Strong Alkaline Environment Research Articles

Effect of waste glass powder on pore structure, mechanical properties and microstructure of cemented tailings backfill

In order to reduce the filling cost of the mine and improve the performance of the cemented tailing backfill (CTB), waste glass powder (WGP) is introduced into the CTB as a substitute for cement in this paper. The study examined pore structure, mechanical properties and microstructure changes of CTB samples based on 0, 10, 20, and 30 % WGP replacement rates. The following conclusions are obtained, the pore size of CTB is divided into micropores, secondary pores, and macropores with the boundary of 20 nm and 200 nm, and the pores in CTB are mainly macropores. The incorporation of WGP can improve the pore structure of CTB. The hydration of CTB with WGP can be divided into two parts. Before the curing time is 56d, cement dominated hydration occurs in CTB. WGP mainly plays the role of micro aggregate effect in filling the pores of CTB, and the strength of CTB decreases with the increase of WGP replacement rate. After 56d of curing, cement hydration rate slows down. The pozzolanic activity of WGP is activated under strong alkaline environment, and the secondary hydration reaction enhances the long-term strength of CTB. Especially for CTB with a replacement rate of 20 %, the particle peeling on the surface of the sample is improved after unconfined compression and its microstructure is more compact, the Ca/Si ratio is significantly increased after long-term curing.

Differential precipitation mechanism of cement and its impact on reservoir quality in tight sandstone: A case study from the Jurassic Shaximiao formation in the central Sichuan Basin, SW China

Permeability heterogeneity of tight sandstone reservoir is mainly determined by the types and quantities of different cements and dissolution processes that occur during the burial. The thin section description, scanning electron microscopy (SEM), x-ray diffraction (XRD), cathodoluminescence imaging (CL), computed tomography (CT) scans, mercury intrusion tests, electron probe analysis, fluid inclusions and isotopic analysis were used to determine genetic mechanism and its impact on reservoir quality of differential cement combinations in Shaximiao Formation tight sandstone in the Central Sichuan Basin, China. Diagenetic minerals in the Shaximiao Formation (J2s) sandstone comprise calcite, laumontite, chlorite and dissolution. The pore space of J2s sandstone mainly comprises primary pores and secondary pores formed after mineral dissolution. The reservoir sandstones can be divided into six types according to different combinations of the laumontite, chlorite and calcite. Authigenic chlorite coating of J2s sandstones occurred via chloritization of smectite during eodiagenesis. Laumontite cements derived from transformation of volcanic rock fragments, were precipitated in a strong alkaline environment with high pH value (9.5–12) and abundant Ca2+, Si4+, Al3+ during eodiagenesis. The δ13C and δ18O isotopic values and petrological characteristics indicate that calcite cement was related to feldspar dissolution and decarboxylation of organic matter. The different cement combinations were determined mainly by the sedimentary facies and subsequent diagenetic environment evolution. Laumontite precipitation needs a stronger alkaline diagenetic environment than that for chlorite and calcite. The early chlorite coating provided sufficient remaining pore-space for pore-filling laumontite and calcite precipitation. The presence of pore-filling laumontite decreased space for calcite precipitation. However, laumontite is more readily soluble than calcite. The different cement combinations have distinct residual pore space combinations meaning that some intervals of rock have sufficient permeability to act as viable reservoir rock whilst other combinations do not.

Effect of TiO2 on preparation condition, mechanical properties and alkali resistance of continuous basalt fibers

The low alkali resistance of basalt fiber limits its utilization in the strong alkaline environment such as cement and concrete as the reinforcing material. Adding additive in the basalt rocks is the feasible method to enhance the alkali resistance. However, it is necessary to develop the efficient additive for basalt fiber. In this work, the effect of TiO2 on the preparation condition, alkali resistance and mechanical properties of basalt fiber was investigated. The preparation conditions were studied by DSC, XRD and high-temperature rotational viscometer. Then the corrosion behavior of TiO2-basalt fibers in NaOH solution was studied via SEM/EDX, FIB/SEM and FTIR. The results indicated that the viscosity of basalt melt decreased significantly with the increasing TiO2 content from 0% to 2%, but the crystallization tendency was not changed with TiO2 below 2%, the upper limit for TiO2 addition. The tensile strength increased by 20–60% because Ti4+ promoted Al3+ into the network structure and intensify the polymerization by entering the network structure as network precursor in the form of [TiO4]. Meanwhile, TiO2 in the basalt fibers formed insoluble titanium hydroxide, so the weight loss of TiO2-basalt fibers in NaOH solution was reduced up to 50%. Through FIB/SEM/EDX, the corrosion of basalt fiber in alkali condition is controlled by ion diffusion. The outward diffusion of Fe, Mg and Ti to the surface of fiber formed the insoluble layer, so the rate of substitution reaction between the OH− and basalt fibers was slowed down, but it also leaded to the non-uniform corrosion.

Study of Concrete Crack Repair using Bacillus megaterium

The low yield of microbial calcium carbonate precipitation due to the strong pH environment has limited the development of biotechnology-based concrete crack repair techniques. In this study, Bacillus megaterium was selected to determine the optimal nutrient formulation through orthogonal tests. The growth and reproduction characteristics and urease activity of this strain were analysed by controlling different pH values, and the calcium carbonate precipitation yield under different pH conditions was investigated, and the lower precipitation yield under strong alkaline conditions was improved by using alkaline environment domestication with the addition of urea to the nutrient solution. It has been shown that higher pH results in lower growth and multiplication of Bacillus megaterium and weaker urease activity, and a strong alkaline environment can significantly suppress its growth and multiplication and urease activity. At pH 7, the growth and multiplication of Bacillus megaterium were the fastest, the urease activity was the strongest, and the precipitation yield was greater. The addition of urea to the nutrient solution to domesticate Bacillus megaterium in an alkaline environment can significantly increase the growth rate and precipitation yield, which can effectively solve the problem of insufficient calcium carbonate precipitation under alkaline conditions. Comparing the effectiveness of microbially induced calcium carbonate precipitation (MICP) in repairing concrete after damage before and after microbial domestication shows that the domesticated Bacillus megaterium is more effective in reducing the permeability characteristics of concrete and improving its strength.

The Core/Shell Structure P Doped MoS2 @Ni3 S2 Nanorods Array for High Current Density Hydrogen Evolution in Alkaline and Acidic Electrolyte.

Electrocatalysis is the most promising strategy to generate clean energy H2 , and the development of catalysts with excellent hydrogen evolution reaction (HER) performance at high current density that can resist strong alkaline and acidic electrolyte environment is of great significance for practical industrial application. Therefore, a P doped MoS2 @Ni3 S2 nanorods array (named P-NiMoS) was successfully synthesized through successive sulfuration and phosphorization. P-NiMoS presents a core/shell structure with a heterojunction between MoS2 (shell) and Ni3 S2 (core). Furthermore, the doping of P modulates the electronic structure of the P-NiMoS; the electrons transfer from the t2g orbital of Ni element to the eg empty orbital of Mo element through the Ni-S-Mo bond at the Ni3 S2 and MoS2 heterojunction, facilitating the hydrogen evolution reaction. As a result, P-NiMoS exhibits excellent HER activity; the overpotential is 290 mV at high current density of 250 mA cm-2 in alkaline electrolyte, which is close to Pt/C (282 mV@250 mA cm-2 ), and P-NiMoS can stably evolve hydrogen for 48 h.

Alkali-excited gel structure and compositions evolution in geopolymers synthesized from the spent FCC catalyst and steel slag

The effect of the alkaline activation process, especially the SiO2/Na2O molar ratio (Ms) in the prepared alkaline activator, on the geopolymer materials prepared using the spent fluid catalytic cracking (FCC) catalyst and steel slag as raw materials is investigated in this study. The results indicate that the compressive strength of prepared geopolymers has been greatly affected by the alkaline environment. The compressive strength of obtained samples is improved obviously in the strong alkaline environment. Meanwhile, the number of amorphous gels in the prepared geopolymers increased with Ms decreasing. It is conducive for the silicon-oxo-aluminate species in the oligomers to polymerize into polymers with 3D polymeric structures, which would lead to the surface of as-prepared samples becoming smoother and the structure becoming denser. Moreover, the strong alkaline environment is beneficial for Ca2+ to involve in the geopolymerization reaction and form the N(C)ASH gel, which can further enhance the compressive strength of the prepared geopolymer.

N-Nitrosodimethylamine formation in metformin hydrochloride sustained-release tablets: Effects of metformin and hypromellose used in drug product formulation

In recent years, nitrosamines have been discovered in some types of drug products that becomes a current regulatory hotspot, and have attracted a lot attention from both regulatory authorities and industry. This manuscript provided an industry perspective on the nitrosamines research. A liquid chromatography coupled with tandem mass spectrometry（LC-MS/MS）method was developed and applied for the quantification of N-nitrosodimethylamine (NDMA) in metformin hydrochloride sustained-release tablets (MET). The key factors resulting in the NDMA formation in MET were identified through forced degradation and drug-excipient studies, which included high temperature, dimethylamine, strong alkali and oxidation conditions, peroxide and alkaline components contained in the formulation as well as the nitrite and nitrate impurities that might be presented in certain excipients. Further, API particle size and water content of the drug product would also affect the growth rate of NDMA. Therefore, the following mitigation strategies to reduce the risk of nitrosamines in the finished drug product are proposed in this manuscript: 1) avoid the use of excipients containing nitrite, nitrate and peroxide impurities; 2) avoid high temperature and strong alkaline environment in the production and storage condition; 3) maintain an appropriate water content level in the formulation. Based on the above principles, it was recommended to add antioxidant or incorporate excipient such as Na2CO3 to modify the formulation pH to weak basic environment in the formulation of MET, which can could effectively prevent formation of NDMA in the stability process.

Enrichment Factors of Soil-Se in the Farmland in Shizuishan City, Ningxia

Shizuishan is a typical exhausted resources-based city in the northern area of the Ningxia Hui autonomous region in China. In order to develop the planting industry of selenium (Se)-rich agricultural products and promote green and sustainable urban development and transformation, investigations on the quality of Se-rich land were carried out in Shizuishan City, where 7399 surface soil (0-20 cm) samples of farmlands, 30 atmospheric precipitation samples, and nine parent rocks were collected. By means of semi variogram model construction by GS+, Kriging interpolation in ArcGIS and statistics via SPSS, such as correlation analysis and mean-value analysis, the content, spatial distribution, and enrichment factors of Se-soil were analyzed. Further, the enrichment characteristics of soil Se in alkaline conditions were summarized. The results indicated that ω(Se) in surface soil was (0.26±0.12) mg·kg-1, and its spatial distribution was highly auto-correlated. The variation in Se content was related to natural factors. Along Helan Mountain, the content of Se in the surface soil was comparatively higher than that where coal mines were located. The parent rock was the principal factor that controlled the enrichment of soil Se. The physical and chemical properties of soil such as organic material, pH, and iron and manganese oxides had crucial effects on the enrichment of soil Se in a surficial environment. Compared to a strong alkaline environment, alkaline conditions were beneficial for the enrichment of Se in the surface soil.

Hydrodeoxygenation of guaiacol to bio-hydrocarbons over Ni catalyst supported on activated coconut carbon in alkaline condition

Pulping black liquor is a serious source of water pollution worldwide, which is very difficult to subsequently treat. Lignin is the main component of the black liquor and is the only natural aromatic recyclable resource, which is burnt as waste in the Kraft pulping industry. Designing an efficient lignin conversion catalyst that suitable for the strong alkaline environment of black liquor harbors tremendous carbon-neutral potential but still remains a scientific and technological challenge. In this work, the strong alkaline environment of black liquor was simulated, and low-cost pretreated Ni/AC catalysts were adopted to the hydrodeoxygenation (HDO) of a lignin model (guaiacol), and a breakthrough was achieved in the efficient transformation of lignin compound into hydrocarbons. By multitechniques, (e.g., FT-IR, XPS, Boehm titration, HRTEM), the relevance between introducing functional acid groups and the surface properties of catalysts was revealed. It is found that the increased acidic groups are responsible for the enhanced C(sp2)-O cleavage reactions, while improving the dispersion of Ni NPs and thus enhance the HDO efficiency. It is worth noting that better selectivity of benzene and lower hydrogen consumption are achieved on Ni/NOAC during the HDO process. Furthermore, the reaction routes of guaiacol on catalysts with different functional acid groups were proposed. This work provides guidance for efficient utilization of lignin in waste black liquor, and is of great significance to the development of sustainable carbon-neutral biorefinery and environmental protection.

Hydrochemical Characteristics and Genetic Analysis of Shallow High-Fluorine Groundwater in Fuyang River Basin

In order to understand the sustainable and effective utilization of groundwater resources in Fuyang River Basin, the chemical characteristics and genetic evolution process of characteristic shallow fluoride groundwater in the region were carried out. The results show that the chemical characteristics of groundwater are zonal in horizontal direction. From the piedmont plain to the central plain, the hydrochemical types of the first and second aquifers are mainly HCO3-Ca-Mg-type water, HCO3-Cl-Ca-Mg-type water, Cl-SO4-Na-Ca-type water, and Cl-SO4-Na-Mg-type water. The main mineral sources of hydrochemical ions are salt rock, carbonate rock, sulfate rock, and silicate rock. F- has a significant positive correlation with HCO3- while it is negatively correlated with K+. In the strong evaporation and alkaline environment created by climatic conditions in the study area, F- mainly comes from the dissolution of minerals. Gypsum and fluorite are in a relatively stable dissolved state continuously providing F- and Ca2+ for groundwater; the adsorption of cation was gradually strengthened from the piedmont plain to the central plain. The high HCO3- content is also conducive to F- desorption in alkaline environments. The samples with F- concentration greater than 1 mg·L-1 accounted for 35.7% and mainly distributed in the south of the study area. In summary, the chemical characteristics of shallow groundwater in Fuyang River Basin are affected by the combined effects including leaching effect, evaporation concentration, ion exchange-desorption, and human factors.

Carbon dioxide-hardened sodium silicate-bonded sand regeneration using calcium carbide slag: The design and feasibility study

Wet regeneration of sodium silicate sand (SBS) can yield a high regeneration rate. However, its large-scale implementation is limited by high cost of reagents and required alkaline wastewater treatment. Therefore, excessive SBS is extensively piled-up or buried, causing a huge waste of resources and environmental pollution. This study aimed to mitigate this problem by regenerating CO2-hardened SBS using a cheap regeneration reagent, namely calcium carbide slag (CCS), which is an easily available industrial waste, and considering the alkaline substance recovery. The regeneration mechanism was explored by macro-tests and micro-analysis. The results proved that CCS causticized the regenerated wastewater, forming a strong alkaline environment and speeding up the sodium silicate film peeling-off. In 20 min, a 92% regeneration rate was reached. The compressive strength of the sand core prepared by regenerated sand (RS) exceeded that of the new sand nearly twice if the same binder is used. At the same time, the regenerated wastewater flocculated after adding CCS, and there was no need to add other reagents. After natural precipitation, an alkaline solution with NaOH purity of 84% was obtained, which could be reused in chemical industry. This method has the advantages of low regeneration energy consumption, small secondary pollution, and excellent regeneration effect, making lucrative implying its large-scale implementation. It also substantiates the further SBS application in construction and chemical industry.

Optimization of the whole-waste binder containing molten iron desulfurization slag from Kambara Reactor for concrete production

Kambara Reactor desulfurization slag (KRDS) is an alkaline solid waste, which is not properly utilized. The potential applications of KRDS in ground granulated blast-furnace slag (GGBS)-based cementitious materials and cement-free concrete were investigated in this study. An orthogonal test was conducted through range analysis and a multivariate nonlinear regression model to examine the effect of three factors: the GGBS content, KRDS/flue gas desulfurization gypsum (FGDG) ratio, and water/binder (W/B) ratio on the compressive strength of mortar. Next, a cement-free concrete was prepared with different strength grades using the cementitious material at the optimal ratios of raw materials. X-ray diffraction (XRD), thermogravimetry-differential scanning calorimetry (TG-DSC), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS) analysis were carried out to reveal the hydration mechanism of the binder. The factors affecting the strength of the mortar are in this order: GGBS > KRDS/FGDG > W/B. The increase in KRDS enhances the early strength of the binder, but shows an adverse effect on its late strength. The optimum contents of GGBS, KRDS, and FGDG in the binder are 55%, 33.7% and 11.3%, respectively, with a W/B of 0.3. High levels of GGBS lead to an inhibitory effect of KRDS/FGDG on the compressive strength of the concrete. In order to improve the utilization rate and strength of KRDS, the level of GGBS should not exceed 55%. The main hydration products of the binder are needle-like ettringite (AFt) and spherical C-(A)-S-H gels. KRDS dissolution provides a strong alkaline environment, which promotes the disintegration of the Si(Al)–O tetrahedron of GGBS and the formation of the hydration products. C30–C40 concrete exhibit a small 1-h slump loss and good fluidity, making them more suitable for ready mix pumped concrete, whereas C50 and C60 concrete with a large slump loss are more suitable for high-strength precast members. This study has a theoretical and practical significance for a comprehensive utilization of multi-solid waste, energy saving, and carbon-emission reduction.

Enhanced catalytic performance of Cu-doped MnFe2O4 magnetic ferrites: Tetracycline hydrochloride attacked by superoxide radicals efficiently in a strong alkaline environment

It is important to develop a catalyst that can maintain good activity in alkaline environment for Fenton or Fenton-like reactions. In order to achieve stable Fenton catalytic degradation in a wide pH range, this study reports Cu-doped MnFe2O4 heterogeneous catalysts still has excellent effect when the pH is extended to 11 for removing organic pollutants, such as tetracycline hydrochloride (TC-HCl). The synergistic effect among Fe, Mn and Cu ions has been proved to enhanced the catalytic activity in this work. When the molar ratio of Cu/Mn = 4:1, the porous Cu0·8Mn0·2Fe2O4 materials had the highest photo-Fenton catalytic activity compared with pure MnFe2O4, CuFe2O4 and other CuxMn1-xFe2O4. The XPS showed that Cu0·8Mn0·2Fe2O4 formed oxygen vacancies, which exposed more active sites to attract more H2O2 for TC-HCl degradation. Results indicated 94.3% of TC-HCl was efficiently degraded by 0.1 g/L Cu0·8Mn0·2Fe2O4 with 50 mM H2O2 at pH = 11 under 30 min visible light irradiation, and the corresponding apparent rate constant was 0.08286 min−1. With free radicals quenching experiment, O2− was responsible for the high catalytic degradation and OH was participated in the photo-Fenton reaction. To sum up, Cu0·8Mn0·2Fe2O4 exhibited high activity, great stability and easily recyclable, which eliminated the pH limitation of the Fenton reaction and provided practical application performance for water purification.

Isoindolinium Groups as Stable Anion Conductors for Anion-Exchange Membrane Fuel Cells and Electrolyzers.

Anion-exchange membrane (AEM) fuel cells (AEMFCs) and water electrolyzers (AEMWEs) have gained strong attention of the scientific community as an alternative to expensive mainstream fuel cell and electrolysis technologies. However, in the high pH environment of the AEMFCs and AEMWEs, especially at low hydration levels, the molecular structure of most anion-conducting polymers breaks down because of the strong reactivity of the hydroxide anions with the quaternary ammonium (QA) cation functional groups that are commonly used in the AEMs and ionomers. Therefore, new highly stable QAs are needed to withstand the strong alkaline environment of these electrochemical devices. In this study, a series of isoindolinium salts with different substituents is prepared and investigated for their stability under dry alkaline conditions. We show that by modifying isoindolinium salts, steric effects could be added to change the degradation kinetics and impart significant improvement in the alkaline stability, reaching an order of magnitude improvement when all the aromatic positions are substituted. Density functional theory (DFT) calculations are provided in support of the high kinetic stability found in these substituted isoindolinium salts. This is the first time that this class of QAs has been investigated. We believe that these novel isoindolinium groups can be a good alternative in the chemical design of AEMs to overcome material stability challenges in advanced electrochemical systems.

Preparation, characterization and cell labelling of strong pH-controlled bicolor fluorescence carbonized polymer dots.

As a class of important carbon nanomaterial, carbonized polymer dots (CPDs), also called carbon dots (CDs), have aroused wide interest owing to their unique water solubility, fluorescence properties, and rich surface functional groups. However, the directional tuning of the fluorescence properties of CPDs remains incomplete because of the influence of many factors like diameter, solvent and surface groups. Particularly, most carbonized polymer dots are synthesized in a neutral pH environment. Herein, by modulating the pH (strongly acidic or alkaline) of dextrin water solution, bicolor fluorescence emission (blue and yellow) CPDs were prepared by a hydrothermal reaction. Through systematic characterization, it was found that the different fluorescence properties are regulated by the diameters and surface groups of the carbon cores. Simultaneously, the pH value affected the nucleation process. Based on the excellent fluorescence properties, cell fluorescence imaging and cytotoxicity were tested. The bicolor fluorescence CPDs obtained by tuning the pH provide an important theoretical basis for the design of broadband CPDs.

A highly sensitive fluorescence probe for methyl parathion detection in vegetable and fruit samples based on N and S co-doped carbon dots

In this work, a highly sensitive fluorescence sensing system based on nitrogen and sulphur co-doped carbon dots (N,S-CDs) was for the first time developed for indirect measurement of methyl parathion (MP) with the aid of alkaline-induced hydrolysis. The N,S-CDs were prepared by using o-phenylenediamine and l-cysteine as precursors via hydrothermal heating. In a strong alkaline environment, MP was hydrolysed to p-NP which can suppress the fluorescence of N,S-CDs via a combination of IFE and dynamic interaction. The N,S-CDs exhibited high selectivity and sensitivity towards MP sensing, achieving a linear range of 0.01–15.0 μg/mL and a detection limit as low as 1.56 ng/mL. The proposed sensing platform was applied for MP detection in vegetable and fruit samples with satisfactory results. The recoveries were in a range of 96.4–104.4 %, and the relative standard deviations (RSDs) were less than 3.02 %.

Alkaline sodium polyacrylate-starch hydrogels with tolerance to cold conditions for stretchable zinc-air batteries

With the advancement of wearable electronic devices, it is critical to create a flexible power source that is high performing, cost effective, and safe. The flexible zinc-air battery as a promising candidate has been widely concerned, while most hydrogel electrolytes lose their stretchability in a strong alkaline environment. Herein, a sodium polyacrylate-starch double-network hydrogel is prepared by simple solution copolymerization and swelling techniques. Not only does the hydrogel exhibit exceptional mechanical strength, toughness, and ionic conductivity, but it also exhibits an exceptional freezing-tolerance capability. The stretchable zinc-air battery with sandwich construction has a high energy efficiency of 68%, a high energy density of 67.5 mW cm −2 , and a high degree of dependability in stretched modes. Additionally, the battery performs well mechanically and electrochemically at a cold environment (−20 °C). The batteries can be incorporated into a range of energy-consuming gadgets, suggesting that they are very practicable as wearable power sources. • a hydrogel electrolyte based on sodium polyacrylate and starch was prepared. • Air cathode and Zn anode were designed based on stainless-steel knitted fabric. • The stretchable zinc-air battery operated both under room and cold conditions.

Catalytic Efficiency of Carbon-Cementitious Microfiltration Membrane on the Ozonation-Based Oxidation of Small Molecule Organic Compounds and Its Alkaline Buffering Effect in Aqueous Solution.

In this study, powdered activated carbon (PAC) was added to replace the silica in a cementitious microfiltration membrane (CM) to solve the problems of the low mechanical strength and short lifetime of CMs. The carbon-cementitious microfiltration membrane (CCM) was fabricated by the dry pressing method and cured at room temperature. The bending strength of CCM was 12.69 MPa, which was about three times more than that of CM. The average pore size was 0.129 μm, and was reduced by about 80% compared to that of CM. The addition of PAC did not reduce the degradation efficiency of membrane catalytic ozonation. Because of the strong alkaline buffering ability of CCM, the CCM–ozone coupling process could eliminate the effect of the pH value of the solution. The strong alkaline environment inside the membrane pores effectively accelerated the ozone decomposition and produced oxidizing radicals, which accelerated the reaction rate and improved the utilization rate of ozone. The CCM–catalytic ozonation reaction of organic compounds occurred within the pores and membrane surface, resulting in the pH of the solution belonging to the neutral range. The addition of PAC accelerated the mass transfer and made the pollutants and oxidant react in the membrane pores and on the membrane surface. The reuse experiments of the CCM–ozone coupling process for removing nitrobenzene demonstrated that CCM has good catalytic activity and reuse stability. It broadens the application scope of CCM in the field of drinking water and provides theoretical support for the practical application of CCM.

Highly permeable carbon nanotubes/polyamide layered membranes for molecular sieving

Traditional nanofiltration membranes (NFMs) formed by interfacial polymerization (IP) present relatively low water permeance due to the limitation of polymer-based supports. This work reports high-performance carbon nanotubes-polyamide (CNTs-PA) NFMs with interlayer and functional layer covalently coupled. These membranes feature an interpenetrating network structure, which leads to an extremely high Congo red rejection of 99.47%. The water permeance of the optimal membrane (48.98 L m-2h−1 bar−1) is much higher than most membranes with similar Congo red rejection. Meanwhile, the obtained membranes show an excellent selectivity to NaCl/dye mixed solution (the selectivity of NaCl/CR is 150.32). Moreover, this work comprehensively demonstrates the aggregation kinetics of dye molecules under different pH environments, which strongly affects the dye rejection of the CNTs-PA membrane. The membrane exhibits a switchable CR release property that the CR rejection is severely disabled (2.12%) under a strong alkaline environment and immediately re-effective (99.38%) after neutralization. Building on these findings, our work expands the possibilities of NFMs in ultrafast molecular sieving and pH-responsive separation.

Superhydrophobic modification of the surface of cellulosic materials based on honeycomb-like zinc oxide structures and their application in oil–water separation

Honeycomb-like zinc oxide structures were prepared on the surface of cellulosic materials including cotton fabric fiber and filter paper fiber through plasma treatment followed by wet chemical reaction, the effect of plasma treatment is to increase the wettability and reactivity of cellulosic materials, so that the zinc oxide can nucleate and grow into a honeycomb-like structure on the cellulose fibers. The superhydrophobic surface was then obtained by modifying stearic acid on the zinc oxide structure. The microstructure, chemical composition and state, and wettability of the cellulosic materials were studied in detail. After the modification, the water contact angle and water sliding angle of the modified cotton fabric were 151° and 3.4°, respectively, and those of the modified filter paper is 154° and 4.5°, which indicates super-hydrophobicity. Due to the structural characteristics of zinc oxide-stearic acid structure, the superhydrophobic structure can maintain superhydrophobic performance in strong acidic or strong alkaline environments or after ultrasonic vibration treatment. Further, superhydrophobic modified cotton fabric and filter paper can be used for oil–water separation and adsorption of oil droplets in aqueous solution, and the oil–water separation efficiency is greater than 90%. This method of superhydrophobic modification of cellulosic materials has broad application prospects.