Adsorbent For Adsorption Research Articles

A data driven machine learning approach for predicting and optimizing sulfur compound adsorption on metal organic frameworks

This study employed some machine learning (ML) techniques with Python programming to forecast the adsorption capacity of MOF adsorbents for thiophenic compounds namely benzothiophene (BT), dibenzothiophene (DBT), and 4,6-dimethyl dibenzothiophene (4,6-DMDBT). Five ML models were developed with the help of a dataset containing 676 rows to correlate the adsorbent features, adsorption conditions, and adsorbate characteristics to the MOF sample’s sulfur adsorption capability. Among the ML approaches, MLP model achieved the best performance with a low mean squared error (MSE) of 0.0032 on the test set and 0.0021 on the training set and mean relative error (MRE) of 15.26% on the test set. Also, Random Forest model yielded a higher test MSE of 0.0045 and MRE of 17.83%. Feature importance analysis was performed by utilizing MLP model and shapely additive plan (SHAP) method, and the findings revealed that “initial concentration of sulfur” (SHAP value 0.51) and “contact time” (SHAP value 0.37) were the crucial factors influenced desulfurization process efficiency. Additionally, a comparative analysis of the features utilizing the MLP network classified the factors into three primary categories: process conditions, adsorbent characteristics, and adsorbate characteristics. Consequently, the process condition was identified as the most significant group compared to others. Finally, the desulfurization process optimization indicated the maximum DBT adsorption of 161.6 mg/g for Zr-based MOF could be achieved when the features including BET, TPV, pore size, oil/adsorbent ration, and temperature were tuned around 756 m2/g, 0.955 cm3/g, 5.96 nm, 449.85 g/g, 20.1 °C, respectively.

Purification of Biodiesel Polluted by Copper Using an Activated Carbon Prepared from Spent Coffee Grounds: Adsorption Property Tailoring, Batch and Packed-Bed Studies

Biodiesel produced via oil transesterification often contains metallic impurities, such as copper, which affects its quality and engine performance. This study explores the use of activated carbon prepared from spent coffee grounds to remove copper from biodiesel. Activated carbon samples were prepared via biomass pyrolysis and chemical activation with KOH and HNO3. The optimal conditions for copper adsorption were determined using a Taguchi L9 design. Maximum adsorption capacities were 13.4 and 17.3 mg/g at 30 and 40 °C, respectively, in batch adsorbers. In packed-bed columns, the axial dispersion reduced the adsorption efficiency obtaining bed adsorption capacities from 1.9 to 5.1 mg/g under tested experimental conditions. Adsorbent characterization and adsorption modeling indicated that copper removal was driven by multi-cationic interactions, where carboxylic groups from carbon surface acted as key active sites. The new adsorbent outperformed commercial bone char, making it a cost-effective alternative to improve biodiesel production contributing to the energy matrix diversification.

Research progress on the source, adsorption treatment and conversion technology of CO2

As an important greenhouse gas, the increase in emissions of carbon dioxide (CO2) has become one of the main drivers of global climate change. This paper systematically discusses the source, adsorption treatment method and conversion technology of CO2. First of all, the sources of CO2 are divided into two categories: natural processes and human activities. Among them, CO2 generated by human activities is the main cause of environmental problems such as global warming. Subsequently, the article introduces the adsorption method as an important means of CO2 treatment, covering the adsorption principle, common adsorbent types, adsorption process and adsorption regeneration methods. Finally, this paper focuses on the conversion technology of CO2, including thermal catalytic conversion, photocatalytic conversion and electrocatalytic conversion. Each method has unique advantages and challenges, and provides different ideas and solutions for the effective conversion and utilization of CO2.

KOH-activated tire pyrolysis char as an adsorbent for chloroorganic water pollutants

Activated carbons (ACs) produced from end-of-life tires with different tire pyrolysis char (TPC)-to-activator (KOH) ratios of 1:2, 1:3, and 1:4 were prepared and characterized. These materials were used as adsorbents for the removal of two common chloroorganic water contaminants such as 2,4-dichlorophenol (DCP) and 2,4-dichlorophenoxyacetic acid (2,4-D). The adsorption kinetics, equilibrium adsorption, and effects of solution pH were investigated. The adsorption of both adsorbates was found to be pH-dependent and preferred in acidic environments. The adsorption kinetics was evaluated using pseudo-first-order and pseudo-second-order kinetic models and mechanism - using Weber-Morris and Boyd models. Results demonstrated that the adsorption of DCP and 2,4-D on all ACs followed the pseudo-second-order model and was controlled by film diffusion. The Langmuir isotherm described the equilibrium data better than the Freundlich isotherm model. The maximum adsorption capacity of DCP adsorbed on AC1:2, AC1:3, and AC1:4 at equilibrium was 0.582, 0.609, and 0.739 mmol/g, respectively, while the maximum adsorption capacities for 2,4-D were 0.733, 0.937, and 1.035 mmol/g, respectively. The adsorption rate and efficiency were closely correlated with the porous structure of the tested adsorbents. The results showed that the activated carbons obtained from the scrap of end-of-life tires as raw materials could be used as a low-cost and alternative adsorbent for the removal of chlorinated organic pollutants from water.

Preparation strategy of molecularly imprinted polymers adsorbent based on multifunctional carrier for precise identification and enrichment of fenthion

Due to the existence of organophosphorus pesticides (OPs) in the environment and their potential hazards to ecosystems and human health, this study aimed to develop a novel adsorbent of OPs using multifunctional carriers and surface molecular imprinting technology (SMIT). SiO2-COOH served as a carrier, and molecularly imprinted polymers (MIPs) constituted a shell, creating a core-shell structured adsorbent. SMIT facilitated rapid and efficient binding between the target molecules and the imprinted cavities. The multifunctional SiO2-COOH enhanced the adsorbent's adsorption capacity, improved its mechanical stability, and strengthened the binding with the MIPs. The adsorbent demonstrated excellent specificity and reusability, achieving an adsorption capacity of 54.4 mg/g and the imprinting factor of 2.94. The relative recovery rate in actual sample detection ranged from 95.1% to 108.7%. This study provides a simple and effective method for detecting hazardous factors in environment protection and food safety fields, with significant scientific value and practical application potential.

Fabrication of tannic acid-incorporated polyvinylpyrrolidone/polyvinyl alcohol composite hydrogel and its application as an adsorbent for copper ion removal

An effective tannic acid-incorporated polyvinylpyrrolidone/polyvinyl alcohol composite hydrogel with high-potential sorption capacity was developed for the removal of copper from aqueous solution. The composite hydrogel exhibited pH-dependent swelling, in which swelling and shrinking occurred reversibly with adjustment of the pH of the medium. At pH 4, the maximal adsorption capacity for copper at 30 °C was 297.0 mg g-1, and the adsorbent dose was 4 g L-1. The adsorption kinetics were best fitted with a pseudo-second order kinetic model. The adsorption behavior was well predicted by the Freundlish isotherm. The thermodynamics parameters indicated a spontaneous and exothermic reaction with an increase in the entropy of the system. The chemical changes in the film structure before and after adsorption treatment were characterized by Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS). The FTIR, XPS and XAS results confirmed that Cu bound to the oxygens in the -OH, C = O and N-(C = O)- functional groups on the T-HD. XAS analysis revealed the chemical composition and molecular geometry of the adsorbed copper ions. The single-solute adsorption and coadsorption mechanisms, which provide insight into cobalt-copper, nickel-copper, or nickel-cobalt-copper complex solutions, were investigated. The composite hydrogel exhibited excellent regeneration ability in EDTA solution. Notably, the adsorbent retained an adsorption efficiency exceeding 87% even after five regeneration cycles. On the basis of both adsorbent characteristics and adsorption performance, it was determined that the composite hydrogel has the potential to be used as a platform for developing materials to treat wastewater containing high levels of metal contaminants such as those from the electroplating industry.

Boosting the phosphorus uptake of La2(CO3)3·8H2O based adsorbents via sodium addition: Relationship between crystal structure and adsorption capacity

Excess phosphate contents in water bodies triggers eutrophication, which posts significant challenges to the aquatic ecosystem. Lanthanum-carbonate based adsorbents exhibit excellent phosphate binding properties for remediating eutrophication. However, they suffer from significant adsorption-capacity loss (>85 %) at high pH. Little has been done on understanding this behavior for improving the phosphorus adsorption of lanthanum-carbonate adsorbents in alkaline environments (e.g. eutrophic water bodies). Here, we discover that La2(CO3)3·8H2O, when produced by a conversion reaction from NaLa(CO3)2·xH2O, exhibits high phosphate adsorption capacity in a wide pH window. Under alkaline conditions (e.g. pH = 10), its adsorption capacity decreases by only 8 % compared to the value under neutral pH. By isolating three different lanthanum-carbonate based compounds and analyzing their molecular structures, we find that the trace amount of Na+ residual in our La2(CO3)3·8H2O alters the chemical environment surrounding the La3+ ions, which may significantly boost the phosphate uptake at high pH. Our results provide molecular insights for further tuning the material structure of phosphate adsorbents to achieve robust performances.

Comparison of biocrude production and characterization from Persian Gulf Sargassum angustifolium macroalgae, Chlorella vulgaris, and Spirulina sp. microalgae using hydrothermal liquefaction (HTL): Potential of solid residue for heavy metal adsorption.

Biocrude production using the hydrothermal liquefaction (HTL) process is a promising alternative energy source to conventional fossil fuels. Using algal feedstock types in this process has many advantages, such as not needing to dry a high moisture content, which consumes much energy. In this study, the feedstock types of Sargassum angustifolium macroalgae, Chlorella vulgaris, and Spirulina sp. microalgae affected the yield and property of the biocrude products were obtained at 350 °C, 18 MPa, 35 min residence time, and 8.7 wt% feedstock concentration. The biocrude yields from Sargassum angustifolium, Chlorella vulgaris, and Spirulina sp. were 26.15 wt%, 55.8 wt%, and 56.32 wt%, respectively. These values revealed that feedstock's carbon and nitrogen contents have the most effect on the biocrude yield, and increasing these elements increases the biocrude yields. Moreover, the properties of the produced biocrudes revealed that the main components were esters, organic acids, ketones, aldehydes, aromatic rings, amides, amines, alcohol, and phenol. The thermal gravimetric analysis (TGA) results of biocrudes showed the decomposition of more organic components at the 175-600 °C temperature range. Also, the simulated distillation of biocrudes showed that most biocrude components from Sargassum angustifolium and Chlorella vulgaris are the same as heavy naphtha, and the biocrude from Spirulina sp. is similar to kerosene. These results showed that the produced biocrude from Chlorella vulgaris has a higher yield and quality than other resources. The quality of the biocrude produced from Sargassum angustifolium is comparable to other biocrudes. Besides, the higher solid-phase yield produced from Sargassum angustifolium was used as a heavy metal biosorbent. The effect of adsorbent concentration and adsorption time on adsorption efficiency was investigated. Results showed that the maximum adsorption efficiency of Fe2+, Zn2+, and Mn2+ was 47.07 wt%, 48.93 wt%, and 42.47 wt%, respectively, at 2 g/L adsorbent concentration and 60 min adsorption time, and the structure destruction of the solid phase was carried out under the biosorption process.

Impact of Adsorbent Weight, Time, and Temperature on Purification Efficiency with Activated Carbon

Based on data from the Indonesian Biofuel Producers Association 2022, biodiesel production will reach 10.8 billion liters, producing crude glycerol of 10-20% of the total product volume in the transesterification process. Crude Glycerol is a by-product of making biodiesel with low purity because it still contains impurities such as methanol, free fatty acids, KOH catalysts, and water. These impurity compounds must be removed so that the quality of glycerol increases and has a high selling value. Adsorption is one method that can be used to absorb these impurity compounds. This research aims to determine the effect of adsorbent weight, adsorption time, and temperature on glycerol purity levels. This experimental research uses an exploratory factorial design method to determine the most influential factors. The low level of adsorbent weight used is 9%, while the high level of adsorbent weight is 15%. The low-level adsorption time is 60 minutes and the high level is 90 minutes. The adsorption temperature used is a low level of 40℃ and a high level of 80℃. The research results showed that the weight of the adsorbent was the factor that had the most influence on the purity level of glycerol

A Review on Adsorption in Nanoporous Adsorbents for Gas Decontamination: Space Applications and Beyond

A Review on Adsorption in Nanoporous Adsorbents for Gas Decontamination: Space Applications and Beyond

Artificial Neural Network Modeling of the Removal of Methylene Blue Dye Using Magnetic Clays: An Environmentally Friendly Approach

In this study, the effectiveness of Fe3O4-based clay as a cost-effective material for removing methylene blue (MB) dye from aqueous solutions was evaluated. The structural properties of the clay and Fe3O4-based clay were analyzed using SEM, XRF, BET, XRD, FTIR, and TGA techniques. In this research, the effects of various aspects, such as adsorbent amount, contact time, solution pH, adsorption temperature, and initial dye concentration, on the adsorption of Fe3O4-based clay are investigated. The experiments aimed at understanding the adsorption mechanism of Fe3O4-based clay have shown that the adsorption kinetics are accurately described by the pseudo-second order kinetic model, while the equilibrium data are well represented by the Langmuir isotherm model. The maximum adsorption capacity (qm) was calculated as 52.63 mg/g at 25 °C, 53.48 mg/g at 30 °C, and 54.64 mg/g at 35 °C. All variables affecting the MB adsorption process were systematically optimized in a controlled experimental framework. The effectiveness of the artificial neural network (ANN) model was refined by modifying variables such as the quantity of neurons in the latent layer, the number of inputs, and the learning rate. The model’s accuracy was assessed using the mean absolute percentage error (MAPE) for the removal and adsorption percentage output parameters. The coefficient of determination (R2) values for the dyestuff training, validation, and test sets were found to be 99.40%, 92.25%, and 96.30%, respectively. The ANN model demonstrated a mean squared error (MSE) of 0.614565 for the training data. For the validation dataset, the model recorded MSE values of 0.99406 for the training data, 0.92255 for the validation set, and 0.96302 for the test data. In conclusion, the examined Fe3O4-based clays offer potential as effective and cost-efficient adsorbents for purifying water containing MB dye in various industrial settings.

Synergistic effects of multi-walled carbon nanotubes and Mn0.4Cu0.6Fe2O4 on mercury removal with high efficiency and sulfur resistance

Although ferrite-based adsorbents are the potential mercury removal materials for the high thermal stability, they usually suffer from a low efficiency in flue gas environment, especially under SO2 condition. In the present paper, the multi-walled carbon nanotubes (MWCNTs) are utilized to improve the adsorption capacity of the Mn0.4Cu0.6Fe2O4 adsorbents as well as inhibit the influence of flue gas composition. The influences of temperature, adsorbent type and the flue gas composition on Hg0 removal efficiency are evaluated by experiments. The physical adsorption property of MWCNTs provides a platform for Hg0 oxidation by Mn0.4Cu0.6Fe2O4. The synergistic effect between MWCNTs and Mn0.4Cu0.6Fe2O4 enhances the mercury removal efficiency as well we the sulfur resistance. The results find that the adsorbent of Mn0.4Cu0.6Fe2O4 containing 14 % MWCNTs has a high mercury removal efficiency of 95.6 % at 120 °C even under 1000 ppm SO2 concentration. The kinetic behaviors of adsorbent adsorption are analyzed by theoretical models. The mechanisms of porous carbon-containing modifier to improve the mercury removal performance of Mn0.4Cu0.6Fe2O4 are explored carefully. The present ferrite-based adsorbent exhibits promising prospects for the practical industrial applications of the low temperature mercury removal from coal-fired flue gas.

Effect of modifiers on Cr (VI) adsorption performance of activated modified-hydrochars

Hexavalent chromium (Cr (VI)) is high toxic and solubility in aquatic systems, which has attracted severe environment issues. In this work, corn straw, as raw biomass material, was modified by citric acid, ZnCl2, NaOH, or (NH4)2Fe(SO4)2 via hydrothermal carbonization process, and further activated by KOH to obtain the activated modified-hydrochars. The influence of different modifiers on the Cr (VI) adsorption performance for activated modified-hydrochars was investigated by controlling adsorbent dosages, adsorption time and different Cr (VI) concentrations at pH of 3.0 under room temperature. Among these absorbents, the activated modified-hydrochar modified by ZnCl2 possessed the excellent microporous characteristics and a high specific surface area of 1532.904 m2 g−1, thus exhibiting the Cr (VI) removal rate of 99.6 wt%. Cr (VI) was reduced to Cr (III) by -OH of activated modified-hydrochars during the Cr (VI) adsorption experiments. Due to higher R2 (>0.99) by kinetics analysis, pseudo-second-order kinetics was confirmed and further the Cr (VI) removal for the activated modified-hydrochars was a chemical adsorption process. The regression coefficients (R2) of the Langmuir model for all activated modified-hydrochars were higher than those of Freundlich model, which meant that Langmuir monolayer chemisorption was more consistent with the Cr (VI) adsorption process in this work.

Synthesis and enhanced adsorption for F− by three novel high entropy LDHs using TEA-assisted hydrothermal technology

Nowadays the design, preparation and application of high entropy LDHs (HE-LDHs) has already become research hotspots. In this paper, three types of high entropy ZnCoCrMgZr-LDHs (HE-LDHs-1, 2 and 3) were successfully prepared for the first time using TEA as alkali source by simple hydrothermal synthesis, and characterized by XRD, TG, SEM, X-ray photoelectron spectroscopy, BET and zeta potential. The effect of triethanolamine (TEA) on the formation of high entropy LDHs and their adsorption behaviour for F− were investigated. Research showed that high content of TEA can maintain and provide more hydroxyl groups required for the formation of LDHs, while the introduction of high valence Zr4+ breaks the regular arrangement of LDHs themselves. Three types of high entropy LDHs have excellent adsorption performance for F− with the maximum adsorption capacities of 113.78 mg/g, 142.12 mg/g and 128.24 mg/g, respectively. They also have strong resistance to anionic interference. The adsorption process is the transition from physical adsorption to chemical adsorption in the F− adsorption process from HE-LDHs-1 to 3. The adsorption isotherm models of LDHs-1 exhibit high R2 values which shown that their F− adsorption behaviour is the result of the combined effect of physical and chemical adsorption. The adsorption behaviour of LDHs-2 and 3 is more in line with the quasi second-order kinetic model and Langmuir model, indicating that the F− adsorption process is a single-layer adsorption based on chemical reaction-controlled kinetics. The lower temperatures are more conducive to the process for all three adsorbents adsorption process generates heat. FLDHs can still re-adsorb the dye CR after four cycles of adsorbing fluoride ions. HE-LDHs exhibit high adsorption, selectivity, and good reuse performance for fluoride ions, making them promising for wastewater treatment applications.

Research on Modification of Oxygen-Producing Adsorbents for High-Altitude and Low-Pressure Environments

In oxygen production on plateaus, pressure swing adsorption (PSA) oxygen production is currently the most commonly used oxygen production method. In plateau regions, low pressure leads to a decrease in adsorbent nitrogen–oxygen separation performance, which affects the performance of PSA oxygen production, so it is particularly important to enhance adsorbent nitrogen–oxygen separation performance. In this paper, Li-LSX (lithium low-silicon aluminum X zeolite molecular sieve) adsorbents were modified using the liquid phase ion exchange method, and five kinds of modified adsorbents were obtained, namely AgLi-LSX, CaLi-LSX, ZnLi-LSX, CuLi-LSX, and FeLi-LSX, respectively. The influences of different metal ions and modification time lengths on the adsorbent nitrogen adsorption and nitrogen–oxygen separation coefficients were analyzed. Through theoretical calculations, the nitrogen and oxygen adsorption and separation performances of the modified adsorbents at different altitudes and low adsorption pressures were investigated. It is shown that the nitrogen adsorption capacity of the AgLi-LSX-1 adsorbent obtained from the modification experiment reaches 27.92 mL/g, which is 3.24 mL/g higher than that of Li-LSX; the nitrogen–oxygen separation coefficients of S1 and S2 are 19.24 and 7.54 higher, respectively; and the nitrogen–oxygen separation coefficients of S4 are 20.85 and 7.54 higher than those of Li-LSX, respectively. With the increase in altitude from 50 m to 5000 m, the nitrogen–oxygen separation coefficient of the AgLi-LSX-1 adsorbent increased rapidly from 20.85 to 57, and its nitrogen–oxygen separation coefficient S4 exceeded that of the Li-LSX adsorbent to reach 47.61 at an altitude of 4000 m. Therefore, the modified adsorbent AgLi-LSX-1 in this paper can enhance the performance of the PSA oxygen process for oxygen production in plateau applications.

Evaluation of potential adsorbents for simultaneous adsorption of phosphate and ammonium at low concentrations

Evaluation of potential adsorbents to tackle eutrophication caused by low concentrations of phosphate and ammonium are rarely reported in the literature. Besides, the dynamics/mechanisms for removal of these pollutants at low concentration are yet to be explored. In this study we used five different adsorbents, including La-modified zeolite (LMZ), MgFe-modified biochar (MgFe-BC), phoslock, activated alumina (AA), and diatomaceous earth (DE) to evaluate the removal of these pollutants. Among the selected adsorbents in this study, LMZ and AA both exhibited effective and simultaneous adsorption for phosphate and ammonium and the maximum adsorption capacities were 2.47 mg/g and 3.07 mg/g, respectively. The presence of SO42− and CO32− negatively impacted phosphate adsorption, while Fe3+ and K+ ions inhibited ammonium adsorption. LMZ adsorption kinetics was over 3 times faster than other adsorbents within 60 min reaction time. Kinetics studies and isotherms revealed that the removal of phosphate and ammonium was primarily driven by chemical interactions and monolayer adsorption and were better fitted by Langmuir isotherm than the Freundlich isotherm and kinetic study was effectively described by Pseudo-second-order kinetic model. FTIR and XPS analysis revealed that the key mechanisms for phosphate adsorption were electrostatic attraction and inner sphere complexation through ligand exchange, whereas ammonium adsorption was mainly governed by ion exchange. Desorption study revealed that LMZ material was stable after three desorption cycles. This study offers vital knowledge on the nature of adsorption and interactions of potential mesoporous adsorbents with eutrophication-causing pollutants in lakes and rivers and proposes effective remedial mean.

Development of Magnetic Porous Polymer Composite for Magnetic Solid Phase Extraction of Three Fluoroquinolones in Milk.

In this study, a magnetic porous polymer composite with both hydrophilic and hydrophobic groups was synthesized for magnetic solid phase extraction (MSPE) of milk substrates. Optimization was conducted on various parameters, including adsorption dose, solution pH, adsorption time, and some elution conditions. Coupled with a high-performance liquid chromatography fluorescence detector, a novel MSPE method for determination of norfloxacin (NFX), ciprofloxacin (CIP), and enrofloxacin (ENR) in milk was developed based on magnetic metal organic framework polystyrene polymer (Fe3O4@MOF@PLS) as adsorbent. The Fe3O4@MOF@PLS exhibited significantly improved adsorption performance compared to MOF and PLS. Under optimized experimental conditions, the method exhibited good linearity for the three fluoroquinolones (FQs) in the range of 0.5-1000 μg/kg, with limit of detections (LODs) ranging from 0.21 to 1.33 μg/kg, and limit of quantitations (LOQs) from 0.71 to 4.42 μg/kg. The relative standard deviation (RSD) for the three FQs were 3.4-8.8%. The recoveries of three FQs in milk samples ranged from 84.2% to 106.2%. This method was successfully applied to the detection of three FQs in 20 types of milk, demonstrating its simplicity, speed, and effectiveness in analyte enrichment and separation. The method presented advantages in adsorbent dosage, adsorption time, LODs, and LOQs, making it valuable for the analysis and detection of FQs in milk.

Development of Fe-Doped Ni2P-POx Electrocatalyst for Oxygen Evolution Reaction

Water electrolysis is extensively researched as a next-generation energy storage method to overcome the intermittency of renewable energy. Electricity generated from renewable sources such as solar and wind power can be converted into pure green hydrogen through water electrolysis. Despite the potential of green hydrogen as a renewable energy storage/carrier medium, the high overpotential resulting from the slow kinetics of oxygen evolution reaction (OER) and the use of expensive noble metals make cost-competitive hydrogen production a significant challenge. Anion exchange membrane water electrolysis (AEMWE) is one method for hydrogen production, offering economic advantages over proton exchange membrane systems as it allows for the use of relatively inexpensive transition metal catalysts like Ni, Fe, and Co due to its alkaline environment.Nickel phosphide (Ni2P)-based catalysts have emerged as highly promising candidates to accelerate the electrocatalytic OER. In particular, the introduction of Fe into Ni2P has been found to induce charge transfer, optimizing the electronic structure and accelerating the OER process. OER catalysts based on transition metal phosphides often exhibit a core-shell structure with phosphide at the core and oxide at the shell during OER measurements. This core-shell structure enhances OER performance through the oxide shell, complementing the deficient electrical conductivity of the phosphide core, resulting in superior catalytic activity and durability. From this perspective, transition metal phosphates are also being studied as electrocatalysts for OER. Phosphates, such as PO3 -, not only promote oxygen adsorbate adsorption but also induce a distorted local metal center geometry that favors OH- adsorption and further oxidation.To address these challenges, this study develops a facile and scalable synthesis of iron-doped nickel phosphide-phosphate (Fe-doped Ni2P-POx) nano-hybrid system as a superior noble-metal free OER powder-catalyst. The utilization of self-filling and pyrolysis approaches facilitates economically viable production of the highly porous phosphide catalyst with a high specific surface area and rough surfaces. X-ray diffractometer, X-ray photoelectron spectroscopy, and electron paramagnetic resonance elucidates the electronic structure modulation, resulting in phosphide-phosphate nano-hybrid structures. Consequently, the catalyst demonstrates excellent OER activity in 1 M KOH, with a significantly low overpotential of 283 mV at 20 mA cm-2, a small Tafel slope of 28.4 mV dec-1, and a superior exchange current density of 8.22 mA cm-2, surpassing state-of-the-art PGM catalysts. Furthermore, its durability over 20 hours indicates its excellent stability, mass transport properties, and mechanical robustness in alkaline media, underscoring its potential as an efficient OER catalyst to facilitate electrocatalytic hydrogen production. Figure 1

Selective recovery of esterase from Trichoderma harzianum through adsorption: Insights on enzymatic catalysis, adsorption isotherms and kinetics

In recent years, numerous attempts have been made to develop a low-cost adsorbent for selectively recovering industrially important products from fermentation broth or complex mixtures. The current study is a novel attempt to selectively adsorb esterase from Trichoderma harzianum using cheap adsorbents like bentonite (BT), activated charcoal (AC), silicon dioxide (SiO2), and titanium dioxide (TiO2). AC had the highest esterase adsorption of 97.58% due to its larger surface area of 594.45 m3/g. SiO2 was found to have the highest selectivity over esterase, with an estimated purification fold of 7.2. Interestingly, the purification fold of 5.5 was found in the BT-extracted fermentation broth. The functional (FT-IR) and morphological analysis (SEM-EDX) were used to characterize the adsorption of esterase. Esterase adsorption on AC, SiO2, and TiO2 was well fitted by Freundlich isotherm, demonstrating multilayer adsorption of esterase. A pseudo-second-order kinetic model was developed for esterase adsorption in various adsorbents. Thermodynamic analysis revealed that adsorption is an endothermic process. AC has the lowest Gibbs free energy of −10.96 kJ/mol, which supports the spontaneous maximum adsorption of both esterase and protein. In the desorption study, the maximum recovery of esterase from TiO2 using sodium chloride was 41.34 %. Unlike other adsorbents, the AC-adsorbed esterase maintained its catalytic activity and stability, implying that it could be used as an immobilization system for commercial applications. According to the kinetic analysis, the overall rate of the reaction was controlled by reaction kinetics rather than external mass transfer resistance, as indicated by the Damkohler number.

Novel activated carbon derived from a sustainable and low-cost palm leaves biomass waste for tetracycline removal: Adsorbent preparation, adsorption mechanisms and real application

Palm leave biomass waste was converted into a new activated carbon through facile chemical activation and pyrolysis. The prepared activated carbon (KAC) was characterized by X-Ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), surface area analyzer (BET), and point of zero charge (pHPZC) measurement. KAC was used as an adsorbent to remove emerging contaminant tetracycline (TC) from water, and systematic TC adsorption studies (i.e. kinetics, isotherm, and thermodynamic) were performed. Moreover, density functional theory (DFT) was applied to simulate the TC adsorption process. The adsorption kinetics data corroborated the pseudo-second-order model perfectly. The maximum monolayer adsorption capacity was 132.94 mg g−1 at 25 °C. According to the thermodynamics study, the adsorption process of TC was favorable and endothermic, while the process increased the randomness of molecules at the interface between water and solid. TC adsorbed onto KAC via π-π interaction, H-bonding, electrostatic interaction, and pore-filling. TC adsorption mechanism elucidated by DFT calculations showed good agreement with the experimental findings. The reusability of KAC in real wastewater was also tested for three cycles. This study shows that converting of the abundant palm leaves biomass waste into a valuable adsorbent for TC removal is promising.