Qm Value Research Articles

Tailored Zeolitic Imidazolate Framework (TSC‐ZIF) for water purification: Evaluating TSC‐ZIF affinity towards heavy metal ions in multi‐metal solutions

In response to the growing concerns surrounding water pollution and the presence of multiple metal ions in environmental matrices, we conducted a comprehensive study to explore the potential of a thiosemicarbazone Schiff base in the Zeolitic Imidazolate Framework (TSC‐ZIF‐1) as an efficient adsorbent for removing harmful metal ions from aqueous solutions. Our investigation assessed the adsorption capacity and efficiency of TSC‐ZIF 1 towards three key metal ions—Hg(II), Ag(I), and Pb(II)—in homo‐ionic, tertiary, and multi‐metal ion systems. TSC‐ZIF 1 exhibited unprecedented adsorption behavior towards all three metal ions in the homo‐ionic system, with the Langmuir isotherm models fitting well (R2 ~ 0.98 to 0.99). The maximum adsorption capacities were found to be 1,667 mg/g for Hg(II), as previously reported; 285 mg/g for Ag(I); and 769 mg/g for Pb(II); these values serve as baseline values. Subsequently, we conducted a comparative analysis for a tertiary system, Hg(II)/Ag(I)/Pb(II), where the three metals co‐existed in one solution. The adsorption capacity for each metal ion was reduced to varying extents; notably, the adsorption capacity for Pb(II) experienced the most significant reduction, reaching a qm value of 57 mg/g, representing an ~93% decrease compared to the homo‐ionic metal system. Conversely, the adsorption capacity for Ag(I) exhibited a minor decrease of ~3%. Despite a decrease in the adsorption capacity for Hg(II) by approximately 34%, the removal capacity remains the highest among the other metals. Our investigation of the competitive adsorption among the metal ions in the Hg(II)/Ag(I)/Pb(II) system revealed an antagonistic effect, indicating strong adsorption competition for available sites on TSC‐ZIF 1. When extending this study to a more complex multi‐metal ion system containing six metal ions, TSC‐ZIF 1 exhibited high selectivity (higher than 60% removal) towards Hg(II), Ag(I), and Pb(II) in a multi‐ionic system, including Hg(II), Ag(I), Pb(II), Cd(II), Ni(II), and Mg(II).

2D Fluorinated Graphene Oxide (FGO)-Polyethyleneimine (PEI) Based 3D Porous Nanoplatform for Effective Removal of Forever Toxic Chemicals, Pharmaceutical Toxins, and Waterborne Pathogens from Environmental Water Samples.

Although water is essential for life, as per the United Nations, around 2 billion people in this world lack access to safely managed drinking water services at home. Herein we report the development of a two-dimensional (2D) fluorinated graphene oxide (FGO) and polyethylenimine (PEI) based three-dimensional (3D) porous nanoplatform for the effective removal of polyfluoroalkyl substances (PFAS), pharmaceutical toxins, and waterborne pathogens from contaminated water. Experimental data show that the FGO-PEI based nanoplatform has an estimated adsorption capacity (qm) of ∼219 mg g-1 for perfluorononanoic acid (PFNA) and can be used for 99% removal of several short- and long-chain PFAS. A comparative PFNA capturing study using different types of nanoplatforms indicates that the qm value is in the order FGO-PEI > FGO > GO-PEI, which indicates that fluorophilic, electrostatic, and hydrophobic interactions play important roles for the removal of PFAS. Reported data show that the FGO-PEI based nanoplatform has a capability for 100% removal of moxifloxacin antibiotics with an estimated qm of ∼299 mg g-1. Furthermore, because the pore size of the nanoplatform is much smaller than the size of pathogens, it has a capability for 100% removal of Salmonella and Escherichia coli from water. Moreover, reported data show around 96% removal of PFAS, pharmaceutical toxins, and pathogens simultaneously from spiked river, lake, and tap water samples using the nanoplatform.

Artificial intelligence models for methylene blue removal using functionalized carbon nanotubes

This study aims to assess the practicality of utilizing artificial intelligence (AI) to replicate the adsorption capability of functionalized carbon nanotubes (CNTs) in the context of methylene blue (MB) removal. The process of generating the carbon nanotubes involved the pyrolysis of acetylene under conditions that were determined to be optimal. These conditions included a reaction temperature of 550 °C, a reaction time of 37.3 min, and a gas ratio (H2/C2H2) of 1.0. The experimental data pertaining to MB adsorption on CNTs was found to be extremely well-suited to the Pseudo-second-order model, as evidenced by an R2 value of 0.998, an X2 value of 5.75, a qe value of 163.93 (mg/g), and a K2 value of 6.34 × 10–4 (g/mg min).The MB adsorption system exhibited the best agreement with the Langmuir model, yielding an R2 of 0.989, RL value of 0.031, qm value of 250.0 mg/g. The results of AI modelling demonstrated a remarkable performance using a recurrent neural network, achieving with the highest correlation coefficient of R2 = 0.9471. Additionally, the feed-forward neural network yielded a correlation coefficient of R2 = 0.9658. The modeling results hold promise for accurately predicting the adsorption capacity of CNTs, which can potentially enhance their efficiency in removing methylene blue from wastewater.

An innovative approach for the synthesis of 4Tris@Porphyrin and anderson polyoxometalate based covalent organic framework to reveal its potential for photocatalytic properties

Herein, a polyhydroxy containing metallo porphyrin linked through amide functional group with Anderson polyoxometalate (POM) was used to form TPMnA-COF. Structure and applications have been unlocked thoroughly by means of FT-IR, UV–visible, 1HNMR, PXRD, SEM and cyclic voltammetric (CV) spectral analysis. The TPMnA-COF was tested as catalyst to explore the photocurrent and photodegradation properties. ITO electrode was fabricated to study optical activity, absorption study and photocurrent generation. The adsorption study of TPMnA-COF has been studied using Langmuir and Freundlich model with calculated Langmuir constants qm, KL, RL and R2 values of about 12.42 mg/g, 0.33 M-1, 0.30 and 0.98 respectively. The 1/n, Kf and R2 values obtained from Freundlich adsorption isotherm were 0.70, 3.16 M-1 and 0.96 respectively. The band gap value evaluated via absorption edge of UV–visible spectra in DMSO solution was 2.75 eV while the band gap value calculated for ultra-thin film was 1.95 eV. The calculated real, imaginary dielectric constants, Urbach edge, refractive index and the electrical conductivity values for ultra-thin film of TPMnA-COF were 518.8, 2.9 × 10−11-8.1 × 10−11, −3.802 meV, 22.8–22.6 and 8.3 × 104−3.4 × 104 S/m), respectively. Responsivity for film was also tested using purple, blue, green, yellow, orange and red colourlights and the observed responsivity for different lower light intensities were 3.05, 2.9, 1.6, 1.55, 1.5 and 1.4 mA/W respectively. Furthermore, photodegradation activity of TPMnA-COF in Methylene-Blue (MB) and Rhodamine B(Rh–B) dyes under 3 W light. The results showed higher photocatalytic efficiency for Rh–B than that for MB with obtained degradation efficiency of 81 % and 60.4 %, respectively after 660 min. The scavengers such as ammonium oxalate (AO, h+), isopropanol (ISOP, •OH), catalase (CAT, H2O2) and superoxide dismutase (SODM, O2−●) were used to find out the effectiveness of each reactive specie to degrade the dyes solution in the mechanism of degradation. It was observed that AO (h+) and ISOP(•OH) were more active species in the photodegradation mechanism than CAT(H2O2) and SODM(O2−●).

Novel Method for the Arsenic Removal Experiment and Mechanism Analysis.

This study focuses on the hydrothermal synthesis of magnetically activated carbon and its efficacy in As(III) adsorption. The successful incorporation of magnetite nanoparticles within the porous carbon structure was confirmed, enriching the adsorbent's properties. Comprehensive characterization was performed to analyze the pore size distribution, zeta potential at varying pH levels, and thermostability using thermogravimetric analysis. These adsorbents exhibited high As(III) removal efficiency with a uniform pore distribution. The zeta potentials were observed to decrease with an increase in pH, suggesting a relationship between adsorbent charge and pH. Adsorption dynamics were rigorously modeled using pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models for different adsorbents labeled as a,b,c, and d. Each adsorbent displayed unique fitted parameters, revealing varied adsorption capabilities. The study further explored the adsorption kinetics and found that the pseudo-second-order kinetics model and the Langmuir model were most appropriate for describing the adsorption process. Adsorption thermodynamics was also fitted to elucidate the underlying adsorption mechanisms. For the a,b,c, and d adsorbents, the pseudo-first-order model, the qe(cal) values for the four adsorbents were 434.2, 418.4, 283.5, and 279.5 μg/g, respectively. Take adsorbent a as an example; the qm values for 298, 303, 308, and 313 K were 702, 673, 605, and 589 μg/g, respectively, and KL values of these temperatures were 0.021, 0.031, 0.018, and 0.009 L/μg, respectively. For the Langmuir model, the R2 values at the four temperatures were 0.999, 0.978, 0.985, and 0.993, respectively, which indicated that the Langmuir model showed higher fitness. For the Freundlich model, the KL values (L/μg) at the parameters of these temperatures are 432, 409, 328, and 294, respectively. For the Freundlich model, the 1/n values at temperatures of 298, 303, 308, and 313 K are 0.049, 0.045, 0.052, and 0.035, respectively. For the Freundlich model, the R2 values at parameters of 298, 303, 308, and 313 K are 0.986, 0.989, 0.982, and 0.872, respectively. For the Temkin model, the B values (in J/mol) are 30.93, 0.894, 0.824, and 0.782 at these temperatures, respectively. The KT values (in L/μg) are 1.02 × 106, 0.07 × 106, 0.003 × 106, and 0.002 × 106, respectively. The R2 values are 0.973, 0.958, 0.972, and 0.894, respectively. In the end, the ΔH, ΔS, and ΔG values for different adsorbents were calculated. Collectively, these findings contribute significant insights into the design and application of magnetically activated carbon adsorbents for effective As(III) removal.

Adsorption of Basic Yellow 28 and Basic Blue 3 Dyes from Aqueous Solution Using Silybum Marianum Stem as a Low-Cost Adsorbent.

In the present study, the ability of an adsorbent (SLM Stem) obtained from the stem of the Silybum Marianum plant to treat wastewater containing the cationic dyes basic blue 3 (BB3) and basic yellow 28 (BY28) from aqueous solutions was investigated using a batch method. Then, the SLM Stem (SLM Stem-Natural) adsorbent was carbonized at different temperatures (200-900 °C) and the removal capacity of the products obtained for both dyes was examined again. The investigation continued with the product carbonized at 800 °C (SLM Stem-800 °C), the adsorbent with the highest removal capacity. The dyestuff removal studies were continued with the SLM Stem-Natural and SLM Stem-800 °C adsorbents because they had the highest removal values. The surface properties of these two adsorbents were investigated using IR, SEM, and XRD measurements. It was determined that the SLM Stem-Natural has mainly non-porous material, and the SLM Stem-800 °C has a microporous structure. The optimal values for various parameters, including adsorbent amount, initial dye solution concentration, contact time, temperature, pH, and agitation speed, were investigated for BY28 dye and were 0.05 g, 15 mg/L, 30 min, 40 °C, pH 6 and 100 rpm when SLM Stem-Natural adsorbent was used and, 0.15 g, 30 mg/L, 30 min, 40 °C, pH 10, and 150 rpm when SLM Stem-800 °C adsorbent was used. For BB3 dye, optimal parameter values of 0.20 g, 10 mg/L, 30 min, 25 °C, pH 7, and 100 rpm were obtained when SLM Stem-Natural adsorbent was used and 0.15 g, 15 mg/L, 40 min, 40 °C, pH 10, and 100 rpm when SLM Stem-800 °C adsorbent was used. The Langmuir isotherm described the adsorption process best, with a value of r2 = 0.9987. When SLM Stem-800 °C adsorbent was used for BY28 dye at 25 °C, the highest qm value in the Langmuir isotherm was 271.73 mg/g. When the study was repeated with actual water samples under optimum conditions, the highest removal for the BY28 dye was 99.9% in tap water with the SLM Stem-800 °C adsorbent. Furthermore, the reuse study showed the adsorbent's efficiency even after three repetitions.

KNN-Based Lead-Free Piezoelectric Ceramics with High Qm and Enhanced d33 via a Donor-Acceptor Codoping Strategy.

The wide application of KNN-based lead-free piezoelectric ceramics is constrained by the contradictory relationship between its mechanical quality factor and piezoelectric constant. From an application point of view, searching for chemical composition with enhanced piezoelectric constant (d33) and mechanical quality factor (Qm) is one of the key points of KNN-based ceramics. In this work, KNN-based ceramics with enhanced d33 and high Qm values were obtained by the solid solution method via a donor-acceptor codoping strategy. The donor dopant Ho3+ enhanced d33 values by refining the domain size, while the acceptor dopant (Cu1/3Nb2/3)4+ improved Qm by the formation of defect dipoles. The composition (KNN-5Ho-4CN) exhibits optimal integrated performances, of which d33, Qm, and TC values are 120 pC/N, 850, and 392 °C, respectively. Moreover, the temperature coefficient of resonant frequency (TCF = -429 ppm/K) indicates that KNN-5Ho-4CN ceramic has good temperature stability. This work provides a new insight for developing KNN-based ceramics with enhanced d33 and high Qm.

Grain Boundary Diffusion Hardening in Potassium Sodium Niobate‐Based Ceramics with Full Gradient Composition and High Piezoelectricity

AbstractReducing mechanical losses and suppressing self‐heating are critical characteristics for high‐power piezoelectric applications. For environmentally friendly Pb‐free piezoelectric ceramics, traditional acceptor doping or annealing treatments have successfully improved the mechanical quality factor (Qm) based on a ceramic matrix with a poor piezoelectric coefficient (d33<100 pC/N). Nevertheless, a ceramic with high Qm and d33 values has not been reported owing to the inverse relationship between Qm and d33. Herein, a novel hardening method called grain boundary diffusion is used to develop Pb‐free potassium sodium niobate ceramics, where Qm increased by more than two‐fold (from 51 to 132) and a high d33 value (d33 = 360 pC/N) is maintained. Significantly, d33 retained 98% of its initial value after 180 days, exhibiting improved aging stability. The established properties are associated with the formation of the core‐shell microstructure and the full gradient composition distribution using structural characterizations and phase‐field simulations, where the core maintains a high d33 and the shell provides a hardening effect. The novel hardening effect in piezoelectric materials, known as grain boundary diffusion hardening, highlights the enhancement of the mechanical quality factor with high piezoelectricity, providing a new paradigm for the design of functional materials.

Microbial, physical and chemical indicators together reveal soil health changes related to land cover types in the southern European sites under desertification risk

Soil microbial communities, which play a key role in the provision of essential ecosystem services, are significantly influenced by several physical and chemical soil properties that may change with land management. This study explores the effect of different land cover types (coniferous tree stands, broad-leaved stands, shrublands, pastures/grasslands and croplands) on physical, chemical and microbial properties (all contributing to soil health) in southern European areas under moderate-high desertification risk selected in Italy, Spain and Portugal. In sites that differ in land cover, we determined microbial biomass (Cmic), activity and indices of microbial metabolism including Cmic/Corg ratio, metabolic quotient (qCO2) and quotient of mineralization (qM). Soil physical and chemical properties were also measured, comprising bulk density (BD), water content (WC), pH, cation exchange capacity (CEC), total organic C (Corg) and some of its labile fractions, extractable C (Cext) and mineralizable C (Cmin), total N content and C/N. Results showed that land cover type played a strong role in determining magnitude of microbial variables with biomass and activity being higher under coniferous tree cover than in other land covers, according to trends in WC, CEC, Corg, Cext, Cmin, N, C/N. Compared to land cover, aridity index had lower effect on investigated variables. In comparison to sites with higher Corg content, sites with lower Corg content (most croplands) tended to lose C more rapidly, as suggested by high qM values, except for Spanish acidic soils. Therefore, urgent actions must be taken to counteract the tendency of C-poorer soils to lose C, promoting land cover types that facilitate soil recovery by ensuring denser and more continuous soil cover over time. We also identified a minimum set of soil variables that provide information on soil health changes in both short term (microbial variables) and longer term (physical and chemical variables) in areas under desertification risk.

Adsorptive removal of Safranine T dye from aqueous solutions using sodium alginate–Festuca arundinacea seeds bio–composite microbeads

In this study, composite microbeads were prepared using Festuca arundinacea seeds and sodium alginate biopolymer at different ratios and utilized as sorbents for the sorption of Safranine T from wastewater. The sorbents were characterized by FTIR, SEM, XRD, and BET analysis. According to BET analysis, the specific surface area of the adsorbents was calculated to be 10.99 m2/g and the surface was found to be mesoporous. The optimum conditions for adsorption studies including initial pH (2−12), concentration (10–50 mg/L), contact time (0–150 min), and adsorbent mass (0.05 g/50 mL-0.25 g/50 mL) were determined at 25 °C. The raw data obtained from sorption tests were applied to Freundlich, Langmuir-1, Langmuir-2, Langmuir-3, Langmuir-4, Temkin, Toth, and Koble-Corrigan isotherm models. The best results were obtained from the Langmuir-2 and accordingly the qm values were calculated as 454.54, 833.33, and 625.00 mg/g for FA, FA-SA-20, and FA-SA-30 at 25 °C, respectively. Adsorption kinetic data illustrated that the process followed the PSO model. Reusability and desorption studies were performed for composite microbeads. Additionally, the thermodynamic studies were performed at 25, 35 and 45 °C. Considering all these results, it was seen that the FA-SA-20 composite had the highest adsorption capacity and the best desorption efficiency.

Differences in the distribution, availability, and sorption-desorption isotherms of phosphorus fractions in soil aggregates from cut slopes with different restoration methods

The construction of highways and other transportation facilities resulted in a large number of exposed cut slopes, leading not only to the alteration of soil structure but also to phosphorus (P) losses from soils with low utilization rates. These negative effects can result in stunted plant growth and the occurrence of heavy rainfall and earthquakes-associated landslide and mudslide disasters, threatening people's lives. However, few studies have investigated soil aggregates P in cut slopes restored with different methods in the Alpine Mountainous areas of Southwest China. Therefore, three types of cut slopes (cut slopes restored by three-dimensional mesh (TCS), cut slopes restored by galvanized wire mesh (GCS), and cut slopes restored by nature (NCS)) were selected for the study, and the present study aims to assess the total phosphorus (TP), available phosphorus (AP), and P fractions, as well as the P sorption-desorption isotherms in cut slope soil aggregates. The obtained results are as follows: (1) The TP contents in the soil aggregates did not differ significantly between the three types of cut slopes (p > 0.05), In addition, the AP contents and P activation coefficient (PAC) showed significant differences between TCS, GCS, and NCS, while the H2O-Pi, NaHCO3-Po, NaOH-Pi, NaOH-Po, HHCl-Pi, and HHCl-Po contents were significantly different between the three types of cut slopes (p < 0.05); (2) The AP contents in the three types of cut slopes showed a decreasing trend with increasing soil aggregate size from < 0.25 mm to > 5 mm; (3) H2O-Pi, NaOH-Pi, and HHCl-Pi were the main P fractions affecting the AP contents in the study area, among which NaOH-Pi exhibited the greatest effect on the AP contents; (4) The lowest P adsorption of soil aggregates was observed in NCS. The maximum P adsorption (Qm) values of the < 0.25 mm aggregates in TCS and GCS were higher than those of the other soil aggregate sizes. In addition, the trend of P desorption to increase with P adsorption was more obvious in large aggregates than in small aggregates. The present study provides a theoretical basis for P management in cut slope soils restored by different methods in the Alpine Mountainous region of Southwest China. Moreover, it provides some references for improving cut slope restoration and ecological slope protection techniques.

Characteristics of glyphosate adsorption with biochar from young coconut waste

Biochar is a carbon-rich by-product of biomass pyrolysis that can limit glyphosate mobility in soil using amelioration technology. Study of the basic principles of glyphosate adsorption behaviour in biochar from young coconut waste using the Kon-Tiki method at temperature (682°C), moisture content (81.27%), and yield ratio (20.87%) at the size of ≤2 mm. The absorption of glyphosate in biochar increased as glyphosate content rose, whereas pH declined. The capacity and adsorption coefficient of glyphosate by biochar from young coconut waste was 0.85 mg g-1 and 56.25 L Kg-1 at a pH of 8.03 and a concentration of 100 mg L-1 glyphosate. The adsorption isotherm of glyphosate occurs in the Freundlich and Langmuir models (Freundlich > Langmuir), wherein the Freundlich model (y = 1.8373x - 2.3971; R2 = 0.9771) with a value of n (0.54) and KF [0.004 (L mg-1)1/n], and the Langmuir model (y = - 17.066x + 251.58; R2 = 0.7239) with a value of Qm (0.06 mg g-1) and KL (0.07 L mg-1).

Methyl orange dye sequestration using polyaniline nanotube-filled sodium alginate bio-composite microbeads

Dye pollution is a significant problem in today's environmental protection, and bio-adsorbents have been getting a lot of attention in wastewater treatment because of their affordability, sustainability, and eco-friendly. Bio-based sodium alginate-polyaniline nanotube (SA-PANINT) composite microbeads were fabricated by a facile cross-linking with calcium chloride solution for the adsorptive removal of methyl orange (MO) dye. Depending on the amount of PANINT in the composite composition, SA-PANINT-10, SA-PANINT-20, SA-PANINT-30, and SA-PANINT-40 composite microbeads were prepared. Among these microbeads, SA-PANINT-30 composite microbeads gave the best results in experimental tests. The obtained SA-PANINT-30 composite microbeads were characterized by FTIR-ATR, SEM, XRD, and BET analyses, and the influence of dose (0.01 g/50 mL–0.15 g/50 mL), pH (2–12), time (0–210 min), and concentration (10–50 mg/L) on the adsorption of MO was examined. From the Langmuir isotherm model, under optimum conditions, the qm value of SA-PANINT-30 microbeads was determined as 370.4 mg/g at 25 °C. It was also obtained that the adsorption process followed the PSO model and the adsorption process took place chemically. From the thermodynamic parameters, the adsorption process for SA-PANINT-30 microbeads was found to be endothermic (ΔHo=24.09 kJ/mol) and spontaneous (ΔGo=−25.56 kJ/mol at 25 °C). Considering all these results, it was seen that the prepared composite microbeads can be used as a highly efficient, low-cost, sustainable, and potential adsorbent in the removal of synthetic anionic dyes from wastewater.

Functionalization of carbon from rubber fruit shells (Hevea brasiliensis) with silane agents and its application to the adsorption of bi-component mixtures of methylene blue and crystal violet.

In this research, activated carbon was obtained from rubber fruit shells (ACRPs). The obtained activated carbon (ACRPs) was modified by magnetite particle coating and silanization with triethoxyiphenylsilane (TEPS) to produce a new magnetic adsorbent (ACRPs-MS). The affinity of as-prepared adsorbent (ACRPs-MS) toward methylene blue (MB) and crystal violet (CV) dyes was tested in mono-component and bi-component solutions. Structural characterization proves the success of the magnetite coating process and the silanization of ACRPs. In the infrared (IR) spectroscopy spectrum of ACRPs-MS, Si-O-Fe and Si-O-Si bonds were identified, which indicated the presence of magnetite and silane. This is also supported by the elemental composition contained in the energy-dispersive X-ray (EDX) diffractogram. In addition, the presence of the porous structure of the surface of the material and the increase in the specific surface area increase the accessibility of contaminants such as MB and CV dyes to be adsorbed to the ACRPs-MS adsorption site effectively. The experimental results showed that the adsorption of mono-component MB and CV dyes by ACRPs-MS was optimum at pH8 and an interaction time of 60min. The adsorption kinetics of mono-component MB and CV dyes by ACRPs-MS tended to follow pseudo-second-order kinetics (PSO) models with PSO rate constant (k2) values of 0.198 and 0.993gmg-1min-1, respectively. The adsorption of MB and CV dyes by ACRPs-MS in a bi-component mixture tends to follow the Langmuir isotherm model with adsorption capacity (qm) values of 85.060 and 90.504mgg-1, respectively. Analysis of adsorption data on the bi-component mixture between MB and CV by ACRPs-MS with the Langmuir isotherm equation for a binary mixture resulted in qm of 22.645 × 10-3mmol equiv g-1. ACRPs-MS material can be used repeatedly five times with adsorption ability > 80%. Desorption of MB and CV dyes was carried out using 0.05M HCl solution. ACRPs-MS material was able to adsorb MB and CV dyes with a large adsorption capacity and could be used in repeated adsorption. Thus, it can be stated that ACRPs-MS can be used as an effective adsorbent for MB and CV dyes, either singly or in a bi-component mixture.

Prediction of heavy metals adsorption by hydrochars and identification of critical factors using machine learning algorithms

Hydrochar has become a popular product for immobilizing heavy metals in water bodies. However, the relationships between the preparation conditions, hydrochar properties, adsorption conditions, heavy metal types, and the maximum adsorption capacity (Qm) of hydrochar are not adequately explored. Four artificial intelligence models were used in this study to predict the Qm of hydrochar and identify the key influencing factors. The gradient boosting decision tree (GBDT) showed excellent predictive capability for this study (R2 = 0.93, RMSE = 25.65). Hydrochar properties (37%) controlled heavy metal adsorption. Meanwhile, the optimal hydrochar properties were revealed, including the C, H, N, and O contents of 57.28–78.31%, 3.56–5.61%, 2.01–6.42%, and 20.78–25.37%. Higher hydrothermal temperatures (>220 °C) and longer hydrothermal time (>10 h) lead to the optimal type and density of surface functional groups for heavy metal adsorption, which increased the Qm values. This study has great potential for instructing industrial applications of hydrochar in treating heavy metal pollution.

Adsorptive Evaluation of Activated Carbonized Avocado Pear Seed (Persea Americana) and Activated Carbonized orange peels (Citrus Sinensis) in Taking out Ni2+ ion in Contaminated Water

Grave and complicated pollution problems are posed by the existence of heavy metals trendy environment and this has been a focus of study all over the world. The Activated carbonized avocado pear seed (ACAPS) and activated carbonized orange peel (ACOP) were each soaked with potassium hydroxide (KOH) solution at a 1:1 ratio, for 48 hours, the outcome was washed, air-dried and separately oven dried at 105℃ for 6 hours and further heated in a muffle furnace (Carbolite AAF1100) at 2500C for 1 hour. The ACAPS and ACOP obtained were physicochemical characterized with scanning electron microscope (SEM) and Fourier-transform infrared (FT-IR) spectrophotometer. Ni2+ ions adsorption route on ACAPS as well as ACOP was considered by means of batch adsorption isotherm investigation. Adsorption forms was assessed by Freundlich, Langmuir, DRK, Tempkin as well as Flory-Huggin isotherm models. SEM picture, show that ACAPS posessed an enormous amount of different dimension pores and the ACOP had smaller amount of pores of smaller sizes. The R2 obtained varies from 0.92 to 1.00 and it points to the fact that all the isotherm simulation was competent to clarify the correlation in the data we got. ACAPS had more adsorption site, however, ACOP took up more Ni2+ ion per adsorption site on comparing Flory-Huggins isotherm model nFH values vis-a-vis Langmuir isotherm model qm values. In conclusion, ACAPS was a superior adsorbent when matched with ACOP, it was more than twice as effective for taking out Ni2+ ions from contaminated water owing to a blend of its enormous amount of different size openings and the functional groups on its surface, with a qm value of 18.18 and 8.70 mg/g in that order.

Experimental study on vertical temperature distribution of the two-layer smoke flow in tunnel during construction

For a tunnel fire during construction, the formation of two-layer smoke flow underneath the ceiling accelerates the smoke descent threatening the personnel evacuation. As an important indicator of smoke diffusion, the gas temperature distribution inside tunnel is worthy of analysis in depth. However, the vertical temperature profiles within this kind of two-layer smoke flow inside tunnel have not been experimentally studied. To fill the gap, this paper conducts a series of fire experiments in a 1/20 reduced-scale tunnel model. Multi-variables including fire heat release rate, fire position, lifting-up height of fire source, inclined shaft slope, are considered. The visible flame shape, O2 volume fraction and gas temperature are recorded and measured. The burning of the propane gas persists steadily for 20 mins without the occurrence of self-extinction. The structural evolutions of the smoke layer are predicted by FDS simulation and traced by the laser sheet. The smoke descent process in the main tunnel is divided into three stages. The effects of fire source position, inclined shaft slope, fire heat release rate and lifting-up height on the gas temperature distributions inside tunnel are analyzed. The measured temperature rise and the perpendicular distance from the ceiling are normalized by ΔTmax and LT, respectively. At various longitudinal positions (1.82 ≤ │X-dm│/Hef ≤ 10.68), the normalized temperature distributions follow the same curve, independent of the values of Qm, dm and hm. The self-similarity of the vertical temperature distribution within the two-layer smoke flow are sufficiently proved. It is found that ΔT/ΔTmax with z/LT shows a two-regional variation. Based on over 1,740 temperature data from 36 experimental cases, an experimental equation is proposed to describe the gas temperature rise in the region between the fire source and the closed end. The proposed model shows good agreement with the measured data, which can help the researchers to better assess the smoke layer height inside tunnel.

π-Electron-Extended Triazine-Based Covalent Organic Framework as Photocatalyst for Organic Pollution Degradation and H2 Production from Water.

Herein, we report the efficient preparation of π-electron-extended triazine-based covalent organic framework (TFP-TPTPh COF) for photocatalysis and adsorption of the rhodamine B (RhB) dye molecule, as well as for photocatalytic hydrogen generation from water. The resultant TFP-TPTPh COF exhibited remarkable porosity, excellent crystallinity, high surface area of 724 m2 g-1, and massive thermal stability with a char yield of 63.41%. The TFP-TPTPh COF demonstrated an excellent removal efficiency of RhB from water in 60 min when used as an adsorbent, and its maximum adsorption capacity (Qm) of 480 mg g-1 is among the highest Qm values for porous polymers ever to be recorded. In addition, the TFP-TPTPh COF showed a remarkable photocatalytic degradation of RhB dye molecules with a reaction rate constant of 4.1 × 10-2 min-1 and an efficiency of 97.02% under ultraviolet-visible light irradiation. Furthermore, without additional co-catalysts, the TFP-TPTPh COF displayed an excellent photocatalytic capacity for reducing water to generate H2 with a hydrogen evolution rate (HER) of 2712 μmol g-1 h-1. This highly active COF-based photocatalyst appears to be a useful material for dye removal from water, as well as solar energy processing and conversion.

Exploration of haematite-loaded rice husk biochar as a low-cost nanosorbent to remove Cr (III) from the aqueous media

ABSTRACT In this study, the biochar of rice husk was modified to a nanosorbent upon loading with haematite for Cr (III) removal from aqueous solutions. Three adsorbents, rice husk, rice husk biochar and haematite-loaded rice husk biochar, were used for equilibrium adsorption studies. SEM and FTIR analysis revealed the presence of pores and various surface active sites on a nanomaterial, which were responsible for the adsorption of Cr (III). C–H, –O–H, C=O stretching vibrations were observed in characterised FTIR peaks. Modelling of adsorption isotherms indicated best fit for Freundlich isotherm with maximum Kf value of 12,218 and 39.5 for linear and non-linear nanomaterial experimental calculations, and positive n value in range of 1–10 for all forms of adsorbents, Dubinin–Radushkevich adsorption saturation capacity qs showed high readings of 9417 and 76.8 for haematite nanomaterial, Elovich isotherm favoured non-linear results in case of nanomaterial with increased Qm values 43.4–112.3 from raw form to nanosorbents and Temkin isotherm with. Kinetic and Thermodynamic results were also summarised. Constants k and h and Qe capacity were tabulated for Pseudo second order model with highest Qe in the range of 20.36–22.52 for haematite loaded biochar nanomaterial. Hence, haematite based rice husk biochar nanostructure was employed as an efficient adsorbent for uptake of chromium.

A simplistic approach for the synthesis of Covalent Organic Frameworks(COFs) comprising of tetrafunctionalized porphyrin and polyoxometalates to uncover catalytic applications

Tetrafunctionalized porphyrins are energetic synthons to prepare MOFs(Metal organic framework) and COFs(Covalent organic framework). Herein, a new tetrafucntionalized metallo porphyrin was used and connected via amide functionality with anderson polyoxometalates(POMs) and assembled two COFs(P@Ni-AndCOF & P@Cu-AndCOF). Structures, properties and their relationships have been unlocked thoroughly by means of FT-IR, UV–visible, 1HNMR, PXRD, SEM and cyclic voltammetric(CV) spectral analysis. The catalysts were tested to uncover the photocatalytic properties such as photocurrent and photodegradation properties. P@Cu-AndCOF and P@Ni-AndCOF were used to fabricate the ITO TiO2 coated electrodes to study optical activity, adsorption study and photocurrent generation. The adsorption study of P@Cu-AndCOF and P@Ni-AndCOF has been studied by using Langmuir and Freundlich model with calculated Langmuir constants qm, KL and RL values of about [7.44(mg/g), 8.02(mg/g)], [0.79(L/mg), 0.69(L/mg)] and (0.22 & 0.23) respectively. The correlation coefficient for adsorption obtained through Langmuir analysis were 0.92, and 0.95 for P@Ni-AndCOF and P@Cu-AndCOF respectively. The 1/n, Kf and R2 values obtained from Freundlich adsorption isotherm for P@Ni-AndCOF and P@Cu-AndCOF were (0.50 & 0.52), (3.325676 mg/g &3.328971 mg/g) and (0.94 & 0.93) respectively. The bandgap values evaluated via absorption edge of UV–visible spectra for P@Ni-AndCOF and P@Cu-AndCOF in DMSO solution were 2.82eV, and 2.83eV respectively while the bandgap values calculated for ultra-thin films were 1.78eV, and 1.85eV for P@Ni-AndCOF and P@Cu-AndCOF correspondingly. The calculated real, imaginary dielectric constants, Urbach edge, refractive index values and the electrical conductivity for ultra-thin film of P@Ni-AndCOF and P@Cu-AndCOF were (1.4x104-1.41x104& 2.19x10−9-2.45x10−9), (6.6x104-7.4x104&1.7x10−10-2.47x10−10), (0.323eV & 0.362eV), (32.9–32.4 & 33–30.4) and (5.8 × 104-2.9 × 104 &6.1 × 104-4.7 × 103 S/m) respectively. Furthermore, photodegradation activity of both catalysts was checked in Methylene-Blue(MB) and Rhodamine B(Rh-B) dyes under 3 W light. They showed higher photocatalytic efficiency for MB than that for Rh-B caused degradation efficiency of 89% and 79.3% for MB and 83% and 71.3% for Rh-B respectively after 660min. The photodegradation activity was also observed in dyes solutions along with some scavenger's ammonium oxalate (AO, h+-scavenger) and isopropanol (ISOP, •OH-scavenger) and it was observed that by the addition of these scavengers photodegradation rate was reduced.