Search Results (58)

Surface-modified waste scallop shells were investigated as a solid flocculant for removing suspended particles, and a light transmission method was examined as a simple approach for evaluating flocculation behavior. Kaolin suspensions (3, 5, 10 g/L, pH 6.95–7.05) were used as model wastewater. Temporal changes in transmitted light intensity were monitored using a white LED–sensor optical system after agitation of the suspension was stopped. The transmitted light intensity, I, was normalized by the intensity measured for particle-free water (I₀), and an optical extinction index, A = −log₁₀(I/I₀), was used to describe the attenuation of light in the suspension. An apparent clarification rate (rate of change in optical extinction), v, was defined from the initial decrease in the optical extinction index and used as an operational kinetic parameter for comparing flocculation behavior under identical conditions. The results showed that the surface-modified scallop shell particles exhibited measurable flocculation activity toward kaolin suspensions, although the performance was lower than that of commercial polymer flocculants. The optical transmission method enabled continuous monitoring of the flocculation process and provided a practical index for comparing the flocculation performance of different materials. Full article

This study provides novel insights into the gradual development of an algal-bacterial self-flocculent biomass in a 400 L pilot-scale raceway pond for wastewater treatment to enhance sustainability and minimize environmental footprint. The synergetic interaction of algal-bacteria consortia improves nutrient removal while enabling biomass concentration increase. Initially, the microalgae-bacteria biomass was gradually developed by increasing the operating volume from 60 to 400 L. After 80 days, the biomass reached a plateau at a concentration of about 4 g L⁻¹, and exhibited excellent settling characteristics. The initial settling velocity was 14.8 cm min⁻¹ and a settling time of 3 min was required to achieve efficient separation. The reactor achieved high treatment efficiency of about 95% for all nutrients (organic matter, nitrogen and phosphorous) after the 80th day. The kinetic analysis showed that nutrient removal followed first-order kinetics, with soluble chemical oxygen demand and ammonia removal reaching 0.017 and 0.020 h⁻¹, respectively. The results demonstrate high pollutant removal efficiencies and design guidelines for the use of increased concentrations of microalgae–bacteria consortia in urban wastewater treatment practice, an alternative green way for solving present-day wastewater treatment problems. Full article

The treatment of spent drilling fluids generated during the drilling of technological wells for uranium production represents an important engineering and environmental challenge associated with high energy consumption, significant waste generation, and the need for rational water use under arid regional conditions. Conventional phase separation methods based on gravitational settling and chemical–mechanical treatment are characterized by limited process controllability, long processing times, and increased consumption of reagents and energy. This study proposes an energy-efficient and reliable hydrodynamic technology for the treatment of spent drilling fluids based on the formation of controlled turbulent structures without the use of mechanical drives. The research object comprised spent drilling fluids (SDFs) generated during the drilling of technological wells for uranium production in the southern regions of the Republic of Kazakhstan and the Kyzylorda region. Experimental investigations were carried out using a laboratory–pilot hydrodynamic disperser with variations in velocity gradient, treatment time, flocculant dosage, and suspension flow rate. A mathematical model linking hydrodynamic process parameters with phase separation kinetics and energy characteristics was developed. Model calibration by weighted nonlinear least squares yielded a stable parameter set with 95% confidence intervals, and model validation demonstrated good agreement between calculated and experimental data (MAPE 8.4%; maximum relative error 11.8%). It was established that the use of a hydrodynamic disperser provides separation efficiency of up to 90–95% under optimal operating conditions while reducing specific energy consumption and maintaining stable repeated-cycle performance within the investigated operating window. Experimental results confirm that implementation of the hydrodynamic technology enables a reduction in sludge volume by 40–60%, recovery of up to 60–80% of process water, and a significant decrease in waste requiring transportation and disposal. The obtained results demonstrate the high environmental and resource-saving efficiency of the proposed technology and its suitability for scaling and industrial implementation at facilities drilling technological wells for uranium production. The developed hydrodynamic approach can be considered an effective engineering platform for creating energy-efficient and sustainable systems for drilling fluid treatment in regions with limited water resources and remote industrial infrastructure. Full article

Ultrafine hematite particles (<10 μm), commonly generated in beneficiation circuits, exhibit poor flocculation and slow settling, posing challenges for solid–liquid separation. This study investigates the influence of the anionic polyacrylamide (APAM) molecular weight on ultrafine hematite flocculation under controlled laboratory conditions, combining macroscopic experiments with molecular dynamics simulations (MDSs). Sedimentation tests show that the APAM molecular weight strongly affects settling kinetics, supernatant clarity, and floc structure, with the settling rate, flocculation-stage reaction time, supernatant turbidity, and underflow concentration exhibiting a non-monotonic trend and optimal performance at seven million. Under this condition, particles aggregate most efficiently, achieving a turbidity of 182 NTU, an underflow concentration of 51.5%, and the largest compact flocs, averaging 379.8 μm with a fractal dimension of 1.71. Higher molecular weights (≥9 million) induce chain coiling, reduce floc compactness, increase water retention, and impair settling. MDS indicates that polymer–surface interactions improve with an increasing polymerisation degree only up to an intermediate chain length; a polymerisation degree of 30 exhibits the most favourable extended–flexible conformation, maximal surface enrichment, strongest coordination between carboxyl groups and surface Fe atoms, lowest adsorption energy, and fastest adsorption kinetics. The functional-group distribution and hydrogen-bond analyses show that –NH₂ and –COO^– groups dominate interfacial interactions, with a polymerisation degree of 30 yielding the highest density of interfacial hydrogen bonds. By correlating macroscopic experiments with molecular-scale observations, this work provides mechanistic insight into how the APAM chain length governs ultrafine hematite flocculation, highlighting the role of polymer conformation and multipoint adsorption in controlling the settling performance. Full article

The use of seawater in mineral processing poses significant challenges for solid–liquid separation, including polymer chain contraction, accelerated coagulation, and brittle aggregate formation. This study evaluates the impact of fractional dosing of anionic polyacrylamide (PAM) on the formation, structure, and sedimentation performance of flocs in quartz-kaolinite suspensions prepared in seawater. Four dosing schemes (1, 2, 3, and 4 pulses) were analyzed, maintaining a total dose of 15 g/t and flocculation times of 75, 90, and 105 s. Sedimentation assays, kinetic monitoring using FBRM, size distributions, fractal dimensions, and bulk density were integrated to characterize the aggregation process. The results show that all fractional strategies outperform single-pulse dosing, with the three-pulse scheme (0–30–60 s) standing out, achieving the highest settling rates, the most significant fines reduction, and the best structural robustness. FBRM kinetics reveal stepped growth, less shear breakage, and more stable maturation when polymer addition is divided temporally. Consistently, fractal dimension and aggregate density reach their maximum values after three 90 s pulses, indicating more compact, less porous structures. Zeta potential analysis confirms a strong polymer-particle interaction in kaolinite under high salinity. The superior performance of the multi-pulse strategy is explained by the progressive availability of active polymer segments during aggregate formation and maturation. Each pulse is incorporated into a partially structured suspension, in which unoccupied mineral surfaces and flocs from the early stages of consolidation still exist. This staggered adsorption avoids local overdosing associated with flash injections, improves bridging efficiency, reduces brittle aggregate formation, and promotes more uniform restructuring. Full article

The time-dependent structuration of cement pastes is a key parameter governing the fresh-state behavior of modern concretes. This study investigates the influence of four supplementary cementitious materials (SCMs): fly ash (FA), slag (S), limestone filler (LF), and metakaolin (MK) on both the total and irreversible structural build-up of cement pastes, under various temperatures (5, 20, 30 °C) and a constant replacement level of 30% at w/b = 0.45. Static yield stress was measured using a vane rheometer with or without re-shear to distinguish between the total (without re-shear) and irreversible (with re-shear) structural build-up. Complementary tests, including mini slump flow, isothermal calorimetry, and bleeding analysis, were conducted to assess the effect of SCMs on rheology, hydration and stability. Results show that all SCMs significantly reduced the rate and intensity of structural build-up compared with reference cement paste: after 90 min at 20 °C, the static yield stress (total structural build-up) was 1740 Pa for the reference mix and between 420 and 840 Pa for the blended systems. The irreversible fraction remained low (<10%) for all blended systems, confirming that early-age structuration is mainly governed by reversible flocculation rather than by hydration-driven bonding. Temperature significantly accelerated the total structural build-up in all mixtures; at 30 °C, the total build-up of slag-, LF-, and MK-blended pastes approached that of plain cement. However, while the reference cement paste exhibited a clear increase in irreversible structuration (from 25% at 20 °C to 35% at 30 °C), SCM-containing systems remained largely governed by reversible mechanisms, with the irreversible fraction consistently below 10%. These findings highlight the distinct roles of particle morphology, clinker dilution, and hydration kinetics in governing early structuration. Understanding these coupled mechanisms is essential for optimizing low-clinker binders used in self-compacting and 3D-printable concretes, where balancing flowability and early stability is critical. Full article

Ultrafine bubbles (UFBs) have been proposed as interfacial agents that modulate colloidal interactions, yet their role in early-stage flocculation remains insufficiently quantified. Using amidine latex (AL) as a cationic model colloid under controlled end-over-end mixing, we combined flocculation kinetics with electrokinetic and interfacial measurements to elucidate the mechanism by which UFBs promote aggregation. Electrophoretic measurements show adsorption-driven charge regulation by bubbles; increasing the UFB-to-AL ratio progressively neutralizes the surface and at sufficient dose reverses its charge. The neutrality point occurs at a characteristic ratio that is only weakly sensitive to background sodium chloride (NaCl). Interfacial measurements reveal a thicker hydrodynamic layer at higher ionic strength, consistent with closer packing of adsorbed UFBs under double layer compression, and micrographs of particle dimers confirm a larger inter-particle separation that directly visualizes this layer. Aggregation accelerates at 10 mM sodium chloride but remains slow at 0.1 mM, indicating that electrolyte screening is required for efficient adsorption and bridging; pH modulated the process secondarily. Together, the results support a coherent picture in which UFB adsorption creates patchy, charge-compensated surfaces and a soft hydrodynamic layer that enlarges the effective collision cross-section, thereby enhancing early-stage flocculation. Full article

Coagulation–flocculation, historically reliant on simple inorganic salts, has evolved into a technically sophisticated process that is central to the removal of turbidity, suspended solids, organic matter, and an expanding array of micropollutants from complex wastewaters. This review synthesizes six decades of research, charting the transition from classical aluminum and iron salts to high-performance polymeric, biosourced, and hybrid coagulants, and examines their comparative efficiency across multiple performance indicators—turbidity removal (>95%), COD/BOD reduction (up to 90%), and heavy metal abatement (>90%). Emphasis is placed on recent innovations, including magnetic composites, bio–mineral hybrids, and functionalized nanostructures, which integrate multiple mechanisms—charge neutralization, sweep flocculation, polymer bridging, and targeted adsorption—within a single formulation. Beyond performance, the review highlights persistent scientific gaps: incomplete understanding of molecular-scale interactions between coagulants and emerging contaminants such as microplastics, per- and polyfluoroalkyl substances (PFAS), and engineered nanoparticles; limited real-time analysis of flocculation kinetics and floc structural evolution; and the absence of predictive, mechanistically grounded models linking influent chemistry, coagulant properties, and operational parameters. Addressing these knowledge gaps is essential for transitioning from empirical dosing strategies to fully optimized, data-driven control. The integration of advanced coagulation into modular treatment trains, coupled with IoT-enabled sensors, zeta potential monitoring, and AI-based control algorithms, offers the potential to create “Coagulation 4.0” systems—adaptive, efficient, and embedded within circular economy frameworks. In this paradigm, treatment objectives extend beyond regulatory compliance to include resource recovery from coagulation sludge (nutrients, rare metals, construction materials) and substantial reductions in chemical and energy footprints. By uniting advances in material science, process engineering, and real-time control, coagulation–flocculation can retain its central role in water treatment while redefining its contribution to sustainability. In the systems envisioned here, every floc becomes both a vehicle for contaminant removal and a functional carrier in the broader water–energy–resource nexus. Full article

The oxidation behaviors of varying Cr-alloyed automotive beam steels—0.015 wt.% Cr, 0.15 wt.% Cr, and 1 wt.% Cr—were investigated using isothermal oxidation experiments. The morphologies of the oxide scale were characterized, and the formation mechanisms were analyzed to understand the change in the oxidation kinetics of the investigated steels. The results show that a small amount of Cr, up to 0.15 wt.%, can reduce oxidation kinetics; the addition of Cr at 1 wt.% causes the oxidation rate to decline at a low isothermal temperature, but the hindrance effect expires when the oxidation temperature is above 1050 °C. The oxidation scale, including the inner FeO layer, the intermediate Fe₃O₄ layer, and the outer Fe₂O₃ layer, exhibits a morphological evolution from marble-like to pore-like, then whisker-like, flocculation-like, fine oxide grains, and finally coarse oxide grains. With increasing Cr addition, the thickness of the FeO layer decreases significantly, leading to a reduction in the total thickness of the oxidation scale. During the oxidation process of the investigated steel with 0.15 wt.% Cr, a Cr-rich layer and FeO-(Cr, Fe, Mn)₃O₄ eutectic form; meanwhile, FeO-(Cr, Fe)₂O₃ eutectic and Si-rich oxides, as well as a (Cr, Si)-rich layer, occur in the oxidation scale when 1 wt.% Cr is added to the steel. The occurrence of voids in the (Cr, Si)-rich layer is responsible for the increasing oxidation kinetics of the 1 wt.% Cr steel when the isothermal temperature is above 1050 °C, and the optimal Cr concentration in automotive beam steel is 0.15 wt.%, considering both oxidation resistance and cost. Full article

The design of emulsions at the nanoscale is a significant application of nanotechnology. For spherical droplets and a given volume of dispersed phase, the nanometre size of droplets inversely increases the total area, $A={\displaystyle \frac{3V}{r}}$, allowing greater contact with organic and inorganic materials during application. In topical applications, not only is cell contact increased, but also permeability in the cell membrane. Nanoemulsions typically achieve kinetic stability rather than thermodynamic stability, so their commercial application requires reasonable resistance to flocculation and coalescence, which can be affected by temperature changes. Therefore, their thermoresponsive characterisation becomes relevant. In this work, we analyse this response in an O/W nanoemulsion of Palmarosa for antibacterial purposes that has already shown stability for one year at controlled room temperature. We now study hysteresis processes and the behaviour of the statistical distribution in droplet size by Dynamic Light Scattering, obtaining remarkable stability under temperature changes up to 50 °C. This includes a maintained chemical composition observed using Fourier Transform Infrared Spectroscopy and the preservation of antibacterial properties analysed through optical density tests on cultures and the Spread-Plate technique for bacteria colony counting. We obtain practically closed hysteresis curves for some tracers of droplet size distributions through controlled thermal cycles between 10 °C and 50 °C, exhibiting a non-linear behaviour in their distribution. In general, the results show notable physical, chemical, and antibacterial stability, suitable for commercial applications. Full article

Currently, there is a demand for effective flocculant systems that can be used without adverse impact on the environment and health. However, the challenge is to find the minimum dose to achieve the same efficacy as conventional flocculants. One technique involves using a mixture of natural and synthetic flocculants, the synergistic effects of which can enhance treatment efficiency. Thus, this work provides an approach using a low-cost chitosan (CH56)–polyaluminum chloride (PAC) mixture as a flocculant system for river water. Therefore, water quality was monitored in the Tamazula and Humaya rivers, which are sources of water for potabilization plants. According to the results of flocculation tests, the use of the mixture required a lower dosage (0.75 mg L⁻¹ of CH56 with 1 mg L⁻¹ of PAC; 0.75 mg L⁻¹ of CH56 with 2 mg L⁻¹ of PAC) than that used with individual flocculants (3 mg L⁻¹ of CH56; 5 mg L⁻¹ of PAC). Conveniently, the mixture produced larger and more compact flocs, favoring sedimentation kinetics and thus flocculation. Fractal dimension (F_D) and lacunarity (Λ) from microscopy images were used as indicators of the quality of the flocs formed. In general, CH56 and the mixture performed better than PAC, and the mixture allowed the best removal of the model microplastic (polystyrene). Flocculant mixtures reduced the concentration of copper ions by 58%, of tetracycline by 22%, of microplastics by 80%, and of bacteria by >90%. Hence, the authors believe that this work offers valuable information that could be used for potabilization plants aiming to reduce the dose of PAC and introduce chitosan into their coagulation–flocculation process. Full article

This study investigates the combined application of coagulation–flocculation–sedimentation (CFS) and adsorption using corncob (CC) biosorbent for the removal of textile dyes from aqueous solutions. Two synthetic dyes Bemacron Blue RS 01 (BB-RS01), a disperse dye, and Bemacid Marine N-5R (BM-N5R), an acid dye were selected for evaluation. The coagulation–flocculation process utilized aluminum sulfate as the coagulant and Superfloc 8396 as the flocculant, with operational parameters including coagulant concentrations ranging from 50 to 600 mg/L, flocculant concentrations between 30 and 125 mg/L, and pH levels spanning from 2 to 11. The corncob biosorbent was characterized using FTIR, SEM, BET, TGA/DTA, and pHpzc analyses. Adsorption isotherm experiments indicated a more favorable correlation with the Langmuir model (R² = 0.92–0.96), which supports monolayer adsorption. At pH 8, the CFS process achieved a dye removal efficiency of 95.1% for BB-RS01 and 92.3% for BM-N5R was achieved at pH 6.5. The maximum adsorption capacities of BB-RS01 were determined to be 99.5 mg/g, while BM-N5R was found to be 46.08 mg/g. These results indicate that the integration of CFS with raw corncob adsorption provides a cost-effective and efficient method for the remediation of textile dyes. Full article

The widespread presence of antibiotics in aquatic environments poses significant ecological and public health risks due to their persistence, antimicrobial activity, and contribution to resistance gene proliferation. This review systematically evaluated the advancements in antibiotic degradation using ionizing radiation (γ-rays and electron beam) from laboratory studies to practical applications. By using keywords such as “antibiotic degradation” and “ionizing irradiation OR gamma radiation OR electron beam,” 328 publications were retrieved from Web of Science, with China contributing 33% of the literature, and a number of global representative studies were selected for in-depth discussion. The analysis encompassed mechanistic insights into oxidative (•OH) and reductive (e_aq⁻) pathways, degradation kinetics influenced by absorbed dose (1–10 kGy), initial antibiotic concentration, pH, and matrix complexity. The results demonstrated ≥90% degradation efficiency for major antibiotic classes (macrolides, β-lactams, quinolones, tetracyclines, and sulfonamides), though mineralization remains suboptimal (<50% TOC removal). Synergistic integration with peroxymonosulfate (PMS), H₂O₂, or O₃ enhances mineralization rates. This review revealed that ionizing radiation is a chemical-free, compatible, and highly efficient technology with effective antibiotic degradation potential. However, it still faces several challenges in practical applications, including incomplete mineralization, matrix complexity in real wastewater, and operating costs. Further improvements and optimization, such as hybrid system development (e.g., coupling electron beam with other conventional technologies, such as flocculation, membrane separation, anaerobic digestion, etc.), catalytic enhancement, and life-cycle assessments of this emerging technology would be helpful for promoting its practical environmental application. Full article

This study applied response surface methodology (RSM) to optimise process parameters for rum fermentation. The primary aim was to enhance ethanol productivity through refined molasses conditioning and fermentation. Polyacrylamide flocculants were evaluated for molasses clarification, identifying an optimised blend which significantly outperformed individual flocculants. Statistical analyses revealed Flopam AN 956 SH as the top performer based on settling behaviour and mud qualities. Mixture modelling exposed optimised flocculant formulations that outperformed individual flocculants, indicating synergistic interactions. A central composite design (CCD) systematically evaluated the effects of temperature, oxygenation, and nutrient supplementation on yeast growth kinetics. It determined that 5 ppm O₂, 32.19 °C, and 2.5% nutrients maximised the specific growth rate at 0.39 h⁻¹ and ethanol yield at 9.84% v/v. The models characterised interactions, revealing nutrient–oxygen synergies that stimulated metabolism. Overall, fermentation efficiency and assurance for ethanol yield were increased through comprehensive multi-scale optimisation utilising factorial designs, validated analytics, and quantitative strain characterisation. Full article

High dewatering costs, resulting from the harvesting and separation of microalgae from the cultivation medium, pose a significant challenge to the large-scale commercial production of algae-based products, accounting for 20–60% of total cultivation expenses. This study presents research findings on the recovery of Baltic green microalgae Chlorella vulgaris BA-167 from water under static sedimentation conditions, evaluating its potential as a cost-effective harvesting method. The study investigates the effect of suspension concentration on the kinetics and efficiency of sedimentation under both autoflocculation and targeted flocculation conditions, using the Flokor 1.2A coagulant, which is commonly employed in industrial water treatment processes in Poland. The novelty of this research lies in the application of the new coagulant Flokor 1.2A to explore its potential for harvesting Chlorella vulgaris BA-167 cultivated under laboratory conditions. The results demonstrate a strong correlation between the algae removal rate and their initial concentration in the suspension, within the range of 0.375–2.380 g/L. Under autoflocculation conditions, the final minimum algae concentration in the liquid after sedimentation ranged from 0.078 to 0.148 g/L, corresponding to initial concentrations of 0.960 g/L and 0.615 g/L, respectively. Experimental results indicate that combining sedimentation with targeted flocculation significantly increases microalgae harvesting efficiency. Flokor 1.2A facilitates the coagulation and agglomeration of microalgae cells, promoting the formation of larger aggregates (flocs) ranging from 20 μm to 690 μm, which settle more easily during gravity-driven sedimentation. Within the coagulant concentration range (C_F) of 0.01–0.36 g/L, sedimentation time was reduced by 3–7 times, and algae harvesting efficiency exceeded 92%. The greatest reductions in algae concentration occurred with 0.12 g/L of coagulant for 0.615 g/L algae and 0.17 g/L for 0.960 g/L algae, achieving maximum harvesting efficiencies of 83.2% and 92.9%, respectively. These results represent a 2.02–2.53-fold improvement over autoflocculation. Full article