Cellulose-based materials in wastewater treatment of petroleum industry

The most abundant natural biopolymer on earth, cellulose fiber, may offer a highly efficient, low-cost, and chemical-free option for wastewater treatment. Cellulose is widely distributed in plants and several marine animals. It is a carbohydrate polymer consisting of β-1,4-linked anhydro-D-glucose units with three hydroxyl groups per anhydroglucose unit(AGU). Cellulose-based materials have been used in food, industrial, pharmaceutical, paper, textile production, and in wastewater treatment applications due to their low cost, renewability,biodegradability, and non-toxicity. For water treatment in the oil and gas industry, cellulose-based materials can be used as adsorbents, flocculants, and oil/water separation membranes. In this review, the uses of cellulose-based materials for wastewater treatment in the oil & gas industry are summarized, and recent research progress in the following aspects are highlighted: crude oil spill cleaning, flocculation of solid suspended matter in drilling or oil recovery in the upstream oil industry, adsorption of heavy metal or chemicals, and separation of oil/water by cellulosic membrane in the downstream water treatment.

Structural limiting factors of mixed-valent tin oxides in photoelectrochemical application:A comparative exploration

Photoelectrocatalytic(PEC)materials for harvesting solar energy can be discovered from existing photocatalytic semiconductors.Nonetheless,mixed valence tin oxides,a group of widely reported visible light active photocatalysts,can hardly be developed into efficient PEC photoelectrodes.To overcome this difficulty by clarifying its origin,two typical mixed valence tin oxides,Sn^(2+):SnO_(2) microrods and porous Sn_(3)O_(4) particles were deliberately prepared as the models.Sn^(2+):SnO_(2) microrods of less porosity exhibited a photocurrent over ten times higher than Sn_(3)O_(4) particles.Photo-electrochemical impedance spectroscopy revealed this was due to their charge kinetics difference,specifically the internal transport/-transfer responding to the morphology.Moreover,hydroxyl residuals from synthesis were found to be very inhibitive for the PEC efficiency as well,which was in coherence with our TGA and Raman spectroscopic study.These finding experimentally proved the necessity of reconsidering the surface area,crystallinity,and defects when developing photocatalysts into efficient PEC structures.

Mechanisms and experimental research of ion-matched waterflooding to enhance oil recovery in carbonate reservoirs: A case of Cretaceous limestone reservoirs in Halfaya Oilfield, Middle East

Based on systematically summarizing the achievements of previous ion-matched waterflooding researches,the diversity and synergy of oil recovery enhancement mechanisms and the interaction between mechanisms are examined according to two classification standards,and the influence of behaviors of different ions on different mechanisms and oil displacement efficiency are investigated.Ionic strength is proposed to characterize the behavior differences of univalent and divalent ions,the relationships between ionic strength,effective concentration,and mechanisms are established to characterize the ion behavior behind various mechanisms,and evaluate the performance of ion-matched injection water.The mechanisms of enhancing oil recovery by ion-matched waterflooding include:(1)The ion-matched water can reduce the ion strength and match the ion composition of formation water,thereby reducing the difference between the effective concentration of univalent ions and divalent ions on the surface of carbonate rocks,and improving the effective concentration of potential determining ions(especially SO42-).(2)It can improve wettability,oil-water interface properties,pore structure and physical properties of the reservoir,and finally enable the establishment of a new ionic equilibrium conducive to waterflooding while breaking the original equilibrium.In this study,experiments such as relative permeability curve,interfacial tension,and core-flooding were carried out on carbonate core samples from the Cretaceous Mishrif Formation reservoirs in Halfaya Oilfield,Middle East,a method for injection water evaluation was established and the injection water suitable for these reservoirs was selected:6 times diluted seawater.Compared with ordinary seawater,oil displacement efficiency can be increased by more than 4.60%and compared with the optimum dilution of formation water,oil displacement efficiency can be increased by 3.14%.

Biomimetic MXene membranes with negatively thermo-responsive switchable 2D nanochannels for graded molecular sieving

Negatively thermo-responsive 2D membranes,which mimic the stomatal opening/closing of plants,have drawn substantial interest for tunable molecular separation processes.However,these membranes are still restricted significantly on account of low water permeability and poor dynamic tunability of 2D nanochannels under temperature stimulation.Here,we present a biomimetic negatively thermo-responsive MXene membrane by covalently grafting poly(N-isopropylacrylamide)(PNIPAm)onto MXene nanosheets.The uniformly grafted PNIPAm polymer chains can enlarge the interlayer spacings for increasing water permeability while also allowing more tunability of 2D nanochannels for enhancing the capability of gradually separating multiple molecules of different sizes.As expected,the constructed membrane exhibits ultrahigh water permeance of 95.6 L m^(-2) h^(-1) bar^(-1) at 25℃,which is eight-fold higher than the state-of-the-art negatively thermoresponsive 2D membranes.Moreover,the highly temperature-tunable 2D nanochannels enable the constructed membrane to perform excellent graded molecular sieving for dye-and antibiotic-based ternary mixtures.This strategy provides new perspectives in engineering smart 2D membrane and expands the scope of temperature-responsive membranes,showing promising applications in micro/nanofluidics and molecular separation.

Instant formation of excellent oxygen evolution catalyst film via controlled spray pyrolysis for electrocatalytic and photoelectrochemical water splitting

The retarded kinetics of oxygen evolution on electrodes is a bottleneck for electrochemical energy conversion and storage systems.NiFe-based electrocatalysts provide a cost-effective choice to confront this challenge.However,there is a lack of facile techniques for depositing compact catalytic films of high coverage and possessing a state-of-the-art performance,which is especially desired in photoelectrochemical(PEC)systems.Herein,we demonstrate a spray pyrolysis(SP)route to address this issue,featuring the kinetic selective preparation towards the desired catalytic-active material.Differing from reported SP protocols which only produce inactive oxides,this approach directly generates a unique composite film consisting of NiFe layered oxyhydroxides and amorphous oxides,exhibiting an overpotential as small as 255 mV(10 mA cm^(−2))and a turnover frequency of∼0.4 s^(−1)per metal atom.By using such a facile protocol,the surface rate-limiting issue of BiVO_(4)photoanodes can be effectively resolved,resulting in a charge injection efficiency of over 90%.Considering this deposition directly start from simple nitrates but only takes several seconds to complete,we believe it can be developed as a widely applicable and welcomed functionalization technique for diverse electrochemical devices.

Molecular dynamics simulation study onπ-πstacking of Gemini surfactants in oil/water systems

Whereas theπ-πstacking interactions at oil/water interfaces can affect interfacial structures hence the interfacial properties,the underlying microscopic mechanism remains largely unknown.We reported an all-atom molecular dynamics(MD)simulation study to demonstrate how the Gemini surfactants with pyrenyl groups affect the interracial properties,structural conformations,and the motion of molecules in the water/n-octane/surfactant ternary systems.It is found that the pyrenyl groups tend to be vertical to the interface owing to theπ-πstacking interaction.Besides,a synergistic effect between theπ-πinteraction and steric hindrance is found,which jointly affects the coalescence of liquid droplets.Therefore,the existence of aromatic groups and a moderate number of surfactants helps to form microemulsion.This work provides a molecular understanding of Gemini surfactants with aromatic groups in microemulsion preparation and applications.

Analysis and countermeasures of natural gas development in China

Natural gas has become a transitional bridge from fossil to green and clean energy worldwide.The importance of natural gas utilization in energy structure optimization and green development is no exception for China.However,the supply of China’s natural gas limits the country’s demand with three factors.(1)China’s natural gas resource is relatively rich,but its quality is poor with deep burial depth.Therefore,the annual plateau yield of natural gas cannot be high,with an estimated value of approximately 260-270 x 109 m3.(2)The demand for natural gas in China’s economic development is growing rapidly.The peak demand is estimated to be approximately 550-650 x 109 m3 per year or even higher.The import volume of natural gas will soon exceed that of domestic self-produced gas.(3)Natural gas is a necessity closely related to livelihood.Particularly,a shortage in natural gas supply affects social stability.Therefore,its external dependency should be under 50%and not exceed 60%.In this study,the future situation of China's natural gas is forecasted,and relevant countermeasures and suggestions are proposed in accordance with research on China’s natural gas resource potential,production trend,supplydemand link,and gas supply safety factors.

Enhancing Li-ion conduction and mechanical properties via addition of fluorine-containing metal–organic frameworks in allsolid-state cross-linked hyperbranched polymer electrolytes

Poly(ethylene oxide)(PEO)-based solid polymer electrolytes(SPEs)are commonly used in lithium metal batteries(LMBs)for their good Li-salt solvating ability and easy processability.However,the relatively low Li-ion conduction ability hinders their further development.In this work,a novel hyperbranched-polyether-type composite solid polymer electrolyte(CSPE)is prepared via a quick cross-linking reaction between aldehyde-terminated polyethylene glycol(PEG)and hyperbranched poly(ethylene imine)(HPEI)in the presence of lithium salt and fluorine-containing Zr-based metal–organic framework(MOF)UiO-66-(F)_(4).The hydrogen bonds between the fluorine atoms and amino groups in the electrolyte help to the better dispersion of UiO-66-(F)_(4) in the polymer matrix,which is beneficial to solving the problem of aggregation of nanofillers.Besides,the CSPEs with the functional MOF fillers show improvements in both electrochemical and mechanical properties.Notably,the Li-ion transference number(t)is considerably enhanced from 0.23 to 0.54.All-solid-state LMBs based on the CSPE also present good cycling performances.A high specific discharge capacity of 141.4 mAh·g^(−1) is remained after 200 cycles at 0.2 C.This study not only provides an effective synthesis method of the cross-linked hyperbranched polymer electrolyte,but also puts forward a new strategy for uniform dispersion of inorganic fillers in CSPEs.

TiO_(2)/CuPc/NiFe-LDH photoanode for efficient photoelectrochemical water splitting

Photoelectrochemical(PEC)water splitting is a promising approach for renewable hydrogen production.However,the practical PEC solar-to-fuel conversion efficiency is still low owing to poor light absorption and rapid recombination of charge carriers in photoelectrode.In this work,we report a ternary photoanode with simultaneously enhancement of light absorption and water oxidation efficiency by introducing copper phthalocyanine(CuPc)and nickel iron-laye red double hydroxide(NiFe-LDH)on TiO_(2)(denoted as TiO_(2)/CuPc/NiFe-LDH).An experimental study reveals that CuPc loading on TiO_(2)bring strong visible light absorption;NiFe-LDH as an oxygen evolution reaction catalyst efficiently accelerates the surface water oxidation reaction.This synergistic effect of CuPc and NiFe-LDH gives enhanced photocurrent density(2.10 mA/cm^(2)at 0.6 V vs.SCE)and excellent stability in the ternary TiO_(2)/CuPc/NiFeLDH photoanode.