Acid Corrosion Research Articles

Research on the decomposition mechanisms of lithium silicate ores with different crystal structures by autotrophic and heterotrophic bacteria

Ores serve as energy and nutrient sources for microorganisms. Through complex biochemical processes, microorganisms disrupt the surface structure of ores and release metal elements. However, there is limited research on the mechanisms by which bacteria with different nutritional modes act during the leaching process of different crystal structure ores. This study evaluated the leaching efficiency of two types of bacteria with different nutritional modes, heterotrophic bacterium Bacillus mucilaginosus (BM) and autotrophic bacterium Acidithiobacillus ferrooxidans (AF), on different crystal structure lithium silicate ores (chain spodumene, layered lepidolite and ring elbaite). The aim was to understand the behavioral differences and decomposition mechanisms of bacteria with different nutritional modes in the process of breaking down distorted crystal lattices of ores. The results revealed that heterotrophic bacterium BM primarily relied on passive processes such as bacterial adsorption, organic acid corrosion, and the complexation of small organic acids and large molecular polymers with metal ions. Autotrophic bacterium AF, in addition to exhibiting stronger passive processes such as organic acid corrosion and complexation, also utilized an active transfer process on the cell surface to oxidize Fe2+ in the ores for energy maintenance and intensified the destruction of ore lattices. As a result, strain AF exhibited a greater leaching effect on the ores compared to strain BM. Regarding the three crystal structure ores, their different stacking modes and proportions of elements led to significant differences in structural stability, with the leaching effect being highest for layered structure, followed by chain structure, and then ring structure. These findings indicate that bacteria with different nutritional modes exhibit distinct physiological behaviors related to their nutritional and energy requirements, ultimately resulting in different sequences and mechanisms of metal ion release from ores after lattice damage.

Computational Modelling and Comparative Analysis of aSchiff Base Ligand and Its Analog as Inhibitors Against Mild Steel Corrosion in 1M HCl

Schiff bases, alternative anticorrosive additive wassynthesized, characterized and investigated for the inhibition of mild steel corrosion in 1M Hydrochloric acid at concentrations of 20 ppm, 40 ppm, 60 ppm, 80 ppm and 100 ppm using weight loss (WL) and electrochemical methods. The novel Schiff base ligands obtained were characterized by Ultraviolet-visible and Fourier-Transform Infrared Spectroscopy. The elemental analysis data for the Schiff base ligands were used to confirm the general formula of the Schiff bases. Fourier-Transform Infrared spectroscopy provided evidence of formation of a complex surface film due to adsorption of the Schiff bases on the mild steel surface. Maximum inhibition efficiency for Schiff base ligand 1 (SBL1) and Schiff base ligand 2 (SBL2) obtained were respectively 76.92% and 86.21% at concentrationof100ppm,andthetrendfollowedSBL2>SBL1, indicating the effectiveness of SBL2 in corrosion prevention as compared SBL1. Potentiodynamic polarization(PDP) measurements showed that the Schiff bases acted as mixed type inhibitors. Electrochemical Impedance Spectroscopic (EIS) measurement revealed that the corrosion process was controlled by charge transfer process. Inhibition efficiency values obtained from the different techniques were comparable. Quantum chemical parameters such as highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital(LUMO) and energy gap (ΔE) were obtained using Hartree-fock Density Functional Theory by Hamiltonian method. The results showed that SBL2 was more reactive than SBL1. In conclusion, the inhibition of mild steel corrosion was due to adsorption of active molecules leading to formation of a protective layer on surface of mild steel.

Chemical resistance and corrosion mechanism of aluminophosphate-based low temperature enamel (LTE) in H2SO4 and NaOH solutions

Enamel coatings, showing advantages in material durability, aesthetics, hardness, corrosion resistance, and high-temperature tolerance, are widely used for corrosion protection of metallic substrate. Recently, a new type of aluminophosphate-based low temperature enamel (LTE) coating was developed to avoid the strength degradation of steel substrate, which was also applicable to relatively low-melting metal and was more environmentally friendly with reduced energy consumption. LTE coating might suffer the corrosion of acids or alkalis in some special cases like kitchen utensils, petroleum pipelines, and reinforcing bars. In this study, the chemical corrosion behavior of aluminophosphate-based LTE was investigated in H2SO4 and NaOH solutions with varying pHs of 1∼13. Results indicated that after 30 days of immersion, LTE survived at pHs 3–10, but severely deteriorated at pHs 1, 2, 12, and 13, with the corroded layer presenting a loose structure, completely losing mechanical strength, and even peeling off. For pH 11, the color changed slightly whereas the mass loss was negligible. Specially, LTE suffered selective corrosion in strong acid and alkali conditions, that is, H2SO4 corroded the Ca-compounds (Ca5(PO4)3F and CaF2) phases to generate CaSO4·2H2O and H3PO4, whereas NaOH corroded the LTE matrix (AlPO4) to generate soluble Na3PO4 and NaAlO2. The findings of this study confirmed the acid and alkali tolerance range of LTE and clarified the corrosion mechanism of LTE under both acid and alkaline environments, which guides the further composition design and application of LTE coatings.

In Vitro Risk Assessment of Dental Acid Erosion Caused by Long-Term Exposure to Oral Liquid Bandages.

Oral mucosa inflammation can cause severe pain and interfere with eating, reducing quality of life. However, few options for self-care are available. An oral liquid bandage forms a protective film over the affected area. We aimed to assess the acid erosion risk when a newly developed oral liquid bandage (ORAPLA) is accidentally deposited on teeth and to examine the relative acid erosion risk at multiple time points of the maximum recommended duration of continuous use. ORAPLA was applied to both enamel and dentin blocks from 45 bovine anterior mandibular teeth, and an acid challenge was performed in a simulated oral cavity with artificial saliva, with one exposure cycle lasting 6 h. The enamel showed substantial defects and a decrease in Vickers hardness after nine cycles, with no change in surface roughness. Dentin showed an increase in parenchymal defects and surface roughness and a trend toward decreased Vickers hardness with increasing exposure time. We found no significant acid corrosion in enamel after up to nine times the upper limit of normal use time or in dentin after up to six times the upper limit. We conclude that the acid erosion risk due to accidental attachment to teeth is low, and in the human oral cavity with salivary buffering and remineralization, likely even lower.

Effect of acid corrosion on the surface roughness and floatability of magnesite and dolomite

To modify surface roughness and improve flotation performance, hydrochloric acid etching pretreatment was performed on magnesite and dolomite. Flotation tests disclosed that acid corrosion improved the flotation kinetics and flotation recovery rates of magnesite and dolomite. Under pulp pH 10 and sodium oleate (NaOl) concentration 20 mg·L−1, the flotation recovery rates of magnesite and dolomite after acid etching increased by 31.05% and 29.20%, respectively, compared with those before acid etching. Adsorption density tests proved that the adsorption density of NaOl on magnesite and dolomite was higher after acid etching than before acid etching, implying that acid etching drives NaOl adsorption. Zeta potential analysis revealed that acid etching reduces the point of zero charge of magnesite and dolomite. Atomic force microscopy and X-ray photoelectron spectroscopy results demonstrated that acid corrosion modified the surface roughness of magnesite and dolomite, increasing the magnesium (Mg) content on the magnesite surface and the calcium and Mg contents on the dolomite surface. Contact angle measurements indicated that acid corrosion slightly reduced the contact angle between magnesite and dolomite. With NaOl present on the surface, the contact angles of magnesite and dolomite after acid etching significantly increased compared with those before acid etching. Therefore, acid etching is effective in improving the floatability of magnesite and dolomite.

A nanozyme based wearable device for colorimetric monitoring of UV radiation exposure in sunlight

In this study, nanozyme is used for monitoring the dose of ultraviolet (UV) in sunlight for the first time. We find that nitrogen-doped carbon dots (N-doped C-dots) can effectively catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) under different UV region including UVA, UVB, and UVC. In comparison, the N-doped C-dots fail to show the catalytic activity under visible light. The finding is applied for distinguishing UV light and visible light through the color change of TMB. More importantly, the photo-oxidation TMB catalyzed by N-doped C-dots can work well in a near neutral pH, which is beneficial for its application in wearable device due to the reducing of acid corrosion. Finally, a wearable bracelet is fabricated by integrating N-doped C-dots and TMB into hydrogels. The bracelet is used for monitoring the UV exposure in sunlight. The color change of TMB in the bracelet can be clearly observed by naked eyes or quantified by a smartphone. The bracelet is also used for distinguishing different weather condition such as sunny/cloudy or different place such as indoor/outdoor during a sunny day. This study provides the first example of nanozyme in wearable UV sensor and will stimulate the applications of nanozyme in wearable device.

Effect of Sulfuric Acid Corrosion on Flotation Performance of Calcite by Changing Surface Roughness.

Surface roughness is a crucial factor that affects the flotation performance of minerals. In this study, the effect of sulfuric acid corrosion on the surface roughness of calcite flotation was investigated through microflotation tests, scanning electron microscopy (SEM-EDS), atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, and contact angle analysis. Microflotation test results show that sulfuric acid treatment has a serious negative effect on the floatability of calcite. When the sulfuric acid dosage was 4 mL (3 mol/L), the flotation recovery of calcite was reduced to less than 19%. SEM-EDS and AFM results verified that the sulfuric acid treatment significantly changed the surface morphology of calcite, reduced the average surface roughness and surface area, and reduced the amount of active Ca2+ sites on the calcite surface. As characterized by FT-IR and contact angle analyses, the sulfuric acid treatment enhanced the hydrophilicity of the calcite surface and reduced the amount of sodium oleate adsorbed on the calcite surface. Consequently, sulfuric acid corrosion can reduce the average surface roughness of calcite and have a serious negative effect on the flotation performance of calcite.

A novel porous titanium with engineered surface for bone defect repair in load-bearing position.

Porous titanium exhibits low elastic modulus and porous structure is thought to be a promising implant in bone defect repair. However, the bioinert and low mechanical strength of porous titanium have limited its clinical application, especially in load-bearing bone defect repair. Our previous study has reported an infiltration casting and acid corrosion (IC-AC) method to fabricate a novel porous titanium (pTi) with 40% porosity and 0.4 mm pore diameter, which exerts mechanical property matching with cortical bone and interconnected channels. In this study, we introduced a nanoporous coating and incorporated an osteogenic element strontium (Sr) on the surface of porous titanium (named as Sr-micro arch oxidation [MAO]) to improve the osteogenic ability of the pTi by MAO. Better biocompatibility of Sr-MAO was verified by cell adhesion experiment and cell counting kit-8 (CCK-8) test. The in vitro osteogenic-related tests such as immunofluorescence staining, alkaline phosphatase staining and real-time polymerase chain reaction (RT-PCR) demonstrated better osteogenic ability of Sr-MAO. Femoral bone defect repair model was employed to evaluate the osseointegration of samples in vivo. Results of micro-CT scanning, sequential fluorochrome labeling and Van Gieson staining suggested that Sr-MAO showed better in vivo osteogenic ability than other groups. Taking results of both in vitro and in vivo experiment together, this study indicated the Sr-MAO porous titanium could be a promising implant load-bearing bone defect.

Heat-induced morphology-dependent corrosion of solid boric acid on carbon steel

The corrosion of solid boric acid (s-BA) has so far remained unnoticed, which could pose a potential hazard to the safety of boron-containing equipment. In this work, a morphology-dependent corrosion behavior of s-BA was found on Q235 carbon steel encompassing temperatures from 160 °C to 240 °C. Concurrent with the corrosion process, s-BA underwent a heat-induced morphology-transition from block-like into sheet-like/flake-like under the delayed decomposition condition, which emerged as a key contributor to the heightened corrosion rates after reducing the volume of the corrosion system. Through integration with the ex-situ pretreatment experiment, our analysis concludes that this morphology-transition accelerated corrosion by facilitating the generation of more Fe5O5[B6O10(OH)3] ·nH2O and filamentous amorphous corrosion products than FeB12O19·5H2O. The crucial relationship between s-BA with distinct morphologies and different types of borate products was also further expounded.

Effect of the surface-area-to-volume ratio on dissolution and deterioration of acid-corroded sandstone

This study investigates the impact of hydro-chemical action on the deterioration of physical and mechanical properties of rock, with a specific focus on sandstone subjected to HCl, and H2SO4 solutions with pH values of 2 and 5. The research explores the role of the surface-area-to-volume (SATV) ratios of 0.65 and 0.70 in influencing the dissolution and deterioration of sandstone. A chemical kinetic model is developed to explore the diffusion-dissolution mechanism. Following acid corrosion, the porosity of sandstone increases, marked by a decline in small pores (r ≤ 1 μm) and an increase in medium (1 μm < r < 10 μm) and large pores (r ≥ 10 μm). Furthermore, uniaxial compression tests reveal a reduction in peak strength and elastic modulus, an increase in peak strain, diminished brittleness, and enhanced ductility. The study underscores the substantial influence of the SATV ratio, particularly in the case of low pH values in HCl solutions. Following 150 days of corrosion by pH = 2 HCl solution under a SATV ratio of 0.70, the peak stress and elastic modulus decreased by 52.845% and 92.712%, and peak strain increased by 386.186%. The acid-rock reaction is characterized by diffusion and dissolution, with parameters exhibiting a negative correlation with the SATV ratio and a positive correlation with the pH value of solutions. The diffusion is more affected by the SATV ratio rather than the dissolution. The insights derived from this research have implications for the theoretical foundation of safety assessments and disaster prevention in practical engineering scenarios under acidic environments.

Development of a sprayable PVA-fiber-enhanced cement mortar with high acid-corrosion resistance for pipeline rehabilitate

The spraying method offers the advantages of environmental protection, convenient construction, and cost-effectiveness, making it widely used in pipeline structure repair. Given the complex service environment of pipelines, there is an urgent demand for high-strength and durable spraying materials. To achieve this goal, a PVA fiber reinforced cement mortar material (PFCM) with high early strength, excellent impermeability and stable acid corrosion resistance was developed through orthogonal test design. The optimal material was obtained through factors such as setting time, fluidity, compressive strength and flexural strength. The effects of the contents of fly ash, redispersible polymer powder and PVA fiber on the working and mechanical properties of the material were investigated, and further research was conducted on its tensile strength, impermeability, acid corrosion resistance. In addition, Thermogravimetric-differential Thermal Analysis (TG-DTA) was utilized to analyze the thermal stability of PFCM. X-ray diffraction (XRD) was utilized to analyze the composition of PFCM. Mercury intrusion porosimetry (MIP) was utilized to analyze the pore structure of PFCM, and the feasibility of the PFCM was verified. The results indicate that the contents of fly ash, redispersible polymer powder and PVA fiber have significant effects on the working and mechanical properties. The optimum initial setting time is 60–80 min, and the optimum fluidity is between 170 and 180 mm. The compressive strength and flexural strength of the mortar prepared with the optimum parameters are 102.5 MPa and 20 MPa, respectively. The material has an excellent spraying effect with no sagging, and exhibits high early strength, outstanding corrosion resistance, low porosity, and exceptional impermeability. This study lays the foundation for achieving high-quality spray repairs of underground drainage pipelines.

Synsepalum dulcificum extract as green corrosion inhibitor for acid corrosion of mild steel in HCl solution

Anticorrosive potential of Synsepalum dulcificum leaf extract on the corrosion of mild steel in HCl solution was investigated using chemical technique. The extract inhibited the deterioration of mild steel in HCl solution and the inhibition efficiency increased with increasing concentration of the extract at 30o C. The results obtained showed that inhibition was as a result of the adsorption of the inhibitor molecule onto mild steel surface and the adsorption obeyed Flory-Huggins adsorption isotherm.

Microscopic insights into acid corrosion effects on chelated MSW incineration fly ash: Mechanisms of chelate destabilization

Sodium dimethyl dithiocarbamate (SDD) is commonly applied to mitigate the release of heavy metals (HMs) into the environment from municipal solid waste incineration fly ash (IFA). Despite this common application, limited research has been conducted on the impact of environmental conditions on chelate destabilization during long-term landfilling. In this study, a batch leaching test was performed on chelated IFA buried for 10 years, revealing that the leaching concentrations of Pb and Cd exceeded landfill standards by 51.7% and 26.0%, respectively, indicating the chelate destabilization occurrence. To elucidate this phenomenon, various physicochemical experiments were conducted to unveil the underlying mechanisms emphasizing changes in HMs fractions (Pb, Cd, Cr, Ni, Zn, Cu) under acidic corrosion, and exploring the microscopic perspective of the chelate destabilization process. The key findings were summarized as follows: (I) The immobilization effect of SDD on Zn and Cd was not highly effective, with most of these metals being fixed on IFA through inorganic complexes. Theses HMs destabilization showed a negative correlation with the pH levels, indicating that higher acidity facilitated the release of HMs (59.0 mg/kg for Zn and 5.8 mg/kg for Cd). (II) After exposure to acid corrosion, the stable fraction of HMs decreased, because HM-SDD complexes decomposed into inorganic salts and carbon disulfide. This process further exacerbates the transporting effect of HMs on chelated IFA, thereby increasing the long-term leaching risk. (Ⅲ) A leaching equilibrium of HMs existed at the IFA surface, primarily influenced by the types and concentrations of anions in the leachate. This study contributes to a deeper understanding of the factors influencing the stability of chelated IFA and provides valuable insights into the long-term environmental implications of such materials in landfill settings.

Increasing service life of concrete in sewage treatment plants using silica fume and natural zeolite

Microbial attacks rapidly degrade concrete structures in wastewater facilities, leading to brief service lifespans. Hence, producing concrete resistant to chemical and sulfuric acid corrosion is more cost-effective. In the present study, a total of six concrete mixtures incorporating 7.5% silica fumes (SF) and 10% natural zeolite (ZE) were immersed in 0.5% and 1% sulfuric acid solutions with a maximum pH threshold of 2 and 1, respectively, for 70 weeks. The specimens were regularly monitored for surface deterioration, mass change and crushing load change. To better understand the relationship between the pore structure of concrete mixtures and resistance to sulfuric acid, various durability tests such as rapid chloride penetration, water absorption, electrical resistivity and chloride diffusion coefficient were performed. Based on the results obtained, converting calcium hydroxide into calcium silicate hydrate gel through pozzolanic reactions and then refining the porosity of concrete with silica fumes (SF) and natural zeolite (ZE) was effective in enhancing the resistance of concrete to attack by sulfuric acid of relatively low concentration. As a result, using silica fumes (SF) and natural zeolite (ZE) is a lower-cost method for reducing corrosion rates to extend the service life of facilities, particularly in lower concentrations.

Deterioration characteristics and damage constitutive model of granite-shotcrete under acid corrosion cycle conditions

The acidic groundwater environment will cause the degradation of tunnel and underground engineering structures, posing a severe threat to their durability and load-bearing performance. This paper analyzed the mechanical properties and microstructural changes of the specimens under the action of the acid cycle by carrying out mechanical, acoustic emission (AE) and scanning electron microscopy (SEM) tests. The evolution rules of elastic wave velocity and acoustic emission characteristic parameters were discussed. A damage constitutive model was established based on the Weibull strength theory. The results show that the specimen interface split tensile stress-strain curve is divided into elastic, interface softening and debonding failure stages. After 20 cycles, the peak strength and elastic modulus of the specimen decreased by 55.63% and 71.43%, respectively. The porosity calculated based on longitudinal wave velocity and mass changes can better explain the changes in the microstructure of the specimen. The fractal dimension value associated with the longitudinal wave velocity of the specimen and the ringing count shows a negative proportional relationship, and its proportional coefficient is 329.29. The stress-strain theoretical curve of the established damage constitutive model has a high degree of agreement with the test curve. The research results can provide an essential reference for disaster prevention and control of tunnels and underground projects in acidic groundwater areas.

Preparation and Performance Study of High-Strength and Corrosion-Resistant Cement-Based Materials Applied in Coastal Acid Rain Areas.

Investigations regarding the preparation and durability of cement-based materials applied in specific coastal acid rain environments are scarce, particularly those involving the addition of four auxiliary cementitious materials (ACMs) to cement for modification. To improve the durability of concrete structures in coastal acid rain areas, a systematic study was conducted regarding the preparation of high-strength and corrosion-resistant cement-based materials using ACM systems composed of fly ash (FA), granulated blast furnace slag (GBFS), silica fume (SF), and desulfurization gypsum (DG) instead of partial cement. Through an orthogonal experimental design, the effect of the water-binder ratio, cementitious ratio, and replacement cement ratio on the compressive strength, corrosion resistance coefficient, and chloride ion permeability coefficient of the materials were analyzed and the mix proportions of the materials were evaluated and optimized using the comprehensive scoring method. The results show that implementing a FA:GBFS:SF:DG ratio of 2:6:1:1 to replace 60% of cement allows the consumption of calcium hydroxide crystals generated through cement hydration, promotes the formation of ettringite, optimizes the pore structures of cementitious materials, and improves the compressive strength, acid corrosion resistance, and chloride ion permeability of the materials. This study provides a reference for selecting concrete materials for buildings in coastal acid rain environments.

Decoration with electronegative 2D materials based on chemical transition layers on CFR-PEEK implants for promoting osteogenesis

Due to the unique lamellar structures, physicochemical and biological properties, electronegative two-dimensional (2D) materials have been explored for surface modification of carbon fibers reinforced polyetheretherketone (CFR-PEEK) composite. Deposition of electronegative 2D materials based on a porous surface created by concentrated H2SO4 has been studied to promote osteogenesis of CFR-PEEK. Generally, a porous layer will be pre-built on CFR-PEEK through severe corrosion of concentrated sulfuric acid to help the loading of 2D materials. However, the severe corrosion will greatly reduce surface mechanical strength, especially wear resistance and hardness, which increases the risk of collapse or even peeling of the bioactive coating by external force. Herein, instead of the severe corrosion, a mild corrosion by concentrated HNO3 was applied to modify the surface of CFR-PEEK to pre-create a dense transition layer for the further surface decoration of electronegative 2D materials (graphene oxide (GO) and black phosphorus (BP), representatively). The results indicated that hardness and wear resistance of the dense transition layer were markedly higher than those of the porous layer. Although GO and BP can be both loaded on these two transition layers, –SO3H on the porous transition layer showed moderate cytotoxicity, while –NO2 on the dense transition layer showed good cytocompatibility. The dense transition layer displayed higher mineralized deposition in vitro and new bone formation rate in vivo than the porous transition layer, moreover, GO and BP coatings improved osteogenesis. This work offers inspirations for the construction of electronegative 2D material coating on CFR-PEEK based on chemical transition layers.

Inhibitory effect of marine Bacillus sp. and its biomineralization on the corrosion of X65 steel in offshore oilfield produced water

The issue of material failure attributed to microbiologically influenced corrosion (MIC) is escalating in seriousness. Microorganisms not only facilitate corrosion but certain beneficial microorganisms also impede its occurrence. This study explored the impact of marine B. velezensis on the corrosion behavior of X65 steel in simulated offshore oilfield produced water. B. velezensis exhibited rapid growth in the initial stages, and the organic acid metabolites were found to promote corrosion. Subsequently, there was an increase in cross-linked “networked” biofilms products, a significant rise in the prismatic shape of corrosion products, and a tendency for continuous development in the middle and late stages. The organic/inorganic mineralized film layer formed on the surface remained consistently complete. Metabolic products of amino acid corrosion inhibitors were also observed to be adsorbed into the film. B. velezensis altered the kinetics of the X65 steel cathodic reaction, resulting in a deceleration of the electrochemical reaction rate. The mineralization induced by B. velezensis effectively slowed down the corrosion rate of X65 steel.

Effect of Curing Mechanism on Sulfuric Acid Corrosion Resistance of Geopolymer Recycled Aggregate Concrete

To explore the effect of curing mechanism on the mechanical properties and sulfuric acid corrosion resistance of the geopolymer recycled aggregate concrete (GRAC), the specimens were cured at high temperature (60°C, 80°C) for 6 h, 24 h and 48 h respectively, and then lasted up to 7 d at room temperature. After the curing period was over, the laboratory accelerated simulation test of specimens was carried out by the periodic immersion method: the GRAC specimens (ϕ 50 × 100 mm) were immersed in the sulfuric acid solution with pH = 1 for 5 d and then dried at room temperature for 24 h, with a total circulation of 90 d. The results showed that after being eroded by sulfuric acid solution, the GRAC specimens cured at 60°C for 48 h had higher compressive strength with 19.9 MPa, lower mass loss rate (only 0.23%) and neutralization depth (5.71 mm) than those under other curing time. The GRAC specimens cured 80°C for 24 h also had a good performance: compressive strength achieved 16.9 MPa and had lower neutralization depth (5.99 mm), which was less affected by sulfuric acid corrosion. However, the GRAC specimens cured at 60°C for 48 h had the better mechanical properties than that cured at 80°C for 24 h. Excessive high temperature curing (80°C) would lead to more voids and microcracks inside GRAC, and destroy the dense structure, thereby reducing mechanical property of concrete. These voids and pores provided more erosion channels for sulfuric acid solution, which accelerated the corrosion rate. From the point of view of energy saving and concrete performance, no more than 60°C of curing temperature is recommended for industrial use.

Preparation and application of microfiltration porous coal gangue–loess‐based ceramic membrane

AbstractThe ceramic membrane is widely used in the field of domestic sewage treatment due to its high flexural strength, acid and alkali corrosion resistance, easy cleaning, and other advantages. This article uses coal gangue and loess as the main raw material (coal gangue:loess = 8:2), calcium carbonate as the pore‐forming agent, and carboxymethyl cellulose as the binder. The ceramic membrane was prepared by extrusion molding method and solid particle sintering method. The effects of pore‐forming agent content and sintering temperature on the physical and chemical properties of the ceramic membrane, such as flexural strength, microstructure, pure water flux, and acid‐base corrosion rate, were investigated. The results show that when the sintering temperature is 1000°C and the pore‐forming agent content is 10wt%, the pure water flux exceeds 1434L/h m2 MPa, the flexural strength exceeds 25.4 MPa, the porosity exceeds 46.9%, and the acid‐alkali corrosion rate of the ceramic membrane below 1.6%/0.15%. At this time, the treatment efficiency of domestic sewage is excellent, the removal rate of COD, suspended solids and ammonia nitrogen exceeds 27.66%, 99.9%, and 26.77%, respectively. This work has trend‐setting significance for the fabrication and application of low‐cost ceramic membranes.