Computational study of ibuprofen removal from water by adsorption in realistic activated carbons

Molecular Dynamics of Hydration Shells of Adsorbates in Entropy-Driven Adsorption (Hydrophobic Bonding) to Activated Carbon Surfaces

Hydrophobic bonding is a phenomenon wherein the adsorption of solutes from aqueous solutions is driven largely by the desire of solvent molecules to interact with each other, thus squeezing out solute molecules onto the adsorbent surface. A novel computational analysis of hydration shell water dynamics was used to study the driving force for the hydrophobic bonding of five small drug molecules to activated carbon. It was demonstrated that the solvation of these drug molecules produced hydration shells of lower density and molecular mobility than bulk water, up to 10.5-14 Å distance. Excellent correlations were found between the simulated water-water hydrogen bonding lifetimes in the hydration shell and the experimental capacity constants of hydrophobic bonding (KHB) obtained from the Two-Mechanism Langmuir-Like Equation. KHB also correlated well with the solute-solvent vdW interaction energies in a manner that could allow future predictions of KHB values from simple simulations. Such correlations were not found with the capacity constant of the well-known enthalpy-driven adsorption. The driving force for hydrophobic bonding has entropic origins due to the elimination of water structuring in the hydration shells. However, unlike a typical entropy-driven process, hydrophobic bonding to activated carbon was also associated with a large exothermic enthalpy change when studied with isoperibol calorimetry.

Evaluating an integrated nano zero-valent iron column system for emerging contaminants removal from different wastewater matrices - Identification of transformation products

The presence of micropollutants in water bodies has become a growing concern due to their persistence, bioaccumulation and potential toxicological effects on aquatic life and humans. In this study, the performance of a column system consisting of zero-valent iron nanoparticles (nZVI) incorporated into a cationic resin and synthesized from green tea extract with the addition of persulfate for the elimination of selected pharmaceuticals and endocrine disruptors from wastewater is evaluated. Ibuprofen, naproxen, diclofenac and ketoprofen were the target pharmaceuticals from non-steroidal anti-inflammatory drugs group, while bisphenol A was the target endocrine disruptor. In this context, different real wastewater effluent matrices were investigated: anaerobic membrane bioreactor (AnMBR), upflow anaerobic sludge blanket reactor (UASB) after microfiltration, tertiary treated by conventional activated sludge system and saturated vertical constructed wetland followed by a sand filtration unit effluent (hybrid). The transformation products of diclofenac and bisphenol A were also identified. The experimental results indicated that the performance of the R-nFe/PS system towards the removal efficiency of the target compounds was enhanced in the order of effluents: tertiary > AnMBR ≈ hybrid > UASB. More than 70% removal was obtained for almost all target compounds when conventional tertiary effluent was used, while the maximum removal efficiency was about 50% in the case of filtered UASB. As far as we know, this is the first time that nZVI has been assessed in combination with persulfate for the removal of micropollutants in a continuous flow system receiving various types of real wastewater with different matrix characteristics.

Biomass based biochar production approaches and its applications in wastewater treatment, machine learning and microbial sensors

Biochar is a stable carbonaceous material derived from various biomass and can be utilized as adsorbents, catalysts and precursors in various environmental applications. This review discusses various feedstock materials and methods of biochar production via traditional as well as modern approaches. Additionally, the biochar characteristics, HTC process, and its modification by employing steam and gas purging, acidic, basic / alkaline and organo-solvent, electro- and magnetic fields have been discussed. The recent biochar applications for real water, wastewater and industrial wastewater for the abstraction of environmental contaminants also reviewed. Moreover, applications in machine learning and microbial sensors were discussed. In the meantime, analyses on commercial and environmental profit, current ecological concerns and the future directions of biochar application have been well presented.

Ultraviolet light spectroscopic characterization of ibuprofen acid aggregation in deionized water

This work provides a description of the aggregation equilibria of ibuprofen acid in deionized water at temperatures between 20 and 40 °C in the 0.1-20.1 ppm concentration range. For this goal, we have made use of UV-Visible spectroscopy. A calculation algorithm was developed to obtain the aggregate orders and thermodynamic parameters from the experimental absorbance values. Monomeric ibuprofen acid was found to be absent in water solutions. In addition to the dimer, two aggregates formed by 32 and 128 monomeric units were found to co-exist in solution at the highest concentration tested. A critical micelle concentration of 7.8 ppm was estimated for this system. The appearance of the first aggregate occurs when the pH drops below the pKa value, which was determined to be 4.62. At higher ibuprofen concentrations, a sudden jump in the electrical conductivity coincides with the onset of formation of the second aggregate. A varied menu of alternatives is offered with respect to the calibration curve of ibuprofen in water, though the linear calibration of ibuprofen concentration with absorbance might be reasonably performed at 224 nm. Finally, the dissolution rate of the commercial ibuprofen used in this work was found to obey the Noyes-Whitney first order equation.

Ibuprofen Adsorption on Activated Carbon: Thermodynamic and Kinetic Investigation via the Adsorption Dynamic Intraparticle Model (ADIM)

The adsorption efficiency of commercial activated carbon toward ibuprofen (IBU) was investigated and described using the adsorption dynamic intraparticle model (ADIM). Although the adsorption capacity of activated carbon has been widely studied, the kinetic models used in the literature are simplified, treating adsorption kinetics with pseudo-kinetic approaches. In this paper, a realistic model is proposed, quantitatively describing the influence of the main operation parameters on the adsorption kinetics and thermodynamics. The thermodynamic data were interpreted successfully with the Freundlich isotherm, deriving an endothermic adsorption mechanism. The system was found to be dominated by the intraparticle diffusion regime, and the collected data allowed the determination of the surface activation energy (ES = 60 ± 7 kJ/mol) and the fluid-solid apparent activation energy (EA = 6 ± 1 kJ/mol). The obtained parameters will be used to design adsorption columns, allowing the scale-up of the process.

Combined molecular dynamics simulations and experimental studies of the removal of cationic dyes on the eco-friendly adsorbent of activated carbon decorated montmorillonite Mt@AC

In recent years, the combination of experimental and theoretical study to explain adsorbate/adsorbent interactions has attracted the attention of researchers. In this context, this work aims to study the adsorption of two cationic dyes, namely methylene blue (MB) and crystal violet (CV), on a green adsorbent Montmorillonite@activated carbon (Mt@AC) composite and to explain the adsorption behavior of each dye by the molecular dynamics (MD) simulation method. The eco-friendly nanocomposite Mt@AC is synthesized and characterized by the analysis methods: XRD, FTIR, BET, TGA/DTA, SEM-EDS, EDS-mapping and zeta potential. The experimental results of adsorption equilibrium show that the adsorption of the two dyes is well suited to the Langmuir adsorption model. The maximum adsorption capacity of the two dyes reaches 801.7 mg g^-1 for methylene blue and 1110.8 mg g^-1 for crystal violet. The experimental kinetics data fit well with a pseudo-first order kinetic model for the two dyes with coefficient of determination R ² close to unity, non-linear chi-square χ ² close to zero and lower Root Mean Square Error RMSE (R ² → 1 and χ ² → 0, RMSE lower). Molecular dynamic simulations are run to gain insights on the adsorption process. According to the RDF analysis and interaction energy calculations, the obtained results reveal a better affinity of the CV molecule with both the AC sheet and montmorillonite framework as compared with MB. This finding suggests that CV is adsorbed to a larger extent onto the nanocomposite material which is in good agreement with the adsorption isothermal experiment observations.

Disagreements Between Calorimetric and Van't Hoff Enthalpies of Adsorption: A New Langmuir-like Model to Account for the Effect of Solvent Displacement Stoichiometry

The reported inconsistencies between calorimetry and the van't Hoff equation hinder the utility of thermodynamics in pharmaceutical research. In ligand binding or adsorption assays, it is believed that the van't Hoff equation falls short because of the lack of stoichiometric treatment in the equilibrium constant. A new modified Langmuir-Like equation that accounts for the stoichiometry of solute adsorption and solvent displacement is proposed in this work. The performance of the model was evaluated by studying the adsorption of phenobarbital from aqueous solutions by commercial activated carbon. The amount of water occupying the adsorption sites was estimated by graphical analysis of the 'knee point' of water-vapor adsorption isotherms and was found to correlate well with the relative percentage of hydroxyl and carbonyl surface groups. It was found that one phenobarbital molecule displaces 2-6 water molecules from the adsorption site. It is shown that adsorption enthalpy was not affected by the adjustment for stoichiometry, supporting the notion that the van't Hoff enthalpy is intrinsic and is independent of the stoichiometry of solvent displacement in Langmuir-based binding. The widely reported disparities between the van't Hoff and calorimetric enthalpies are unlikely to be from a stoichiometric origin.

Adsorption free energy of phenol onto coronene: Solvent and temperature effects

Molecular modeling can considerably speed up the discovery of materials with high adsorption capacity for wastewater treatment. Despite considerable efforts in computational studies, the molecular modeling of adsorption processes has several limitations in reproducing experimental conditions. Handling the environmental effects (solvent effects) and the temperature effects are part of the important limitations in the literature. In this work, we address these two limitations using the adsorption of phenol onto coronene as case study. In the proposed model, for the solvent effects, we used a hybrid solvation model, with n explicit water molecules and implicit solvation. We increasingly used n=1 to n=12 explicit water molecules. To account for the temperature effects, we evaluated the adsorption efficiency using the adsorption free energy for temperatures varying from 200 to 400K. We generated initial configurations using classical molecular dynamics, before further optimisation at the ωB97XD/aug-cc-pVDZ level of theory. Polarisable continuum solvation model (PCM) is used for the implicit solvation. The adsorption free energy is evaluated to be -1.3kcal/mol at room temperature. It has been found that the adsorption free energy is more negative at low temperatures. Above 360K, the adsorption free energy is found to be positive.

Role of Basic Surface Groups of Activated Carbon in Chlordecone and β-Hexachlorocyclohexane Adsorption: A Molecular Modelling Study

The influence of nitrogen-containing surface groups (SGs) onto activated carbon (AC) over the adsorption of chlordecone (CLD) and β-hexachlorocyclohexane (β-HCH) was characterized by a molecular modelling study, considering pH (single protonated SGs) and hydration effect (up to three water molecules). The interactions of both pollutants with amines and pyridine as basic SGs of AC were studied, applying the multiple minima hypersurface (MMH) methodology and using PM7 semiempirical Hamiltonian. Representative structures from MMH were reoptimized using the M06-2X density functional theory. The quantum theory of atoms in molecules (QTAIM) was used to characterize the interaction types in order understanding the adsorption process. A favorable association of both pesticides with the amines and pyridine SGs onto AC was observed at all pH ranges, both in the absence and presence of water molecules. However, a greater association of both pollutants with the primary amine was found under an acidic pH condition. QTAIM results show that the interactions of CLD and β-HCH with the SGs onto AC are governed by Cl···C interactions of chlorine atoms of both pesticides with the graphitic surface. Electrostatic interactions (H-bonds) were observed when water molecules were added to the systems. A physisorption mechanism is suggested for CLD and β-HCH adsorption on nitrogen-containing SGs of AC.

Grand Canonical Monte Carlo Simulations to Determine the Optimal Interlayer Distance of a Graphene Slit-Shaped Pore for Adsorption of Methane, Hydrogen and their Equimolar Mixture

The adsorption—for separation, storage and transportation—of methane, hydrogen and their mixture is important for a sustainable energy consumption in present-day society. Graphene derivatives have proven to be very promising for such an application, yet for a good design a better understanding of the optimal pore size is needed. In this work, grand canonical Monte Carlo simulations, employing Improved Lennard–Jones potentials, are performed to determine the ideal interlayer distance for a slit-shaped graphene pore in a large pressure range. A detailed study of the adsorption behavior of methane, hydrogen and their equimolar mixture in different sizes of graphene pores is obtained through calculation of absolute and excess adsorption isotherms, isosteric heats and the selectivity. Moreover, a molecular picture is provided through z-density profiles at low and high pressure. It is found that an interlayer distance of about twice the van der Waals distance of the adsorbate is recommended to enhance the adsorbing ability. Furthermore, the graphene structures with slit-shaped pores were found to be very capable of adsorbing methane and separating methane from hydrogen in a mixture at reasonable working conditions (300 K and well below 15 atm).

Sorptive and microbial riddance of micro-pollutant ibuprofen from contaminated water: A state of the art review

Continuous discharge of ibuprofen, a pharmaceutical compound in local water systems is becoming a budding concern as seen from data procured from the past few decades. Increased concentrations of the compound in water reservoirs resulted in adverse effects on the environment. In order to prevent the deleterious impacts of increasing ibuprofen concentration in water bodies, application of cost effective and energy efficient elimination of ibuprofen (IBP) is needed. As a result, various techniques over time have been tested for IBP expulsion from aqueous media. However, adsorption and bioremediation are still the most realistic approaches to remove ibuprofen than conventional methods, like precipitation, reverse osmosis, ion exchange, nano-filtration etc., because of their lower initial cost, reduced electricity consumption, minimized sludge generation, local availability of precursor material etc. Various researchers have reported the applicability of the adsorption and bioremediation process in remediation of ibuprofen from water. Therefore, the present review article confers both the biosorption and bioremediation process towards IBP removal from water bodies and explicates the performances of various adsorbents and microorganisms derived from various sources. The presented review also substantially emphasizes on the effect of different parameters on sorptive uptake of ibuprofen, various isotherms and kinetic models, sorption mechanism and assessment of costs, which could enable future researchers to determine widespread use of reported adsorbents and microbes towards effective elimination of IBP from aqueous media.

Removal of ibuprofen from aqueous media by adsorption: A comprehensive review

Ibuprofen (IBP) is a non-steroidal anti-inflammatory drug released into the environment through hospital and medical effluents, pharmaceutical wastewater and veterinary use. The aim of this paper is to review the empirical findings on the adsorption of IBP from aqueous media. A preliminary ecotoxicological assessment confirmed the environmental risk of IBP in the aqueous environment. Open literature works considered in this review were for the past decade (2010-2020). Carbon-based adsorbents are the best class of adsorbent for the uptake of IBP and the highest reported maximum adsorption capacity (q_max) for IBP is 496.1 mg/g by SWCNTs. The range of adsorption capacities for IBP uptake in this review is between 0.0496 and 496.1 mg/g. The mechanism of uptake is majorly by hydrophobic interactions, π - π stacking, hydrogen bonds, electrostatic interactions and dipole-dipole interaction. IBP uptake was best fit to a wide variety of isotherm models but was well suited to the pseudo-second order kinetics model. The thermodynamics of IBP uptake depends majorly on the nature of the adsorbent and desorption from the solid phase is based on an appropriate choice of the eluent. Knowledge gaps were observed in used adsorbent disposal and process improvement. In the future, interest would increase in scale-up, industrial applications and practical utilisation of the research findings which would help in sustainable water resource management.

Predicting the Adsorption of Amoxicillin and Ibuprofen on Chitosan and Graphene Oxide Materials: A Density Functional Theory Study

The occurrence, persistence, and accumulation of antibiotics and non-steroidal anti-inflammatory drugs (NSAIDs) represent a new environmental problem due to their harmful effects on human and aquatic life. A suitable absorbent for a particular type of pollutant does not necessarily absorb other types of compounds, so knowing the compatibility between a particular pollutant and a potential absorbent before experimentation seems to be fundamental. In this work, the molecular interactions between some pharmaceuticals (amoxicillin, ibuprofen, and tetracycline derivatives) with two potential absorbers, chitosan and graphene oxide models (pyrene, GO-1, and coronene, GO-2), were studied using the ωB97X-D/6-311G(2d,p) level of theory. The energetic interaction order found was amoxicillin/chitosan > amoxicillin/GO-1 > amoxicillin/GO-2 > ibuprofen/chitosan > ibuprofen/GO-2 > ibuprofen/GO-1, the negative sign for the interaction energy in all complex formations confirms good compatibility, while the size of Eint between 24-34 kcal/mol indicates physisorption processes. Moreover, the free energies of complex formation were negative, confirming the spontaneity of the processes. The larger interaction of amoxicillin Gos, compared to ibuprofen Gos, is consistent with previously reported experimental results, demonstrating the exceptional predictability of these methods. The second-order perturbation theory analysis shows that the amoxicillin complexes are mainly driven by hydrogen bonds, while van der Waals interactions with chitosan and hydrophobic interactions with graphene oxides are modelled for the ibuprofen complexes. Energy decomposition analysis (EDA) shows that electrostatic energy is a major contributor to the stabilization energy in all cases. The results obtained in this work promote the use of graphene oxides and chitosan as potential adsorbents for the removal of these emerging pollutants from water.

Using coarse-grained molecular dynamics to rationalize biomolecule solubilization mechanisms in ionic liquid-based colloidal systems

Solubilizing agents are widely used to extract poorly soluble compounds from biological matrices. Aqueous solutions of surfactants and hydrotropes are commonly used as solubilizers, however, the underlying mechanism that determines their action is still roughly understood. Among these, ionic liquids (IL) are often used not only for solubilization of a target compound but in liquid-liquid extraction processes. Molecular dynamics simulations can shed light into this issue by providing a microscopic insight of the interactions between solute and solubilising agents. In this work, a new coarse-grained (CG) model was developed under the MARTINI framework for gallic acid (GA) while the CG models of three quaternary ammonium ionic liquids and salts (QAILS) were obtained from literature. Three QAILS were selected bearing in mind their potential solubilising mechanisms: trimethyl-tetradecylammonium chloride ([N1,1,1,14]Cl) as a surfactant, tetrabutylammonium chloride ([N4,4,4,4]Cl) as a hydrotrope, and tributyl-tetradecylammonium chloride ([N4,4,4,14]Cl) as a system combining the characteristics of the other compounds. Throughout this hydrotrope-to-surfactant spectrum and considering the most prevalent GA species across the pH range, the solvation of GA at two concentration levels in aqueous QAILS solutions were studied and discussed. The results of this study indicate that dispersive interactions between the QAILS and GA are generally the driving force in the GA solubilization. However, electrostatic interactions play an increasingly significant role as the GA becomes deprotonated, affecting their placement within the micelle and ultimately the solvation mechanism. The hydrotropic mechanism seen in [N4,4,4,4]Cl corroborates recent models based on the formation of a hydrotrope-solute aggregates driven by dispersive forces. This work contributes to the application of a transferable approach to partition and solubilization studies using molecular dynamics, which could complement experimental assays and quickly screen molecular candidates for these processes.

Comparison of the behavior of ZVI/carbon composites from both commercial origin and from spent Li-ion batteries and mill scale for the removal of ibuprofen in water

Zero valent iron/carbon composites were successfully synthesized from commercial iron oxide and graphite (ZVI/C) and also by using graphite obtained from spent Li-ion batteries and iron oxide from mill scale (ZVI/C-X) as a new approach for the valorization of these waste. The composites were synthesized through carbothermic reactions and tested as catalysts for the degradation of ibuprofen from water by Fenton reaction. The optimal conditions for synthesizing ZVI/C composites were a temperature of 1000 °C maintained for 2 h. The structural, and textural features of ZVI/C with different ZVI mass ratios were characterized by different techniques. ZVI/C composites with higher ZVI mass ratios showed higher degradation rates for the removal of ibuprofen both in presence and absence of H₂O₂. Moreover, ZVI/C-X composite, obtained from industrial waste, showed activity even after four consecutive cycles of use with very low concentration of iron ions in solution after reaction (4.8 mg L^-1 after 4 h), which supports the high stability and low Fe-lixiviation of ZVI/C-X composite. The results of this study prove the possibility of synthesizing composites using graphite from spent Li-ion batteries and iron oxide from mill scale, and their potential for the degradation of ibuprofen in water, with comparable activities to those obtained from commercial feedstocks.

Treatment of isopropanol wastewater in an anaerobic fluidized bed microbial fuel cell filled with macroporous adsorptive resin as multifunctional biocarrier

The isopropanol (IPA) wastewater was treated in an anaerobic fluidized bed microbial fuel cell (AFB-MFC) filled with macroporous adsorptive resin (MAR) particles as multifunctional biocarrier. MAR was used as a biological carriers and adsorbent. MAR was characterized by scanning electron microscope. The diffusion of isopropanol in MAR was studied by Materials Studio (MS) software, and diffusion coefficients were analyzed and calculated by molecular dynamics simulation. The simulation results were qualitatively consistent with the available experimental data. The diffusivity of IPA in MAR increased firstly, with the increasing IPA weight, and then decreased. The maximum diffusivity was resulted to be 0.3722 Å²/ps. In addition, the response surface methodology (RSM) and Box-Behnken design were used to study the effects of initial IPA concentration, flow rate and external resistance on performance of power output and pollutant degradation. The optimal experimental condition was observed as initial IPA concentration of 483.49 mg/L, a flow rate of 57.70 mL/min, and external resistance of 5225.78 Ω. After 21 h of operation under the optimized conditions, the maximum power density was 135.73 ± 0.17 mW/m² and the COD removal was 68.21 ± 0.24%, which increased by 65.85% and 9.29%, respectively.

Recent advances in biochar application for water and wastewater treatment: a review

In the past decade, researchers have carried out a massive amount of research on the application of biochar for contaminants removal from aqueous solutions. As an emerging sorbent with great potential, biochar has shown significant advantages such as the broad sources of feedstocks, easy preparation process, and favorable surface and structural properties. This review provides an overview of recent advances in biochar application in water and wastewater treatment, including a brief discussion of the involved sorption mechanisms of contaminants removal, as well as the biochar modification methods. Furthermore, environmental concerns of biochar that need to be paid attention to and future research directions are put forward to promote the further application of biochar in practical water and wastewater treatment.

Molecular Dynamics of Water Embedded Carbon Nanocones: Surface Waves Observation

We employed molecular dynamics simulations on the water solvation of conically shaped carbon nanoparticles. We explored the hydrophobic behaviour of the nanoparticles and investigated microscopically the cavitation of water in a conical confinement with different angles. We performed additional molecular dynamics simulations in which the carbon structures do not interact with water as if they were in vacuum. We detected a waving on the surface of the cones that resembles the shape agitations of artificial water channels and biological porins. The surface waves were induced by the pentagonal carbon rings (in an otherwise hexagonal network of carbon rings) concentrated near the apex of the cones. The waves were affected by the curvature gradients on the surface. They were almost undetected for the case of an armchair nanotube. Understanding such nanoscale phenomena is the key to better designed molecular models for membrane systems and nanodevices for energy applications and separation.

Performance and microbial community of an electric biological integration reactor (EBIR) for treatment of wastewater containing ibuprofen

Electric biological integration reactor (EBIR) was designed and built for the treatment of wastewater containing ibuprofen. This study evaluates the removal performance of EBIR by comparison with biological aerated filter (BAF), while also discussing the optimal operational parameters of EBIR within the context of the response surface methodology. The results indicate that EBIR exhibits higher average removal rates of ibuprofen, chemical oxygen demand (COD) and NH₄⁺-N, i.e. 93.48%, 86.72% and 85.19%, representing an increase by 61.59%, 14.57% and 10.49%, respectively, compared with BAF. The optimal conditions for EBIR were 12.73 A/m² current density (CD), 3.5 h hydraulic retention time and 0.08 mg/L influent ibuprofen concentration. In addition, microbial community structures were detected using an Illumina Miseq PE300 system, which were different at the phylum, class, and genus levels between EBIR and BAF. The microbial communities of EBIR, including mainly Trichococcus, Aeromonas, Saprospiraceae_uncultured, Thiobacillus, Aeromonas Flavobacterium, Sphingopyxis, Candidate_division_TM7_norank, Acinetobacter and physicochemical properties indirectly confirmed the excellent removal performance at 12.73 A/m² CD.

Statistical optimization of preparing marine macroalgae derived activated carbon/iron oxide magnetic composites for sequestering acetylsalicylic acid from aqueous media using response surface methodologys

This study focuses on the optimization of synthetic conditions for preparing marine macroalgae-derived activated carbon/iron oxide magnetic composites (AC/Fe-MC) and its feasibility for the removal of acetylsalicylic acid from aqueous media. Response surface methodology coupled with a 3^k Box-Behnken design was applied to determine the optimal conditions (independent variables: impregnation ratio, activation temperature, and activation time) towards two response variables (production yield and adsorption capacity). According to the analysis of variance and numerical desirability function approaches, the optimal conditions were impregnation ratio of 2.62:1, activation temperature of 727 °C, and activation time of 129 min. Physicochemical properties of the prepared composite revealed that AC/Fe-MC possesses a porous structure and superparamagnetic property, which substantially contributed to the effective adsorption capacity and separation from the solution using an external magnetic field. Adsorption kinetics and equilibrium studies delineated that the pseudo-second-order and Sips isotherm models represent the adsorption behavior of AC/Fe-MC accurately. The maximum adsorption capacity of AC/Fe-MC was found to be around 127 mg/g at 10 °C, as fitted by Sips isotherm model, which is higher than that of other adsorbents reported in the literature. Intraparticle diffusion and Boyd models suggested that the adsorption process was mainly controlled by film diffusion mechanism. Lastly, thermodynamic and isosteric heat of adsorption analyses demonstrated that the adsorption process was controlled by physisorption and exothermic mechanisms.

Comparison of organic matter removals in single-component and bi-component systems using enhanced coagulation and magnetic ion exchange (MIEX) adsorption

Natural organic matter (NOM) in aquatic environments have a significant impact on NOM-organic compound interactions, which could strongly affect the distribution and transformation of organic compounds during water treatment. This study focused on the removals of NOM (humic acid, HA) and synthetic organic matter (ibuprofen, IBP) through enhanced coagulation and magnetic ion exchange (MIEX) resin adsorption in single and bi-component systems. Two coagulants, traditional aluminum sulfate (AS) and lab-prepared polyaluminum chloride (PACl), were employed. The charge properties, particle size distribution, and fractal dimension (D_f) during organic matter removal were studied in both the single and bi-component systems to explore the purification behaviors and mechanistic effects of interactions between coagulants, MIEX, and organic matters. The experimental results indicated that the Al-based coagulants could remove over 80% of HA in both the single and IBP-HA combined systems, while the presence of HA could considerably improve the IBP removal rate. The aggregates formed during single-component coagulation were larger, but weaker and more loosely structured than those formed in the bi-component system under the same coagulation conditions. In the single-component system, the maximum removal efficiencies of IBP and HA by MIEX adsorption were 65% and 72%, respectively, at a resin dosage of 20.0 mL/L and mixing time of 60 min. Under the same conditions, the removals of these components in the bi-component system were improved to 68% and 98%, respectively. The reaction rate between IBP and MIEX resin was found faster than that between HA and MIEX resin.

Pharmaceutical Removal from Water Effluents by Adsorption on Activated Carbons: A Monte Carlo Simulation Study

Adsorption on activated carbons of five pharmaceutical molecules (ibuprofen, diclofenac, naproxen, paracetamol, and amoxicillin) in aqueous mixtures has been investigated by molecular simulations using the Grand Canonical Monte Carlo (GCMC) method. A virtual nanoporous carbon model based on polyaromatic units with defects and polar-oxygenated sites was used for this purpose. The simulation results show excellent agreement with available experimental data. The adsorption capacities of the carbons for the five drugs were quite different and were linked, essentially, to their molecular dimensions and atom affinities. The uptake behavior follows the trend PRM > DCF, NPX > IBP > AMX in all the studied structures. This work is a further step in order to describe macroscopic adsorption performance of activated carbons in drug removal applications.