Papers by Keyword: Adsorption

Abstract: This study examines the adsorption behavior of textile dyes Crystal Violet (CV), Methylene Blue (MB), and Congo Red (CR) within cyclodextrin-based metal-organic frameworks (CD-MOFs) using simulated annealing and molecular dynamics simulations. The lowest-energy configurations revealed that CV is predominantly trapped within the central cavity of CD-MOF, stabilized by strong hydrogen bonding between cyclodextrin moieties and the amine group of CV. The adsorption energy of -74.84 kJ mol^-1 suggests strong interaction, indicative of chemisorption-like behavior. MB and CR, in contrast, were primarily adsorbed within the side cavities of CD-MOF, exhibiting adsorption energies of -47.55 kJ mol^-1 and -718.17 kJ mol^-1, respectively. The stability of these dye-CD-MOF complexes was confirmed by molecular dynamics, with low root-mean-square deviations (RMSD) and consistent radii of gyration over 10 ns simulations. Electrostatic and van der Waals interactions played a critical role in maintaining dye entrapment, ensuring prolonged retention within the MOF structure. These results highlight the potential of CD-MOFs as effective adsorbents for dye removal in wastewater treatment, with strong and stable dye-MOF interactions preventing desorption and ensuring efficient pollutant capture.

Abstract: This study evaluated the adsorption of Zn²⁺ from simulated mining wastewater using unmodified sugarcane bagasse-derived biochar (U-SCBB) and NaClO-modified sugarcane bagasse-derived biochar (SH-SCBB). The effectiveness of NaClO modification in enhancing the biochar's adsorption capacity was a key focus of this research. Results indicated that both U-SCBB and SH-SCBB exhibited significant Zn²⁺adsorption capabilities, with SH-SCBB showing superior performance. Specifically, SH-SCBB achieved the highest Zn²⁺ removal efficiency at pH 5 and adsorbent dosage of 0.9 g. Adsorption behavior and maximum Zn²⁺ removal were modeled using various isotherms, including Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Flory-Huggins (F-H), and Temkin. It was determined that the SH-SCBB was best described by the D-R isotherm with a coefficient of determination or R² equivalent to 0.96. Kinetic data were analyzed with Pseudo-First Order (PFO), Pseudo-Second Order (PSO), Elovich, and Intra-Particle Diffusion (IPD) models, and it was found to pattern out a PSO model with an R² of 0.99, suggesting a physisorption process with an equilibrium time of 75 minutes. Optimal adsorption considering statistical significance was at pH 5 with 0.7 g of SH-SCBB, underscoring its potential as a cost-effective and environmentally sustainable adsorbent for Zn²⁺removal in mining wastewater treatment.

Abstract: Brown seaweed (Sargassum sp.) is one of the most abundant biomass wastes widely available along the Philippine coast and has potential for alginate production. This alginate is a natural polysaccharide, having potential properties in adsorbing contaminants, such as heavy trace metals, through to its properties. In this study, pure sodium alginate (Na-ALG) was extracted and characterized from Sargassum sp. via modified Microwave-Assisted Extraction (MAE), an inexpensive and efficient method for extraction. The Cu (II) ion adsorption capability of the extracted Na-ALG in an aqueous solution was also investigated to address the increasing levels of harmful metals (i.e. Cu) on the coast of Batangas, Philippines. The novel extraction process yielded 44.0±10.8% Na-ALG, with desirable physicochemical properties. Also, Na-ALG’s surface morphology, functionalities, and crystallinity index attested to its capability to adsorb contaminants, such as heavy metals, which is through the presence of pores, functional groups of COO-, and semi-crystalline structures, resulting in adsorption-surface complexation, ionic exchange, and electrostatic interactions. Moreover, the adsorption parameters of Cu (II) concentration, Na-ALG dosage, contact time, and pH were investigated and optimized using the Response Surface Methodology Central Composite Design (RSM-CCD). The optimized adsorption process resulted in a metal concentration of 30 mg/L, alginate dosage of 2.5 g, contact time of 120 min, and pH of 3, exhibiting good adsorption efficiency of 35.96%. Thus, the results proved the adsorption efficiency based on each parameter, and the relationship of the Na-ALG properties to its Cu (II) ion adsorption capability in an aqueous medium. Conclusively, this study showed that Na-ALG extracted from Sargassum sp. via MAE can efficiently adsorb Cu (II) ions in aqueous solutions.

Abstract: Manganese dioxide-modified montmorillonite (MnO₂/MMT), a one-step hydrothermal procedure was utilized for fabricating the composites. The structure, morphology and the particulars of the components were explained by XRD, SEM and BET, which proved that MnO₂/MMT composites were successfully synthesized. Conclusions of the experiment show that the adsorption efficiency of MnO₂/MMT reached 99.63% after 5 hours of adsorption for Cr(VI) solution, which was considerably greater than that of the unmodified montmorillonite under the same conditions. The above study highlights how MnO₂/MMT can be used in the wastewater treatment.

Abstract: The current study was carried out by determining structural and energetic parameters to theoretically validate the experimental results of the adsorption efficiency of amine-functionalized porous carbon for the elimination of Cu²⁺ ions and Pb²⁺ and detail the reaction mechanism in the aqueous medium. The Density Functional Theory calculations, molecular dynamics, and Monte Carlo simulations were used to investigate the adsorption enhancement mechanism. The calculations were performed using the Dmol3 module of the Materials Studio program (MatS) using the exchange-correlation function M-11L2. DFT calculations were determined for porous carbon (PC) and porous carbon functionalized by ethylene diamine (PC-ED). Indeed, this study aims to reveal the functionalization influence on improving the adsorption efficiency of Cu²⁺ and Pb²⁺ by porous carbon (PC). Overall, the study attempts to explain the experimental results of the improved interactivity of porous carbon functionalized by ethylene diamine concerning Cu²⁺ and Pb²⁺ ions, compared to the reactivity of these ions with the group carboxyl characterizes the porous carbon (PC). The Molecular dynamics and Monte Carlo simulations were used to clarify the interactions between Cu²⁺ or Pb²⁺ ions and porous carbon modelled in the presence or absence of ethylene diamine (PC–ED) function. Hence, the theoretical study showed that the presence of ethylene diamine (C₂H₄(NH₂)₂)_m forms more ligands towards the ions of metal M²⁺ with the interaction bounds lower than ≤ 2.5 Å. The same result is shown by the small adsorption energy obtained in the range of -1140 to -200 kcal/mol for and -1200 to -600 kcal/mol for Pb²⁺ and Cu²⁺, respectively. Therefore, more adsorption of Cu²⁺ and Pb²⁺ ions. The theoretical results obtained agree with the experimental results.

Abstract: The use of activated carbon for waste water treatment has been established based on sustainability and cost. This study delves into the intricate process of producing activated carbon from cow and goat bones and explores the efficiency of this material in removing contaminants from distillery wastewater. The samples were carbonized at 700°C in a muffle furnace, then crushed in a mortar after cooling. The crushed samples were activated using 0.4M phosphoric acid for 24 hours and washed with distilled water, and finally oven dried. The elemental and microstructural was carried on the prepared activated carbon (AC) samples using X-ray Fluorescence (XRF) and Scanning Electron Microscopy (SEM). The heavy metals in the treated water were tested using Atomic Absorption Spectroscopy (AAS). The AC was used to treat waste water and factors on which adsorption depend, such as contact time (35 minutes and 60 minutes), adsorbent dosage (2.5g and 5g), and initial contaminant concentration (100% and 50%) were varied for each activated carbon sample (cow bone AC, goat bone AC, and a mixture of equal ratios of both). It was reported that activated carbon prepared from animal bones is rich in calcium. Also, chemical activation with phosphoric acid led to an increase in the external surface area of the particles with irregular cavities and pores. AC prepared from the mixture of cow and goat bones was most effective for distillery wastewater purification.

Abstract: Water resources are crucial in any region's overall natural resource complex. This research focuses on addressing these pollution issues through water treatment processes. The primary objective of this study was to examine the adsorption of phosphates using both natural and synthetic adsorbents, particularly aluminosilicates. Under static and dynamic conditions, the research assessed the sorption characteristics of natural zeolite, specifically clinoptilolite obtained from the Sokyrnytsia mineral deposits. Results indicated that the adsorption of phosphates is more effective in acidic environments. It was observed that clinoptilolite exhibits a higher adsorption capacity for unsubstituted phosphates, which diminishes when alkali metal ions replace orthophosphoric acid. Additionally, the study highlighted the significant influence of pH levels on the sorption properties of clinoptilolite, especially about P₂O₅. The kinetic coefficients of the adsorption process were determined using experimental data and theoretical frameworks. Furthermore, mathematical modelling was employed to describe the adsorption dynamics of the active components by granular sorbents, effectively capturing the transient nature of diffusive-kinetic processes in complex, multicomponent systems. This research deepens our understanding of phosphate adsorption mechanisms. It provides valuable insights into optimising water treatment strategies using natural adsorbents, which could play a critical role in mitigating the effects of water pollution in the region. Zeolites derived from fly ash produced by the Dobrotvir thermal power plant have been synthesised and modified to enhance their properties. This study focuses on the characteristics of these zeolites, with a particular emphasis on thermogravimetric analysis, to understand their stability and performance under varying conditions. The adsorption capabilities of the natural zeolite were tested against common pollutants found in wastewater from meat-processing plants, specifically targeting ammonium and phosphate contaminants. Experimental data allowed for determining equilibrium adsorption capacities and corresponding isotherms were constructed at a standard temperature of 20°C. The results indicate that zeolite adsorbs phosphates more effectively than ammonia nitrogen. Further analysis revealed that clinoptilolite's adsorption capacity is higher when interacting with single-component systems but decreases when it simultaneously adsorbs two different substances from the solution. This decrease suggests competitive adsorption dynamics when multiple contaminants are present. Given the finite availability of natural zeolite resources, this research highlights the importance of synthesising synthetic zeolites as a sustainable alternative.

Abstract: Polystyrene (PS) is widely used in industries like packaging and insulation, but its performance can be enhanced by incorporating calcium carbonate as a filler. To improve polymer-filler compatibility, calcium carbonate was surface-modified with oleic acid, and PS-calcium carbonate composites were synthesized using the melt blending method, followed by citric acid treatment. X-ray diffraction (XRD) and FTIR analyses revealed no chemical interaction between the phases, with a reduction in calcium carbonate content due to citric acid treatment, suggesting partial dissolution of the filler. Scanning electron microscopy (SEM) images showed the formation of cavities in the matrix, especially in TPS3. Hardness testing indicated a decrease in hardness with increasing oleic acid concentration, with TPS3 exhibiting the lowest hardness (63.4 Shore D). Photoluminescence measurements showed a blue shift at lower oleic acid concentrations, while higher concentrations caused a red shift and broader emission, which was stabilized by citric acid treatment. Solvent absorption tests indicated that citric acid-treated composites had an enhanced absorption capacity, with TPS3 showing 38.3 % absorption in vegetable oil, suggesting potential for adsorption applications. Overall, the oleic acid and citric acid treatments significantly modified the mechanical, morphological, and optical properties of PS-calcium carbonate composites, creating tunable materials with potential for sensing applications.

Abstract: The escalating levels of atmospheric carbon dioxide (CO₂) emissions and the consequential threat of global warming necessitate urgent measures for CO₂ reduction. This study explores the development of CO₂ adsorbents from biomass, specifically charcoal derived from empty palm bunches, focusing on the impact of different activating agents and activation temperatures on their properties. The research methodology involves the hydrothermal carbonization of empty palm fruit bunches followed by activation using three different materials: potassium hydroxide (KOH), urea, and a combination of KOH and urea, at three distinct activation temperatures (180°C, 200°C, and 220°C). The investigation encompasses a comprehensive analysis of the functional groups and surface morphology through Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques. The findings demonstrate that the choice of activating agent and activation temperature significantly influences the characteristics of the resultant charcoal. Notably, higher activation temperatures lead to reduced lignin content and increased pore distribution. Among the various combinations, the KOH + Urea activating agent at 220°C exhibits the most favorable attributes, including the weakest lignin peak intensity and the highest pore distribution. In conclusion, this research underscores the potential of empty palm bunch charcoal as a promising CO₂ adsorbent, offering insights into optimized conditions for its production. This contributes to the ongoing global efforts to combat climate change by mitigating CO₂ emissions.

Abstract: The exceptional properties of chitosan and its effective technique of adsorbing contaminants even to near-zero concentrations are the primary reasons for special attention. The adsorption studies analyzed various elements, including pH, concentration, contact time, and adsorbent dose. The study used these factors as input data, with the output data concentrating on MB removal efficiency. For prediction and optimization, MB adsorption used response surface methodology/central composite design (RSM-CCD), artificial neural network (ANN), and adaptive neuron-fuzzy inference system (ANFIS) models. For developing the ANN and ANFIS models, 70% of the data was allocated for training, and 15% was dedicated to validation and testing. Based on the RSM-CCD findings, the optimization outcome for the process parameters was obtained at pH 7, contact time 55 minutes, 6.0 grams of adsorbent, and MB concentration of 125 mg/L. However, an ideally trained neural network is described using training, testing, and validation phases, and the R² values at these phases were found to be 0.99987, 1, and 1, respectively. The statistical findings showed that the ANFIS approach outperforms the RSM and ANN model approaches.