Inlet Concentration Research Articles

Online estimation of inlet contaminant concentration using Eulerian-Lagrangian method of fundamental solutions and Bayesian inference

The advection-diffusion equation is fundamental to modeling various transport phenomena, including the distribution of chemical species in surface or groundwater flow. In cases where the concentration at the source is unknown, inverse problem formulations are required to estimate the desired states by assimilating concentration monitoring data from specific points along the watercourse using a Bayesian approach. This paper proposes a combination of the Eulerian-Lagrangian method and the meshless method of fundamental solutions to solve the advection-diffusion equation. Moreover, the method was used as an evolution model for the sequential importance resampling particle filter algorithm to reconstruct the time-dependent inlet pollutant concentration in inverse problems. Numerical smooth and discontinuous inlet function results show that the particle filter - Eulerian-Lagrangian method of fundamental solutions combination can reconstruct inlet concentration time series.

Multiscale effects of radial mixing on mixotrophic microalgal growth and macromolecular synthesis in tubular bubble-column photobioreactors

Extremophillic microalga Chlorella sorokiniana is grown mixotrophically in a 5 L externally-illuminated tubular bubble-column photobioreactor with an external light intensity of 10,500 lx (≈195 μmol-photons.m−2.s−1) at atmospheric (0.04 %), 1 %, 2 %, 3 %, 4 %, and 5 % CO2 concentrations, with acetic acid and urea as the organic carbon and nitrogen sources, respectively, for 6–8 days. Two different setups are employed: one permits axial air flow, and another promotes radial mixing of algal particles, dissolved CO2 and nutrients along with axial sparging. We show that radial mixing increases biomass yields by reducing both photo-limitation and photo-inhibition up to CO2 concentrations <3 %, above which substrate (CO2) inhibition necessitates lower reactor mixing. Radial mixing increases the lipid yield from 1.06 and 1.61 g/L to 1.27 and 1.78 g/L at 2 % and 3 % CO2, respectively, in nitrogen-limited cases, resulting in a 10–20 % increase. We show that complete reactor mixing, facilitated by the dual effects of branched (radial) and axial sparger, is preferred only in the absence of substrate (CO2) inhibition. Subsequently, we stratify the tubular photobioreactor design strategy into two regimes based on CO2 inlet concentrations. In one regime (for inlet CO2 < 3 %), we recommend the deployment of branched sparger to facilitate both radial and axial mixing simultaneously, thereby creating a well-mixed reactor at lower CO2 concentrations. In the other regime (for inlet CO2 > 3 %), axial sparging alone is recommended since complete mixing of CO2 increases substrate inhibition by reducing the reactor pH below 7.5.

Periodic open cellular structures (POCS) as catalyst support for intensified heat transport in the partial oxidation of methanol to formaldehyde

Heat transport in catalytic reactors is one of the most important factors in reactor design, especially for highly endo- or exothermic reactions. The limited thermal conductivity of randomly packed beds can be significantly improved when alternative catalyst supports are used. A new generation thereof are periodic open cellular structures (POCS), which are used in this study as catalyst support for the partial oxidation of methanol to formaldehyde, an exothermic gas phase reaction. A comparison to traditional packed bed reactors revealed that a POCS made of the highly conductive alloy AlSi10Mg can significantly reduce the hot-spot temperature, allowing almost isothermal operation at optimal reaction conditions. The improved temperature control allows for operation with higher methanol inlet concentrations and wall temperatures as compared to the commercial process. The beneficial heat transport properties of POCS were used to conduct isothermal kinetic measurements at elevated temperature. Based on these findings and the design freedom of additive manufacturing, an optimized cellular structure was designed and fabricated, which improved the heat transport especially in the critical inlet section of the reactor.

Oxidative Dissolution Process of Sphalerite in Fe2(SO4)3-O3 System: Implications for Heavy Metals Removal and Recovery.

Metal sulfides in waste rocks and tailings are susceptible to serious soil and water contamination due to the generation of acid mine drainage (AMD) during stockpiling. The hydrometallurgical process is one of the most essential heavy metal remediation technologies through harmless disposal and resource utilization of the waste sulfides. However, atmospheric hydrometallurgy of sulfides still faces great challenges due to low leaching efficiency and high cost. In this work, we proposed a cooperative leaching system (Fe2(SO4)3-O3) and investigated the oxidative dissolution process of sphalerite (ZnS). Under the optimal conditions, the extracted zinc reached 97.8%. Reactive oxygen species (ROS) (·OH, 1O2 and ·O2-) were identified in the radical quenching experiments. The dissolution of sphalerite did not show passivation due to the ozone's capability to oxidize the sulfur in sphalerite to sulfate. In addition, stirring rate, O3 inlet concentration, and Fe2(SO4)3 concentration had a significant effect on the dissolution of sphalerite. Meanwhile, the apparent activation energy was 24.11 kJ/mol based on kinetic fitting, which indicated that the controlling step of the reaction was mainly a diffusion process. This work demonstrated the cooperative effect of sphalerite leaching in the O3-Fe2(SO4)3 system and provided a theoretical reference for efficient and atmospheric dissolution of sphalerite.

Removal of Metal Ions from Wastewater Using Co‐integrated Superparamagnetic Nanoparticles

AbstractThe column performance of silica‐coated, amino‐functionalized, superparamagnetic nanoparticles co‐integrated with Cynodon dactylon and Murraya koenigii plant extracts for the removal of CuII ions was evaluated. The co‐integrated nanoparticles were used as sorbent materials in fixed‐bed column studies, and the effects of inlet concentration, adsorbent bed depth, and flow rate were analyzed. Breakthrough time was calculated for various CuII inlet concentrations, depths of the adsorbent bed, and volumetric flow rates. Models such as Thomas, Yoon‐Nelson, and the bed depth model were evaluated to determine the experimental fit. The maximum breakthrough time for CuII ions of 1200 min was attained for a CuII inlet concentration of 100 mg L–1, sorbent bed depth of 3 cm, and volumetric flow rate of 1 mL min–1.

Unveil carbon dioxide recycling potential throughout distributor-type membrane reactor

With the cost of green hydrogen production decreasing year by year, methanation, a carbon dioxide hydrogenation reaction, is becoming a more critical technology for the realization of a carbon-neutral society. Here, we show the procedure of membrane preparation for a distributor-type membrane reactor that simultaneously captures and recycles CO2 together with experimental tests of the proposed reactor design. To decrease the temperature gradient in the reactor and to improve methane recovery from the inlet gas mixture, a three-dimensional computational fluid dynamics simulation of the reactor was conducted. The numerical results suggest that the distributed feed design results in a uniform distribution of carbon dioxide, preventing localized reactions at the reactor inlet. In addition, it reduces the temperature rise in the reactor by up to about 300 K compared to the case where the carbon dioxide and hydrogen gas mixture is fed from a single inlet. The effect of the feed CO2 concentration on reactivity is also discussed. Simulation results show that the membrane reactor with inlet concentration of about 15 %, such as those emitted from industrial boilers, is capable of recovering methane at concentrations about 1.5 times higher in comparison to 100 % CO2 concentration at the inlet in a classical reactor.

Adsorption of an antiseptic in a functionalized fixed-bed: Analysis of breakthrough scenarios and validation of simplistic models defending a novel proposition

BackgroundChlorhexidine gluconate (CHG) and cetrimide, which are widely used in various pharmaceutical compositions, are considered potentially hazardous compounds. This combination was largely used during and after Covid 19 pandemic for sanitization. Removal of these two compounds from pharmaceutical waste-water with commercial and functionalized activated carbon in a packed bed column is reported. MethodsEffects of changes in bed height, flow rate, and initial concentration on the performance of the packed bed are analyzed using Yoon-Nelson, BDST and Thomas models for commercial scale-up operation. The effects of primary design parameters like bed depth and operating parameters like inflow rate and inlet concentration of influent wastewater are studied on the extent of removal of cetrimide and chlorhexidine gluconate. Granular activated carbon (GAC) is functionalized using HF and NH4OH. The extent of enhanced adsorption using the functionalized GAC is demonstrated using breakthrough curves. Significant findingsK. H. Chu's iconic proposition is validated. Breakthrough time (BT) increases with bed heights and it is less in the case of cetrimide as compared to chlorhexidine gluconate. This shows that cetrimide wins in the competition and occupies the pores much faster than CHG.Mostly, BT-CHG (GAC) < BT-CHG (FAC-HF) < BT-CHG (FAC-NH3) and BT-cetrimide (GAC) < BT-cetrimide (FAC-NH3) < BT-cetrimide (FAC-HF) for a particular bed height.BT−CHG(FAC−HF)BT−cetrimide(FAC−HF)<BT−CHG(FAC−NH3)BT−cetrimide(FAC−NH3)<BT−CHG(GAC)BT−cetrimide(GAC)

Ambient wind conditions impact on energy requirements of an offshore direct air capture plant

This study proposes an off-grid direct air (carbon) capture (DAC) plant installed on the deck of an offshore floating wind turbine. The main objective is to understand detailed flow characteristics and CO2 dispersion around air contactors when placed in close proximity to one another. A solid sorbent DAC design is implemented using a commercially deployed air contactor configuration and sorbent. The sorbent is assumed to undergo a temperature vacuum swing adsorption cycle. Computational fluid dynamics (CFD) is used to determine the local conditions entering each unit based on varying wind speed and angle. Two-dimensional (2D) simulations were used to determine the pressure drop through a detailed air contactor design considering the sorbents APDES-NFC, Tri-PE-MCM, MIL-101(Cr)-PEI-800, and Lewatit VP OC 106. Only APDES-NFC was explored for further analysis in the three dimensional (3D) CFD dispersion model. 3D simulations were used to model flow patterns and CO2 dispersion using passive scalars. A worst case scenario is analyzed for all DAC units in adsorption mode with fans running simultaneously. 2D simulations show an under utilization of contactor length, and quantify pressure loss curves for four common sorbents. One commercially deployed sorbent is considered for further analysis; a pressure drop of 390.62 Pa is experienced for a flow velocity of 0.73 m s−1 through a 1.5m×1.5m×1.5m contactor. Using 3D simulations, fan energy demands are computed based on flow velocities and applied pressure gradients. There is found to be a decrease in overall fan power demand as wind speed increases. High wind speeds can passively drive the adsorption process with fans shut off at certain wind directions. This occurs at an average contactor inlet velocity of 17.5 m s−1, correlating to a hub height (150 m) wind speed of 24 m s−1. Thermal energy demands are computed based on inlet CO2 concentrations entering downstream units. Thermodynamic work for desorption based on an assumed second law efficiency is compared to thermal energy for desorption computed using a simplified isotherm method, taking into account the impacts of humidity on CO2 adsorption. Going from 414.72 ppm to 300 ppm CO2 inlet concentration requires an additional 63.9 kWh (t- CO2)−1 using the 2nd law thermodynamic efficiency method and 25.9 kWh (t- CO2)−1 using the isotherm method. Contactor arrangement, wind angles, and wind speeds have a significant impact on flow patterns experienced, and resulting CO2 dispersion. High wind speeds assist in CO2 dispersion, resulting in higher inlet concentrations to downstream DAC units and decreased thermal energy requirement.

In-situ template method to synthesize metal/non-metal doped carbon for SO2 adsorption at low concentration: DFT and experimental studies

SO2 is one of the most significant air molecular contaminants (AMC). The development of materials for capturing low-concentration SO2 at room temperature is of great importance for industrial production and environmental safety. In this study, hierarchical porous carbon materials with Zn–N–C active structures were synthesized in one step using an in-situ template method. Among them, Zn/AC-2 exhibited a high specific surface area (1143.73 m2/g) and micropore volume (0.42 cm3/g). Dynamic adsorption tests were conducted under the conditions of an inlet concentration of 90 ppm, with a temperature of 23 °C and a humidity of 50%. The results indicated that the material showed an excellent capturing performance for SO2, with a breakthrough adsorption capacity of 3.37 mmol/g. Through characterization techniques including XPS, XRD, and SEM-EDS, it was found that the metal elements were dispersed in atomic form within the carbon framework, demonstrating the effectiveness of the modification method. A comparative study of the new adsorbent and spent adsorbent proved that SO2 reacts with extremely high catalytic efficiency on the material surface to generate SO3, revealing the reaction mechanism on the material surface. Finally, based on density functional theory, the microscopic reaction mechanism of the interaction between SO2 and the prepared material surface was studied at the molecular level. The results showed that the reaction energy barrier on the material surface is only 1.01 eV, and the reaction releases 3.14 eV of energy, indicating that the reaction can spontaneously occur at room temperature.

Temporal variations in micropollutant inlet concentrations matter when planning the design and compliance assessment of stormwater control measures

Stormwater Control Measures (SCMs) contribute to reducing micropollutant emissions from separate sewer systems. SCM planning and design are often performed by looking at the hydrological performance. Assessment of pollutant removal and the ability to comply with discharge concentration limits is often simplified due to a lack of data and limited monitoring resources. This study analyses the impact of using different time resolutions of input stormwater concentrations when assessing the compliance of SCMs against water quality standards. The behaviour of three indicator micropollutants (MP - Copper, Diuron, Benzo[a]pyrene) was assessed in four SCM archetypes, which were defined to represent typical SCM removal processes. High resolution MP data were extrapolated by using high resolution (2 min) measurements of TSS over a long period (343 events). The compliance assessment showed that high resolution input concentrations can result in a different level of compliance with water quality standards, especially when discharged concentrations are close to the limit values. This study underlines the importance of considering the high temporal variability of stormwater micropollutants when planning and designing SCMs to identify the most effective solutions for stormwater pollution management and to ensure a thorough consideration of all the environmental implications.

Enhanced benzene vapor adsorption through microwave-assisted fabrication of activated carbon from peanut shells using ZnCl2 as an activating agent

Herein, microwave-assisted activated carbon (MW-AC) was fabricated from peanut shells using a ZnCl2 activator and utilized for the first time to eliminate benzene vapor as a volatile organic compound (VOC). During the MW-AC production process, which involved two steps—microwave treatment and muffle furnace heating—we investigated the effects of various factors and achieved the highest iodine number of 1250 mg/g. This was achieved under optimal operating conditions, which included a 100% impregnation ratio, CO2 as the gas in the microwave environment, a microwave power set at 500 W, a microwave duration of 10 min, an activation temperature of 500 °C and an activation time of 45 min. The structural and morphological properties of the optimized MW-AC were assessed through SEM, FTIR, and BET analysis. The dynamic adsorption process of benzene on the optimized MW-AC adsorbent, which has a significant BET surface area of 1204.90 m2/g, was designed using the Box-Behnken approach within the response surface methodology. Under optimal experimental conditions, including a contact duration of 80 min, an inlet concentration of 18 ppm, and a temperature of 26 °C, the maximum adsorption capacity reached was 568.34 mg/g. The experimental data are better described by the pseudo-second-order kinetic model, while it is concluded that the equilibrium data are better described by the Langmuir isotherm model. MW-AC exhibited a reuse efficiency of 86.54% for benzene vapor after five consecutive recycling processes. The motivation of the study highlights the high adsorption capacity and superior reuse efficiency of MW-AC adsorbent with high BET surface area against benzene pollutant. According to our results, the developed MW-AC presents itself as a promising adsorbent candidate for the treatment of VOCs in various industrial applications.

Carbon neutrality in wastewater treatment plants: An integrated biotechnological-based solution for nutrients recovery, odour abatement and CO2 conversion in alternative energy drivers

Wastewater treatment plants play a crucial role in water security and sanitation, ensuring ecosystems balance and avoiding significant negative effects on humans and environment. However, they determine also negative pressures, including greenhouse gas and odourous emissions, which should be minimized to mitigate climate changes besides avoiding complaints. The research has been focused on the validation of an innovative integrated biological system for the sustainable treatment of complex gaseous emissions from wastewater treatment plants. The proposed system consists of a moving bed biofilm reactor coupled with an algal photobioreactor, with the dual objective of: i) reducing the inlet concentration of the odourous contaminants (in this case, hydrogen sulphide, toluene and p-xylene); ii) capturing and converting the carbon dioxide emissions produced by the degradation process into exploitable algal biomass. The first reactor promoted the degradation of chemical compounds up to 99.57% for an inlet load (IL) of 22.97 g m−3 d−1 while the second allowed the capture of the CO2 resulting from the degradation of gaseous compounds, with biofixation rate up to 81.55%. The absorbed CO2 was converted in valuable feedstocks, with a maximum algal biomass productivity in aPBR of 0.22 g L−1 d−1. Dairy wastewater has been used as alternative nutrient source for both reactors, with a view of reusing wastewater while cultivating biomass, framing the proposed technology in a context of a biorefinery within a circular economy perspective. The biomass produced in the algal photobioreactor was indeed characterized by a high lipid content, with a maximum percentage of lipids per dry weight biomass of 35%. The biomass can therefore be exploited for the production of alternative and clean energy carrier. The proposed biotechnology represents an effective tool for shifiting the conventional plants in carbon neutral platform for implementing principles of ecological transition while achieving high levels of environmental protection.

Investigating the behavior of six limestones in presence of steam in dual interconnected fluidized beds, under operating conditions relevant for sorption-enhanced gasification

This paper presents results on the behavior, in terms of CO2 capture capacity and attrition/fragmentation tendency, for six limestones processed in a dual interconnected fluidized beds system under operating conditions simulating those of sorption-enhanced gasification in presence of water vapor. Ten calcination/carbonation cycles have been carried out for each sorbent; in particular, carbonation has been carried out at two temperature levels (650 °C and 700 °C), with a CO2 and H2O inlet concentration of 10% for both gases. Degree of CaO carbonation (with related modelling) along the cycles, and particle size distribution at the end of the cycles, have been analyzed and discussed, together with results coming from ex situ impact fragmentation tests carried out in a specifically devoted apparatus. The discussion has been extended to particular cases in which the system was operated in the absence of steam, to analyze the role of this species on the sorbent behavior.

Impact of drying technique on umbu‐cajá pulp with the addition of probiotic culture: Optimization, cell viability, physicochemical, and functional properties

AbstractThis study aimed to assess the effects of spouted bed (SB) drying and freeze‐drying (FD) on the properties of probiotic umbu‐cajá pulp. The strain Bifidobacterium animalis ssp. lactis was employed to obtain this pulp. Initially, the study was conducted with two separate experimental designs, one for SB and another for FD, encompassing variables such as inlet temperature and concentrations of drying adjuvants (maltodextrin and inulin). This approach aimed to identify the most favorable conditions in terms of yield and cell viability. Both drying methods proved effective in preserving probiotic cells, with comparable viable cell counts (12 Log CFU g−1) and process yield of up to 30.68%. Additionally, FD exhibited advantages in preserving and increasing levels of bioactive compounds, including phenolics and carotenoids, in the final product. In contrast, SB drying stood out for retaining carotenoids and exhibiting lower degradation of ascorbic acid. In summary, this study demonstrated that both SB drying and FD are promising approaches in producing powders from probiotic umbu‐cajá pulp. However, the selection between the methods should be guided by specific production goals, considering the desired characteristics of the final product.

Evaluation of bovine carbonic anhydrase for promoting CO2 capture via reaction with KOH and high-salinity reject brine

In this study, we investigate the preliminary effect of bovine carbonic anhydrase (BCA) catalyst on CO2 capture via a reaction with potassium hydroxide (KOH) and reject brine under different operational conditions. Experiments were performed at a constant gauge pressure of 2 bar, with a CO2 inlet concentration of 10% and a CO2 flow rate of 776 mL/min. First, the impact of the BCA catalyst on CO2 capture in the absence of the alkaline material (KOH) was studied. Results showed that using 3-mg/L BCA increases the CO2 capture by 181% compared with the case without BCA. Second, the effect of BCA on CO2 uptake and ions reduction was examined in the presence of KOH. At a KOH concentration of 10-g/L, BCA concentration of 50-mg/L, and temperature of 40℃, a CO2 uptake value of 0.08 g CO2/g KOH was obtained. In comparison, adding 30-g/L KOH and 50-mg/L BCA increased the CO2 uptake by 737.5% (0.67 g CO2/g KOH). Furthermore, the sodium (Na+) reduction percentage reached a maximum of 40.8% at KOH and BCA concentrations of 30 g/L and 50 mg/L, respectively. However, increasing the BCA concentration to 100 mg/L negatively impacted CO2 capture and ion removal, indicating that the BCA concentration could be better optimized to achieve maximum efficiency. Additionally, when the BCA concentration was increased from 50 to 100 mg/L, the reaction rate remained nearly constant at 0.0047 mol/L·min.

Effect of commutation on pressure drop and microbial diversity in a horizontal biotrickling filter for toluene removal.

A horizontal biotrickling filter (HBTF) was designed to understand the toluene removal process and microbial community structures. The start-up time of the HBTF, immobilized by the dominant fungi was only about 6 days and the toluene removal efficiency was found to be more than 95% when the inlet toluene concentration remained at around 1560.0 mg/m3. In the stable operation stage of the HBTF, based on not greatly reducing the removal efficiency, a simple and convenient periodic commutation was adopted to reduce the pressure drop (△P) and regulate the distribution of microorganisms in the packing area of the HBTF. The △P decreased from about 90 Pa to 10 Pa after the commutation, which indicated its feasibility. The performance of the HBTF was improved by changing the inlet direction of waste gas flow. When the inlet concentration of toluene was about 640mg/m3, the removal efficiency was nearly 70.0% before commutation and it remained 95.0-98.0% after commutation. Microbial abundance and diversity analysis showed that the corresponding Shannon-Weiner index was 2.73 and 1.84, respectively. The front section of the HBTF, which was exposed to toluene earlier, consistently exhibited higher microbial diversity than that in the back section. Following commutation, microbial diversity decreased in both the front and back sections, with a maximum decline of around 50%. The main fungi treating toluene were Aplanochytrium, Boletellus, and Exophiala.

Screening of toluene absorbents based on molecular simulation and experimental investigation on novel compound solvents

This work aims to screen out absorbents with excellent performance to control toluene pollution. Based on density functional theory (DFT), this article calculated the binding energy between toluene and organic solvents molecules with specific functional groups, and comprehensively examined the physical and chemical properties of the solvents to screen out suitable toluene absorbents. The computational binding energy and the experimental absorption efficiency have the same change tendency, that is, the value of the binding energy determines the ability of the solvents to absorb toluene. Pentaethylene glycol dimethyl ether (PGDE), 1-methyl-2-pyrrolidinone (NMP), dioctyl phthalate (DOP) and sulfolane (SUL) were initially selected as toluene absorbents. Atoms in molecules (AIM) analysis, reduced density gradient (RDG) analysis and symmetry-adapted perturbation theory (SAPT) analysis were used to explore the microscopic mechanism of toluene absorption by four organic solvents. The results show that the interactions between organic solvents and toluene are weak interactions dominated by dispersion attraction. The experiment used polyethylene glycol dimethyl ether (NHD) with very low volatility as the main solvent, which is a polymer containing the main component PGDE, and compounded it with NMP, DOP, and SUL respectively. The absorption experiment investigated the efficiency of compound solvents with different mass fractions of compound components on toluene under the conditions of normal pressure, liquid-to-gas ratio 2.5 L/m3, gas flow rate 4 L/min, temperature 30°C, inlet concentration approximately 6000 mg/m3, and packing height 60 cm. The results show that the toluene absorption efficiency of the three compound solvents is more than 91%. Considering the absorption performance, consumption and stability of the solvent, NHD-SUL solvent (20 wt.% SUL) was finally selected as the new compound solvent. The new compound solvent regenerated lean solution still maintains a good absorption efficiency of 90% after 13 desorption cycles. Theoretical and experimental research are of great significance for the future treatment of exhaust gas pollution.

Removal of polystyrene microplastics using biochar-based continuous flow fixed-bed column.

In the realm of environmental challenges, microplastics have emerged as a pressing threat, presenting risks to both individuals and ecosystems. Conventional treatment plants are presently not equipped for effectively removing these minute contaminants. This study presents an investigation into the potential of a continuous flow biochar column, utilizing biochar derived from banana peel through a nitrogen-free slow pyrolysis process for the removal of microplastics. A systematic exploration of various parameters, including bed height, flow rate, inflow microplastic concentration, and microplastic size is undertaken to discern their impact on polystyrene removal efficiency. A peak removal efficiency of 92.16% has been achieved under specific conditions: a 6-cm bed height, a 3-mL/min flow rate, an inlet concentration of 0.05g/L, and microplastic sizes ranging from 150 to 300µm. The removal efficiency was inversely affected by flow rate while directly influenced by bed height. To deepen the understanding of polystyrene removal on biochar, a detailed characterization of the synthesized material was carried out. The removal of microplastics by banana peel biochar (BPB) is observed to be dominated by adsorption and filtration processes. The entanglement of microplastics with minuscule biochar granules, capture between particles, and entrapment in the porous system were identified as the mechanisms of removal. Leveraging the hydrophobic nature of polystyrene microplastics, interactions with the hydrophobic functional groups in BPB result in effective adsorption. This is further complemented by self-agglomeration and filtration mechanisms that synergistically contribute to the elimination of larger agglomerates. The findings thus provide a comprehensive understanding, offering hope for a more effective strategy in mitigating the environmental impact of microplastics.

Experimental study on flow characteristics of ash band in a cyclone separator using HPIV techniques

In a reversed cyclone separator, the ash bands were frequently observed on the wall surface, which were formed by the separated particles and rotated down. Nevertheless, the flow characteristics of the ash bands are rarely measured and discussed in the previous literatures. In this study, the flow characteristics of the ash bands were experimentally investigated by use of the High-speed Particle Image Velocimetry (HPIV) method. The experiments were conducted on a ϕ160mm cyclone at inlet velocity of 12, 16, 20 m/s and inlet concentration of 30, 50, 70, 100 g/m3. The test powders were catalyst and iron powder. The ash band's geometric characteristics, including width, slope angle and pitch, were extracted through advanced image analysis algorithms. Results revealed that the slope angle and pitch of the ash band were different in the cylindrical section and cone section. The width decreased as the ash band moved downwardly. Additionally, the ash band's flow parameters were measured. As the particle movement changed from suspension pattern in the separation space to sliding pattern on the wall surface along the radial, the particle velocities decreased. And the particle velocities further decreased as ash band forming. Particle velocities exhibited non-uniform and fluctuating behavior within the ash band. Notably, the velocities were lower in the central region of the ash band than that at the outer layer. Meanwhile, the particle concentration gradually increased, leading to a particle concentration in the ash band being 450 times higher than the inlet concentration. Along the axial, the ash band averaged velocity initially increased in the cylindrical section and then decreased in the cone section, varied with the inlet velocity, inlet concentration and particle properties such as particle size and density. This study revealed mechanisms behind particle aggregation in cyclone separator and analyzed the dynamic flow characteristics of ash band in detail.

Dual-alkali treatment of Y-type zeolite synthesized from lithium-silicon powder waste for enhanced adsorption removal of low-concentration toluene

In this study, the dual-alkali treatment of the Y-ZLSP zeolite recycled from lithium-silicon powder (LSP) waste for enhanced adsorption removal of low-concentration toluene was systematically studied. The results revealed that a mild condition dual-alkali treatment of Y-ZLSP significantly improved its toluene adsorption performance, as well the regenerability and robustness. The Y-ZLSP-NT(1/1) that was obtained under the conditions of NaOH and TPAOH molar ratio at 1/1, total concentration of 0.0050 M, and treated at 55 °C for 0.5 h showed the best adsorption property, with a saturated adsorption capacity (qs) of 139.7 mg/g at 1000 mg/m3 inlet concentration. Importantly, it had an up to 112.1 mg/g high of breakthrough adsorption capacity (qb). Toluene adsorption on Y-ZLSP-NT(1/1) was governed by physical adsorption, primarily due to pore filling and hydrogen bonding. The dual-alkali treatment resulted in a controllable pore evolution and greatly enriched the surface acid functional groups of Y-ZLSP. The evolved microporosity provided more adsorption sites, the mesoporosity afforded mass transfer channels. The toluene adsorption on Y-ZLSP-NT(1/1) follows a pseudo-first-order model and is typically an entropy-driven exothermic process with ΔH, ΔG and ΔS of −1.98 kJ/mol, −8.29 kJ/mol and 34.50 J/(mol·K), respectively.