Fouling behavior of poly(vinylidene fluoride)(PVDF)ultrafiltration membrane by polyvinyl alcohol(PVA)and chemical cleaning method

Severe fouling to poly(vinylidene fluoride)(PVDF)membrane is usually caused as filtrating the papermaking wastewater in the ultrafiltration(UF)process.In the paper,fouling behavior and mechanism were investigated,and the low-concentration polyvinyl alcohol(PVA)contained in the sedimentation tank wastewater was found as the main foulant.Consequently,the corresponding cleaning approach was proposed.The experiment and modeling results elaborated that the fouling mode developed from pore blockage to cake layer along with filtration time.Chemical cleaning conditions including the composition and concentration of reagents,cleaning duration and trans-membrane pressure were investigated for their effect on cleaning efficiency.Pure water flux was recovered by over 95% after cleaning the PVDF membrane using the optimal conditions 0.5 wt% NaClO(as oxidant)and 0.1 wt% sodiumdodecyl benzene sulfonate(SDBS,as surfactant)at 0.04MPa for 100 min.In the chemical cleaning method,hypochlorite(ClO−)could first chain-scissor PVA macromolecules to small molecules and SDBS could wrap the fragments in micelles,so that the foulants were removed from the pores and surface of membrane.After eight cycling tests,pure water flux recovery maintained above 95% and the reused membrane was found intact without defects.

Application of response surface methodology to the chemical cleaning process of ultrafiltration membrane

A numerical model was established to predict and optimise the chemical cleaning process of Polyvinylidene Fluoride(PVDF)Ultra filtration(UF)membranes with the results from the experiment that applied the Response Surface Method(RSM)and Central Composite Design(CCD).The factors considered in the experimental design were sodium hydroxide(NaOH)concentration,sodium hypochlorite concentration(NaClO),citric acid concentration and cleaning duration.The interactions between the factors were investigated with the numerical model.Humic acid(20 mg·L-1)was used as the model foulant,and chemical enhanced back flush(CEB)was employed to simulate the chemical cleaning process.The concentrations of sodium hydroxide,sodium hypochlorite,citric acid and cleaning duration tested during the experiments were in the range of 0.1%–0.3%,100–300 mg·L-1,1%–3%and 0.5–1.5 h,respectively.Among the variables,the sodium hypochlorite concentration and the cleaning duration showed a positive relationship involving the increased ef ficiency of the chemical cleaning.The chemical cleaning ef ficiency was hardly improved with increasing concentrations of sodium hydroxide.However,the data was sharply decreased when at a low level of sodium hydroxide concentration.In total,54 sets of cleaning schemes with 80%to 100%cleaning ef ficiency were observed with the RSM model after calibration.

Influence of wet chemical cleaning on quantum efficiency of GaN photocathode

GaN samples 1-3 are cleaned by a 2：2：1 solution of sulfuric acid（98%） to hydrogen peroxide（30%） to de-ionized water;hydrochloric acid（37%）;or a 4：1 solution of sulfuric acid（98%） to hydrogen peroxide（30%）.The samples are activated by Cs/O after the same annealing process.X-ray photoelectron spectroscopy after the different ways of wet chemical cleaning shows：sample 1 has the largest proportion of Ga,N,and O among the three samples,while its C content is the lowest.After activation the quantum efficiency curves show sample 1 has the best photocathode performance.We think the wet chemical cleaning method is a process which will mainly remove C contamination.

A Giant of China's Cleaning Industry——The Blue Star Chemical Cleaning Group Corporation

First business: to clean a tea pot. Income: RMB 0.20 (less than 10 US cents at the time). Second business: to clean a boiler. Income: RMB 1, 200. Three months later, incomereached RMB 240, 000. Ten years later, the company had 350 subsidiaries across China and four joint ventures abroad, with an annual output value of more than RMB 300 million. The data are simple but intriguing, recording the history of the Blue

Super-hydrophobic and Self-cleaning PVDF Film Fabricated by Chemical Bath Deposition

Self-cleaning surfaces have received a great deal of attention recently,both in theoretical studies and commercial applications.The self-cleaning surface of lotus leaf is hydrophobic and rough,showing a micro-and nano-scale morphology.The micro-reliefs of lotus leaf were mimicked using polyvinylidene fluoride(PVDF)film and nano-scale peaks on the top of the micro-reliefs were implemented by the reaction between methyltrichlorosilane and the reactive groups of PVDF film treated by oxygen plasma.A lotus-leaf-like surface of the PVDF film was clearly observed by scanning electronic microscopy(SEM)and atomic force microscope(AFM).Elemental composition analysis by X-ray photoelectron spectroscopy(XPS)revealed that the material of the nanostructure of PVDF film was polymethylsiloxane.The superhydrophobic property of the mimicked self-cleaning surface was validated by the water contact angle and sliding angle on the lotus-leaf-like PVDF film,which were 156.6° and 4°,respectively.In this case,water droplets can easily move across the PVDF film surface,carrying dirt particles away,leaving no contamination.

Study of Oil-Bearing Drill Cuttings Cleaning and De-Oiling Treatment Method for Shale Gas Reservoirs

Due to its extensive use in shale gas exploration and development,oil-based drilling fluids generate large amounts of oil-bearing drill cuttings during the drilling process.The large amount of oil-bearing drill cuttings generated during the drilling process can lead to serious secondary contamination.In this study,a wetting agent FSC-6 with good hydrophobic and oleophobic properties was synthesized to construct an efficient oil removal system.For the first time,the mechanism of this system was analyzed by using the theory of adhesion function,interfacial tension and wettability.At the same time,a combined acoustic-chemical treatment process was applied to the wastewater and slag generated after the cleaning of the oil-bearing drill cuttings.The experimental results show that the application of this pollution-free technology can effectively solve the environmental pollution and resource recovery problems of oil-bearing drill cuttings.It meets the standard of drilling chips with oil content less than 2%in SY/T7422-2018“Oil-based drilling fluid drilling chips treatment system for oil and gas drilling equipment”.

Experimental investigation on coal pore-fracture variation and fractal characteristics synergistically affected by solvents for improving clean gas extraction

Chemical solvents instead of pure water being as hydraulic fracturing fluid could effectively increase permeability and improve clean methane extraction efficiency.However,pore-fracture variation features of lean coal synergistically affected by solvents have not been fully understood.Ultrasonic testing,nuclear magnetic resonance analysis,liquid phase mass spectrometry was adopted to comprehensively analyze pore-fracture change characteristics of lean coal treated by combined solvent(NMP and CS_(2)).Meanwhile,quantitative characterization of above changing properties was conducted using geometric fractal theory.Relationship model between permeability,fractal dimension and porosity were established.Results indicate that the end face fractures of coal are well developed after CS2and combined solvent treatments,of which,end face box-counting fractal dimensions range from 1.1227 to 1.4767.Maximum decreases in ultrasonic longitudinal wave velocity of coal affected by NMP,CS_(2)and combined solvent are 2.700%,20.521%,22.454%,respectively.Solvent treatments could lead to increasing amount of both mesopores and macropores.Decrease ratio of fractal dimension Dsis 0.259%–2.159%,while permeability increases ratio of NMR ranges from 0.1904 to 6.4486.Meanwhile,combined solvent could dissolve coal polar and non-polar small molecules and expand flow space.Results could provide reference for solvent selection and parameter optimization of permeability-enhancement technology.

Status and Suggestion for Modern Coal Chemical Industry and Coal Clean Technology

Coal is fossil fuel abundant and widespread all over the world. It is a vital resource for energy security in our country, because the supply is stable. In this paper, the important role of coal played in the total primary energy supply was described, and the status of modern coal chemical industry and clean coal technologies was analyzed. Based on the scientific research experiences of author, strategy and suggestion for Chinese development were proposed according to the regulation of scientific panning. In China, there are more social benefits and strategic meaning for developing the coal high-efficiency utilization technology. Considering of the general situation of our countries, these technologies with the features of can be industrialized, advanced, applicative, mature and feasible should be developed preferentially. The high-expend, low economic effectiveness and behindhand technologies should be abandoned. So, the development of coal clean technology in China should meet the natural resources, restrictive condition and elements of our countries industry situations. Based on these analysis, the most important technologies and fundamental researches should be prior developed in China.

Preparation of chemical manganese dioxide from manganese sulfate

Chemical Manganese Dioxide (CMD) was prepared by an alkali-oxidation method. There are several virtues to this environmental friendly and clean process, including the nontoxic and harmless reagents and products, easy operations, no pollutants, easily obtained raw materials and moderate reaction conditions. The synthesized manganese dioxide was characterized by XRD and SEM. The particles were small, consisting primarily of α-MnO2 and γ-MnO2. Experimental results showed that the optimum conditions were: MnSO4?H2O to NaOH ratio, 1.0:2.4; catalyst concentration (catalyst TF-2), 6% of the MnSO4; initial solution pH, 11; reaction time and temperature, 20 min and 80 °C; air flow, 0.20 m3/h; and, agitation rate, 700 r/min. The conversion of MnSO4 can exceed 80% under these optimum conditions.

Cleaning of nitrogen-containing carbon contamination by atmospheric pressure plasma jet

Atmospheric pressure plasma jet(APPJ)was used to clean nitrogen-containing carbon films(C–N)fabricated by plasma-assisted chemical vapor deposition method employing the plasma surface interaction linear device at Sichuan University(SCU-PSI).The properties of the contaminated films on the surface of pristine and He-plasma pre-irradiated tungsten matrix,such as morphology,crystalline structure,element composition and chemical structure were characterized by scanning electron microscopy,grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy.The experimental results revealed that the removal of C–N film with a thickness of tens of microns can be realized through APPJ cleaning regardless of the morphology of the substrates.Similar removal rates of 16.82 and 13.78μm min^(-1)were obtained for C–N films deposited on a smooth pristine W surface and rough fuzz-covered W surface,respectively.This is a remarkable improvement in comparison to the traditional cleaning method.However,slight surface oxidation was found after APPJ cleaning,but the degree of oxidation was acceptable with an oxidation depth increase of only 3.15 nm.Optical emission spectroscopy analysis and mass spectrometry analysis showed that C–N contamination was mainly removed through chemical reaction with reactive oxygen species during APPJ treatment using air as the working gas.These results make APPJ cleaning a potentially effective method for the rapid removal of C–N films from the wall surfaces of fusion devices.

Application of heat-activated peroxydisulfate process for the chemical cleaning of fouled ultrafiltration membranes

Na Cl O has been widely used to restore membrane flux in practical membrane cleaning processes,which would induce the formation of toxic halogenated byproducts.In this study,we proposed a novel heatactivated peroxydisulfate(heat/PDS)process to clean the membrane fouling derived from humic acid(HA).The results show that the combination of heat and PDS can achieve almost 100%recovery of permeate flux after soaking the HA-fouled membrane in 1 mmol/L PDS solution at 50℃ for 2 h,which is attributed to the changes of HA structure and enhanced detachment of foulants from membranes.The properties of different treated membranes are characterized by scanning electron microscopy(SEM),atomic force microscope(AFM),attenuated total reflection Fourier transform infrared spectroscopy(ATRFTIR),and X-ray photoelectron spectroscopy(XPS),demonstrating that the reversible and irreversible foulants could be effectively removed by heat/PDS cleaning.The filtration process and fouling mechanism of the cleaned membrane were close to that of the virgin membrane,illustrating the good reusability of the cleaned membrane.Additionally,heat/PDS which can avoid the generation of halogenated byproducts shows comparable performance to Na Cl O on membrane cleaning and high performance for the removal of fouling caused by sodium alginate(SA),HA-bovine serum albumin(BSA)-SA mixture and algae,further suggesting that heat/PDS would be a potential alternative for membrane cleaning in practical application.

新型能源体系发展背景下煤炭清洁高效转化的挑战及途径

当今世界地缘政治风险加剧、气候环境问题凸显,能源转型变革加快。在此背景下,构建更加适应形势变化的能源体系对提高我国能源供应系统的可持续性及安全稳定性意义重大。目前我国化石能源仍占据主体地位。油气资源存在能源安全问题及新能源技术水平有待提升,中国短期内对煤炭能源仍将保持较高依赖性。因此,推进煤炭清洁高效转化对于新型能源体系的构建具有重要意义。首先对新型能源体系的具体内涵与构建方向展开讨论,并在此基础上,对新时代中国煤化工产业的发展现状以及面临的机遇与挑战进行了阐述,以期为煤炭的清洁高效转化技术的进步及煤化工产业的未来发展提供建议。新时代要求赋予新型能源体系更多的内涵。因此从战略上看,未来能源体系应具备“安全高效、清洁低碳、多元协同、智能普惠”多个特征,这也对煤炭产业的清洁高效发展提出了更高的要求。我国的煤炭清洁高效转化已取得显著进步,但多个关键技术仍亟待突破。结合煤炭产业转型发展与“双碳”目标关系的系统性认识,在新型能源体系建设的需求下,推进煤炭清洁高效转化对于社会经济发展、助力“双碳”目标实现具有重要意义,其关键在于加强该领域相关学科专业的基础研究和煤炭清洁高效转化技术的创新开发。

硫酸钡锶的结垢机理与化学除垢技术的研究现状

结垢会给油田生产带来严重危害,严重威胁生产流程的进行,降低生产流量,导致生产损失。注入的水、原生水与岩石之间存在化学作用,导致储层流体的组成复杂,因此难以控制无机结垢地层。碳酸盐(钙)、硫化物(铁、锌)和硫酸盐(钙、钡、锶)垢在油田中更为常见,结垢的形成取决于各种因素,包括但不限于温度、压力、溶液饱和度、流体动力学行为等。本文介绍了油气生产中常见的无机结垢类型、形成机理、热力学溶积度、结垢预测,以及化学除垢剂的研究现状与发展趋势,以期为油田硫酸钡锶垢的预防与除垢提供参考。

海上油田污水回注井高效解堵技术研究与应用

针对污水回注井酸化效果不理想的问题,利用岩心流动实验、悬浮物含量及粒径测试、X射线衍射对堵塞情况进行了分析。在此基础上,利用填砂管流动和岩心溶蚀实验研发了一套兼具污油清洗与高溶蚀率的酸液体系。此外,结合储层特征优化了酸液置放工艺。结果表明,污油和固体悬浮物在近井地带形成的复合堵塞物是造成储层堵塞的主要原因;1%水基清洗剂洗油率达到86.44%,高溶蚀酸对固体悬浮物溶蚀率达到89.77%,二者复配体系能够快速瓦解油泥小球;化学微粒分流剂可对储层形成有效暂堵分流,且酸化后自动溶解。该技术矿场应用8井次,平均视吸水指数提高1.74倍。该技术适用于污水回注井解堵,并为提高海上污水回注井酸化效果提供理论和实践依据。

一种新型绿色汞清洗剂的应用研究

主要研究了一种二烷基二硫代次膦酸盐和乙醇组成的汞清洗剂,利用二烷基二硫代次膦酸盐与汞形成配位化合物、采用乙醇作为溶剂体系,在溶剂和配位体作用下,可以让大汞珠转变为细微的配位体颗粒物,分散于乙醇中,无搅拌情况下剥离沉积在壁面的汞,并实现了对沉积于设备内壁的汞的清洗。该工艺的含汞配位体通过简单过滤实现与清洗剂分离,汞清洗剂可循环利用,含汞物可作固废处理,而且所用的清洗剂不腐蚀设备,是一种绿色汞清洗剂。分析了影响洗汞效果的各种因素,得到了最优的洗汞工艺:2%的浓度,保持中性或弱碱性,室温处理,漫灌浸泡不少于6hr。

二沉池出水造成的超滤膜污染在NaClO溶液中化学清洗效能研究

二沉池出水中含有大量微生物代谢产物,这些物质在采用超滤膜对二沉池出水进行深度处理时会产生严重的膜污染,NaClO溶液常用于化学清洗有机物及微生物造成的膜污染。该研究采用NaClO溶液对二沉池出水造成的超滤膜污染进行化学清洗,结合膜通量、膜表面形貌、官能团、主要元素组成在NaClO溶液清洗前后的变化深入分析了NaClO化学清洗膜污染的效能及对膜特性的影响。结果表明NaClO溶液化学清洗可高效去除膜污染并恢复膜通量,但会改变膜表面形貌及元素组成;清洗温度、清洗时间、初始pH及NaClO浓度都会对清洗效能产生影响,在近中性、常温条件下,将污染膜浸泡在100 mg/L NaClO溶液内2 h即可有效去除膜污染,且过度清洗会导致膜损伤。因此,采用NaClO溶液化学清洗二沉池出水造成的膜污染时,需要严格控制清洗条件以实现膜污染高效去除并减少对膜结构特性的影响。

我国化学纤维纺丝专件清洗技术的研究进展

为了提高对纺丝专件清洗技术的认识和开发,进而提升化学纤维的生产效率和产品质量,对国内纺丝专件清洗存在的问题进行详细分析,从物理、化学和复合清洗技术3方面出发,综述了纺丝专件清洗技术和设备在清洗质量、清洗效率和节能减排上的研究进展,总结了当前纺丝专件清洗技术的发展趋势,并指出加强纺丝过程中污垢物理特性的基础研究、复合清洗技术的应用研究、清洗标准的理论研究以及清洗过程中节能减排的综合研究是推动纺丝专件清洗技术不断进步的关键。

废水处理中纳滤膜化学清洗技术研究现状、挑战与展望

纳滤技术由于其操作压力较低、对二价离子截留率高等优势,在市政污水、纺织废水、制药废水等废水处理领域有广阔的应用前景。然而膜污染问题的存在限制了纳滤技术的发展,膜污染不仅会导致膜通量衰减、分离性能下降,还会大大缩短膜的使用寿命。化学清洗可有效缓解膜污染,但常用的清洗剂均会对膜结构和分离性能产生影响,还可能引发生物耐药性及膜清洗废水二次污染等问题。本文对不同类型废水处理中纳滤膜的污染特征及化学清洗方法进行综述,并且重点阐释了酸、碱、次氯酸钠等化学清洗剂与聚酰胺纳滤膜的作用机制,以及频繁的化学清洗对膜面微生物的影响和所引发的生物风险,最后对有关问题的解决措施提出展望,以期为膜污染控制方法的优化提供参考。