Filter Cake Research Articles

Modelling sludge dewatering in treatment reed bed considering sludge deposit formation

AbstractThe accumulation of sludge deposits is a crucial factor in the dewatering efficiency of sludge treatment reed bed (STRB). This paper presents an improved one-dimensional process-based mathematical model to simulate the dewatering mechanism in STRBs, in which the compressible cake filtration (CCF) theory was implemented to simulate the sludge deposits accumulation on the surface of the reed bed, while the varying sludge deposit thickness was accounted for using the moving mesh method. The proposed model also included the dual porosity variably saturated flow model and the Penman–Monteith equation to describe the dewatering through gravity drainage and evapotranspiration, respectively. The results from the model were validated with experimental data from laboratory-scale STRBs treating septage. The simulation results showed that considering the sludge deposit layer as a specific flow resistance effectively avoids the overprediction of water infiltration rate in the reed bed. The predicted results showed excellent agreement with the actual data, where only five cases of the root mean square error were above 10% compared to the average effluent flux. Further, the effect of evapotranspiration was found to be insignificant within a short-term simulation. The consideration of the influence of sludge deposit formation on drainage dewatering using the CCF model and moving mesh model has delivered a more robust simulation for sludge dewatering in STRBs, and the proposed model is capable of facilitating the understanding of the interactions between the sludge dewatering in STRB with respect to the bed characteristics, hydraulic load, and solid load.

Numerical simulation study on impact factors to dynamic filtration loss

During drilling operations, naturally, fractured formations are prone to show serious mud losses, which hinder drilling and increase nonproductive time and costs. The influencing factors of dynamic fluid loss are important for optimizing drilling parameters, reducing drilling fluid loss, and protecting oil and gas reservoirs. In this study, we simulated the dynamic filtration loss of drilling fluid during drilling under formation conditions using commercial software CMG (Computer Modelling Group). The effects of filtration time, filtrate viscosity, pressure difference, internal filter cake permeability, and external filter cake permeability on filtration loss were investigated. The simulation results showed that the permeability of the external mud cake is an important factor to control the fluid loss, and the pressure consumed by the external mud cake with low permeability can account for more than 90% of the total pressure difference. When the permeability of the external mud cake is high, the permeability of the internal mud cake also has a significant influence on the dynamic fluid loss. Under formation conditions, the dynamic fluid loss of radial fluid loss is still proportional to the filtration time and pressure difference, and inversely proportional to the filtrate viscosity of drilling fluid. Under the simulated conditions, the pressure will quickly transfer to the boundary, and the formation pressure at the same position in the formation will gradually increase, while the increase is relatively small with a constant filtration rate. The results of this paper can be used to the real site for drilling optimization. This numerical analysis method can be easily applied to filtrate loss analysis, formation damage area calculation, and other radial flow-related study.

Decreasing the stick-slip vibration during drilling wells using water and polymer drilling mud modified with NanoSiO2 particles

Stick-slip in drilling happens when the drill bit and assembly repeatedly stop and slide due to factors like friction and torque. Using better lubricants in the drilling mud can help reduce friction, lessening stick-slip issues. Nanotechnology has improved drilling mud, making it more resistant to heat and enhancing its viscosity and friction properties. This research extensively investigates the use of nanofluids in drilling processes through thorough lab tests. It examines the impact of introducing NanoSiO2 into two types of drilling mud—freshwater bentonite (FWB) and polymer-based mud—at concentrations of 0.04%, 0.08%, 0.15%, and 0.31% under higher temperatures. The study also explores two methods of dispersing NPs using ultrasonic and solvent techniques. The results show that SiO2 nanoparticles notably improve the flow and filtering abilities of FWB mud but have negative effects on polymer-based mud. A 0.05% addition of NanoSiO2 significantly reduces friction by 52% in FWB mud. In FWB mud, all NanoSiO2 concentrations lead to a 25% decrease in mud cake thickness. Furthermore, adding NanoSiO2 to FWB mud decreases torque, with the most substantial reduction of 40% observed at 0.09% concentration (0.35 gm). On the contrary, incorporating NanoSiO2 into polymer-based mud increases fluid loss volume for all concentrations, reaching up to 36% compared to the base mud. Additionally, filter cake thickness increases eightfold, while lubricity factor doubles. This study offers insights into the advantages of using SiO2 nanoparticles in drilling mud and their impact on the fluid properties during drilling.

Discrete pore and particle size distributions during pore blocking and cake filtration

Modeling membrane filtration is important for plenty industrial applications. The understanding of the phenomena and related mechanisms aims at the improvement of techniques in different areas. Therefore, different authors have proposed models to describe the mechanisms related to the filtration process involving either cake build-up or blocking processes, a few of them however have proposed both concepts simultaneously, although none considered pore and particle size distribution during the process, which is the proposal brought up in this paper. Transient solutions for filtrate volume and filter cake thickness as a function of initial pore and particle size distributions are obtained. Good matching between the studied experimental data and the proposed model was observed. In general, the results showed that permeability reduction and filtrate volume are strongly influenced by the initial pore and particle size distributions. In addition, the cake build-up rate depends on both the particle size distribution and the residual flow through blocked pores. It was observed that, after all the largest particles have blocked the smaller pores, effective permeability and flow rate vary only due to cake build-up. Finally, because the proposed empirical parameters do not depend on the pore size distribution, this model can be applied for predicting permeability decline for any feed concentration.

The effect of high-temperature environment on the rheology and filtration properties of Rhizophora spp. tannin-lignosulfonate as bio-based additive in water-based drilling fluid

Bentonite suspension in water-based drilling fluid is susceptible to deterioration in high-temperature environments, hence requiring a deflocculant to stabilize the solid particles. Considering the use of highly toxic chrome-based deflocculant in the industry, Rhizophora spp. tannin-lignosulfonate (RTLS) was synthesized in this study as an alternative deflocculant. A viscometer was used to study the rheological properties, and the filtration performance was evaluated using low-pressure low-temperature and high-pressure high-temperature filter press in accordance with the American Petroleum Institute standard procedure. The addition of 0.5 wt% RTLS to water-based drilling fluid (WBDF) was effective in a significant reduction of the plastic viscosity (PV) and yield point (YP) of WBDF at elevated temperatures. As the amount of RTLS added to the suspension exceeds 0.5 wt%, the effect on PV and YP becomes negligible. A higher fluid loss of 13 mL was observed in the WBDF without RTLS aged at 177 °C. The addition of 2.0 wt% RTLS reduced the fluid loss to 10.7 mL. This suggests that RTLS is an effective deflocculant that can be used to improve the filtration properties of WBDF at high temperatures. The morphology of RTLS filter cakes was examined using field emission scanning electron microscopy with energy-dispersive X-ray spectroscopy (FESEM-EDX). The interlayer between clay particles was identified as RTLS, a natural additive that plays a vital role in enhancing filtration while minimizing fluid loss. The outcomes of this research are promising, and this non-toxic deflocculant has the potential to replace chrome-based deflocculants that are still in use for borehole drilling.

Life cycle assessment of a novel production route for scandium recovery from bauxite residues

Scandium (Sc) has various technological applications, but the concentrations of Sc in ores are low. Both, the mining of low concentrated Sc and the production of industrial-grade Sc are a heavy burden on the environment. Bauxite residue (BR) from alumina production represents one of the major sources of Sc in Europe (Ochsenkühn-Petropulu et al., 1994). The goal of this study is to assess the environmental impacts from cradle to gate of a novel production route developed in the Scandium Aluminium Europe project (SCALE) to extract Sc at concentrations <100 ppm from BR, to concentrate and upgrade it to pure ScF3 and Sc2O3 and ultimately to refine it to an aluminium scandium master alloy with 2 % Sc mass fraction (AlSc2 %). Results show that the global warming potential (GWP), measured in CO2-eq per kg Sc2O3, generated with the novel route is about half the GWP of the state-of-the-art Sc2O3 production from rare earth tailings when applying equal allocation principles. The initial process step to dissolve BR and extract Sc consumes elevated amounts of acid and energy and is responsible for at least 80 % of the route’s total environmental impact. The amount of the generated filter cake (FC) is equal to the amount of the BR input and is a potential resource for cement clinker production. The ecotoxicological study indicates that both FC and BR are slightly ecotoxic.

Composting of distillery spent wash

Distillery spent wash, a by-product of the alcoholic beverage industry, is an organic waste whose management poses significant challenges due to its acidity, high organic load, notable content of polyphenols, macronutrients, micronutrients and heavy metals. In Europe, billions of liters of distillery waste are generated annually and its eco-unfriendly disposal can cause severe environmental and health impacts. Composting is a viable management strategy to treat and manage distillery slop promoting the recycling and stabilization of organic matter and nutrients in the material. The review examines different composting methods, such as single composting, co-composting and vermicomposting, along with their benefits and drawbacks. To optimize composting effectiveness, various materials, such as sewage sludge, vinasse, green and animal manure, inorganic amendments, bagasse, filter cake and municipal solid waste, among other agro-food and animal bio-wastes, can be used as a source of nitrogen and microorganisms. Also, the usage of different materials and mixtures aims to enhance the composting process increasing the degradation rate and the quality of the compost. The challenges of distillery spent wash composting are also covered in the paper which are mainly due to its characteristics, including high salt content, low carbon-to-nitrogen ratio, low pH and potential phytotoxicity. The paper concludes that composting distillery spent wash is an effective and sustainable waste management solution for recovering valuable nutrient resources and producing a stable nutrient-rich organic soil amendment. The produced compost can improve crop yields, nutrient absorption by plants and plant biomass and contribute to soil properties and restoration. The review provides insights into the current state of distillery spent wash composting and recommends future research directions to improve efficiency and expand potential applications.

One-step fabrication of asymmetric alumina ceramic membranes with tunable pore parameters for oil-water separation

Porous ceramic membranes with low-cost and high performance are desirable in industrial filtration field. To improve the performance while reducing the production cost, various measures were developed, however, pre-sintering of supports, preparation of membrane-forming suspensions and adoption of extensive organic additives that involved were adverse to cost reduction. Herein, cost-effective one-step co-pressing and co-sintering technique was proposed to prepare asymmetric ceramic membranes. The results revealed that pore parameters and performance of the fabricated membranes could be adjusted by altering mole ratio of Al2O3 to SiO2 (Al2O3/SiO2) in the support and sintering temperature. The influence of supports on the permeation flux of membranes surpassed that of the parameters of membrane layer. Additionally, the oil rejection rate of the membranes exceeded 96 % within 2 min and even reached 100 % (~60 min), the water flux and steady-state feed flux were 1330–1730 L·m−2·h−1 and 470–620 L·m−2·h−1 at 1 bar, respectively. Moreover, cake filtration was the main fouling mechanism throughout the separation process. This research provides a feasible and simple method for preparing low-cost high-performance ceramic membrane for wastewater treatment.

A membrane-assisted green strategy for purifying bioactive compounds from extracted white wine lees

This work was aimed at investigating the recovery of wine-derived bioactive compounds from white wine lees through a combination of hydroalcoholic extraction and membrane-based operations, as a potential alternative for winery wastewater treatment and valorisation.Hydroalcoholic extracts obtained in selected conditions of solid–liquid ratio, extraction time and working temperature (1:10, 25 % and 32 ± 2 °C, respectively) were previously clarified by ultrafiltration (UF) in order to produce a clarified solution free of suspended solids and colloidal substances. The concentration of bioactive compounds from the clarified extract was investigated by using three different spiral-wound NF membranes with molecular weight cut-off (MWCO) in the range of 200–1000 Da (TS40, XN45 and NP010, all from Microdyn-Nadir); their performance was analysed in terms of productivity, fouling index and retention towards target compounds (polyphenols, flavonoids, sugars) and antioxidant activity.Low molecular weight polyphenols (i.e. gallic acid, catechin, vanillic acid, epicatechin and caffeic acid) were highly rejected by the selected membranes despite their difference in MWCO; on the other hand, the rejection index for total phenolic content (TPC), flavonoids and glucose was in agreement with the MWCO. The TS40 membrane, with a lowest cut-off (200–300 Da), showed the highest rejection for flavonoids (100 %) and rejections for total phenolic compounds of 85 % resulting in concentrated fractions containing 1.7 g of gallic acid equivalents per liter (GAE/L); most of the components analysed in the retentate samples showed a concentration factor of approximately 3.5 in agreement with the weight reduction factor of the NF process. The analysis of fouling mechanisms according to the Hermia’s model revealed that the cake filtration mechanism was the predominant one for all selected NF membranes.

Experimental study of hydrophilic additives on filter cake permeability and filtrate losses

AbstractIn the past few years, great emphasis has been placed on developing the water‐based mud system in drilling operations because its properties are suitable for the environment and it is a better choice than oil‐ and synthetic‐based muds. Despite research and development in this field, water‐based muds still have filtration issues that lead to drilling problems, and attempts must be continued in this regard. Therefore, this work aims to reduce the filtrate loss of water‐based mud by affecting the drilling cake and making the permeability as low as possible with enhanced properties that resist the filtration of the drilling fluid. Special care was taken to develop suitable mud rheological properties in terms of plastic viscosity, yield point, and gel strength compared to API standards. To this end, some hydrophilic materials were added to the mud, such as thinners (spersene and trisodium phosphate [TSP]) and some polymers (sodium silicate [SS] and poly acryl amide [PAA] (to compare with the basic mud. The results showed that using thinners and polymers without carboxymethyl cellulose (CMC) and baryte reduced filtrate loss and permeability by a small percentage. On the other hand, adding CMC and baryte to the four additives (spersene, TSP, SS, and PAA) each separately reduced the permeability by 66.1%, 67.7%, 74.1%, and 79%, and reduced filtrate loss by 50.1%, 51.4%, 55.3%, and 58.6%, respectively. It was concluded that adding PAA with CMC and baryte can effectively reduce filtrate losses due to its ability to provide a membrane of low permeability.

Simulation of Filter-Cake Formations on Vertical and Inclined Wells Under Elevated Temperature and Pressure

Summary Drilling fluids consist of colloidal suspensions that are made up of solid particles suspended in liquid. The aqueous component of the drilling mud invades a permeable formation due to differential pressure, leaving solid deposits on the drilled formation walls, forming a filter cake. Typical drilling fluids should create a thin, slick filter cake and fluid loss control to seal permeable zones as swiftly as possible. Tight holes, elevated levels of rotational resistance and friction, wellbore obstruction, fluid loss into formations, suboptimal well-log data, and reservoir formation impairment result from thick filter cakes and excessive filtration. Controlling infiltration of fluids to establish a minimal, low-porosity filter cake is frequently required to avoid drilling and production issues. In this study, we used computational fluid dynamics (CFD) to model the development of filter cakes induced by pipe rotation in vertical and inclined wellbore walls under elevated temperature and pressure during deep drilling. Multiple tests validate the basic model for application in both shallow and deep drilling operations. By use of an Eulerian-Eulerian approach to describe drilling fluids as a binary-phase system, including particles in suspension in the non-Newtonian fluid, our research investigates the power-law and Herschel-Bulkley rheological models. These models successfully predict the flow pattern of drilling fluid at the bottom region of deep drilling operations. The study further explores filter-cake formation by examining the influence of overbalanced pressure on filter-cake thickness at various pressures. Drilling simulations, incorporating pipe rotation and eccentricity effects under realistic operating parameters, accurately project filter-cake thickness, aligning closely with experimental measurements and existing CFD literature in this domain.

Membrane fouling and control in algae-rich water treatment

Microfiltration and ultrafiltration membrane technology has now become one of the important methods for algae-rich water treatment due to its better solid-liquid separation effect and microbial retention capacity, while the existence of membrane fouling has been restricting the full-scale promotion and application of low-pressure membrane technology. The main foulants causing membrane fouling in algal-rich water include algal cells, algal debris and algal organic matter AOM (EOM and IOM). In this paper, the mechanism of membrane fouling caused by algal foulants in MF/UF for high algal water treatment is analysed in terms of both individual and composite fouling. Both individual and composite effects of algal foulants can lead to severe membrane fouling, in which algal cells and algal debris mainly dominate the accumulation of filter cake, while AOM mainly leads to membrane pore blockage membrane fouling is exacerbated by compounding effects, with severe reversible and irreversible fouling caused by filter cake formation and membrane pore shrinkage. This paper also discusses several common membrane fouling control methods, including pretreatment (oxidation, coagulation, combined oxidation-coagulation and adsorption) and membrane modification, and it is found that these several membrane fouling control methods can achieve good results.

An experimental investigation into the rheological behavior and filtration loss properties of water-based drilling fluid enhanced with a polyethyleneimine-grafted graphene oxide nanocomposite.

The modern oil and gas industry, driven by a surging global energy demand, faces the challenge of exploring deeper geological formations. Ensuring the robust performance of drilling fluids under harsh wellbore conditions is paramount, with elevated temperatures and salt contamination recognized as detrimental factors affecting the rheological and filtration loss properties of drilling fluids. We successfully synthesized a polyethyleneimine-grafted graphene oxide nanocomposite (PEI-GO), and its functional groups formation and thermal stability were verified through Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). Our findings demonstrated a significant improvement in the plastic viscosity and yield point of the base drilling fluid with the addition of PEI-GO. The inclusion of 0.3 wt% PEI-GO outperformed the base drilling fluid at 160 °C, improving the yield point/plastic viscosity (YP/PV) value and reducing filtration loss volume by 42% and 67%, respectively. The Herschel-Bulkley model emerged as the superior choice for characterizing rheological behavior. PEI-GO exhibited compatibility with high-salt formations, maintaining satisfactory filtration volumes even when subjected to sodium chloride (NaCl) and calcium chloride (CaCl2) contamination concentrations of up to 20 and 10 wt%, respectively. The remarkable rheological and filtration properties of PEI-GO are attributed to its electrostatic interactions with clay particles through hydrogen and ionic bonding. These interactions lead to pore plugging in the filter cake, effectively preventing water infiltration and reducing filtration loss volume. This study emphasizes the potential of PEI-GO in water-based drilling fluids, particularly in high-temperature and salt-contaminated environments.

Fluorescent microspheres in particle migration studies during geotextile dewatering: Proof of concept

Understanding the mobility of small particles in geotextile dewatering applications is important when considering highly toxic sediments containing dioxins and furans. These contaminants are often strongly associated with organic matter that are colloidal in size. Microspheres have been used in the soil science research community for tracking the mobility of colloids through porous media for various applications (e.g., bacteria, virus). In this paper, the use of microspheres as a surrogate for small particles (2μm) in geotextile dewatering tests is investigate. Establishment of a reliable and repeatable method for microsphere visualization with a microscope is presented, both for detection and quantification. A simple geotextile dewatering test is conducted in which a soil filter cake is established and the microspheres are passed through the filter cake, followed by the passing of distilled water. It is shown that the microspheres in the effluent can help assist in better understanding the transport of small particles during dewatering which can help us better understand risk of particle transport in these types of tests.

Retenção de água em solos arenosos de diferentes materiais de origem com adição de biocarvão

ABSTRACT This study evaluated biochar influence on water retention in sandy soils with different source materials. Samples from Horizon A of six profiles of Neossolos Quartzarênicos (Salto das Nuvens, Utiariti, Pantanal, Coberturas Detrito Lateríticas Ferruginosas, Botucatu e Bauru formations), collected in different regions of the state of Mato Grosso, Brazil, were used to determine the hydro-physical characteristics with the addition of biochar. The biochars assessed were produced from two sources of raw material (sugarcane filter cake and cotton husks) under pyrolysis at a temperature of 400 °C. Retention curves for soils with and without biochar, the field capacity, permanent wilting point, available water in the soil, total porosity, macroporosity, and microporosity were determined. The results evidenced that the application of biochar increases the microporosity (86.7% with cotton husks biochar and 67.9% with filter cake biochar) and reduces the microporosity of sandy soils (38.2% with cotton husks biochar and 36.0% with filter cake biochar); also, there was a higher increase in water availability with biochar from cotton husks (57.1%). There was an increase in soil microporosity and a reduction in macroporosity due to the influence of biochar addition in the sandy soils from the Salto das Nuvens, Utiariti, Pantanal e Coberturas Detrito Lateríticas ferruginosas, with no changes in the Botucatu and Bauru Formations. Biochar increases water retention in sandy soils; however, this does not occur for all geological formations studied.

Examination of the Efficiency of Fabric Filter Media in Two-Stage Crossflow Pre-Filtration of Turbid Surface Water Using the Davies Flow Equation

Clogging of rapid sand filters during heavy rainfall causes surface water treatment plants to stop their operations until the river water turbidity decreases to a level that the rapid sand filter is capable of filtering. As clogging of rapid sand filters is impediment in surface water treatment, two-stage crossflow pre-filtration with fabric filter media (linen, crepe-backed satin, burlap, and cotton) was considered in a previous study by Davis and Ekwue (2020) as a possible solution. Pre-filtration with linen fabric filter medium was found to be the most efficient at retaining particles. The present paper incorporated properties of various fabrics previously measured and identified by Davis and Ekwue (2020) with the aim of identifying ideal fabric properties that were effective in removing particles from turbid water. Mechanisms of filtration (surface straining, depth filtration and cake filtration) depicted by each selected fabric during two-stage crossflow pre-filtration were identified and compared to the operation of standard filter media (absorbent, adsorbent, biological and woven). The Davies equation was used to calculate the flow of water through single layer and four layers of fabric filter media. Results indicate that no one specific fabric property could be used to proclaim a fabric as the ideal filter media, but rather all properties of the various fabric contribute to their performance during filtration.Linen fabric was once again determined as the fabric type most efficacious at retaining particles during two-stage crossflow pre-filtration of turbid river water and is therefore recommended.

Effects of Organic Substrate Amendments on Selected Organic Fractions and Biochemical Parameters under Different Soils.

The application of organic substrates can affect soil respiration, dehydrogenase (DH-ase) activity, dissolved organic carbon (DOC), and humic acid (HA) fractions. This study aimed to evaluate the effects of five organic substrates in the organic fractions of degraded alluvial soil, acid sulfate soil, and sandy soils and the physicochemical properties of the soil. Soil samples were amended at a rate of 5 tons ha-1 with (1) water hyacinth compost, (2) sugarcane filter cake compost, (3) biogas sludge-rice straw compost, (4) vermicompost, and (5) sludge. The results showed that soil respiration and DH-ase activity increased rapidly within the first 5 days of incubation, while the concentrations of DOC and HA decreased throughout the incubation period. The highest respiration and DH-ase activity occurred after the application of vermicompost. DOC was found to be the highest in soils amended with sugarcane. The highest concentration of HA was observed with the application of sugarcane residues, regardless of the type of soil. The application of water hyacinth and biogas sludge stimulated cumulative HA only in the acid sulfate soil, while vermicompost improved HA only in the degraded soil. The largest stimulation in respiration and DH-ase activity was observed in degraded and sandy soils, regardless of the type of amendment. In the acid sulfate soil (3.7 mg·C·g-1), larger amounts of DOC and HA were observed than in both degraded (1.7 mg·C·g-1) and sandy soils (1 mg·C·g-1). However, DH-ase activity was the lowest in acid sulfate soil.

Green leaching of cold filter cakes using choline chloride-maleic acid deep eutectic solvent and molecular dynamics simulation.

Deep eutectic solvents (DESs) represent a novel class of solvents characterized by their favorable biodegradability and compatibility, which have been used for dissolving various metals. In this study, choline chloride-maleic acid (ChCl-Me) DES was synthesized, and the FTIR technique was used to investigate the formation of DES. Then, ChCl-Me DES was applied to dissolve cold filter cakes (CFCs), and FTIR analysis proved the stability of DES during leaching. Response surface methodology (RSM) was used to investigate the effects of time, temperature, DES to CFC ratio, and stirring speed on the leaching efficiency of Zn, Ni, and Cd. Analysis of variance (ANOVA) showed that the leaching time has a significant effect on all three metals' leaching efficiency. Also, the DES to CFC ratio and the interaction between time and the DES to CFC ratio significantly affect Zn leaching efficiency. Moreover, the second order of the DES to CFC ratio significantly affects Cd leaching efficiency. Optimal conditions were determined as follows: a time of 20 hours, a DES to CFC ratio of 70, a temperature of 60 °C, and a stirring speed of 300 rpm. The UV-vis spectra of the leaching solution showed that metals leached as chlorides in DES. Also, CFC characterization by FESEM-EDS before and after leaching via ChCl-Me DES proved almost complete leaching of metals. Therefore, this solvent can be used as a suitable solvent for the cumulative dissolution of Zn, Ni, and Cd metals with a dissolution efficiency of 90%. Molecular dynamics (MD) simulation and density functional theory (DFT) were employed to obtain detailed information about the complexes formed by Zn, Cd, and Ni ions. The surface charge density, obtained from COSMO computations, shows the notable impact of Cl anions and O atoms within ChCl and Me compounds, respectively, on the Zn2+, Cd2+, and Ni2+ complexes. The radial distribution function (RDF) result highlights strong attractive interactions between ions and Cl- in ChCl, extending to bonded atoms. In addition, RDF results show that oxygen atoms in Me have an impact on CFC dissolution in ChCl-Me DES.

Effect of nano Fe3O4-(CMC-Na)-PFS coagulant on coagulation–ultrafiltration process for treatment of algae -rich water

A novel composite flocculant (PCNF) was prepared using nano Fe3O4 as the condensed core, sodium carboxymethyl cellulose (CMC-Na) as the binder, and polyferric sulfate (PFS). The results indicate that the mass ratio of Fe3O4 to PFS is the key factor determining the flocculation effect of PCNF. When the mass ratio of Fe3O4 to PFS is 1:3, the Zeta potential value is approximately − 1.5 mV, indicating better removal of algae through adsorption electroneutralization. The resulting floc, characterized by negative charge and a loose structure, forms a filter cake layer that is easily backwashed on the surface of the ultrafiltration membrane. This floc also creates strong electrostatic repulsion with the membrane surface. Experimental results demonstrate that the specific flux decreased to 0.69, the total relative pollution was 0.33, and the proportion of irreversible pollution was only 34.65%, all of which were superior to traditional flocculant like PACl. Through microinterface mechanism analysis, it is concluded that the new PCNF flocculant, in combination with algal matter, forms a floc structure critical for mitigating ultrafiltration membrane pollution caused by high algal content in natural surface water.

Coupling pretreatment of ultraviolet/ferrate (UV/Fe(vi)) for improving the ultrafiltration of natural surface water.

Ultrafiltration (UF) is a high-potential technology for purifying natural surface water; however, the problem of membrane fouling has limited its widespread application. Herein, ultraviolet (UV)-activated ferrate (Fe(vi)) was used to purify natural surface water and improve the performance of the UF membrane. The combination of UV and Fe(vi) could generate active species (Fe(v), Fe(iv), ˙OH and O2˙-) to degrade pollutants, while the in situ produced Fe(iii) had the effect of coagulation. With the above action, pollutants were removed, and the pollution load of natural surface water was reduced. After treatment with the UV/Fe(vi) system, dissolved organic carbon was reduced by 49.38%, while UV254 was reduced by 45.00%. The removal rate was further increased to 54.88% and 51.67% after UF treatment. In addition, the fluorescent organics were reduced by 44.22%, and the molecular weight of the organics became smaller. In the stage of UF, the terminal J/J0 was increased from 0.61 to 0.92, and the membrane fouling resistance was decreased by 85.94%. The analysis of the membrane fouling mechanism indicates that the role of cake filtration was weakened among all the mechanisms. Fourier transform infrared spectroscopy showed that less pollutants were accumulated on the membrane surface, and scanning electron microscopy revealed that the membrane pore blockage was relieved. In summary, the UV/Fe(vi) co-treatment process proposed in this study can significantly improve the purification efficiency of the UF systems in natural surface water treatment.