Initial Contact Time Research Articles

Graphene oxide intercalated Alk-MXene adsorbents for efficient removal of Malachite green and Congo red from aqueous solutions

Currently, adsorbents with high adsorption performance for eliminating pollutants from discharged wastewater have received many researchers’ attention. To this aim, a novel AMXGO absorbent was fabricated by intercalating graphene oxide (GO) into alkalized MXene (Alk-MXene) layer which exhibited high efficacy for the removal of cationic Malachite Green (MG) and anionic Congo Red (CR). Analysis of FTIR, XRD, SEM and TG presented that AMXGO absorbent have a typical three-dimensional layer by layer structure and abundant oxygen-containing groups and its thermal stability was remarkably improved. BET results elucidated that AMXGO1 adsorbent has larger specific surface area and pore volume (16.686 m2 g−1, 0.04733 cm3 g−1) as compared to Alk-MXene (4.729 m2 g−1, 0.02522 cm3 g−1). A dependence of adsorption performance on mass ratio between Alk-MXene and GO, initial dye concentration, contact time, temperature and pH was revealed. Maximum adsorption capacity of MG (1111.6 mg/g) and CR (1133.7 mg/g) were particularly found for AMXGO1 absorbent with a mass ratio of 3:1 and its removal for both dyes were higher than 92%. The adsorption process of AMXGO1 adsorbent for both MG and CR complies with pseudo-second-order kinetic model and Freundlich isotherm model. In addition, adsorption mechanism was explored that synergism effects as electrostatic attraction, π-π conjugates, intercalation adsorption and pore filling were the main driving force for the high adsorption performance of dye. Therefore, AMXGO adsorbent has a potential application prospect in the purification of dye wastewater.

Preparation of novel green adsorbent (Tabernaemontana divaricata leaf powder) and evaluation of its dye (malachite green) removal capacity, mechanism, kinetics, and phytotoxicity

In this study, a novel green adsorbent, Tabernaemontana divaricata leaf powder (TD), was prepared, and its efficacy in removing malachite green (MG) dye from water, along with the associated mechanism and kinetics, was systematically evaluated for the first time. Characterization of TD was carried out using scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). Optimization of MG dye removal was conducted by varying parameters such as pH, initial dye concentration, contact time, and TD dosage. Results demonstrated that TD exhibited a high adsorption capacity for MG dye (5.2131 mg.g−1), achieving a maximum removal efficiency of 89.5 % under optimized conditions: pH 7.0, initial dye concentration of 20 ppm, contact time of 120 min, TD dosage of 4 g/L, and temperature of 28.1 °C. Kinetic and isotherm models were applied to analyze the experimental data, revealing that the adsorption process most accurately followed Ho's pseudo-second-order kinetic model (R2 = 0.999). The high heats of adsorption observed in the isotherm study suggest prominent electrostatic interactions between adsorbate molecules and the surface, governing the chemisorption mechanism that dominates at the solid-liquid interface. This study underscores the potential of Tabernaemontana divaricata (jasmine) leaf powder as a cost-effective, environmentally friendly, and efficient adsorbent for the remediation of MG dye-contaminated water.

Adsorbent Biomaterials Based on Natural Clays and Orange Peel Waste for the Removal of Anionic Dyes from Water

This study demonstrates the efficient removal of Alizarin Yellow R anionic dye (AY) from aqueous solutions using green adsorbents. Natural kaolin clay (A1), acid-modified natural clay (A2), chemically treated orange peel (C1) and biochar produced by the thermal treatment of orange peel (C2) were tested for the adsorption of AY. The characteristics of the sorbents were determined by instrumental methods: SEM, EDS, FTIR, BET and TGA. The adsorption experiments were performed under different conditions, including the initial AY dye concentration, adsorbent weight, pH, temperature and contact time. The maximum adsorption capacities had values between 15.72 and 74.62 mg/g at 298 K and the optimal pH of 6.5 at initial concentrations ranging from 30 to 70 mg/L for all adsorbents. The equilibrium data were used for the adsorption isotherm models: Freundlich, Langmuir and Temkin. The Freundlich model fit best for the adsorbents A2, C1 and C2, and the Langmuir isotherm had the highest regression value for the adsorbent A1 (R2 = 0.9935). Thermodynamic parameters indicated the spontaneous and favorable adsorption process of AY. A study of the adsorption kinetics proved that they best fit the pseudo-second-order model, with the highest coefficients of determination (R2), outperforming the pseudo-first-order model. The results of this study indicate the potential for the valorization of locally available clays and orange peel waste in the purification processes of water.

Sequestration of an Azo Dye by a Potential Biosorbent: Characterization of Biosorbent, Adsorption Isotherm and Adsorption Kinetic Studies.

This study explores the detailed characterization of a biosorbent (Hen Feather) and its efficient use in eradicating the azo dye Metanil Yellow (MY) from its aqueous solutions. Effects of a range of experimental parameters, including pH, initial dye concentration, biosorbent dosage and contact time on the adsorption, were studied. A detailed physical and chemical characterization of the biosorbent was made using SEM, XRD, XPS and FTIR. During the optimization of adsorption parameters, the highest dye uptake of almost 99% was recorded at pH 2, dye concentration 2 × 10-5 M, 0.05 g of biosorbent and a contact period of 75 min. Various adsorption isotherm models were studied to gather different adsorption and thermodynamic parameters. The linearity of the Langmuir, Freundlich and D-R adsorption isotherms indicate homogeneous, multilayer chemisorption with high adsorption affinity between the dye and biosorbent. Values of the changes in the Gibbs free energy (ΔG°) and the enthalpy (ΔH°) of the adsorption process have been calculated, these values indicate that it is a spontaneous and endothermic process. Kinetics of the adsorption were also measured, and it was established that the adsorption of MY over Hen Feather follows a pseudo-second-order kinetic model at temperatures 30, 40 and 50 °C. The findings of this investigation clearly indicate that the studied biosorbent exhibits a high affinity towards the dye (MY), and it can be effectively, economically and efficiently used to sequestrate and eradicate MY from its aqueous solutions.

Artificial neural network-based modeling of Malachite green adsorption onto baru fruit endocarp: insights into equilibrium, kinetic, and thermodynamic behavior

In this study, artificial neural network (ANN) tools were employed to forecast the adsorption capacity of Malachite green (MG) by baru fruit endocarp waste (B@FE) under diverse conditions, including pH, adsorbent dosage, initial dye concentration, contact time, and temperature. Enhanced adsorption efficiency was notably observed under alkaline pH conditions (pH 10). Kinetic analysis indicated that the adsorption process closely followed a pseudo-second-order model, while equilibrium studies revealed the Langmuir isotherm as the most suitable model, estimating a maximum adsorption capacity of 57.85 mg g−1. Furthermore, the chemical adsorption of MG by B@FE was confirmed using the Dubinin–Radushkevich isotherm. Thermodynamic analysis suggested that the adsorption is spontaneous and endothermic. Various ANN architectures were explored, employing different activation functions such as identity, logistic, tanh, and exponential. Based on evaluation metrics like the coefficient of determination (R 2) and root mean square error (RMSE), the optimal network configuration was identified as a 5–11-1 architecture, consisting of five input neurons, eleven hidden neurons, and one output neuron. Notably, the logistic activation function was applied in both the hidden and output layers for this configuration. This study highlights the efficacy of B@FE as an efficient adsorbent for MG removal from aqueous solutions and demonstrates the potential of ANN models in predicting adsorption behavior across varying environmental conditions, emphasizing their utility in this field.

Adsorption Performance of Acidic Modified Fly Ash: Box–Behnken design

Fly ash (FA) and modified fly ash (mFA) were used as adsorbents to remove methylene blue (MB) dye from aqueous solutions. The adsorbents were characterized using crystal structures with XRD, surface functional groups with FTIR, and surface morphologies with SEM. Response surface methodology (RSM) with Box-Behnken design (BBD) was used to optimize adsorption parameters such as MB dye concentration (A: 10-20 mg/L), solution pH (B: 3-11), and contact time (C: 30-180 min). ANOVA analysis shows the significant inter-actions between initial concentration, solution pH value, and solution pH value, contact time was found to be significant in the removal of MB (p-value=< 0.0001, 0.0040), whereas between the effect of initial concen-tration and contact time was not significant (p-value = 0.0881). The adsorption kinetics followed the pseudo-second-order (PSO) kinetic model and the adsorption isotherm followed the Langmuir model. At 28°C, the adsorption capacity of fly ash-HNO3 for MB was found to be 7.67 mg/g.

Eriochrome Black T dye removal from an aqueous solution using graphene oxide-modified activated carbon materials

ABSTRACT The presence of a toxic anionic dye, like Eriochrome Black T (EBT) in the aquatic environment, is the major cause of water contamination. Considering this, we synthesised activated carbon, (AC) derived from the Carica papaya seeds, which is effective, low-cost, simple to design and with a higher surface area. The prepared materials (GO/AC) will be employed for the efficient removal of toxic EBT dye. The synthesised GO/AC composite was further analysed using FTIR, XRD, FE-SEM, EDX and Raman spectra. The adsorption performance of GO/AC materials towards EBT dye removal was checked through a batch adsorption experiment. Various parameters, including initial dye concentration, contact time, adsorbent dosage, stirring speed and pH, were batch-wise varied for the adsorption experiment. The higher correlation coefficient (R 2 = 0.99) indicated that the Langmuir isotherm model was followed by the experimental data suggesting that the adsorption process is a monolayer. The maximum adsorption capacity of EBT dye was found to be 51.84 mg/g. The pseudo-second-order kinetic model was well-fitted. The thermodynamic study suggested that the adsorption process is endothermic and spontaneous. Furthermore, the desorption efficiency of the GO/AC materials was tested through reusability in five cycles. An adsorption mechanism was also performed for the removal of EBT dye.

Calcined MgFe layered double hydroxides for magnetic separation and enhanced adsorption performance of methyl orange: Mechanism based on the memory effect

This study successfully synthesized magnetic MgFe-layered double oxides (MgFe-LDO-500 °C) by calcining MgFe-layered double hydroxides (MgFe-LDHs) at 500 °C. Calcination temperature was identified as a critical factor for optimizing adsorption capacity and activating a memory effect, with 500 °C being particularly effective. The adsorption performance of MgFe-LDO-500 °C towards methyl orange (MO) in aqueous solutions was evaluated across varying pH levels (2–12), initial MO concentrations (50–1800 mg/L), contact times (0–1440 min), and temperatures (25–45 °C). The results indicated that MgFe-LDO-500 °C adsorption conforms to the pseudo-second-order kinetic and Langmuir models, achieving a theoretical maximum adsorption capacity of 5087.76 mg/g. Characterization through scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Zeta potential analysis revealed that the outstanding adsorption performance of MgFe-LDO-500 °C towards MO involves a combination of electrostatic attraction, memory effect, and surface complexation. Moreover, after four regeneration cycles, the material maintained a 73 % MO removal efficiency and could be efficiently separated using magnetic separation technology. In conclusion, MgFe-LDO-500 °C represents a promising adsorbent for wastewater treatment.

Enhanced adsorption and removal of Cd(II) from aqueous solution by amino-functionalized ZIF-8

Zeolite imidazolate framework-8 (ZIF-8), which is a special subgroup of metal–organic frameworks (MOFs), was synthesized and modified by ethylenediamine (ZIF-8-EDA) to prepare an efficient adsorbent for the high sorption of Cd2+ ions from solution. The synthesized and modified ZIF-8 (ZIF-8-EDA) were characterized by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, Brunauer–Emmett–Teller (BET), field emission scanning electron microscopy (FE-SEM) with energy dispersive spectroscopy (EDS), and transmission electron microscopy (TEM) analysis. The optimum conditions for dosage of adsorbent, initial ion concentration, pH, and contact time were 0.05 g/l, 50 mg/l, 6, and 60 min, respectively, for cadmium ion sorption from aqueous solutions with a removal efficiency of 89.7% for ZIF-8 and 93.5% for ZIF-8-EDA. Adsorption kinetics and equilibrium data were analyzed using the Langmuir and Freundlich equations. The Langmuir model fitted the equilibrium data better than the Freundlich model. According to the Langmuir equation, the maximum uptake for the cadmium ions was 294.11(mg/g). The calculated thermodynamic parameters (ΔG°, ΔH°, and ΔS°) indicated that the adsorption process was feasible, spontaneous, and endothermic at 20–50 °C. Based on the results, the amino functionalized ZIF-8 had improved adsorption performance due to the replacing of the starting linker with organic ligands that had effective functional groups, leading to chemical coordination due to the interaction of metal ions with the non-bonding pair of electrons on the N atoms of the amino functional group. The selectivity toward metal ion adsorption by ZIF-8-EDA was Cd2+ > Pb2+ > Ni2+‏.

BIO-ADSORPTION OF HEAVY METAL ION FROM WATER USING ACTIVATED CARBON

The discharge of effluent polluted with heavy metals have become a growing concern for researchers around the world. This study evaluated the removal efficiency of commercial activated carbon and rice husk activated carbon as adsorbents for the removal of copper ion in water. A nominal size of 1 mm was obtained after sieving the Rice Husk, washed with distilled water, dried in an oven t at 80 ℃ for 12 hours, and pyrolyzed in a furnace at 550 ℃ for 30 minutes. The chars produced were later air-dried and then activated with lemon juice. The Rice Husk Activated Carbon (RHAC) and Commercial Activated Carbon (CAC) purchased from the market were both subjected to the following analyses: bulk density, X-ray Fluorescence (XRF), Brunauer–Emmett–Teller (BET), Scanning Electron Microscope (SEM) and Energy Dispersive X-ray (EDX) in order to characterise the adsorbents and to understand their suitability for the removal of copper ion in water. One of the properties of an adsorbent is large pores which is exhibited by the activated carbons as revealed by the SEM analysis. Likewise, the XRF and EDX analyses confirmed that the adsorbents had larger proportion of Silica (50.1 – 50.25%), Carbon (60.06 – 84.87 wt .%) and Oxygen (15.13 – 21.60 wt. %) which is a property of a good adsorbent. BET analysis showed that the surface areas of the rice husk activated carbon and the commercial activated carbon were 998.35 and 1208.25 m2/g, respectively. The bulk densities of the rice husk activated carbon and the commercial activated carbon were 0.3325 and 0.2812 g/cm3, respectively. The maximum removal efficiency using RHAC was observed at 60 ℃ and 120 minutes at 83.96 and 89.21 %, respectively while for CAC the maximum removal efficiency was observed at 60 ℃ at 84.61 % and 30 minutes at 83.3 %. Initial concentration of 20 mg/l was observed to have the highest removal efficiency for the two activated carbon specimens. The modelled effect of initial concentration, temperature and contact time on removal efficiency yielded R2 values of 1, 0.918; 1,1 and 1,1 respectively for the CAC and RHAC.

More Is Faster: Why Population Size Matters in Biological Search.

Many biological scenarios have multiple cooperating searchers, and the timing of the initial first contact between any one of those searchers and its target is critically important. However, we are unaware of biological models that predict how long it takes for the first of many searchers to discover a target. We present a novel mathematical model that predicts initial first contact times between searchers and targets distributed at random in a volume. We compare this model with the extreme first passage time approach in physics that assumes an infinite number of searchers all initially positioned at the same location. We explore how the number of searchers, the distribution of searchers and targets, and the initial distances between searchers and targets affect initial first contact times. Given a constant density of uniformly distributed searchers and targets, the initial first contact time decreases linearly with both search volume and the number of searchers. However, given only a single target and searchers placed at the same starting location, the relationship between the initial first contact time and the number of searchers shifts from a linear decrease to a logarithmic decrease as the number of searchers grows very large. More generally, we show that initial first contact times can be dramatically faster than the average first contact times and that the initial first contact times decrease with the number of searchers, while the average search times are independent of the number of searchers. We suggest that this is an underappreciated phenomenon in biology and other collective search problems.

Ru@Co3O4@g-C3N4 as a novel adsorbent for enhanced copper and cadmium abolition

Elimination of heavy metals from contaminated water systems is of prime distress due to their capacity to prompt toxic impact on the flora and fauna. The usage of innovative nano-engineered materials predominantly opens up smart prospects for the treatment of persistent heavy metal adulterated water resources. This study presents an ultrasonic-assisted sol-gel production of Ru@Co3O4@g-C3N4 nanostructure that was utilized to remove Cu+2 and Cd+2 ions from aqueous solutions. The X-ray diffraction investigation revealed the development of RuO2, Co2O3 and g-C3N4 phases, and the relevant elemental composition was verified by the photoelectron spectroscopy and EDX. The dispersion of the metal oxides within the nitride sheets was evidenced by scanning and transmission electron microscopy. The initial metal ions concentration, pH, and contact time effects were investigated through batch experiments. The adsorption isotherm models matched the Langmuir isotherm well, whereas the kinetics model data perfectly fitted the pseudo-second-order model. The maximum adsorption capacities of Cu+2 and Cd+2 ions on the nanocomposite Ru@Co3O4@g-C3N4 were 696.9 and 564.5 mg/g, respectively. A mechanism based on a viable covalent type of bonding developed by the delocalized -conjugated electrons of the triazine ring and functional groups were efficiently involved in the metal ions anchoring and ultimate elimination. Thus, the suitability of the Ru@Co3O4@g-C3N4 nanocomposite for eradicating heavy metals, including Cu+2 and Cd+2, was established.

Magnetic Magnetite-Graphene Oxide (Fe3O4-GO) Nanocomposites for Removal of Dyes from Aqueous Solution

AbstractMagnetic magnetite-graphene oxide (Fe3O4-GO) was synthesized using an in-situ precipitation technique and applied in the adsorption of cationic rhodamine B (RhB) and anionic methyl orange (MO) dyes from aqueous solution. The nanocomposite was characterized by different techniques including FTIR, XRD, Raman, XPS, PPMS, BET, SEM and TEM techniques. Batch adsorption studies were conducted to investigate the effect of solution pH, initial metal ion concentration, adsorbent dosage and contact time. The synthesized Fe3O4-GO exhibited characteristic magnetic properties (saturation magnetization of 34 emu/g) and it separated from aqueous solution with ease through the application of an external magnetic field. The adsorption equilibrium time on the adsorption of RhB and MO onto Fe3O4-GO showed best removal of 99.12% for RhB after 60 min, while MO was removed efficiently after 120 min with a removal efficiency of 97.60%. The adsorption of the azo dyes followed the pseudo-second-order kinetics model with high correlation coefficients (0.99995) for RhB and (0.99925) for MO. Maximum removal of the dye pollutants by occurred at pH 8 for RhB and pH 4 for MO, while the optimal adsorbent dosage was 30 mg. The results showed that adsorption equilibrium data were fitted to Langmuir isotherm model and maximum monolayer adsorption capacities for RhB and MO at 70.64 and 15.94 mgg−1, respectively. The magnetic adsorbents were reused for a maximum of 7 cycles and showed reasonable stability and reproducibility. Furthermore, the results showed that Fe3O4-GO nanocomposite can be used as an effective material in the removal of dyes from wastewater.

A promising approach for the removal of hexavalent and trivalent chromium from aqueous solution using low-cost biomaterial.

Heavy metal pollution is an enduring environmental challenge that calls for sustainable and eco-friendly solutions. One promising approach is to harness discarded plant biomass as a highly efficient environmental friendly adsorbents. In this context, a noteworthy study has spotlighted the employment of Euryale ferox Salisbury seed coat (E.feroxSC) for the exclusion of trivalent and hexavalent chromium ions. This study aims to transform discarded plant residue into a novel, environmentally friendly, and cost-effective alternative adsorbent, offering a compelling alternative to more expensive adsorption methods. By repurposing natural materials, we can contribute to mitigating heavy-metal pollution while promoting sustainable and economically viable solutions in environmental remediation. The effect of different parameters, i.e., chromium ions' initial concentration (5-25mg L-1), solution pH (2-7), adsorbent dosage (0.2-2.4g L-1), contact time (20-240min), and temperature (298-313K), were investigated. E.feroxSC proved highly effective, achieving 96.5% removal of Cr(III) ions at pH 6 and 97.7% removal of Cr(VI) ions at pH 2, with a maximum biosorption capacity of 18.33mg/g for Cr(III) and 13.64mg/g for Cr(VI), making it a promising, eco-friendly adsorbent for tackling heavy-metal pollution. The adsorption process followed the pseudo-second-order kinetic model, aligning well with the Langmuir isotherm, exhibited favorable thermodynamics, and was characterized as feasible, spontaneous, and endothermic with physisorption mechanisms. The investigation revealed that E.feroxSC effectively adsorbed Cr(VI) which could be rejuvenated in a basic solution with minimal depletion in its adsorption capacity. Conversely, E.feroxSC's adsorption of Cr(III) demanded rejuvenation in an acidic milieu, exhibiting comparatively less efficient restoration.

Guar gum, Ulva lactuca L. biomass, and xanthan gum-based copolymer novel biosorbent for adsorptive removal of acid orange 10

The textile industry's wastewater discharge into water bodies has become a significant environmental concern due to its toxicity and adverse impact on the ecosystem. In response, this study presents the development of a highly effective adsorbent (GG@ULB@XG composites) by employing guar gum (GG), Ulva lactuca L. biomass (ULB), and xanthan gum (XG), using the ionic gelation method. Various characterization techniques including XRD, SEM, TGA, Zeta Sizer, Zeta Potential, BET, FTIR, and Point of Zero charge (pHPZC) were utilized to analyze the properties of the GG@ULB@XG composites. The removal efficiency of the composite for Acid Orange 10 dye was found to be exceptional, achieving a remarkable 93% removal rate. Optimal adsorption parameters were determined, including initial AO10 concentration (100 ppm), temperature (298K), pH (3), adsorbent concentration (100 mg), and contact time (15 min) at 480 λmax. The thermodynamic analysis provided valuable insights into the thermal stability of the adsorbent. Additionally, a comprehensive investigation of adsorption isotherms (linear and non-linear), such as Elovich, Freundlich, D-R, Langmuir, and Temkin Isotherms, was conducted to better understand the adsorption behavior. Various linear and non-linear adsorption kinetics models, including Elovich, first-order, interparticle diffusion, and second-order kinetic models, were employed to gain deeper insights into the chemistry of the adsorption process. This study highlights the potential of GG@ULB@XG composites as an effective and environmentally friendly solution for water treatment and dye removal in industrial wastewater and sets a foundation for future studies in the field of environmental remediation.

Green synthesis of manganese ferrite magnetic nanoparticle and its modification with metallic-organic frameworks for the tetracycline adsorption from aqueous solutions: A mathematical study of kinetics, isotherms, and thermodynamics

In the current investigation, MnFe2O4/ZIF-8 nanocomposite was generated as a magnetic nanoadsorber using the extract of Dracocephalum plant and characterized by XRD, FTIR, VSM, BET, FESEM, EDS-mapping, TEM, XPS, TPD-NH3, and TGA analyses. Also, to determine its efficiency in the adsorption process of tetracycline, the effect of pH (3–9), nanocomposite dose (0.025–2 g/L), initial pollutant concentration (5–100 mg/L), contact time (5–200 min), and temperature (5–50 °C) were studied. The results of the morphological properties of the magnetic nanocomposite confirmed the spherical shape of this nanoadsorber with an average size of 54 ± 31 nm. BET analysis showed that modification of MnFe2O4 material with ZIF-8 as a new nanoadsorber leads to excellent modification of SBET (143.8 m2/g) and VTotal (0.44 cm3/g). The highest removal efficiency of tetracycline in optimal conditions (pH = 7, contact time = 120 min, nanocomposite dose = 1.5 g/L, and temperature = 20 °C for a tetracycline concentration of 20 mg/L) was 90.11%. As the temperature increased, the removal efficiency increased from 40.46% to 95.06% during 120 min, which indicates that the adsorption reaction is endothermic. In addition, the data obtained from the isotherms of Langmuir (R2 = 0.958), Freundlich (R2 = 0.534), and Temkin (R2 = 0.747) showed that the tetracycline adsorption is monolayer and on the homogeneous surface of the synthesized magnetic nanoadsorber. The elimination process of tetracycline by nanoadsorber followed the pseudo-second order model (R2 = 0.998). Investigating the effect of interfering ions also confirmed the decrease in the adsorption efficiency. Also, the investigation of the reusability of the synthesized magnetic nanoadsorber in tetracycline adsorption indicates that after eight cycles, the efficiency decreases by %16.51. According to the results, the magnetic nanocomposite synthesized in this work can be a suitable and economical adsorber for the removal of tetracycline from aqueous environments.

Efficiency of dry drinking water treatment sludge as adsorbent for methylene blue and acid red 97 removal from aqueous solutions

In this study, drinking water treatment sludge (DWTS) was applied after drying as adsorbent for the removal of methylene blue (MB) and acid red 97 (AR97) from aqueous solutions. DWTS powder was characterized by X-ray fluorescence, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods. The thermal behavior of DWTS was examined and leaching tests were carried out to study its chemical stability. DWTS is mainly composed of aluminum (24.65%) and silicium (6.157%) and it has a mesoporous structure with a surface area of 92 m2.g−1. Batch adsorption experiments of MB and AR97 were achieved taking into account the effect of pH, initial dye concentration, adsorbent mass, contact time and temperature. The pseudo-second-order kinetic model provided the best correlation for both dyes, and the intra-particle diffusion is not the only rate-limiting step during the adsorption. Furthermore, the adsorption of MB and AR97 followed the Langmuir isotherm model with a maximum adsorption capacity equal to 46.30 mg.g−1 and 135.13 mg.g−1, respectively. Thermodynamically, the negative values of ΔG° for both the dyes assumes that the adsorption is favored and spontaneous and that the reaction is endothermic (ΔH°>0) and exothermic (ΔH°<0) for MB and AR97, respectively. The entropy ΔS° is positive and proves that there is randomness at the liquid/solid interface during the adsorption process. The results also exhibited that the adsorption of both dyes is a physical process. Finally, DWTS can be considered an effective and low-cost adsorbent due to its simple physical conditioning requiring only dewatering and grinding.

Adsorption of Scandium Ions by Amberlite XAD7HP Polymeric Adsorbent Loaded with Tri-n-Octylphosphine Oxide.

In an actual economic context, the demand for scandium has grown due to its applications in top technologies. However, further development of new technologies will lead to an increase in the market for Sc related to such technologies. The present study aims to improve and upgrade existing technology in terms of efficient scandium recovery, proposing a new material with selective adsorptive properties for scandium recovery. To highlight the impregnation of Amberlite XAD7HP resin with tri-n-octylphosphine oxide extractant by the solvent-impregnated resin method, the obtained adsorbent material was characterized by physico-chemical techniques. Further, the specific surface of the adsorbent and the zero-point charge of the adsorbent surface have been determined. Different parameters, such as initial concentration, adsorbent amount, contact time, or temperature, have been studied. The initial pH effect was investigated when a maximum adsorption capacity of 31.84 mg g-1 was obtained at pH > 3, using 0.1 g of adsorbent and a contact time of 90 min and 298 K. An attempt was made to discuss and provide a clear representation of the studied adsorption process, proposing a specific mechanism for Sc(III) recovery from aqueous solutions through kinetic, thermodynamic, and equilibrium studies. Adsorption/desorption studies reveal that the prepared adsorbent material can be reused five times.

Preparation of versatile polymer particles and their application for elimination of bromophenol blue and phenol from aqueous environment

Cellulose, activated carbon, zeolite, and similar materials have a weak effect against anionic pollutants. Therefore, further modifications are needed for the use of such substances. In this study, polymer particles (GD) that were economical and directly effective against anionic pollutants were synthesized as an alternative. GD particles were synthesized with glutaraldehyde and diethylenetriamine as monomers for the first time. The polymer particles were characterized in detail. Then, GD particles were used in the adsorption of anionic Bromophenol blue (BPB) and phenol (PH). As a result, it was determined that i) the adsorption process between GD particles, Bromophenol blue and phenol was chemisorption, ii) the adsorption of BPB and PH on to GD particles obeyed the Langmuir isotherm and pseudo second order kinetic model. pH, temperature, initial dye concentration, adsorbent dosage, and contact time were determined orderly 4, 50 °C, 300 mg L−1, 10 mg, and 180 mins for BPB and 5, 50 °C, 10 mg L−1, 15 mg, and 30 mins for PH. The maximum adsorption capacities of GD polymer particles for BPB and PH were ascertained as 136.40 mg g−1 and 98.26 mg g−1, respectively. As a result, it was produced economical, simple, feasible, and functional adsorbents against anionic pollutants.

Neuromuscular Performance of World-Class Judo Athletes on Bench Press, Prone Row and Repeated Jump Tests

Judo is a sport that requires multiple high-intensity moments during the fight and high neuromuscular performance. Although not often, the explosive actions of the lower limbs can be decisive to winning in combat. This study aims to identify the differences in the neuromuscular features of the range of movements of the upper and lower limbs between the top-elite and elite male judo athletes. This cross-sectional study included 63 high-level male judo athletes, who were classified into two level groups: (i) top-elite (n = 30; age: 23.5 ± 3.2 years) and (ii) elite (n = 33; age: 22.6 ± 2.9 years). All the participants went to the laboratory for neuromuscular evaluations in the bench press (BP), prone row (PR), and repeated jump in 30 s (RJ30) tests. The results show that the top-elite judo athletes are superior in all the upper-body neuromuscular attributes studied. These differences were significantly superior in (i) BP peak velocity (p &lt; 0.01), maximum load 1RM, power (peak and mean), force (peak and mean), force mean to peak power, and rate of force development (RFD) (all, p &lt; 0.001); and (ii) RP maximum load 1RM (p &lt; 0.01), power load (kg, p &lt; 0.001; % 1RM, p &lt; 0.05), peak power (p = 0.010), power mean (absolute, p &lt; 0.01; relative, p &lt; 0.05), force mean (p &lt; 0.05), force mean to peak power (absolute, p &lt; 0.05) and RFD (p &lt; 0.001). However, no significant differences were observed in the BP and PR time to peak force, time to peak power, and time between peaks (power and force). In the RJ30, it was observed that the initial contact time (T1) of top-elite athletes is significantly lower than that of elite athletes (p &lt; 0.05) and that power at 15 (T2) and 30 (T3) seconds is significantly higher in top-elite athletes (T2, p &lt; 0.05; T3, p &lt; 0.01). The main effect of the performance group was significant in contact time (p &lt; 0.05), and the main effect of time was statistically significant in jump height (p &lt; 0.001), power (p &lt; 0.001), force (p &lt; 0.001) and velocity (p &lt; 0.01). In addition, jump height (p &lt; 0.01; η2p = 0.088) and power (p &lt; 0.05; η2p = 0.068) showed a significant interaction between time and performance group. These results suggested that the observed superiority of the top-elite judo athletes in neuromuscular attributes can determine success in judo competitions. This observation reinforces that neural and metabolic profiles must be considered to increase the effectiveness of maximal power training for the upper and lower body.