Filter Cake Research Articles

Alkaline Hydrolysis of Waste Acrylic Fibers Using the Micro-Water Method and Its Application in Drilling Fluid Gel Systems.

Filtrate reducer is a drilling fluid additive that can effectively control the filtration loss of drilling fluid to ensure the safe and efficient exploitation of oilfields. It is the most widely used treatment agent in oilfields. Due to its moderate conditions and controllable procedure, alkaline hydrolysis of high-purity waste polyacrylonitrile has been utilized for decades to produce filtrate reducer on a large scale in oilfields. However, the issues of long hydrolysis time, high viscosity of semi-finished products, high drying cost, and tail gas pollution have constrained the development of the industry. In this study, low-purity waste acrylic fiber was first separated and purified using high-temperature hydroplastization, and the hydrolyzed product was obtained using alkaline hydrolysis with the micro-water method, which was called MW-HPAN. The hydrolysis reaction was characterized using X-ray diffraction, scanning electron microscopy, infrared spectroscopy, and thermogravimetric analysis, and the elemental analysis showed a hydrolysis degree of 73.21%. The experimental results showed that after aging at 180 °C for 16 h, the filtration volume of the freshwater base slurry with 0.30% dosage and 4% brine base slurry with 1.20% dosage was 12.7 mL and 18.5 mL, respectively. The microstructure and particle size analysis of the drilling fluid gel system showed that MW-HPAN could prevent the agglomeration of clay and maintain a reasonable particle size distribution even under the combined deteriorating effect of high temperature and inorganic cations, thus forming a dense filter cake and achieving a low filtrate volume of the drilling fluid gel system. Compared with similar commercially available products, MW-HPAN has better resistance to temperature and salt in drilling fluid gel systems, and the novel preparation method is promising to be extended to practical production.

Chemical-free vacuum ultraviolet irradiation as ultrafiltration membrane pretreatment technique: Performance, mechanisms and DBPs formation

Membrane fouling induced by natural organic matter (NOM) has seriously affected the further extensive application of ultrafiltration (UF). Herein, a simple, green and robust vacuum ultraviolet (VUV) technology was adopted as pretreatment before UF and ultraviolet (UV) technology was used for comparison. The results showed that control effect of VUV pretreatment on membrane fouling was better than that of UV pretreatment, as evidenced by the increase of normalized flux from 0.27 to 0.38 and 0.73 after 30 min UV or VUV pretreatment, respectively. This is related to the fact that VUV pretreatment exhibited stronger NOM degradation ability than UV pretreatment owing to the formation of HO•. The steady-state concentration of HO• was calculated as 3.04 × 10−13 M and the cumulative exposure of HO• reached 5.52 × 10−10 M s after 30 min of VUV irradiation. And the second-order rate constant between NOM and HO• was determined as 1.36 × 104 L mg−1 s−1. Furthermore, fluorescence EEM could be applied to predict membrane fouling induced by humic-enriched water. Standard blocking and cake filtration were major fouling mechanisms. Moreover, extension of UV pretreatment time increased the disinfection by-products (DBPs) formation, the DBPs concentration was enhanced from 322.36 to 1187.80 μg/L after 210 min pretreatment. However, VUV pretreatment for 150 min reduced DBPs content to 282.57 μg/L, and DBPs content continued to decrease with the extension of pretreatment time, revealing that VUV pretreatment achieved effective control of DBPs. The variation trend of cytotoxicity and health risk of DBPs was similar to that of DBPs concentration. In summary, VUV pretreatment exhibited excellent effect on membrane fouling alleviation, NOM degradation and DBPs control under a certain pretreatment time.

Intelligent control of emulsion stability and evaluation of selective water shutoff performance

Using hydrophobic nano-SiO2 and a tiny amount of non-ionic and anionic surfactants as stabilizers, a Pickering emulsion system for oil-in-water in high-temperature and high-mineralization reservoirs was developed. At high temperatures (120 °C) and high mineralization (37000 mg/L), the emulsion system shows outstanding stability. The addition of the auxiliary agent can effectively control the time of emulsion breaking and nanoparticle release. The auxiliary agent will "compete" with the surfactant for adsorption on nanoparticles at the oil/water interface, weakening the surfactant's anchoring effect and causing a decrease in the surface roughness of the nanoparticles, resulting in a decrease in the mechanical strength of the interfacial film. Furthermore, the presence of H+ in the solution neutralizes part of the negative charges on the surface of emulsion droplets, which is detrimental to emulsion stability because electrostatic repulsion between droplets is diminished. The released SiO2 particles agglomerate in the pore throat to form a hydrophobic filter cake, which can be used to achieve intelligent water control in high-temperature and high-mineralization reservoirs (1000 mD), with an aqueous phase plugging rate of 95.83% and an oil phase plugging rate of 25.32%.

Strength, mineralogical, microstructural and CO2 emission assessment of waste mortars comprising excavated soil, scallop shells and blast furnace slag

The construction sector is actively seeking alternatives to Portland cements, with a view to decarbonising cementitious construction materials, such as mortars and concretes. Using pozzolanic industrial mineral wastes (e.g. fly ash and slags) as supplementary cementitious materials (SCMs) is an effective strategy. However, further investigation is required to identify more SCMs that have longevity in supply, with a view to benefiting the circular economy. Excavated soil and scallop shell wastes are becoming increasingly abundant due to urbanisation and aquaculture sectoral expansion. Managing these wastes through their valorisation as construction materials is more sustainable and therefore highly desirable over disposing them to landfill. This study investigates the use of excavated soil and scallop shell wastes as raw materials for manufacturing low-carbon cementitious mortars. Mechanochemical and thermal techniques were investigated as alternatives to alkali reagents for activating strength-gaining properties of the soil waste. Mixtures comprising mechanochemical+thermally activated soil waste with 10% blast furnace slag produced the highest strengths (2.43 MPa) after 28-days and generated ∼50% less CO2 emissions compared with CEM-I-treated mixtures. Furthermore, the compressive strengths performance recorded for mechanochemical+thermally activated soil waste with 10% scallop shells (1.07 MPa) were only 8% less compared with strengths for equivalent mixtures containing 10% type 1 Portland cement. Based on results from regression analyses, Si/Al was the most effective elemental ratio for predicting 7- and 28-day compressive strength of mortars based on filter cake that had been mechanochemical and/or thermally treated through linear functions. Exponential functions were more appropriate for predicting strength based on other elemental ratios, which considered one or a combination of Ca, Na, K and Fe.

Novel coating of slow-release nitrogen fertilizers: Characterization and assessment

Developing novel fertilizers that reduce nitrogen release rate receives worldwide interest as a potential means for improving nitrogen utilization efficiency. Making these fertilizers sustainable, this work introduces various attempts to prepare slow-release nitrogen using different materials comprised of agro-industrial wastes such as sugarcane (SC) and beet filter cakes (mud) besides, sulfur, gypsum, and zeolite to cover two nitrogen sources. The prepared coated nitrogen fertilizers were characterized using SEM-EDX. Afterward, an incubation trial was conducted to appraise the produced slow-release fertilizers via mixing with three soils (from Egypt and Sudan) at various incubation periods. The tested coating process enhanced the surface morphology of the fertilizer grains, in which the surface became smoother and all the cracks and cavities were filled with the coating material, which is critical for the physical barrier property and preventing moisture penetration into the core. ANOVA analysis indicated that the released values of N were significantly varied according to the soil type, source of N, and the coating material. Zeolite was effective as a coating material for all nitrogen fertilizers. The coated granules by SC material provided a steady, adequate nitrogen supply throughout the incubation. Beet mud treatments showed the lowest N release among all coating materials, but the liberation of N gradually increased with time elapsed. The beet and sugarcane mud can be considered promising covering materials for developing environmentally friendly and cost-effective slow-release fertilizers. The results showed continuous release of N in the soils from all prepared coated fertilizers til the end of the incubation, enhancing the feasibility for agricultural application.

Synthesis and mechanism study of an environmentally friendly filtrate reducing agent from humic acid and organic silicon

AbstractIn this study, organic silicon was introduced to humic acid for the first time, and set the novel polymer NaHm/AMPS/AM/TSP‐L12 (HASSi) as an environmentally friendly filtrate reducing agent, which was developed by using silica modified material (TSP‐L12), sodium humic acid (NaHm), 2‐acrylamido‐2‐methylpropanesulfonic acid sodium (AMPS), and acrylamide (AM) as raw materials. The molecular structure, chemical composition of HASSi has been investigated and results show that HASSi shows the chemical structure was conformed to the molecular design. Differential scanning calorimetry–thermogravimetric analysis results illustrate that thermal decomposition temperature of HASSi under nitrogen was 250°C. Though temperature resistance evaluations, HASSi could withstand temperature up to 230°C. Salt and calcium resistance evaluations confirmed its resistance of NaCl could reach up to 5% and CaCl2 to 0.5%. The filtrate reduce mechanism of HASSi was investigated through various methods, including scanning electron microscope analysis of HASSi aqueous solution, microstructure of filter cake, measurements of zeta potential, and particle size distribution, results showed that HASSi participation in the formation of mud cakes and illustrated an excellent filtration reduction effect. In addition, HASSi was identified as an environmentally friendly filter loss reducing agent through environmental performance evaluation, which shows a great application prospect in oilfield.

Formation damage challenges and solutions in cased hole gravel pack completions in deep offshore unconsolidated laminated sandstone formations in the Sakarya Field

A comprehensive experimental formation damage study for the Sakarya Field was conducted to identify production impairment mechanisms induced by operational fluids. The study reveals that the retention of operational fluids leads to irreversible reductions in gas permeability to a certain degree. This fluid retention is associated with the amount of loss and retention time of operational fluids into the reservoir, as well as the types of clays present in the gas bearing zone. Fluid retention damage is more severe for samples with lower permeability and higher silt content. While sandy plugs typically experience a reduction in permeability of less than 10%, low-permeability silty samples can exhibit reductions as high as 35%. The most effective approach to minimize this damage includes maintaining the lowest possible overbalance pressure, applying completion methodologies with minimal fluid invasion, and ensuring timely and effective cleanup. Another source of damage appears to result from acidic dissolution of native carbonate minerals and destabilization of delicate clays (e.g., chlorite). This leads to slight compaction and associated immediate reduction in permeability, reaching as high as 50% when combined with other operational fluid damage in some cases. In such environments, it is recommended to use a milder alternative acid solution that specifically targets the filter cake and debris around perforations, minimizing the dissolution of native carbonate minerals and interaction with clays. Due to the low uniaxial compressive strength (UCS) of the formation, evidence of sanding and proppant embedment was observed. To mitigate this issue, an optimum gravel pack design and execution during well completion is vital. Additionally, avoiding abrupt bean-up and bean-down during well tests and production will help limit sanding and proppant embedment. The novel experimental methodology and field implications derived from this study may serve as a guideline to solve formation damage challenges in similar fields facing similar issues. Initiating such detailed studies in the early stages of field development is critical to ensure maximum recovery from the least damaged and disturbed reservoirs.

Adubação orgânica e mineral determina o desempenho agronômico de cultivares de girassol e atributos químicos do solo

ABSTRACT This study aimed to verify the effect of the application of filter cake, via soil and in association with mineral fertilization, on sunflower cultivars (Helianthus annuus L.) and the chemical properties of the soil. The experimental design used was randomized blocks in a 3 × 2 factorial scheme with six replicates, totaling 36 experimental units. Three sunflower cultivars (Sany 66, Nusol 4140, and Nusol 4170) and two fertilization strategies (mineral fertilization with and without filter cake) were used. Resorting to the filter cake increased the oil concentration in Sany 66. Mineral fertilization did not significantly affect achene production, with mean values being 2561.58 kg ha-1. However, including filter cake resulted in a 21% increase in phosphorus (P) content in the 0-0.20 m soil layer in sunflower crops of the Nusol 4140 variety. Therefore, fertilization with filter cake, in combination with chemical fertilizers or alone, can be an effective strategy to increase soil P content and oil concentration in sunflower cultivation.

Role of Additives: Modified Hemihydrate Phosphogypsum Morphology and Enhanced Filtration Performance of Wet-Process Phosphoric Acid.

The morphology of hemihydrate phosphogypsum crystals is of vital importance in the hemihydrate-dihydrate (HH-DH) wet-process phosphoric acid production for high filtration strength. The morphology of hemihydrate phosphogypsum is commonly needlelike due to the strong acidic crystallization environment, which is unfavorable to the following filtration process. In this study, the crystal habit of hemihydrate phosphogypsum with a large aspect ratio was skillfully modified by additives to achieve a higher filtration strength. d-Glucitol (DG) reduces the theoretical aspect ratio of hemihydrate phosphogypsum crystals from 2.076 to 1.583 by interacting with the (002) face of CaSO4·0.5H2O preferentially, and poly(vinyl alcohol) (PVA) facilitates the aggregation of small grains to gather into a clusterlike structure. The modified morphologies of hemihydrate phosphogypsum have a lower bulk density and a larger porosity of the formed filter cake, which increases the filtration strength up to 45.9% when DG is added. Our work provides an in-depth explanation of the evolution mechanism of hemihydrate phosphogypsum morphology with the additives and its influence on the filtration performance. The improved filtration strength would reduce the water content of hemihydrate phosphogypsum and relieve the storage pressure of the phosphogypsum slag dump, which is meaningful to the clean production and process emission reduction of the phosphorus chemical industry.

Preparation and performance evaluation of PDDSA-MS composite as high temperature and high salinity filtration additive

Drilling operations in deep and ultra-deep wells encounter challenges arising from high temperature and saltwater intrusion, leading to reduced drilling efficiency and deteriorated performance of water-based drilling fluids. In order to alleviate the problem of increased filtration of drilling fluid under harsh environment, the composite (PDDSA-MS) was prepared by free radical polymerization using N, N-dimethyl acrylamide (DMAA), Dimethyl diallyl ammonium chloride (DMDAAC), Sodium styrene sulfonate (SSS), 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and KH570 modified SiO2 as raw materials. This composite contained absorption groups, hydration groups, rigid groups and nanomaterials. Through rigorous performance evaluations, it was observed that the addition of 1 wt% composite to a fresh water drilling fluid, resulting in a remarkably low filtration of 8.8 mL after aging at 260 °C. Furthermore, when 3 wt% composite was added to the 15 wt% NaCl salt water drilling fluid, the filtration was 8 mL after aging at 220 °C. This was attributed to the particle size of the composite and its ability to maintain the dispersion stability of drilling fluid, decelerate bentonite agglomeration, and make the surface of the formed filter cake dense and smooth. These findings demonstrated the thermal stability exhibited by composite, offering an effective solution for drilling operations in deep and ultra-deep wells.

Digital Cake Analysis: A Novel Coal Filter Cake Examination Technique Using Microcomputed Tomography

Filtration is crucial for separating solids and liquids in various industries. Understanding slurry properties and filter cake structures is essential for optimising filtration performance. Conventional methods focus on interpreting filtration data to improve the understanding of filtration mechanisms. However, examining fragile filter cakes is challenging, and current techniques often alter their structure. Conventional methods only provide an average representation of cake porosity, neglecting variations in porosity and pore distribution across the cake thickness. This study introduces the Digital cake analysis, a non-destructive technique for evaluating filter cake structure. Filtration experiments using a custom-built unit were conducted on coal slurries to obtain filter cake samples. X-ray-microcomputed tomography (µCT) imaging was utilized for cake analysis. Image enhancement techniques were employed to improve the quality of the µCT images. The enhanced images were segmented into three phases (resolved pore, subresolution pore, and solid phases) for quantitative analysis. This segmentation technique allocated partial pore volume to voxels in the subresolution phase based on their intermediate grey-scale intensity, enabling more accurate porosity calculations. Unlike conventional methods, this approach computed porosity values for resolved (100% void) and subresolution (partially void) pores. This image segmentation technique facilitated accurate computations of porosity, pore size distribution, and pore properties, significantly advancing the understanding of cake structures. Digital cake analysis produced porosity measurements similar to the experimental results.

Rapid and clean dewatering of dredged sediment via coupling of a two-step flocculation and geotextile filtration

The use of flocculation processes coupled with geotextile technology for dredged sediment dewatering is promising in recent years. However, two main issues are encountered: firstly, the occurrence of clogging resulting in reduced dewatering rate, and secondly, contamination of the residual water, necessitating additional treatment, consequently leading to an increase in operational costs. Therefore, this study proposed an innovative approach employing a two-step flocculation combined with geotextile filtration method to achieve rapid and clean dewatering of dredged sediment. The jar test implementation of a two-step flocculation process at the optimal flocculation dosages resulted in a dewatering rate that was about 16.7 times compared to commercial flocculant (APAM) conditioning. The increased dewatering rate is mainly attributed to the formation of large and compact flocs aggregates (d50 > 160 μm) formed through the two-step flocculation. These aggregates facilitate the formation of a filter cake with a high porosity of 45 %, a low tortuosity of 1.53, a uniform pore-throat structure, and excellent connectivity of pore space. Compared with APAM, the value of turbidity, COD, NH4+-N, and phosphorus in the residual water can be decreased from 36.4 to 3.8 NTU, 28.6 to 8.3 mg/L, 2.3 to 1.6 mg/L, 0.15 to 0.04 mg/L, respectively, which meet the environmental quality standards for surface water (type V) in China. In addition, the technology is proven to be economical as the cost of flocculants is less than half the cost of other reported flocculants. Overall, this work presents a new and cost-effective approach for achieving both rapid and clean dewatering of dredged sediments, which is very promising for practical applications.

Analytical and numerical modelling of the effect of filter medium resistance on the mechanical dewatering of wastes and industrial filter cakes

A nonlinear model is proposed to predict the effect of filter medium resistance on the filter cake compression and dewatering at constant pressure. This model is based on the Darcy-Terzaghi-Shirato filtration-compression equations presented in material coordinates and modified to consider the power-law pressure dependence of the specific cake resistance α. Above mentioned model is extended to consider the filter medium resistance Rmintroducing the number of Biot, Bi=αavWRm.Local profiles of compressive pressure and filter cake characteristics, as well as consolidation ratio and cake dryness, are simulated and compared for different moderately and highly compressible filter cakes (silica, activated sludge, Baker’s yeast, and CaCO3) based on the analytical and numerical solutions of the model. It is shown that the behavior of cake compression and dewatering significantly depends on the filter medium resistance Rm, especially at the small numbers of Bi≤1.

MECHANISM OF MEMBRANE FOULING IN HYBRID MEMBRANE PHOTOCATALYTIC REACTOR FOR PALM OIL MILL SECONDARY EFFLUENT TREATMENT

Palm oil mill secondary effluent (POMSE) is a byproduct of the biological treatment of palm oil mill effluent. This research aims to investigate the mechanism of membrane fouling in the treatment of POMSE using a hybrid membrane photocatalytic reactor (MPR). The effectiveness of MPR in POMSE treatment is currently limited due to membrane fouling on the membrane surface. This study focuses on understanding the various mechanisms of membrane fouling, including complete blocking, intermediate blocking, standard blocking, and cake filtration. The determination of each fouling mechanism is achieved through an analysis of normalized flux data employing the Wiesner and Aptel equation. The results demonstrate a high degree of model fitness (R2 = 0.9576) for MPR Run 3, confirming its effectiveness. Based on the (R2) values and the fitted parameter (Ks^(-1)), it is evident that, under varying pH levels, catalyst types, catalyst loading, and initial POMSE concentrations, the cake formation fouling mechanism prevails in MPR Run. In conclusion, this research holds promising potential for implementation in the wastewater treatment industry while ensuring compliance with environmental regulations.

Karakteristik Pupuk Organik Cair Berbasis Limbah Vinasse Melalui Teknologi Aktivasi

Utilization of vinasse waste as POC has great potential in the agricultural sector. This is because there is an abundance of vinasse waste originating from the bioethanol industry sector. So action is needed so that vinasse waste can be utilized into a profitable product. This research aims to test the potential of vinasse waste if it is processed into POC. Apart from using vinasse waste as the main raw material, the formula also added organic ingredients such as straw ash, humate, husk charcoal and filter cake dregs which were fermented for 5 weeks. Based on the research results, the content of N, P, K and C-organic elements cannot comply with the 2019 Ministry of Agriculture Quality Standards. Meanwhile, the content of Na and pH elements is appropriate, but for Fe only the F2 and F4 T1 treatments can be appropriate.

Investigation on permeability of filter cake with different particle sizes: Experimental and simulation study

Cake permeability is a crucial macroscopic physical property in characterizing filtration behavior for coal slurry. However, there is still no appropriate model derived to establish the essential relationship between the cake permeability and complex particle property. In this study, the three-dimensional microstructures with different particle gradation and porosity were generated using particle discrete element software. The permeability of each constructed model was calculated utilizing Lattice Boltzmann Method (LBM). Simulation result shows that the Kozeny–Carman (KC) model is proper to predict the permeability of porous media with different gradations. When the gradation parameters are not considered, it shows that d30 can best represent the particle size characteristics of the particle systems. When the porosity and average particle size remain unchanged, the permeability increases with the increasing of the non-uniformity coefficient (Cu) and the curvature coefficient (Cc). Moreover, we proposed an analytical expression for the permeability estimation with different gradation characteristics, which contains the parameters that can be easily measured in engineering. Then a set of coal slurry samples with different particle size distributions were selected to conduct the filtration test, the permeability of each sample was measured to compare with the predicted results of the gradation permeability model. It is clear that the KC equation in this case can not calculate the cake permeability effectively. Although the gradation model is relatively appropriate to estimate the cake permeability, its accuracy still needs to be improved by considering the pore structure property to eliminate the effect of constant terms.

MnFe2O4 composited polyvinylidene fluoride catalytic ultrafiltration membrane via peroxymonosulfate activation for humic acid treatment: Exploration of synergistic mechanisms

Membrane separation has become the most promising technology in the field of wastewater purification, but there will inevitably be membrane fouling. Catalytic polymer membranes combining membrane filtration and advanced oxidation technologies (AOPs) offered an alternative for mitigating membrane fouling. This work successfully synthesized a MnFe2O4 catalytic polyvinylidene fluoride (MnFe2O4-PVDF) ultrafiltration membrane and systematically investigated the performance of peroxymonosulfate (PMS)/MnFe2O4 membrane oxidation filtration system for removing humic acid (HA). The results showed that the PVDF@MnFe2O4/PMS synergistic system oxidized HA into small molecules and further repelled them to the membrane surface by size exclusion to form a filter cake layer. The PVDF@MnFe2O4/PMS system exhibited the lowest irreversible fouling (0.414 × 1010m−1) and the highest HA removal efficiency (83.4 %) compared with PVDF single filtration. After hydrodynamic cleaning, PVDF@MnFe2O4 can achieve 73.2 % water flux recovery. The membrane fouling mitigation mechanisms were investigated by the Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory and the combined pore blockage-cake filtration model. Quenching experiment and density functional theory calculation (DFT) revealed the HA degradation as a result of the synergistic action of free radicals (SO4⋅-, ⋅OH) and non-free radicals(1O2) in PVDF@MnFe2O4/PMS system. Additionally, we evaluated the effectiveness of the system in the removal of natural organic matter (NOM) from surface water. The results suggested that the PVDF@MnFe2O4/PMS system could validly remove the main fluorescent matters from surface water. In conclusion, this work provides a promising route for solving the membrane fouling caused by NOM in water.

Effects of nanosilica on the properties of brine-base drilling fluid

In the process of drilling oil and gas wells, the shrinkage and falling of wellbore walls are often caused by the expansion of mud shale water. To date, conventional additives have been unable to plug the pore throats of shale rock with nanoscale pores and thus cannot effectively solve the problem of wellbore instability encountered in shale formation drilling. In view of this situation, the idea of using nanosilica to plug the nanopore throat of mud shale is proposed to reduce its permeability and to slow water intrusion. The influences of nanosilica on the properties of brine-base drilling fluid drilling fluid are evaluated by measuring the viscosity, filtration loss and swelling of the drilling fluid. The results of laboratory experiments show that the improvement in drilling fluid properties can only be achieved on the basis of salt resistance; that is, a salt-resistant soil slurry should be used. A concentration of 1–5% nanosilica can improve the viscosity of the drilling fluid by increasing the internal friction between particles. However, nanosilica materials are sensitive to salt concentration. Nanosilica particles can be deposited on the surface of a filter cake to block the pores of the filter paper, and the filtration loss reduction rate can reach 40.2%. Blocking the pores of the clay plays a role in preventing the clay from absorbing water and expanding. The optimal addition amount of silica is 3%, and its salt resistance can reach 16%. Considering the experimental results of filtration loss, swelling amount and cost performance, 3%NP + 4%NaCl + SWM-B is selected as the optimal formula. The results of this study can be applied to effectively improve the phenomenon of wellbore instability during drilling in shale formations, and it has important application value.

Ultrasonic intensification of flocculation filtration for kaolinite: Unraveling mechanisms and performance gains

The mining industry produces substantial tailings, which present environmental challenges. This necessitates the adoption of efficient solid–liquid separation technologies to convert these tailings into a dewatered and environmentally manageable dry stack form. This work aims to investigate the transformative potential of ultrasonic treatment in the context of flocculation filtration for kaolinite dewatering and to elucidate the underlying mechanism. Through Uniform Design optimization, we determined the optimal conditions: 40 W ultrasound power, 12 min duration, and 40 kHz frequency. Experimental validation emphasized the effectiveness of these parameters, revealing a 2.02 % reduction in filter cake water content alongside a significant 2.5-fold enhancement in filtration rate. Furthermore, this combined treatment surpassed the performance of flocculation alone, resulting in the formation of smaller, more desirable flocs. The 3D structural analysis of the filter cake using micro-CT revealed that the synergistic application of ultrasound and flocculation led to a notable decrease in overall porosity. More significantly, there was a substantial reduction of isolated pores (down to 9.32 %). This phenomenon remarkably improved pore connectivity, enlarged pore and channel radii, and effectively mitigated capillary resistance during water transport. Additionally, the filter cake subjected to ultrasound and flocculation treatment showcased a uniform distribution of pore space, indicative of a promising trend towards homogenization across different sections. Ultrasound plays a role in refining flocs and suppressing segregation during tailings flocculation and filtration processes, primarily attributed to the cavitation and acoustic streaming effects of ultrasound. This comprehensive investigation sheds light on the transformative role of ultrasonic treatment in advancing the efficiency and performance of kaolinite dewatering processes.

Silicon Poisoning and Effects of Tantalum on AlSi Alloys

Grain refinement in Al-Si alloys is crucial for enhancing material castability and mechanical properties. Industrial practice involves adding inoculants, composed of TiB2 particles coated with metastable Al3Ti via adsorption, to the melt. This introduces essential free titanium for metastable phase formation and subsequent growth restriction. The superstoichiometric grain refiner Al-5Ti-1B, with 2.2 wt.% free titanium, is applied for this purpose. A peritectic reaction forms α-aluminium from this layer. However, when silicon content exceeds 3.5 wt.%, grain coarsening occurs due to silicon’s detrimental effect. This study quantified silicon poisoning in an Al-10Si alloy using stoichiometric and superstoichiometric grain refiners through ASTM-standardized TP1 tests. Adding 0.02 wt.% tantalum acted as an antidote to the τ1 phase, resulting in a finer microstructure. This was attributed to the formation of a Ta-rich layer on TiB2 particles, which causes α-aluminium formation via a peritectic reaction without generating ternary phases with Ti or Si. Correlating to the increasing particle size curves from the TP1 tests, phases were collected in the filter cake with the help of a PoDFA apparatus. These could be examined more closely on the SEM and identified as needle- or plate-shaped. By using an EDS unit, the phases found were assigned to the poisoning phase and further investigated. After the addition of tantalum, a solubility of tantalum could be detected in former poisoning phases. In combination with the gradients of the grain size, it can thus be assumed that tantalum is both an antidote for silicon poisoning in the Al-Si-Ti system and can itself have a grain-refining effect in this system.