% compared to 38% of rejection and 59% of relative flux observed for N30F.     

Preparation and characterization of PAA/PVDF membrane-immobilized Pd/Fe nanoparticles for dechlorination of trichloroacetic acid

Poly(vinylidene fluoride) (PVDF) microfiltration (MF) membrane was successfully hydrophilized by coating with a novel hydrophilic layer, which was mainly composed of polyvinyl alcohol (PVA), glutaraldehyde, and polyethylene glycol (PEG). Pd/Fe nanoparticles (NPs) were prepared and immobilized in hydrophilized polyacrylic acid (PAA)/PVDF MF membrane. The unmodified and modified PVDF MF membranes were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The membrane-supported Pd/Fe NPs exhibited high reactivity in the dechlorination of trichloroacetic acid (TCAA). The effects of several important parameters, including Pd content, Pd/Fe NP loading, the preservation time of Pd/Fe NP membrane system on the dechlorination of TCAA were investigated. The stability of Pd/Fe NP membrane system was tested, and the kinetics and product distribution of dechlorination of TCAA by Pd/Fe NP membrane system were discussed.     

Investigation of the effect of coagulation bath composition on PVDF/CA membrane by evaluating critical flux and antifouling properties in lab‐scale submerged MBR

Ultrafiltration membranes were prepared from blends of poly(vinylidene fluoride) (PVDF)/cellulose acetate (CA) via phase inversion method. The effect of different coagulation bath compositions on the morphology and performance of the blend membrane prepared from casting solution of PVDF/CA with ratio of 80/20 was investigated using sewage wastewater. NaCl and ethanol were used as additives of coagulation bath. Fouling analysis was conducted with Bovine Serum Albumin solution and critical flux evaluation was performed using a lab‐scale membrane bioreactor. In terms of morphological structure, the macrovoids decreased and changed to finger‐like structure. The irreversible fouling reduced and the flux recovery ratio (FRR) of the modified membranes increased remarkably while the reversible fouling caused by deposition of foulants on the surface of the membranes increased. The maximum values of FRR and critical flux of irreversibility were reached by the membrane which was prepared in the coagulation bath containing the highest concentration of NaCl.     

Synthesis,characterisation and application of new tamarind triethylamine (TTEA) resin for removal of toxic metal ions from the effluent of Puneet Steel Industry,Jodhpur, Rajasthan

A new ion exchange resin tamarind triethylamine (TTEA) was chemically synthesised by modified Porath's method of functionalisation of polysaccharides. The prepared resin was characterised on the basis of ion exchange capacity, elemental analysis, Fourier transform infrared (FTIR) spectra and thermogravimetric analysis (TGA). Chemical resistivity of TTEA resin was assessed in several acidic, basic media. The present method is simple and rapidly applicable for the removal and recovery of metal ions from effluent of industries. The distribution coefficient (K _d) values of metal ions have been determined by batch method. Owing to the large differences in K _d values of toxic metal ions at different pH, removal and recovery of metal ions from their aqueous solutions and effluent of Puneet Steel Industry, Jodhpur has been studied systematically. The adsorption of different metal ions on TTEA resin follows the order; Fe²⁺ > Zn²⁺ > Cu²⁺ > Pb²⁺ > Cd²⁺. The Ion exchange capacity (IEC) of TTEA resin was 2.04%.     

TiO2 and polyvinyl alcohol (PVA) coated polyester filter in bioreactor for wastewater treatment

Prepared by coating TiO₂/polyvinyl alcohol (PVA) on a low cost polyester filter cloth (22 μm), a composite membrane (10 μm pore size) was successfully used in an anoxic/oxic membrane bioreactor (A/O-MBR) for treating a simulate wastewater in removing nitrate/ammonium for water reuse in a polyester fiber production plant. Its permeate flux and the anti-fouling properties against extracellular polymeric substances (EPS) were studied. Comparing with a commercial (0.1 μm) PVDF (polyvinylidene fluoride) membrane, similar effluent qualities were achieved, meeting the basic COD requirements for reuse. Anti-EPS accumulation, the TiO₂/PVA Polyester composite membrane had higher sustained permeability and required less frequent cleaning. Its filtration time was 4 times longer when operated at a higher flux than the PVDF membrane. The nano-TiO₂ enhances the interaction between PVA and polyester, forms a more hydrophilic surface, drastically reduces the contact angle with water and reduces EPS fouling. The slow (trans-membrane pressure) TMP rise, loose cake layer, the low filtration resistances, and the EPS, SEM analysis confirmed the advantage of the composite membrane. Potential in lowering the membrane cost, the operation and maintenance cost, and in enhancing MBR waste water treatment efficiency is expected by the use of this new composite membrane.     

大型超滤水厂PVC和PVDF膜运行特性差异与优化

超滤技术已广泛应用于城镇给水处理厂,使得饮用水水质得到显著改善。不同材质超滤膜的运行周期、膜通量、跨膜压差(TMP)等的变化规律会有显著的差异,需要根据各自的特点对超滤系统进行运行参数调控与优化,以保证超滤系统的长期稳定运行。分析了山东某大型超滤水厂超滤系统长期运行的特点,对比了PVC膜和PVDF膜孔结构特征、膜通量、跨膜压差变化趋势及膜过滤阻力特性,调控和优化超滤系统运行参数,并进行了长时间的运行验证。结果表明,膜孔径和膜孔结构不同造成的膜污染是PVC膜与PVDF膜过滤特性差异的主要因素,恒定过滤周期运行模式下PVC膜通量加速衰减时段为82~220 min,造成PVC膜通量衰减了9. 14%,并形成了约5%的永久衰减膜通量,而PVDF膜的通量衰减并不明显,使得水厂超滤系统在恒定过滤周期(180min)运行模式下,出现了PVC膜的污染速率明显高于PVDF膜、系统的运行工况出现显著差异的现象。按照恒定过滤阻力模式运行时,PVC膜和PVDF膜的最佳过滤周期范围分别为82~108 min和96~155 min。水厂超滤系统在恒定过滤阻力运行模式下将PVC膜与PVDF膜在高温期和低温期的过滤周期分别调整为110、90 min和150、120 min,TMP的增长速率和化学维护清洗周期均基本一致,超滤系统实现了长期稳定运行。研究成果为我国超滤水厂中不同材质超滤膜的运行参数优化及协同稳定运行提供了参考。     

The influence of the high and low molecular weight fractions of a bleach kraft mill effluent on the microbial activity of activated sludge

The high molecular weight (HMW) fraction (> 1000 Da) of bleached kraft mill effluent (BKME) is the principal source of adsorbable organic halide (AOX), colour and chemical oxygen demand in treated effluent. The influence of HMW material on the microbial activity of activated sludge microorganisms was studied in a series of batch growth experiments using fractionated effluent. The HMW material in the untreated effluent comprised 80% of the AOX but only 20% of the soluble COD. Multivalent metal ions had a greater affinity for this HMW fraction. The addition of HMW material to the LMW fraction had a stimulatory effect on microbial activity as measured by increases in biomass and substrate utilization. Chemical characterization and subsequent growth experiments revealed that nitrogen, which was deficient in the LMW effluent, was primarily associated with the HMW material. The association of nitrogen with the HMW fraction may have an important role on the behaviour of nitrogen within a biological treatment system and in the receiving environment.     

Comparison of fouling characteristics of two different poly-vinylidene fluoride microfiltration membranes in a pilot-scale drinking water treatment system using pre-coagulation/sedimentation, sand filtration, and chlorination

Two pilot-scale hybrid water treatment systems using two different poly-vinylidene fluoride (PVDF) microfiltration (MF) membranes (i.e. symmetric and composite) were operated at a constant permeate flux of 104.2l m(-2)h(-1) (=2.5 md(-1)) with a pre-coagulation/sedimentation, sand filtration (SF), and chlorination to produce potable water from surface water. Turbidity was removed completely. And humic substances, Al, and Fe were removed very well by the pilot-scale membrane system. To control microbial growth and mitigate membrane fouling, a NaOCl solution was injected into the effluent from SF before reaching the two membranes (pre-chlorination). However, it adversely affected membrane fouling due to the oxidization and adsorption of inorganic substances such as Al, Fe, and Mn. In the next run, the NaOCl was introduced during backwash (post-chlorination). As compared with the result of pre-chlorination, this change increased the operating period of the symmetric and the composite membranes from about 10 and 50 days to about 60 and 200 days, respectively.