Maximum Equilibrium Research Articles

Fabrication of ferulic acid‐cellulose nanocrystal enhanced stretchable and antibacterial hydrogels

Hydrogels are widely utilized in biomaterials, medicine, and food science due to their versatile properties. This study developed a ferulic acid (FA) and cellulose nanocrystals (CNC) hydrogel within a polyacrylamide matrix, polymerized using ammonium persulfate and crosslinked with N‐methylenebisacrylamide. The FA@CNC hydrogel demonstrated exceptional tensile ductility and elasticity. Antibacterial evaluations against Escherichia coli and Staphylococcus aureus revealed significant efficacy, with activity increasing proportionally to FA concentration. Swelling studies indicated a maximum equilibrium swelling ratio of 1210% after 36 h, showcasing the hydrogel’s ability to undergo substantial expansion while maintaining its original shape and structural integrity. It was indicated that the synthesized hydrogels were capable of absorbing large volumes of exudate while preserving a moist environment conducive to accelerated wound healing. Scanning electron microscopy analysis confirmed a regular and dense microstructure, which contributes to the hydrogel’s mechanical stability and robustness. The optimized preparation process developed in this study resulted in hydrogels with significantly enhanced performance. These findings underscore the hydrogel’s superior mechanical and functional properties, paving the way for innovative applications across biomaterials, medical, and food‐related industries.

Enhancing core loss and thermal performance for wireless EV charging with a cross-laminated core structure

This paper explores the implementation of laminated cores in inductive power transfer (IPT) systems for wireless EV charging. Two conventional structures are initially evaluated: the horizontally laminated core (H-cores) and the vertically laminated cores (V-cores). Fe-based nanocrystalline materials are applied for these structures due to their excellent core loss properties. The study introduces material modelling and loss analysis methods that combine toroidal measurements with eddy current losses from norm flux. Finite Element Method (FEM) simulations reveal that both structures experience significant flux density and thermal imbalances, creating operational challenges for IPT systems. To address these issues, a cross-laminated structure is proposed, combining the benefits of both horizontal and vertical laminations to reduce thermal imbalances. Simulation results show improved system performance, confirmed by experimental tests. Using the cross-lamination approach, the operational duration of IPT systems can be extended, and the maximum equilibrium temperature at an output current of 10 A is reduced by over 40°C, from 90.4 °C to 47.2 °C. Additionally, efficiency improves by over 0.4 % at 11.1 kW output power. This innovative core design provides a practical solution for implementing laminated cores in high-power wireless EV charging applications, enhancing efficiency and thermal performance.

Numerical and experimental study on local scour in front of OWC-BWS under waves

In this paper, a system of an oscillating water column wave energy converter integrated with a vertical breakwater (OWC- BWS) was established, and the scour mechanism in front of OWC-BWS under wave actions was studied by laboratory scale experiments and gas-liquid-particle flow numerical simulation, respectively. The experiment investigates the comparison of scour test results between a conventional vertical breakwater and OWC-BWS. It shows that compared to a vertical breakwater without an OWC, the local scour phenomenon in front of the OWC-BWS was effectively mitigated (test results showed a 46.7% reduction in the maximum scour depth). For numerical simulation, a scour model under wave actions was established for further research on the local scour mechanism in front of the OWC-BWS. It was found that the local scour topography of an OWC-BWS is different from that of a vertical breakwater. The OWC device effectively weakens the scour in front of the OWC-BWS, which is because the flow field in front of the OWC-BWS shows frequent generation and shedding of vortexes. In addition, as a crucial part of the OWC-BWS, the effect of PTO was also studied, which found that the maximum equilibrium scour depth was significantly influenced under different PTO.

Nano-Silver-Loaded Activated Carbon Material Derived from Waste Rice Noodles: Adsorption and Antibacterial Performance.

This study demonstrates, for the first time, the conversion of waste rice noodles (WRN) into a cost-effective, nano-silver-loaded activated carbon (Ag/AC) material capable of efficient adsorption and antibacterial activity. The fabrication process began with the conversion of WRN into hydrothermal carbon (HTC) via a hydrothermal method. Subsequently, the HTC was combined with silver nitrate (AgNO3) and sodium hydroxide (NaOH), followed by activation through high-temperature calcination, during which AgNO3 was reduced to nano-Ag and loaded onto the HTC-derived AC, resulting in a composite material with both excellent adsorption properties and antibacterial activity. The experimental results indicated that the incorporation of nano-Ag significantly enhanced the specific surface area of the Ag/AC composite and altered its pore size distribution characteristics. Under optimized preparation conditions, the obtained Ag/AC material exhibited a specific surface area of 2025.96 m2/g and an average pore size of 2.14 nm, demonstrating effective adsorption capabilities for the heavy metal Cr(VI). Under conditions of pH 2 and room temperature (293 K), the maximum equilibrium adsorption capacity for Cr(VI) reached 97.07 mg/g. The adsorption behavior of the resulting Ag/AC fitted the Freundlich adsorption isotherm and followed a pseudo-second-order kinetic model. Furthermore, the Ag/AC composite exhibited remarkable inhibitory effects against common pathogenic bacteria such as E. coli and S. aureus, achieving antibacterial rates of 100% and 81%, respectively, after a contact time of 4 h. These findings confirm the feasibility of utilizing the HTC method to process WRN and produce novel AC-based functional materials.

One-pot solvothermal synthesis of Ca-Fe-La composite for advanced removal of phosphate from aqueous solutions in a fixed-bed column: Modeling and resource utilization

The Ca-Fe-La composite was synthesized by the one-pot solvothermal method and applied to the advanced removal of phosphate from aqueous solutions in a fixed-bed column. The effects of some important process parameters on the phosphate adsorption were examined. It was found that the maximum equilibrium loading was 121.1 mg g−1 at an influent phosphorus concentration of 30 mg L−1, flow rate of 2.5 mL min−1, adsorbent mass of 0.5 g and pH of 5.14. The Thomas and fractal-like Thomas models were used to analyze the measured breakthrough curves. Their fitting quality was diagnosed by the adjusted coefficient of determination (Adj. R2), the root of mean squared error (RMSE) and the residual plot. According to the Thomas and fractal-like Thomas models, the breakthrough time and the saturation time were solved by the fzero command of MATLAB software. Akaike information criterion (AIC) and Bayesian information criterion (BIC) were adopted to further determine the optimal model. In all cases, the phosphate adsorption on the Ca-Fe-La composite followed the fractal-like Thomas model. The phosphate loaded Ca-Fe-La composite could be used as a slow-release fertilizer and promote tomato plant growth. This work aimed to provide reliable assessment methods for the modeling of the breakthrough curves and allow for waste management and resource utilization of the phosphate loaded Ca-Fe-La composite.

Determination of morphine sulfate anti-pain drug solubility in supercritical CO2 with machine learning method

Accurate solute solubility measuring and modeling in supercritical carbon dioxide (ScCO2) would address the best working conditions and thermodynamic boundaries for material processing with this type of fluid. Theory- and data-driven methods are two general modeling approaches. Using theory-driven methods, the solubility is estimated based on the principles of thermodynamics, while data-driven methods are developed by training the algorithms. Despite acceptance of each of these methods, more experimental solubility data are still needed to promote modeling performances. In this study, for the first time, solubility of morphine sulfate is determined and modeled by a set of 13 semi-empirical (theory-driven) and random forest (data-driven) models. Using a laboratory system with an ultraviolet-visible (UV-Vis) spectroscopy, the experimental solubilities including 48 data points were obtained at different temperatures (308–338 K) and pressures (12–27 MPa). The minimum (0.806 × 10−5) and maximum (5.902 × 10−5) equilibrium mole fractions were observed at working pressures of 12 and 27 MPa, respectively, both at the same temperature of 338 K. It was indicated that random forest model (with AARD% of 1.29%) had an excellent predictive performance against semi-empirical models (with AARD% from 9.33 to 19.76%). The results showed that solute molecular weight had the highest effect on random forest modeling. Using modeling results from Chrastil and Bartle models, total and vaporization enthalpies of dissolution of morphine sulfate in ScCO2 were found to be 35.12 and 59.04 kJ/mole, respectively.

Exploring the adsorption of catechol and resorcinol onto Croton caudatus activated carbon: An integrated experimental and theoretical approach

The present work aimed to examine the process for adsorption of Catechol (CT) and Resorcinol (RS) onto activated carbon that was obtained from Croton caudatus biomass (CAB). Using a batch method, the maximum removal efficiencies of 99.23 % for CT and 98.68 % for RS was achieved at adsorbent dosage-0.2 g L−1, reaction time-60 min; concentration-100 mgL−1 CT and 80 mgL−1 RS; and pH 6.0 CT and pH 4.0 RS, respectively. A maximum equilibrium adsorption of 56.05 mgg−1 and 61.85 mgg−1 was achieved at pH 6.0 and pH 4.0 for CT and RS. The adsorption behavior of both adsorbates on activated carbon were best described by the Langmuir model (correlation coefficients (R2) = 0.996 for CT and 0.995 for RS) and the pseudo-second order kinetic model. The values of ΔG, ΔS, and ΔH suggest that the adsorption process is spontaneous and endothermic. Additionally, the adsorption process is easily reversible, enabling the reuse of the adsorbate even after fifth cycle. Further, density functional theory (DFT) simulations demonstrated that the CT and RS adsorption onto the AC adsorbent is favorable. Among the oxygen functional groups analysed, the carboxyl group showed the greatest effect on the adsorption process, exhibiting the most negative adsorption energy at −44.869 (CT) and −45.082 kJmol-1 (RS), respectively. Therefore, the activated carbon derived from CAB has significant potential for effectively removing phenolic contaminants from wastewater.

Copper supported Dowex50WX8 resin utilized for the elimination of ammonia and its sustainable application for the degradation of dyes in wastewater

To obtain high efficient elimination of ammonia (NH4+) from wastewater, Cu(II), Ni(II), and Co(II)) were loaded on Dowex-50WX8 resin (D-H) and studied their removal efficiency towards NH4+ from aqueous solutions. The adsorption capacity of Cu(II)-loaded on D-H (D-Cu2+) towards NH4+ (qe = 95.58 mg/g) was the highest one compared with that of D-Ni2+ (qe = 57.29 mg/g) and D-Co2+ (qe = 43.43 mg/g). Detailed studies focused on the removal of NH4+ utilizing D-Cu2+ were accomplished under various experimental conditions. The pseudo-second-order kinetic model fitted well the adsorption data of NH4+ on D-Cu2+. The non-linear Langmuir model was the best model for the adsorption process, producing a maximum equilibrium adsorption capacity (qmax = 280.9 mg/g) at pH = 8.4, and 303 K in less than 20 min. The adsorption of NH4+ onto D-Cu2+ was an exothermic and spontaneous process. In a sustainable step, the resulting D-Cu(II)-ammine composite from the NH4+ adsorption process displayed excellent catalytic activity for the degradation of aniline blue (AB) and methyl violet 2B (MV 2B) dyes utilizing H2O2 as an eco-friendly oxidant.

Chitosan/Poly(maleic acid-alt-vinyl acetate) Hydrogel Beads for the Removal of Cu2+ from Aqueous Solution.

Covalent cross-linked hydrogels based on chitosan and poly(maleic acid-alt-vinyl acetate) were prepared as spherical beads. The structural modifications of the beads during the preparation steps (dropping in liquid nitrogen and lyophilization, thermal treatment, washing with water, and treatment with NaOH) were monitored by FT-IR spectroscopy. The hydrogel beads have a porous inner structure, as shown by SEM microscopy; moreover, they are stable in acidic and basic pH due to the covalent crosslinking. The swelling degree is strongly influenced by the pH since the beads possess ionizable amine and carboxylic groups. The binding capacity for Cu2+ ions was examined in batch mode as a function of sorbent composition, pH, contact time, and the initial concentration of Cu2+. The kinetic data were well-fitted with the pseudo-second-order kinetic, while the sorption equilibrium data were better fitted with Langmuir and Sips isotherms. The maximum equilibrium sorption capacity was higher for the beads obtained with a 3:1 molar ratio between the maleic copolymer and chitosan (142.4 mg Cu2+ g-1), compared with the beads obtained using a 1:1 molar ratio (103.7 mg Cu2+ g-1). The beads show a high degree of reusability since no notable decrease in the sorption capacity was observed after five consecutive sorption/desorption cycles.

Sequential assembly enhanced selectivity on magnetic imprinted polymers for specific capture of naringin: A combination of synergistic dual sites and imprinted effect

Green and sustainable recovery of high-value natural flavonoids in agricultural wastes could not only improve natural resource utilization, but also could effectively reduce environmental pollution. Recently, great efforts have been made for research on the development of magnetic imprinted composite adsorbent, but the simultaneous promotion of stable selectivity and high adsorption amounts still faces its challenges. Inspired by “Sandwich-like” transport channels with proper steric and specific affinity sites, herein we designed a new kind of surface-imprinted magnetic colloidal nanocrystal clusters (MCNCs) with dual recognition sites (MCNCs@DR-MIPs) via sequential surface imprinted strategy. A two-step sequential surface-initiated atom transfer radical polymerization (SI-ATRP) was employed to construct the double imprinted sites, which can significantly improve the adsorption selectivity and adsorption amounts. In this design, the metal ion Zn(II) and the low pKa boronic acid APBA (1-allylpyridine-3-boronic acid, pKa = 7.4) could effectively tune the appropriate yolk-shell confinement sites, the obtained artificial double imprinted binding sites establishes the promising chemical environment for selective separation. As expected, the adsorption equilibrium experiments exhibited adsorption kinetics (180 min) and the maximum equilibrium binding capacity (34.60 µmol g−1). In virtue of unique advantages of magnetic separation materials, this novel absorbent exhibited a green and environmentally friendly enrichment process for naringin (NRG). Meanwhile, MCNCs@DR-MIPs showed excellent selectivity (imprinted factor 2.15) and regeneration properties (only decreased by 8.22 % after 7 cycles) for NRG. Additionally, the commercially available NRG could be effectively extracted and concentrated to 94.78 %. This study offers a sustainable effective strategy for flavonoids purification of magnetic separation materials and promotes advance the other natural compounds from agricultural wastes.

Methacrylonitrile‐based adsorbents for recovery of VFAs from fermentation broth

AbstractBACKGROUNDAdsorption is a promising affinity separation technique to target a sorbate in extremely dilute solutions. In this work, methacrylonitrile (MAN)‐functionalized resins were investigated to recover volatile fatty acids (VFAs) from a mimicked fermentation broth as an alternative for the already known amine‐based resins and non‐functionalized poly(styrene‐divinylbenzene) (PS‐DVB), aiming for high VFA capacity and selectivity.RESULTSNext to comparison with commercial PS‐DVB resin, also several PS‐DVB resins were synthesized as non‐functionalized analogues for the new MAN‐functionalized resins. For MAN‐functionalized resins, the maximum equilibrium VFA loading of about 153 (g acid/kg adsorbent) was found, which is higher than the 125 (g acid/kg adsorbent) for the PS‐DVB non‐functionalized resins. The water uptake of the PS‐DVB resins was with 0.53–0.87 (g water/g adsorbent) significantly lower than for the MAN‐DVB resins taking up 0.99–1.85 (g water/g adsorbent).CONCLUSIONOverall, the MAN‐functionalized adsorbents retained higher loading capacity for corresponding acid, compared to the PS‐DVB resins, while also taking in more water. Acid uptake is due to the hydrogen bonding between the nitrile groups of the resins with carboxyl group of the acids. Moreover, none of the adsorbents displayed an affinity towards the salts present in the fermentation broth. © 2024 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Carbonation of waste concrete: An effective and green strategy for enhancing its heavy metals removal from wastewater

Water pollution, especially Pb2+, Cd2+, Co2+, and Ni2+ released from industrial and mine wastewater, harms human health and is a global environmental concern. At the same time, the effective disposal of waste concrete originating from constructs is a global challenge. In this study, carbonated recycled concrete powder (CRP) is efficiently prepared by carbonizing waste concrete powder, which not only might enhance its adsorptive performance but also sequestrate CO2 in the form of mineral carbon. Characterization techniques revealed CRP forms calcium carbonate and highly polymerized silica gel. Batch adsorption experiments indicate that the CRP is found to have strong adsorption properties. The maximum equilibrium adsorption capacities calculated by the Langmuir model were determined as 997.03, 199.56, 148.85, and 76.69 mg/g for Pb2+, Cd2+, Co2+, and Ni2+, respectively, outperforming most waste concrete and industrial wastes reported. The adsorption mechanism mainly includes electrostatic interactions, precipitation, and ion exchange. This study proposes a method to synthesize low cost, good performance, high chemical stability, and facile preparation adsorbent using waste concrete powder, with promising applications in wastewater treatment.

Adsorption mechanism of hexavalent chromium on electron beam-irradiated aged microplastics: Novel aging processes and environmental factors

Microplastics are widely present in the natural environment and exhibit a strong affinity for heavy metals in water, resulting in the formation of microplastics composite heavy metal pollutants. This study investigated the adsorption of heavy metals by electron beam-aged microplastics. For the first time, electron beam irradiation was employed to degrade polypropylene, demonstrating its ability to rapidly age microplastics and generate a substantial number of oxygen-containing functional groups on aged microplastics surface. Adsorption experiments revealed that the maximum adsorption equilibrium capacity of hexavalent chromium by aged microplastics reached 9.3 mg g−1. The adsorption process followed second-order kinetic model and Freundlich model, indicating that the main processes of heavy metal adsorption by aged microplastics are chemical adsorption and multilayer adsorption. The adsorption of heavy metals on aged microplastics primarily relies on the electrostatic and chelation effects of oxygen-containing functional groups. The study results demonstrate that environmental factors, such as pH, salinity, coexisting metal ions, humic acid, and water matrix, exert inhibitory effects on the adsorption of heavy metals by microplastics. Theoretical calculations confirm that the aging process of microplastics primarily relies on hydroxyl radicals breaking carbon chains and forming oxygen-containing functional groups on the surface. The results indicate that electron beam irradiation can simultaneously oxidize and degrade microplastics while reducing hexavalent chromium levels by approximately 90%, proposing a novel method for treating microplastics composite pollutants. Gas chromatography-mass spectrometry analysis reveals that electron beam irradiation can oxidatively degrade microplastics into esters, alcohols, and other small molecules. This study proposes an innovative and efficient approach to treat both microplastics composite heavy metal pollutants while elucidating the impact of environmental factors on the adsorption of heavy metals by electron beam-aged microplastics. The aim is to provide a theoretical basis and guidance for controlling microplastics composite pollution.

In Ukrainian

An important environmental problem is the removal of contaminants and the purification of domestic and industrial water from pollutants of various nature. There is a separate issue of cleaning the effluents of pharmaceutical enterprises. Various chemical and physical methods are used to solve these problems, such as settling, coagulation, filtration, and sorption techniques. Adsorption with using efficient and reusable adsorbents is the most effective and cheap. In recent years special attention has been paid to the use of sorption materials based on hydrolysis lignin, which has a high sorption activity in relation to ions of some heavy metals, dyes, organic compounds and pharmaceuticals. The use of lignin as an adsorbent simultaneously solves two problems: the disposal of paper production waste and the purification of sewage from various types of pollutants. The aim of this work was to study the sorption properties of hydroylysis lignin in aqueous solution in relation to some medical substances of different chemical nature, existing in solution in cationic, anionic or neutral forms. The point of zero charge of hydrolysis lignin was determined, which is equal to рНPZC = 4.95. The adsorption of rivanol, proflavin, doxorubicin, levofloxacin, furacilin, and salicylic acid by hydrolysis lignin was studied as dependence on the pH of the solutions and the concentration of adsorbates. It was found that adsorption largely depends on the structure of the pharmaceuticals and the pH values of the solutions. It is shown that the studied medical compounds, which exist in the solution in the form of cations, are adsorbed the best (rivanol, proflavin, doxorubicin). Adsorption of these substances occurs mainly due to electrostatic interaction with negatively charged surface groups. Adsorption of anionic form (salicylic acid) is the smallest and is observed only at quite low pH values. Levofloxacin is adsorbed mainly in the form of zwitter ions, and furacilin is in neutral form. The adsorption of these both compounds occupies an intermediate value of adsorption amount. The obtained adsorption isotherms are well lined up in Langmuir coordinates. Quantitative parameters of adsorption values - of maximum adsorption and equilibrium constants were calculated. Quite high values of these parameters indicate that hydrolysis lignin can be used as an adsorbent for the removal of these pharmaceuticals.

Coal gasification fine slag derived porous carbon-silicon composite as an ultra-high capacity adsorbent for Rhodamine B removal

The extensive release of industrial solid wastes and organic dyes has led to severe environmental pollution, underscoring the urgent need to recycle these solid wastes and to remove the dyes. Herein, a porous carbon-silicon composite (PC-SiO2) is synthesized using coal gasification fine slag (CGFS) as a precursor via an alkali (KOH) activation and an acid (HCl) etching process, and used as an adsorbent for the Rhodamine B (RhB) removal. The as-synthesized PC-SiO2 possesses an ultra-high specific surface area of 1275.63 m2/g, a large pore volume of 0.26 cm3/g, and enriched reactive functional groups (e.g., Si-OH and –COOH). Due to these features, the actual adsorption capacity and removal ratio of the PC-SiO2 for RhB were as high as 1383.72 mg/g and 92.25 %, respectively, at 298.15 K and pH = 7. Further studies indicate that the adsorption of RhB on PC-SiO2 fits both the pseudo-second-order kinetic model and the Langmuir model, with the maximum equilibrium adsorption capacity being 1388.89 mg/g as predicted by the Langmuir model. The adsorption process involves the electrostatic attraction, hydrogen bonding, π-π interaction, and pore-filling mechanism. This work not only offers a novel approach for removing organic dyes from industrial wastewater but also provides an effective strategy for producing high-value-added materials from industrial solid wastes.

Construction and evaluation of biomass-modified mesoporous silica nanoparticles as enzyme-responsive and pH-Responsive drug carriers for the controlled release of quercetin

This study constructed a biomass-modified mesoporous silica nanoparticle with enzyme-responsive and pH-responsive properties. The nanoparticles were used to evaluate the loading and release capacities of quercetin (QU). The multifunctional nanoparticles (MSN@CMCS-HA) were constructed by using hyaluronic acid (HA) and carboxymethyl chitosan (CMCS) as shells and mesoporous silica nanoparticles (MSN) as cores. The carrier's structure and properties were evaluated utilizing zeta, FTIR, TGA, XPS, XRD, BET, SEM, and TEM. The drug adsorption test revealed that the maximum equilibrium adsorption capacity of MSN@CMCS-HA for QU was 314.4 mg/g. In vitro drug release demonstrated that, under the influence of hyaluronidase (100 μg/mL) and pH of 5, the high drug release rate (63.73 %) was achieved. In addition, hemolysis and CCK8 tests confirmed the high biocompatibility of MSN@CMCS-HA. Consequently, MSN@CMCS-HA exhibited promising potential as an enzyme-responsive and pH-responsive drug carrier.

Enhanced Chromate Sorption Using Zinc‐Manganese Oxide Mesoporous Structures Decorated Carbon Nanocomposite Prepared from Battery Wastes

Mesoporous zinc-manganese oxide decorated carbon nanocomposites, as promising low-cost candidates for chromate(VI) sorption, were developed via a one-pot facile route based on battery wastes. The improved-based carbon composite with (ZnMn2O4+MnO(OH)/Mn2O3·H2O/C (I-C)) was produced by in-situ hydrothermal growth. Furthermore, the treated composite of carbon with adding ZnSO4 solution (ZnMn2O4/C (T-C)). Nanocomposites were characterized comprehensively using FTIR, XRD, HR-TEM, XPS, EDX, and BET analyses. The T-C nanocomposite showed a significant enhancement of chromate sorption by 1.5 fold in comparison with I-C in terms of maximum capacity and equilibrium time. Langmuir and pseudo-second-order fit the experimental data well. The sorption process is spontaneous, endothermic, and governed by entropic. The interaction mode was elucidated via FTIR, XRD, and XPS data, unveiling a synergistic ion-pair sorption and redox mechanism. Elution and sorbent regeneration were successfully achieved using HCl (0.2 M) with high durability over seven cycles. Finally, both nanocomposites, especially T-C, demonstrated exceptional efficiency and selectivity in removing high levels of Cr(VI) from wastewater from tannery industries.

Scour depth dynamics in varied spacing spur dike configurations: A comprehensive analysis

Spur dikes, vital for enhancing river ecosystem biodiversity, also contribute to the creation of intricate flow patterns and scour phenomena. In the context of existing research, which predominantly concentrates on single spur dikes, this study stands out by specifically delving into the temporal changes in scour depth near initial spur dike in multiple spur dikes. Varied spacings, lengths and flow velocities are considered in this exploration. After comprehensive literature analysis, it could be asserted that use of multiple spur dikes consistently results in shallower equilibrium scour depths compared to a single spur dike. The study introduces a predictive model by examining the impact of different influencing factors, including spacing, length, and flow velocity, on scour depth.The proposed equation establishes a robust correlation between the observed and estimated scour depth values. The study explores the temporal changes in scour depth, revealing that the time needed to arrive at equilibrium scour depth is drastically reduced when employing multiple spur dikes. Furthermore, the investigation highlights that in multiple spurs in series, the maximum equilibrium scour is lower compared to that in single spur dikes. The model, encompassing various parameters such as flow velocity, spacing, length, and time, demonstrates high predictive accuracy. Overall, this study provides valuable insights into the dynamic behaviour of scour at multiple spur dikes and offers a predictive tool for effective riverbank protection and ecosystem management. In doing so it contributes to the overarching aim of achieving Sustainable Development Goals (SDGs) in river management ecosystem preservation.

Phase behavior of rubber and supercritical CO2: Operating parameters and swelling characteristics

AbstractThis study aims to compare the difference in the swelling process between styrene butadiene rubber (SBR) and natural rubber (NR) in ScCO2. A high‐pressure visual stainless‐steel autoclave was used to carry out swelling measurements based on the sample dimensions. The swelling rates for both rubbers followed a first‐order kinetic model. The diffusion coefficient for CO2 was determined from the change in the swelling degree with time. The shrinking process for the expanded rubber obeyed a second‐order kinetic model. A 2‐level full factorial experimental design was employed to discuss the influence of variables on rubber swelling and CO2 diffusion. Temperature and pressure were found to have a great influence on the equilibrium swelling degree, swelling rate and diffusion coefficient. For both SBR and NR, the maximum equilibrium swelling degrees were observed at 120°C and 20 MPa, yielding values of 1.18 and 1.16, respectively. The maximum diffusion coefficient reached approximately 3 × 10−9 m2 s−1 for both types of rubber at 120°C and 8 MPa. The crosslink density failed to affect these three responses, but the volume of expansion and the shrinkage rate were found to significantly decrease and increase, respectively, with increasing crosslink density. The motion of polymer segments forced by ScCO2 led to rearrangement of the material structure, which governed the nature of swelling, expansion, and shrinkage. Due to a lower number of entanglements and a weak electrostatic interaction exists between CO2 and the π‐system, SBR can absorb more CO2 and easily restructure than NR under the same conditions, resulting in higher equilibrium swelling degree, larger expansion and faster shrinkage than NR.Highlights Swelling of nature rubber and styrene‐butadiene rubber in ScCO2 is compared. Swelling degree is positively correlated with temperature and pressure. Diffusion coefficient increases with temperature but decreases with pressure. Swelling degree varies with rubber type, while CO2 diffusion dose not. Crosslink density significantly affects expansion and shrinkage of rubber.

Copper Oxide Nano Biochar from Spent Coffee Grounds for Phosphate Removal and its Application as an Antibacterially Active Entity

From the viewpoint of both eutrophication and sustainable use of phosphate, the removal and recovery of phosphate from wastewater are important. Adsorption is seen as a viable alternative for effective phosphate removal, even at low concentrations. It is very simple to operate and cheaper. Among the various adsorbents tested, biomass-derived nanomaterials, such as nanobiochar, have shown promising efficiency. However, the use of pristine biochar is often less effective and difficult to recycle. In the present study, copper oxide-modified nanobiochar from spent coffee grounds is presented as an effective phosphate adsorbent. The adsorbent was prepared by the acid digestion of spent coffee grounds, followed by the co-precipitation of copper metal. The developed adsorbent was characterized by BET, FTIR, and XRD. Batch mode adsorption studies were conducted to assess the adsorption efficiency of the developed adsorbent and to investigate the effect of pH, initial concentration, contact time, and adsorbent dose. It was observed that acidic conditions favored the adsorption of phosphate, with maximum adsorption efficiency (93%) at pH 3. The maximum equilibrium phosphate adsorption capacity in this study was 50.2 mg/g at 25 oC, pH 3, a phosphate concentration of 20 mg/L, and an adsorbent dose of 35 mg/mL. The batch experimental data fit the Freundlich isotherm with regression (R2 = 0.991), which signifies that the surface of the adsorbent is heterogeneous. Adsorption kinetic data were best fitted with the pseudo-second-order kinetic model (R2 = 0.996), indicating that the adsorption process was dominated by chemisorption. The copper oxide nanoparticles and Cu/NBC showed relatively higher zone inhibition in gram-positive bacteria than in gram-negative bacteria at similar concentrations. This might be due to the higher activity of the nanoparticle extract on gram-positive bacteria, as most nanoparticle extracts were more active in gram-positive bacteria. This difference may be explained by the difference in the structure of the cell wall in gram-positive bacteria, which consists of a single layer, and in gram-negative bacteria, which has a multi-layered structure and is quite complex. In the majority of test bacteria, Cu/NBC showed better activity. The higher activity of this nanomaterial might be associated with the number of bioactive metabolites and their synergetic activities.