Response Surface Design Research Articles

Revealing the Potential of Star Anise Essential Oil: Comparative Analysis and Optimization of Innovative Extraction Methods for Enhanced Yield, Aroma Characteristics, Chemical Composition, and Biological Activities

ABSTRACTStar anise has been used for a long time in improving human health and curing diseases, owing to its unlimited components with complex chemical structures and a wide range of bioactivities. This study is aimed to investigate the influence of extraction methods (steam distillation, ethanol Soxhlet extraction, supercritical carbon dioxide extraction, subcritical n‐butane extraction) on the yield, aroma properties, chemical composition, and bioactivity of star anise essential oils. Electronic nose detection revealed the essential oils from subcritical extraction exhibited the most intense aroma, while the essential oils from ethanol Soxhlet extraction had a more complex aroma profile. Fourier‐transform infrared analysis showed the presence of benzene rings, carbonyl groups, C=C, and aromatic ether bonds in the essential oils extracted through different methods. The major components were heterocyclic olefins, heterocyclic oxygenates, and aromatic oxygenates, as well as certain amounts of flavonoids and polyphenols. Correlation analysis revealed the relative contents of volatile trans‐anethole, wormwood, d‐limonene, cineole, and trans‐α‐citronelene were strongly associated with the antibacterial activity of the essential oils. Similarly, the contents of volatile components (d‐limonene, cineole) and non‐volatile components (total flavonoids and total polyphenols) were strongly correlated with the DPPH scavenging activity of the essential oils. These results confirm the effectiveness of the ethanol Soxhlet extraction method in retaining the bioactivity of the essential oils. Finally, with a Box–Behnken central composite design of response surface and single‐factor experiments, the optimal extraction conditions for the ethanol Soxhlet method were determined: ultrasonic frequency of 80 kHz, crushing particle size of 60 meshes, liquid–material ratio of 8:1 (mL:g), and ultrasonic time of 35 min. Under these conditions, the essential oil yield was 25.51% ± 0.21%. Overall, these findings highlight the significance of extraction methods in obtaining high‐quality star anise essential oils with desirable aroma properties and potent bioactivities.

Influence of multi-stress factors on the growth of Chlorella pyrenoidosa and Scenedesmus abundans using response surface methodology.

This study evaluated the biofuel production potential of two algal species, Chlorella pyrenoidosa and Scenedesmus abundans, under stress conditions induced by nutrient supplementation or starvation at varying light intensities. Central composite face-centered design response surface methodology (CCFD-RSM) was employed to optimize stress conditions by varying the sodium nitrate (NaNO3), potassium dihydrogen phosphate (KH2PO4), dipotassium hydrogen phosphate (K2HPO4), cultivation time, and light intensity. The study included both C. pyrenoidosa and S. abundans, which presented increased biomass yields when subjected to nutrient starvation. Under the optimized conditions, the dry biomass yield was 98.26mg/L for C. pyrenoidosa and 110mg/L for S. abundans. Lipid yields were approximately 22.47% for C. pyrenoidosa and 29.06% for S. abundans under these optimized growth conditions. The optimized parameters for maximum biomass and lipid production were identified as C. pyrenoidosa, and the optimized conditions required 0.805g/L NaNO3, 0.052g/L K2HPO4, 0.099g/L KH2PO4, 17days of culture, and 5168.39lx of light intensity. For S. abundans, the optimal conditions were 1.065g/L NaNO3, 0.071g/L K2HPO4, 0.058g/L KH2PO4, 22days of cultivation, and 2897lx of light intensity. Overall, both C. pyrenoidosa and S. abundans have emerged as promising candidates for sustainable biodiesel production, highlighting their potential under stress conditions induced by nutrient modulation and variable light intensities.

Degradation Polysaccharides from Benincasa hispida var. chieh-qua How: Unveiling Bioactive Properties of Degraded Compounds.

This study reported an effective method for the degradation of Chieh-qua (Benincasa hispida var. Chieh-qua How) polysaccharides (BHCP) by a hydrogen peroxide-ascorbic acid oxidation (H2O2-VC) system. The degradation conditions were optimized using a Box-Behnken response surface design as concentration of H2O2-VC 19.5 mM, degradation temperature 46.4 ºC and degradation time 1.0 h. The average molecular weight was decreased and total sugar content was raised of the degraded polysaccharide (DBHCP). Two refined degraded polysaccharides (DBHCP-1, DBHCP-2) were purified and prepared, and their structures were analyzed by chemical and spectral analysis. The in vitro experiments showed that degraded polysaccharides (DBHCP and DBHCP-1) have better antioxidant and anti-tyrosinase activity than natural polysaccharide BHCP. These findings support the potential application of Chieh-qua polysaccharides in the food and medical industries.

Selenocyanate removal using combined system of TiO2- photocatalysis and Fe(III)/SiO2 adsorption {UV-TiO2/[Fe(III)/SiO2]}: Complex destruction and simultaneous selenium species adsorption

Selenocyanate (SeCN‾) species, commonly found in industrial effluents from crude oil refineries and mining operations, present substantial health risks to humans and animals. This study investigates the treatment of selenocyanate-contaminated streams using a combination of TiO2 photocatalysis and Fe(III)/SiO2 binary oxide adsorption {UV-TiO2/[Fe(III)/SiO2]}. The Fe(III)/SiO2 binary oxide was synthesized and characterized using X-ray diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy. XRD analysis revealed non-crystalline Fe-oxide phases, while FTIR indicated the presence of various Fe and O functional groups on the Fe(III)/SiO2 surface. Adsorption studies using Fe(III)/SiO2 showed its selenocyanate uptake capacity ∼ 2.1 mg/g, with the respective data closely aligning with the Langmuir isotherm model. This Fe(III)/SiO2 adsorption feature was successfully combined in the {UV-TiO2/[Fe(III)/SiO2]} system in which the hydroxyl radicals (●OH) generated by the UV-TiO2 facilitated the breakdown of the selenocyanate complex, while the resulting selenite and selenate were simultaneously adsorbed by the Fe(III)/SiO2 within a 240-min reaction time. A mathematical model developed using a face-centered central composite design-response surface methodology (FCD-RSM) showed significant predictive capability with an insignificant lack of fit. Optimal conditions for selenium removal were determined to be 20 mg/L selenocyanate, 1 g/L TiO2, and 1 g/L Fe(III)/SiO2, at pH 5, within a 240-min reaction time. Kinetic analysis demonstrated that selenocyanate degradation followed pseudo-first-order kinetics, while total selenium removal adhered to pseudo-second-order kinetics, confirming the proposed selenium species removal mechanism. Overall, this integrated approach offers a promising solution for effective selenocyanate remediation in industrial wastewater.

OPTIMIZATION OF THE SYNERGISTIC ANTIOXIDANT EFFECT OF SELECTED PHENOLIC COMPOUNDS (GALLIC ACID, ROSMARINIC ACID and CAFFEIC ACID) AND INVESTIGATION OF THEIR ABILITY TO PREVENT FORMATION OF DNA BASE DAMAGE

Considering the areas of use of phenolic compounds, it is important to determine the concentrations at which they show synergistic and antagonistic interactions for their integration into various systems and their correct use. In this study, the synergistic interaction concentration of rosmarinic acid, gallic acid, and caffeic acid was determined by Folin–Ciocalteu and FRAP methods. The central composite design–response surface methodology was used to determine the optimum concentration for synergistic interaction. As a result of the optimization, caffeic acid, rosmarinic acid, and gallic acid showed synergistic interaction at 7.87 μM, 6.75 μM and 9.42 μM concentrations for Folin–Ciocalteu method; 8.03 μM, 9.34 μM and 6.00 μM concentration for FRAP method respectively. The capacity of phenolic compounds to prevent the formation of DNA base damage products was evaluated by GC–MS/MS. As a result, the synergistic concentration of three phenolics reduces the DNA damage products at 37.17% (FOLIN) and 40.17% (FRAP).

Extraction, Characterization, and Antioxidant Activity of Eucommia ulmoides Polysaccharides.

Herein, the ultrasound-assisted extraction conditions affecting the yield of EUPS (Eucommia ulmoides polysaccharide) were analyzed using a Box-Behnken response surface design. The alleviation effect of EUPS on diquat-induced oxidative stress in mice was also studied. A maximum EUPS yield of 2.60% was obtained under the following optimized conditions: an extraction temperature of 63 °C, extraction time of 1 h, and ratio of liquid to raw materials of 22:1. EUPS exhibited strong 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical-scavenging ability (87.05%), 2'-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS) radical-scavenging ability (101.17%), and hydroxyl radical-scavenging ability (62.92%). The administration of EUPS increased the activities of superoxide dismutase, catalase, and glutathione peroxidase and decreased malondialdehyde levels in the livers of mice exposed to diquat. EUPS may inhibit the downregulation of NAD(P)H:quinoneoxidoreductase 1 and heme oxygenase 1 mRNA expression in the livers of diquat-administered mice through the Nrf2-Keap1 signaling pathway. Moreover, the abundance of Firmicutes and Ligilactobacillus was enhanced, whereas that of Helicobacter decreased in the gut of the remaining groups of mice compared with that of the diquat-treated mice. Therefore, EUPS exhibited an antioxidant effect and improved oxidative stress and intestinal flora abundance in mice.

Techno-economic optimization of enhanced geothermal systems with multi-well fractured reservoirs via geothermal economic ratio

Enhanced Geothermal System (EGS) shows vast potential for exploiting deep geothermal energy sources, although its techno-economic feasibility remains uncertain. The current research challenge lies in the absence of a reliable tool to rapidly evaluate the economic gains associated with the design of geothermal reservoirs. This study aims to develop an evaluation metric to assess the geothermal economic ratio of EGS. The efficacy, practicality, and simplicity of the proposed metric were demonstrated through its application to reservoir cases involving six fracture structures and four influencing parameters. The geothermal economic ratio of the system was enhanced through the augmentation of injection mass and the expansion of production well spacing. However, it was reduced by higher injection temperatures and wider primary fracture apertures. Using response surface design, the optimal parameters were found to be an injection temperature of 24 °C, an injection mass of 30 kg/s, a primary fracture aperture of 6.192 mm, and a production well spacing of 200 m. These parameters facilitated a reservoir heating efficiency of 0.322, a reservoir flow efficiency of 0.514, and a geothermal economic ratio of 1.026 × 10−20. The proposed metric and results would offer a concise and informative analysis of the market potential of EGS.

Mathematical and Statistical Analysis of Fused Filament Fabrication Parameters for Thermoplastic Polyurethane Parts via Response Surface Methodology

This work aims to analyze the effects of the main process parameters of fused filament fabrication (FFF) on the mechanical properties and part weight of 3D-printed thermoplastic polyurethane (TPU). Raster angle (RA), infill percentage (IP), and extruder temperature (FFF) in the ranges of 0–90°, 15–55%, and 220–260 °C, respectively, were considered as the FFF input parameters, and output variables part weight (PW), elongation at break (E), maximum failure load (MFL), ratio of the maximum failure load to part weight (Ratio), and build time (BT) were considered as responses. The Response Surface Methodology (RSM) and Design of Experiments (DOE) were applied in the analysis. Subsequently, the RSM approach was performed through multi-response optimizations with the help of Design-Expert software. The experimental results indicated a higher maximum failure load is achieved with an increased raster angle and decreased extruder temperature. ANOVA results show that ET has the most significant effect on elongation at break, with elongation at break decreasing as ET increases. The raster angle does not significantly affect the part weight of the TPU samples. The ratio of the maximum failure load to part weight of samples decreases with an increase in IP and ET. The results also indicated that the part weight and build time of FFF-printed TPU samples increase with an increase in IP. An ET of 220 °C, RA of 0°, and IP of 15% are the optimal combination of input variables for achieving the minimal part weight; minimal build time; and maximum elongation at break, maximum failure load, and ratio of the maximum failure load to part weight.

Modeling and Optimization of Sisal Fiber Degradation Treatment by Calcined Bentonite for Cement Composite Materials

ABSTRACT The treatment of sisal fiber by pozzolanic materials like kaolin and silica-fume has been explored; however, no study has modeled and optimized the effect of sisal fiber degradation treatment using calcined bentonite. Therefore, the present study investigate the effects of treating sisal fiber with different doses of calcined bentonite, bentonite calcination temperatures, and times on fiber breaking load, degradation resistance, and water absorption using the central composite design-response surface method (CCD-RSM). The best performance of the optimum treated sisal fiber selected from the CCD-RSM based on the established goal of maximizing breaking load and degradation resistance with minimum water absorption, it was obtained a calcined bentonite dose of 30.067%, a bentonite calcination temperature of 800°C, and a calcination time of 179.99 min. Based on these factors, experimentally found sisal fiber breaking load 12.87 N, degradation resistance 98.44%, and water absorption 39.05%, all are within the 95% confidence level compared to the optimum numerical suggested values. Hence, the optimum treated sisal fiber improved breaking load by 33.37% and degradation resistance by 98%, while it reduced water absorption by 60.95%, compared to raw sisal fiber. Besides these, the optimum treated sisal fiber exhibits higher surface roughness and lower porosity than the raw sisal fiber.

Dynamic mixing characteristics of a soft elastic tubular reactor (SETR): Experimental investigation and numerical simulation

In an innovative effort to mitigate material damage and enhance overall mixing performance, the use of a soft elastic tubular reactor (SETR) was explored. In this study, the mixing of tracer in SETR was observed with the help of non-invasive method. The effect of different parameters such as pusher squeezing frequency (F), distance between pushers (D) and pusher squeezing mode (M) on the flow field inside the SETR was also analyzed with the help of numerical simulations. The study also further optimized the operating parameters of the reactor. The experimental results proved the accuracy of the subsequent simulation model. Through the combination of response surface design and numerical simulation methods, it was found that all three factors have a significant effect on the mixing time. The results of this work add to our understanding of the mixing mechanism within SETR and present new opportunities for designing highly efficient industrial reactors.

Valorisation of sodium lignosulfonate from wood pulping industries for the enhancement of moisture management properties of nylon fabric

Nylon fabric has poor moisture management properties due to the absence of hydroxyl groups. In this work, an attempt has been made to enhance the moisture management properties of nylon fabric using sodium lignosulfonate (SLS). SLS is an essential by-product of the wood pulping industry. Various concentrations of the SLS were prepared in an aqueous medium, and the nylon fabric was treated with them using the exhaust method. The effects of the parameters of the treatment process are analyzed using Box–Behnken response surface design of experiment and analysis of variance (ANOVA). Upon testing the water vapour transmittance rate (WVTR), it was found that the SLS treatment is efficacious in improving moisture management. Water contact angle is reduced to 10.6° from 105.3° after the coating, which proves the achievement of hydrophilic surface. The average wetting time of nylon fabrics decreased by 78% after the SLS treatment. A significant increase in the bending modulus, flexural rigidity, and coefficient of the SLS-treated fabrics is observed when SLS concentration is high. After the SLS treatment, wetting time decreases, absorption rate increases, spreading speed increases, and overall moisture management capacity (OMMC) increases significantly. The SLS coating over the nylon surface is found to be durable with excellent rating for light and washing fastness.

Efficient mercury ion abatement through highly porous cellulose nanofibrils combined with microporous organic polymer enhancements

Pristine microporous organic polymer (p-MOP), owing to the presence of heteroatoms, has emerged as a significant platform for sensing and adsorption of heavy metal ions. The present work is a novel approach for developing highly porous hybrid architectures with trimesic acid and phenylene diamine-based p-MOP embedded over rice straw-derived cellulose nanofibers (ACNFs/MOP) for the sensing and remediation of mercury ions in the aqueous medium. The ACNFs/MOP were successfully characterized by various techniques, such as FTIR spectroscopy, BET surface area analysis, X-ray diffraction, XPS, HR-TEM, and TGA. The hybrid exhibited excellent porosity and crystallinity. The ACNFs/MOP hybrid was highly selective for Hg(II) ions, displaying substantial enhancement in fluorescence intensity with an LOD of 3.927 nM while also facilitating simultaneous adsorption. The adsorption showed a strong fit with pseudo-second-order kinetics and Langmuir isotherm models with an excellent adsorption capacity of 416.18 mg g−1, attributed to electrostatic interactions, coordination surface complexation, and metal-π interactions, as confirmed by XPS studies. Thermodynamic studies indicated an endothermic adsorption process. Box-Behnken Design-Response Surface methodology with Design Expert Software-13 was applied to model the process parameters. The hybrids were 97 % efficient even after five cycles of reusability, exhibiting their excellent potential for removing perilous Hg(II) ions from wastewater.

Mix proportion design and life cycle assessment of ultra-high-performance lightweight concrete with hollow microspheres

Achieving high strength and low weight in cement-based composites remains a critical objective in material and structure engineering. This study presents the development of an ultra-high-performance lightweight concrete (UHPLC) composite with a density not exceeding 1950 kg/m³ and a compressive strength of at least 100 MPa. The UHPLC mix design was optimized using the central composite design (CCD) response surface methodology, and a life cycle assessment (LCA) was conducted for the first time on UHPLC from cradle to gate. The interactions between cement content, hollow microspheres, and their effects on workability, mechanical properties, and durability were analyzed. The results show that using the CCD response surface method for designing UHPLC mix proportions is feasible, allowing effective optimization for various objectives, such as balancing both strength and density, highlighting low density, or emphasizing ultra-high strength. the designed UHPLC exhibits mechanical and durability properties comparable to or better than UHPC. LCA results show higher energy consumption and environmental impact for UHPLC in the cradle-to-gate stage, mainly due to the microsphere production phase. Monte Carlo uncertainty analysis reveals that ADP, HTP, POCP, and EP are most sensitive to microsphere content, while GWP and AP are more affected by cement content. The optimized UHPLCs in this study can be selected depending on specific technical or environmental scenarios. Introducing HMs into the UHPC system for UHPLC production shows excellent performance, making it a promising material for advanced structural applications.

Ultrasonic-Assisted Water-Rich Natural Deep Eutectic Solvents for Sustainable Polyphenol Extraction from Seaweed: A Case Study on Cultivated Saccharina latissima.

This case study introduces a green, 1 h single-step method using water-rich natural deep eutectic solvent (WRNADES) for ultrasound-assisted extraction (UAE) of polyphenols fromSaccharina latissima, a commercially cultivated brown seaweed. The extraction efficiency was evaluated using a selective quantitative NMR method (s-qNMR) and the traditional nonselective colorimetric total phenolic content assay (TPC). Initial 6 h extractions in traditional solvents (methanol, ethanol, acetone, and ethyl acetate) showed a 40-60% increase in polyphenolic yields in 50% aqueous solutions measured by the TPC method. Six different water-rich (50%) NADES (WRNADES) combinations were tested (choline chloride/betaine with lactic acid, citric acid, and 1,3-butanediol), with betaine and 1,3-butanediol (1:1) proving most effective. Parameters for the WRNADES were optimized using Box-Behnken design response surface methodology, resulting in a 1:20 w/w biomass to solvent ratio and a 1 h extraction time at 50 °C. The WRNADES extraction process was refined into a scalable, single-step procedure and compared with traditional solvent extractions (6 h, 50% aqueous methanol and acetone). A final XAD-7 polyphenol recovery step was included in all extractions. The optimized WRNADES extraction yielded 15.97 mg GAE/g of the dry weight recovered polyphenolic extract (s-qNMR), exceeding the 6 h 50% aqueous methanol (12.4 mg GAE/g) and acetone (11.4 mg GAE/g) extractions. Thus, the UAE-WRNADES method presented in this case study provides a cost-effective, sustainable, and eco-friendly alternative for the extraction of phenolic compounds from seaweed. It promotes the development of environmentally friendly production processes within the seaweed biorefinery.

Optimization and characterization of GGBFS-FA based alkali-activated CLSM containing Shield-discharged soil using Box-Behnken response surface design method

With the rapid growth of shield-discharged soil (SDS), there is an increasing demand for effective recycling and transformation methods. This study aims to develop an alkali-activated controlled low-strength material (CLSM) by utilizing ground granulated blast furnace slag (GGBFS) and fly ash (FA) as precursors, SDS as fine aggregate, and sodium hydroxide (NaOH) solution as an activator. The Box-Behnken design (BBD) within the response surface methodology (RSM) framework was employed, considering liquid-to-solid ratio, alkali equivalent, aggregate-to-binder ratio, and foam agent content (FC) in SDS as key factors. Regression models were constructed to analyze the effects of these factors on flowability, bleeding rate, setting time, compressive strength, elastic modulus, and water absorption. The results confirmed the effectiveness of RSM in determining optimal conditions for material performance. In addition, microscopic analyses were conducted to explore hydration products, microstructural characteristics, and pore distribution. The findings revealed that the fresh density of the CLSM ranged from 1460 to 1740 kg/m³, classifying it as a low-density material. The 28-day compressive strength varied from 1.837 to 7.884 MPa, while the setting time ranged between 1.2 and 5.6 hours. These properties comply with the ACI 229 standard and are suitable for practical applications. Interestingly, when the aggregate-to-binder (A/B) ratio was between 0.2 and 0.4, increasing the ratio did not lead to a consistent reduction in mechanical properties. Instead, the properties initially decreased and then improved. Moreover, an increase in foam agent content (FC) extended the setting time and reduced mechanical strength. The correlation coefficients of all models exceeded 0.98, with a coefficient of variation below 10 % and a signal-to-noise ratio greater than 4, demonstrating strong reliability and accuracy of the models. Additionally, the average relative error between predicted and experimental values in six scenarios was under 6 %, validating the feasibility of optimizing the design of alkali-activated CLSM using RSM. The formation of Ca(OH)₂ crystals facilitates early strength development, resulting in final cementitious materials reticular, fibrous C-S-H, C-A-H, and other gel-like hydration products. Calcium promotes the formation of gels such as C-S-H, shortening the setting time and enhancing microstructural density. This study provides valuable insights for optimizing the design of alkali-activated CLSM containing SDS, thereby expanding methods for utilizing construction and demolition waste.

Prediction and optimization of wet bulb efficiency in solar energy-based novel evaporative cooling system: Response Surface Method Approach

Abstract The wet bulb efficiency is an essential parameter in performance of Indirect evaporative cooling systems, as it impacts efficiently cool air while minimizing energy usage. This paper focuses on model and optimize multi tubular type wet channel for indirect evaporative cooler system. The optimized wet bulb efficiency based on Box-Behnken experimental design model and response surface method. The methodology included predicting and optimizing input process and working flow parameters of indirect evaporative cooling system to maximize wet bulb efficiency. A quadratic model of response surface method was used to evaluate influence of each factor on wet bulb efficiency, which was validated through analysis of variance results. The study found a maximum WBE of 89.65% under specific conditions, with a relative error of 3.25% between predicted and experimental result. This optimization process, governed by RSM, determined essential parameters for enhancing efficiency of system. These parameters include inlet process temperature of 28°C, working air velocity of 3.5 m/s, relative humidity of 45%, and inlet working air temperature of 24°C. These results demonstrate practical significance of current research, providing useful insights for optimal design and optimization of indirect evaporative cooling systems to fulfil cooling requirements while minimising energy consumption.

Preparation, Structural Analysis, and Growth-Promoting Effects of Amomum longiligulare Polysaccharide 1-Mg (II) Complex.

In this study, Amomum longiligulare polysaccharide 1 (ALP1) is used to chelate with magnesium (Mg) to synthesize the ALP1-Mg (II) complex (ALP1-Mg). Based on Box-Behnken response surface design, the optimum technological conditions are 22mgmL-1 trisodium citrate, 2.10molL-1 MgCl2, reaction at 70 °C for 2.9h, resulting in a maximum Mg content of 2.13%. Next, the physicochemical properties and structural characteristics of ALP1 and ALP1-Mg are characterized, and the results show that the morphology, conformation, crystallinity, and thermal stability of ALP1-Mg are changed. In addition, dietary supplementation of 500mgkg-1 ALP1-Mg significantly reduces the feed conversion ratio during the grower (15-35 d). Meanwhile, the villus height/crypt depth of the duodenum and ileum are significantly increased, and the relative abundance of Lactobacillus is significantly elevated. Taken together, the results suggest that ALP1-Mg is a potential growth-promoting feed additive.

Construction of controlled hyper-crosslinked nanofibrous tubes for Cr(VI) removal: Response surface, kinetics, and isotherm

Porous organic polymers (POPs) exhibit significant potential for adsorbing toxic metal ions in wastewater. Developing POPs with controlled morphologies is a pivotal direction in this field. This study synthesized a series of novel hyper-crosslinked nanofibrous tubes designated HCNT-Cn (n = 4, 8, 12, 16) via Friedel-Crafts alkylation and quaternization reactions. These reactions were fine-tuned through a post-synthetic strategy involving varying alkyl chain lengths. These materials were characterized using FT-IR, SEM, N₂ adsorption-desorption isotherms, among others, and they were specifically evaluated for their ability to adsorb Cr(VI). Among the variants, HCNT-C₄ exhibited the highest specific surface area (495.26 m2 g−1), superior hydrophilicity (CA = 48.7°), and optimal adsorption performance. The adsorption kinetics of HCNT-C₄ conformed to a pseudo-second-order model, while its adsorption isotherm aligned with the Langmuir model. An investigation into the impact of Cr(VI) removal was conducted using three independent variables in a Central Composite Design (CCD) response surface model, revealing that under optimal conditions, the Cr(VI) removal efficiency reached 98%. Additionally, a mechanism for Cr(VI) adsorption on HCNT-C₄ was proposed. It was also found that HCNT-C₄ could be reused up to four times, maintaining a removal efficiency of 70%. This study suggests potential applications for removing Cr(VI) from contaminated wastewater.

Response Surface Design Models to Predict the Strength of Iron Tailings Stabilized with an Alkali-Activated Cement

Tailing storage facilities are very complex structures whose failure generally leads to catastrophic consequences in terms of casualties, serious environmental impacts on local biodiversity, and disruptions in the mineral supply. For this reason, structures at risk must be reinforced or decommissioned. One possible option is its reinforcement with compacted filtered tailings stabilized with binders. Alkali-activated binders provide a more sustainable solution than ordinary Portland cement but require an optimization of the tailing–binder mixture, which, in some cases, can lead to a substantial experimental effort. Statistical models have been used to reduce the number of those experiments, but a rational design methodology is still lacking. This methodology to define the right mixture for a required strength should consider both the mixture components and in situ conditions. In this paper, response surface methods were used to plan and interpret unconfined compression strength test results on an iron tailing stabilized with alkali-activated binders. It was concluded that the fly ash content was the most important parameter, followed by the liquid content and sodium hydroxide concentration. From the obtained results, several statistical models were defined and compared according to the definition of a strength prediction model based on a mixture index parameter. It was interesting to observe that models with the porosity cement index still provide reasonable adjustment even when different tailings’ water contents are considered.

Using gardenia pigment for ultrasonic natural dyeing of hemp fiber: A step towards sustainable dyeing

In recent years, with the country advocating the establishment of a resource-saving and environmentally friendly society, people have been pursuing a green and healthy quality of life. The non-toxic, harmless, and biodegradable characteristics of grass and wood dyeing have brought this method back to people's lives. Despite the presence of antibacterial substances such as tetrahydrocannabinol in cannabis fibers, they are still susceptible to microbial attacks. In recent years, scholars have conducted more research on the separation and purification of gardenia flower pigments, but there has been less analysis on the dyeing fibers and performance testing of gardenia flowers. The renewable characteristics, fewer side effects, and low cost increase the use of natural drugs as antibacterial agents in plant extracts or their active ingredients. This experiment used gardenia flowers as the raw material for dyeing experiments, and the dyeing percentage was used as the inspection index. Ultrasonic dyeing was carried out on hemp fibers after degumming treatment. It also aims to endow these dyed fabrics with natural antibacterial properties. During the sorting process, a liquid bath ratio of 1:20 was selected and experiments were conducted under different parameter variations. During the dyeing process, potassium aluminum sulfate (alum) is used as a mordant, and ultrasound is used as an auxiliary dyeing method. After dyeing, evaluate the fibers based on the percentage of exhaustion of obtained fiber and antibacterial activity against Staphylococcus aureus and Escherichia coli. At the same time, the FT-IR analysis, strength, and color fastness of the sorted samples were also checked. Single factor experiments were conducted by controlling the ultrasonic frequency, dyeing temperature, time, and mordant concentration to analyze the effect of gardenia pigment on the dyeing percentage. Response surface design experiments were used to optimize the dyeing process parameters. The research results indicate that the optimal process conditions for dyeing gardenia flowers are ultrasonic power of 85 %, dyeing temperature of 77 ℃, dyeing time of 60 min, and mordant concentration of 15 g/L. The main and secondary order of factors affecting the dyeing effect of hemp fibers is: mordant concentration>ultrasonic power>dyeing temperature. After optimal dyeing process, the hemp fiber shows a bright yellow color with a dyeing percentage of 57.32 %. The single fiber strength is not affected, and the color fastness to water washing and sun exposure meets the requirements for consumption. The infrared spectrum shows good dyeing effect. It has a certain antibacterial effect on Staphylococcus aureus, but the antibacterial effect on Escherichia coli is not significant. Due to these processes, it has been determined that hemp fiber can obtain antibacterial activity through the use of gardenia flowers and can be effectively colored.